Estimação clássica e Bayesiana em modelos de sobrevida com fração de cura

In Survival Analysis, long duration models allow for the estimation of the healing fraction, which represents a portion of the population immune to the event of interest. Here we address classical and Bayesian estimation based on mixture models and promotion time models, using different distributions (exponential, Weibull and Pareto) to model failure time. The database used to illustrate the implementations is described in Kersey et al. (1987) and it consists of a group of leukemia patients who underwent a certain type of transplant. The specific implementations used were numeric optimization by BFGS as implemented in R (base::optim), Laplace approximation (own implementation) and Gibbs sampling as implemented in Winbugs. We describe the main features of the models used, the estimation methods and the computational aspects. We also discuss how different prior information can affect the Bayesian estimates

Análise de resíduos em modelos de tempo de falha acelerado com efeito aleatório

We present residual analysis techniques to assess the fit of correlated survival data by Accelerated Failure Time Models (AFTM) with random effects. We propose an imputation procedure for censored observations and consider three types of residuals to evaluate different model characteristics. We illustrate the proposal with the analysis of AFTM with random effects to a real data set involving times between failures of oil well equipment

Estimação de parâmetros genéticos para resistência à infecção por IMNV em camarões Litopenaeus vannamei por meio de análise de sobrevivência

The main specie of marine shrimp raised at Brazil and in the world is Litopenaeus vannamei, which had arrived in Brazil in the `80s. However, the entry of infectious myonecrosis virus (IMNV), causing the infectious myonecrosis disease in marine shrimps, brought economic losses to the national shrimp farming, with up to 70% of mortality in the shrimp production. In this way, the objective was to evaluate the survival of shrimps Litopenaeus vannamei infected with IMNV using the non parametric estimator of Kaplan-Meier and a model of frailty for grouped data. It were conducted three tests of viral challenges lasting 20 days each, at different periods of the year, keeping the parameters of pH, temperature, oxygen and ammonia monitored daily. It was evaluated 60 full-sib families of L. vannamei infected by IMNV in each viral challenge. The confirmation of the infection by IMNV was performed using the technique of PCR in real time through Sybr Green dye. Using the Kaplan-Meier estimator it was possible to detect significant differences (p <0.0001) between the survival curves of families and tanks and also in the joint analysis between viral challenges. It were estimated in each challenge, genetic parameters such as genetic value of family, it`s respective rate risk (frailty), and heritability in the logarithmic scale through the frailty model for grouped data. The heritability estimates were respectively 0.59; 0.36; and 0.59 in the viral challenges 1; 2; and 3, and it was also possible to identify families that have lower and higher rates of risk for the disease. These results can be used for selecting families more resistant to the IMNV infection and to include characteristic of disease resistance in L. vannamei into the genetic improvement programs

Distribuição diária do comportamento da mosca da fruta Anastrepha zenildae Zucchi, (Diptera: Tephritidae) em laboratório.

The knowledge of Anastrepha zenildae behavioral aspects combined with the biology of Tephritidae may contribute to monitoring and control programs of this fruit fly that is considered as economically important to the Rio Grande do Norte state. In order to characterize the daily activity profile of this species, we studied the behaviors of resting, locomotion, feeding, cleaning, courtship, copulation and oviposition of animals submitted to an artificial 12:12h light-dark cycle (750:1lux) with controlled temperature (26±2 °C). The observations were made with groups of 16 males and 16 females during 3 consecutive days each generation from parental to F5. Resting, locomotion, feeding and cleaning data were recorded as frequency and time of occurrence by scanning technique in 15 minutes windows per hour, with a record each minute. Courtship, copulation and oviposition were recorded as frequency, time of occurrence and duration by al occurrences technique. Resting was the most frequent behavior with males resting more than females. Locomotion was more evident in the first half of the ligh phase with higher values in females. Cleaning and feeding behaviors were more frequent in the second half of the light phase for both sexes with females eating more frequently than males. During the courtship, males were grouped in lek formations showing wings vibration and pheromone liberation. Courtship occurred more frequently 4 to 7 h after lights on (81,9%) with copulations being more frequent 6 h after lights on with a mean duration of 58,1±40,4 min. Copulation attempts were observed in males inside and outside the lek with aggressive behavior being observed only between males in the lek. Oviposition behavior was similar to that described for other species of the genus with a peak of this activity 2-3 h after the lights on, mean duration of 43, 7±34, 8 sec and 2 to 5 eggs by event. According to the results, sexual behavior of A. zenildae is temporally different of other sympatric species of the genus, being favorable to the reproductive isolation as well as the use of resources as oviposition substrate.

