Formulação e caracterização de pastas espumadas por incorporação de ar e estabilizantes minerais

Cementing operations may occur at various stages of the life cycle of an oil well since its construction until its definitive abandonment. There are some situations in which the interest zones are depleted or have low fracture pressure. In such cases, the adoption of lowdensity cement slurries is an efficient solution. To this end, there are basically three ways to reduce the density of cement slurries: using microspheres, water extending additives or foamed cement. The objective of this study is to formulate, to study and to characterize lowdensity foamed cement, using an air entrainment surfactant with vermiculite or diatomite as water extenders and stabilizers. The methodology consists on preparation and evaluation of the slurries under the American Petroleum Institute (API) and the Brazilian Association of Technical Standards (ABNT) guidelines. Based on calculated densities between 13 and 15 ppg (1.559 and 1.799 g/cm3), the slurries were prepared with fixed surfactant concentration, varying the concentrations of vermiculite and diatomite and were compared with the base slurries. The results of plastic viscosity, yield point and gel strength and the compressive strength for 24 h showed that the slurries presented suitable rheology and mechanical strength for cementing operations in oil wells, and had their densities reduced between 8.40 and 11.89 ppg (1.007 and 1.426 g/cm3). The conclusion is that is possible, under atmospheric conditions, to obtain light weighted foamed cement slurries with satisfactory rheological and mechanical properties by means of air entrainment and mineral additions with extenders and stabilizers effects. The slurries have great potential for cementing operations; applicability in deep wells, in low fracture gradient formations and in depleted zones and bring cost savings by reducing the cementing consumption

Modelagem numérica de escoamento em padrão anular com transferência de calor e massa

Annular flow is the prevailing pattern in transport and energy conversion systems and therefore, one of the most important patterns in multiphase flow in ducts. The correct prediction of the pressure gradient and heat transfer coefficient is essential for optimizing the system s capacity. The objective of this work is to develop and implement a numerical algorithm capable of predicting hydrodynamic and thermal characteristics for upflow, vertical, annular flow. The numerical algorithm is then complemented with the physical modeling of phenomena that occurs in this flow pattern. These are, turbulence, entrainment and deposition and phase change. For the development of the numerical model, axial diffusion of heat and momentum is neglected. In this way the time-averaged equations are solved in their parabolic form obtaining the velocity and temperature profiles for each axial step at a time, together with the global parameters, namely, pressure gradient, mean film thickness and heat transfer coefficient, as well as their variation in the axial direction. The model is validated for the following conditions: fully-developed laminar flow with no entrainment; fully developed laminar flow with heat transfer, fully-developed turbulent flow with entrained drops, developing turbulent annular flow with entrained drops, and turbulent flow with heat transfer and phase change

Saguis (Callithrix jacchus) sob ciclo claro-escuro de 21 h: um modelo de dessincronização forçada em primata diurno

The circadian system consists of multiple oscillators organized hierarchically, with the suprachiasmatic nucleus (SCN) as the master oscillator to mammalians. There are lots of evidences that each SCN cell is an oscillator and that entrainment depends upon coupling degree between them. Knowledge of the mechanism of coupling between the SCN cells is essential for understanding entrainment and expression of circadian rhythms, and thus promote the development of new treatments for circadian rhythmicity disorders, which may cause various diseases. Some authors suggest that the dissociation model of circadian rhythm activity of rats under T22, period near the limit of synchronization, is a good model to induce internal desynchronization, and in this way, enhance knowledge about the coupling mechanism. So, in order to evaluate the pattern of the motor activity circadian rhythm of marmosets, Callithrix jacchus, in light-dark cycles at the lower limit of entrainment, two experiments were conducted: 1) 6 adult females were submitted to the LD symmetric cycles T21, T22 and T21.5 for 60, 35 and 48 days, respectively; 2) 4 male and 4 female adults were subjected to T21 for 24 days followed by 18 days of LL, and then back to T21 for 24 days followed by 14 days of LL. Vocalizations of all animals and motor activity of each one of them were continuously recorded throughout the experiments, but the vocalizations were recorded only in Experiment 1. Under the Ts shorter than 24 h, two simultaneous circadian components appeared in motor activity, one with the same period of LD cycle, named light-entrained component, and the other in free-running, named non-light-entrained component. Both components were displayed for all the animals in T21, five animals (83.3%) in T21.5 and two animals (33.3%) in T22. For vocalizations both components were observed under the three Ts. Due to the different characteristics of these components we suggest that dissociation is result of partial synchronization to the LD cycle, wherein at least one group oscillator is synchronized to the LD by relative coordination and masking processes, while at least another group of oscillators is in free-running, but also under the influence of masking by the LD. As the T21 h was the only cycle able to promote the emergence of both circadian components in circadian rhythms of all Callithrix jacchus, this was then considered the lower entrainment limit of LD cycle promoter of dissociation in circadian rhythmicity of this species, and then suggested as a non-human primate model for forced desynchronization

Caracterização do ritmo de atividade/repouso do Mocó (Kerodon Rupestris) em fotoperíodo artificial

Kerodon rupestris (rock cavy, mocó) is an endemic caviidae of Brazilian northeast that inhabits rocky places in the semi arid region. The aim of this study was to characterize the activity/rest rhythm of the rock cavy under 12:12 h LD cycle and continuous light. In the first stage, seven animals were submitted to two light intensities (LD; 250:0 lux and 400:0 lux; 40 days each intensity). In the second stage four males were kept for 40 days in LD (470:<1 lux), for 18 days in LL 470 lux (LL470) and for 23 days in red dim light below 1 lux (LL<1). In the third stage three males were initially kept in LD 12:12 h (450:