Resposta comportamental e hormonal de machos não reprodutores de sagüi, callithrix jacchus, a estímulos sensoriais de filhotes não aparentados

Parental care in mammals is influenced by somatosensory stimuli from infants, such as vocalization and sight and by changes in the hormone levels of caretakers. The aim of this study was to evaluate the behavioral and hormonal responses of twelve non reproductive adult male common marmosets (Callithrix jacchus) to infant cues, vocalization recordings, sight and physical contact with newborn. Six out of twelve males had previous experience in caretaking. In article 1, adult males were exposed to newborn vocalizations for 10 minutes. On control condition no sound was presented. In article 2, males were tested on two conditions: a) Control: an empty acrylic transparent box (test box) was placed in male s cage for 15 minutes, and b) Experimental: males were exposed to newborns into a closed text box for 15 minutes. The cage was kept closed to prevented from tactile, smell and acoustic stimulation by the infant on common marmoset males. In article 3, males were exposed to an open or closed text box, which allowed or not their access to and social interaction with the infants. After each observation sessions, blood samples were collected to evaluate the cortisol levels of males. In all studies, behavioral response of adult males was significantly modified by newborns sight, vocalization and physical contact. Males approached and spent more time near the sound source and showed an increase in locomotion during sound exposure. Furthermore, males approached, smelled and spent more time near the test box when the newborn was inside it. There was no difference in behavioral pattern between experienced and non-experienced males in articles 1 and 2. In article 3, behavioral pattern of males was influence by previous caretaking experience. Experienced males recovered quicker and carried the infants more than the inexperienced ones. However, inexperienced males showed a decrease in recovery latency and an increase in carrying time after successive exposure to infants. Cortisol levels changed after exposure to infant s vocalization, especially for experienced adult males. Male hormonal profile was not affected by the sight of infants neither by their previous experienced in caretaking. The occurrence of social interaction between the caretaker and infant did not modify the hormonal profile of common marmoset males; however, as much as experienced males carried the infants their cortisol levels decreased. Thus, members of a social group or potential caretakers common marmosets exposed to sensory cues from dependent infant such as vocalization, sight, smell and physical contact, changed their behavioral and hormonal responses that are physiological modulators of parental behavior in common marmoset

Expressão de zif-268 durante a aquisição, evocação e extinção de uma memória aversiva

In the behavioral paradigm of discriminative avoidance task, both short and long-term memories have been extensively investigated with behavioral and pharmacological approaches. The aim of the present study was to evaluate, using the abovementioned model, the hippocampal expression of zif-268 - a calcium-dependent immediate early gene involved with synaptic plasticity process - throughout several steps of memory formation, such as acquisition, evocation and extiction. The behavioral apparatus consisted of a modified elevaated plus-maze, with their enclosed arms disposed in "L". A pre-exposure to the maze was made with the animal using all arms enclosed, for 30 minutes, followed by training and test, during 10 minutes each. The between sections interval was 24h. During training, aversive stimuli (bright light and loud noise) were actived whenever the animals entered one of the enclosed armas (aversive arm). Memory acquisiton, retention and extinction were evaluated by the percentage of the total time spent exploring the aversive arm. The parameters evaluated (time spent in the arms and total distance traveled) were estimated with an animal tracking software (Anymaze, Stoelting, USA). Learning during training was estimated by the decrease of the time spent exploring the aversive arm. One hour after the beginning of each section, animals were anaesthetized with sodium-thiopental (i.p.) and perfused with 0.9% heparinized saline solution followed by 4% paraformaldehyde. Brains were cryoprotected with 20% sucrose, separeted in three blocks and frozen. The middle block, containing the hippocampus, was sectioned at 20 micro meters in the coronal plane and the resutant sections were submitted to zif-268 immunohistochemistry. Our results show an increased expression of zif-268 in the dentate gyrus (DG) during the evocation and extinction stages. There is a distinct participation of the DG during the memory evocation, but not during its acquisition. Inaddition, all hippocampal regions (CA1, CA3 and DG) presented an increased zif-268 expression during the process of extinction.

Efeito do exercício físico matinal realizado sob luz solar no ciclo vigília-sono de adolescentes

The sleep onset and offset delay at adolescence in relation to childhood. Besides biological causes, some external factors as academic obligations and socialization contributes, increasing the burden of school and socialization. However, morning school schedules reduce sleep duration. Besides light strong effect, studies in humans have indicated that exercise influence circadian synchronization. To evaluate the effect of the morning exercise under sunlight on sleep-wake cycle (SWC) of adolescents, 160 high school students (11th year) were exposed to the following conditions: lesson in usual classroom (Group C), lesson in swimming pool exposed to sunlight (Group E), half of them carrying through physical activity (EE) and the other resting (EL). Each experimental group met two stages: assessment of SWC 1 week before and 1 week during the intervention, which was held in Monday and Wednesday between 7:45 and 8:30 am. In the baseline, there were applied the questionnaires "Health and Sleep" and cronotype evaluation (H & O). In addition, students were evaluated before and during the intervention by "Sleep Diary", "Karolinska Sleepiness Scale" (KSS), Psychomotor Vigilance Test (PVT) and actimetry. During the intervention, there was a delay in wake-up time on the weekend and a trend to greater sleep duration on week for the three groups. At the weekend, only the groups EE and EL increased sleep duration. There was no difference in bedtime, irregularity of sleep schedules and nap variables. The sleepiness showed a circadian pattern characterized by higher alertness levels at 11:30 am and sleepiness levels at bedtime and wake-up time on week. On weekends there were higher levels of alertness in these times. In the days of intervention, there was an increase of sleepiness at 11:30 am for groups EL and EE, which may have been caused by a relaxing effect of contact with the water of the pool. In addition, the group EE showed higher alert levels at 14:30 pm on Monday and at 8:30 am in the Wednesday, possibly caused by exercise arousal effect. The reaction time assessed through the TPV did not vary between the stages. The sleep quality improved in the three groups in the second stage, making impossible the evaluation of intervention effect. However, the sleep quality increased on Monday and Tuesday only on the group EE. From the results, it is suggested that the intervention promoted effects on the sleepiness at some day hours. In other SWC variables there were no effects, possibly due to a large SWC irregularity on weekends. Thus, the evaluation of higher weekly frequency EF is necessary, since only two days were insufficient to promote greater effect on adolescents SWC

Caracterização do ciclo sono/vigília de professores do ensino médio em natal/rn

In the school environment is fundamental the knowledge about the sleep-wake cycle (SWC), because we find children and adolescents with excessive sleepiness and learning difficulties. Furthermore, teachers with high demand and with different work schedule, which may contribute to changes in SWC. The aim of this study was to describe the SWC of high school teachers in Natal/RN. Habits and knowledge about sleep, chronotype, SWC, daytime sleepiness, sleep quality and job satisfaction were described in 98 high school teachers from public and private school. These parameters were compared according to the characteristics of work, family structure and gender. Data collection was performed with the use of questionnaires in two stages: 1) "health and sleep" (general characterization of sleep habits), Horne & Ostberg questionnaire (characterization of chronotype), Epworth Sleepiness Scale and the Index of Pittsburg Sleep Quality, 2) The sleep diary for 14 days. From the results, we observe that the teachers woke up and went to bed earlier in the week and showed a reduction of time in bed around 42min comparing to weekend. This reduction in time in bed during the week was accompanied by an increase in nap duration on weekend. In addition the teachers woke up earlier on Saturdays than on Sundays, probably due to housework and leisure. The teachers' knowledge about sleep was low in relation to individual differences and effect of alcoholic beverages on sleep, and high in the consequences of sleep deprivation. The differences found in comparisons on the characteristics of work, family structure and gender were punctual, except concerning the work schedule. The teacher who started work in the morning and finished in the night, woke up earlier, went to bed later and had less time in bed, when compared to teachers who work only in two shifts. In addition, teachers with late chronotypes who begin the work in the morning had a greater irregularity in the wake up time compared to teachers with earlier and intermediate chronotypes. Half of teachers have excessive sleepiness, which was positive correlated with work dissatisfaction. In general, teachers showed IPSQ averages equivalent to poor sleep quality and the women showed worst averages. From the results, it is suggested that the SWC of teachers varies according to work schedule, leading to irregularity and partial sleep deprivation in the week, although these responses vary according to chronotype. These changes are accompanied by excessive daytime sleepiness and poor sleep quality. However, it is necessary to expand the sample to clarify the influence of variables related to work, family structure and gender together

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

Influência de fotoperíodo artificial no comportamento de um primata neotropical diurno (Callithrix jacchus)

One of the main environmental cues for the adjustment of temporal organization of the animals is the light-dark cycle (LD), which undergoes changes in phase duration throughout the seasons. Photoperiod signaling by melatonin in mammals allows behavioral changes along the year, as in the activity-rest cycle, in mood states and in cognitive performance. The aim of this study was to investigate if common marmoset (Callithrix jacchus) exhibits behavioral changes under short and long photoperiods in a 24h cycle, assessing their individual behaviors, vocal repertoire, exploratory activity (EA), recognition memory (RM) and the circadian rhythm of locomotor activity (CRA). Eight adult marmosets were exposed to a light-dark cycle of 12:12; LD 08:16; LD 12:12 and LD 16:08, sequentially, for four weeks in each condition. Locomotor activity was recorded 24h/day by passive infrared motion detectors above the individual cages. A video camera system was programmed to record each animal, twice a week, on the first two light hours. From the videos, frequency of behaviors was registered as anxiety-like, grooming, alert, hanging position, staying in nest box and feeding using continuous focal animal sampling method. Simultaneously, the calls emitted in the experimental room were recorded by a single microphone centrally located and categorized as affiliative (whirr, chirp), contact (phee), long distance (loud shrill), agonistic (twitter) and alarm (tsik, seep, see). EA was assessed on the third hour after lights onset on the last week of each condition. In a first session, marmosets were exposed to one unfamiliar object during 15 min and 24h later, on the second session, a novel object was added to evaluate RM. Results showed that long days caused a decreased of amplitude and period variance of the CRA, but not short days. Short days decreased the total daily activity and active phase duration. On long days, active phase duration increased due to an advance of activity onset in relation to symmetric days. However, not all subjects started the activity earlier on long days. The activity offset was similar to symmetric days for the majority of marmosets. Results of EA showed that RM was not affected by short or long days, and that the marmosets exhibited a decreased in duration of EA on long days. Frequency and type of calls and frequency of anxiety-like behaviors, staying in nest box and grooming were lower on the first two light hours on long days. Considering the whole active phase of marmosets as we elucidate the results of vocalizations and behaviors, it is possible that these changes in the first two light hours are due to the shifting of temporal distribution of marmoset activities, since some animals did not advance the activity onset on long days. Consequently, the marmosets mean decreased because the sampling was not possible. In conclusion, marmosets synchronized the CRA to the tested photoperiods and as the phase angle varied a lot among marmosets it is suggested that they can use different strategies. Also, long days had an effect on activity-rest cycle and exploratory behaviors

Identidade, espaço e tempo: negociações de sentido sobre a "gente de rua"

This research examines the street children s identity construction processes. Recently, the research about this population has focused on the socialization processes that organize their everyday, their situations of interaction, the meanings of their social practices, their street experience. The concept of identitary forms gives coherence to the set of these phenomena, articulating them theoretically, in order to describe their life conditions and details of their trajectories. This research utilized an ethnographic approach with a group of 11 street people, 9 of them boys and girls 16-18 years old, during 3 months. It included participant observation, informal and formal interviews, that resulted in young s narratives of lifestory. These narratives were interpreted according to the principles of positioning analysis and the Labovian Analysis model of oral narratives of personal experience. The observation of interaction among the studied group and other groups has showed that their social practices, supported on many particular bodily technologies, recreate space and time of these interactions semantically, as mediation of meaning negotiations among groups. Such meanings transform again the environment of these interactions, disclosing interpretative systems by means of which the groups apprehend this interaction in a particular way. These street children s bodily technologies imply identitary forms based on scarcity and abandonment, paradoxicalally related to their self-concept. The analysis of narratives revealed diversity and complexity in the meanings assembly for their street experience; it showed that the semantic arrangements reconstruct the temporal experience, creating a moral climate for each lifestory, and determining more or less aperture of identitary forms to change. The study concludes that space and time, builders of interaction regimes, produce identitary forms; that the narratives and the social practices of the studied group are sustained upon a master discourse that opposes the meanings of the home and the life in the streets

Adaptação e validação da escala de dependência de exercício físico em versão tradicional e informatizada

While providing physical and psychological benefits, excessive exercise could be or cause a compulsive behavior, making the individual dependent on it. In a parallel discussion, computerized psychological instruments, for a hand, reflects the development of information technology and your applicability to other areas, but also shows little advance for Psychological Assessment. In this perspective, this study aims to adapt the Exercise Dependence Scale (EDS-R) in two formats (paper-and-pencil and computerized) and evaluate evidence of factorial and convergent validity, and reliability of each version and compare them with each other. It is also proposed to observe the relationship of some bio-demographic (Sex, age, frequency, duration and intensity of practice exercise) and the exercise dependence (DEF). For this purpose, 709 regular physical activity practitioners, selected by procedures non-probabilistic sampling, responded a adapted version of EDS-R, Muscle Appearance Satisfaction Scale (MASS), Body Modification Scale (BMS) and a demographic questionnaire, analyzed through Exploratory Factor Analysis, Cronbach's Alpha and not parametric tests. Both the traditional version and the computer showed a seven factors structure, explaining 57 and 62% of the variance, respectively, and Cronbach's alphas of 0.83 and 0.89. Factors were: (1) intentionality, (2) continuity, (3) tolerance, (4) reduction of other activities, (5) lack of control, (6) abstinence and (7) time spent on exercise. Relationships were observed between the Exercise Dependence and the variables: age, diets, consumption of food supplements and medicines for weight change, desire to do plastic surgery and body satisfaction. We observed also a positive correlation between the DEF and the frequency, duration and intensity of exercise, and the factor "Dependence on exercising" from MASS, indicating convergent validity of the EDS-R. Finally, comparisons between the two formats were equivalent, with few changes: computerized version achieved higher DEF scores. Based on these results, it can be concluded that the EDS-R has factorial and convergent validity, reliability, to measure exerceise dependence on traditional e computerized formats. DEF is related to actions used to body modification and behaviors toward exercise. Finally, it was found equivalence between the formats, especially in psychometric parameters, thus suggesting feasibility of a computerized assessment. However, it was observed that the computerized data has sample recruiting strategies more limited

Desempenho auditivo ao longo do tempo e satisfação dos usuários de implante coclear com perda auditiva pós-lingual

Most cochlear implant (CI) users, who suffer from post lingual hearing loss, are able to perceive sounds and comprehend speech after the implant. The prediction of maximal benefit over time, with the use of CI, can be useful for counseling patients about their expectations in using the new device. The measurement of satisfaction should be of primary interest in medical intervention, as the results may be used for intervention feedback. The purpose of this study is to analyze auditory performance of CI over time, as well as to evaluate users‟ satisfaction. Therefore two types of study designs were employed: a) retrospective cohort study with the analysis of medical records from 59 subjects about auditory performance before and after surgery. Results were submitted to the Kaplan -Meier estimator of cumulative probability and compared to prognostic factors of auditory performance using the logrank test. b) A sectional study design was conducted to evaluate the satisfaction of 51 subjects. The instrument consists of two specific questionnaires: Satisfaction with Amplification in Daily Life SADL and International Outcome Inventory Cochlear Implant IOI- CI. Results show statistical significant differences (p<0,001) in auditory performance before and after CI. The majority obtained satisfactory results of CI use during the first six months. Logrank tests does not indicate significant correlation between the analyzed covariates and the time in which adequate speech perception occurs. SADL e IOI-CI questionnaires indicate that most of the CI users are satisfied with their devices. The SADL detected a 27, 5% insatisfaction amongst CI users in relation to services and costs involved with the CI. The results of the IOI show 4% of insatisfaction with the use of CI and the social environment. In conclusion CI is capable to rehabilitate social auditory function in a short period of time and CI users demonstrate satisfaction with auditory, social and psychological gain offered through CI device

A história do intemperismo na Província Borborema Oriental, Nordeste do Brasil: implicações paleoclimáticas e tectônicas

Until some years ago, weathering geochronology was primarily based on the K-Ar and 40Ar/39Ar dating of supergene minerals. Recent advances in the analysis of supergene goethite by the (U-Th)/He method expanded the number of suitable minerals for such purpose, as well as the time of application for weathering geochronology. This study represents the first systematic approach in Brazil, combining both the 40Ar/39Ar e (U-Th)/He methodologies to improve the knowledge on the weathering and the age of nonfossiliferous sediments. Supported by geologic and geomorphologic correlations, we identified different types of weathering profiles occurring in the interior and coastal areas of northeastern Brazil. These profiles were correlated to main regional geomorphological domains: the Borborema Plateau , the Sertaneja Depression , and the Coastal Cuestas and Plains, and respective planation surfaces, which study is fundamental to understand the landscape evolution of the northern portion of the eastern Borborema Province. The depth and stratigraphic organization of the weathering profiles in each of the geomorphological domains permitted to establish that: (i) the profiles on the highlands that cap the Borborema Surface are deeper (up to 100 m) and can be considered as typical lateritic profiles; (ii) on the lowlands that form the Sertaneja Surface , the weathering profiles are shallow and poorly developed (2-5 m deep); (iii) the profiles along the coastal area are moderately developed (up to 25 m deep), and are characterized by thick saprolites and mottle zones. Aiming to establish the timing of the evolution of northeastern Brazil, we studied 29 weathering profiles representing distinct topographic levels of the Borborema Province, from the highlands to the coast, through the analysis of 248 grains of supergene manganese oxides using laser step-heating 40Ar/39Ar geochronology. Additionally, we applied the (U-Th)/He method in 20 weathering profiles, by dating 171 grains of supergene iron oxides and hydroxides. Geochronological results for 248 grains of manganese oxides analyzed by the 40Ar/39Ar method indicate that the weathering profiles in the study area record the history of weathering from the Oligocene to the Pleistocene, with ages in the order of 31.4 ± 1.0 Ma to 0.8 ± 0.4 Ma. Dating of 171 grains of goethite by the (U-Th)/He method yielded ages ranging from 43.2 ± 4.3 Ma to 0.8 ± 0.1 Ma, suggesting the weathering processes last from the Eocene to the Pleistocene. The precipitation of supergene goethite in this interval confirms the age of the weathering processes identified from the manganese oxides record. 105 goethite grains from 8 different occurrences of the Barreiras Formation were dated by the (U-Th)/He method. Five grains collected from the cement in the Barreiras Formation sandstones, in the Lagoa Salgada and Rio do Fogo coastal cuestas, yielded ages of 17.6 ± 1.8 Ma, 17.3 ± 1.7 Ma, 16.3 ± 1.6 Ma, 16.2 ± 1.6 Ma and 13.6 ± 1.4 Ma. Results of 69 goethite grains from authigenic pisoliths collected in 7 different localities also yielded concordant ages, varying from 17.8 ± 1.8 to 7.5 ± 0.8 Ma. Results obtained from 31 detrital grains are concordant in 3 distinct localities (Lagoa Salgada, Praia da Garças e Ponta Grossa); they vary in the range of 43.2 ± 4.3 to 21.6 ± 2.2 Ma, and indicate that the maximum age for the Barreiras Formation deposition is around 22 Ma. 40Ar/39Ar results for 15 manganese oxides grains associated with the Barreiras Formation weathering profiles, in 3 different localities, vary from 13.1 ± 0.9 to 7.7 ± 0.4 Ma, in the same range of ages obtained by the (U-Th)/He method. The systematic application of the 40Ar/39Ar and (U-Th)/He methods, respectively for manganese oxides and goethites, show that the Barreiras Formation sediments were already deposited since ca. 17 Ma, and that the weathering processes were active until ca. 7 Ma ago. The ages obtained from manganese oxides collected in the Cenozoic basalts (Macau Formation) also reveal a weathering history between 19 and 7 Ma, pointing to hot and humid conditions during most of the Miocene. 40Ar/39Ar ages yielded by manganese oxides associated with the Serra do Martins Formation vary from 14.1 ± 0.4 to 10.5 ± 0.3 Ma. On the other hand, (U-Th)/He ages from iron oxides/hydroxides collected in the Serra do Martins Formation mesas vary from 20.0 ± 2.0 to 5.5 ± 0.6 Ma, indicating that those sediments are older than 20 Ma. 40Ar/39Ar and (U-Th)/He results produced in this study are in agreement with paleoclimatic interpretations based on stable isotopes and clay index values measured in the Atlantic Ocean sediments, validating the use of weathering geochronology to investigate paleoclimatic variations. The direct dating of the Barreiras Formation permitted, for the first time, confident inferences on the age of the brittle deformation recorded by this sedimentary unit in the Rio Grande do Norte and Ceará states. The first event, syn-deposition, occurred during the early Miocene; an younger event, related to the post-depositional deformation of the Barreiras Formation, is associated with tectonic activity from the very early Miocene to the Holocene. In agreement with data from other areas, results obtained in this study reveal that the depth and complexity of the weathering profiles reflect the time of exposition of such areas to the weathering agents close to the surface. However, there is no clear relationship between ages vs. altitude. The depth and the stratigraphic organization of weathering profiles in northeastern Brazil, contrary to the southeastern Brazil pattern, do not vary toward the coast. In our study area, field observations reveal the presence of ancient, thick and complex lateritic profiles preserved in the sedimentary mesas on the Borborema Plateau, as younger, narrow and incipient ones occur in the dissected areas. Geochronological results obtained for these profiles yielded older ages on the high altitudes, and younger ages in the lowlands, suggesting the scarp retreatment is the most reliable model to explain the regional landscape evolution. However, in the coastal lowlands, the relatively older ages obtained indicate that more complexes processes were involved in the modeling of the local relief

Monitoramento ambiental da costa do Rio Grande do Norte com base em sensoriamento remoto e geodésia de precisão

This paper presents models of parameters of Sea Surface Layer (SSL), such as chlorophyll-a, sea surface temperature (SST), Primary Productivity (PP) and Total Suspended Matter (TSM) for the region adjacent to the continental shelf of Rio Grande do Norte (RN), Brazil. Concentrations of these parameters measured in situ were compared in time quasi-synchronous with images AQUA-MODIS between the years 2003 to 2011. Determination coefficients between samples in situ and bands reflectance sensor AQUA-MODIS were representative. From that, concentrations of SSL parameters were acquired for the continental shelf of the RN (eastern and northern) analyzing the geographic distribution of variation of these parameters between the years 2009-2012. Geographical and seasonal variations mainly influenced by global climate phenomena such as El Niño and La Niña, were found through the analysis of AQUA-MODIS images by Principal Components Analysis (PCA). Images show qualitatively the variance and availability of TSM in the regions, as well as their relationship with coastal erosion hotspots, monitored along the coast of the RN. In one of the areas identified as being of limited availability of TSM, we developed a methodology for assessment and evaluation of Digital Elevation Models (DEM) of beach surfaces (emerged and submerged sections) from the integration of topographic and bathymetric data measured in situ and accurately georeferenced compatible to studies of geomorphology and coastal dynamics of short duration. The methodology consisted of surveys with GNSS positioning operated in cinematic relative mode involved in topographic and bathymetric executed in relation to the stations of the geodetic network of the study area, which provided geodetic link to the Brazilian Geodetic System (GBS), univocal , fixed, and relatively stable over time. In this study Ponta Negra Beach, Natal / RN, was identified as a region with low variance and availability of MPS in the region off, as characterized by intense human occupation and intense coastal erosion in recent decades, which presents potential of the proposed methodology for accuracy and productivity, and the progress achieved in relation to the classical methods of surveying beach profiles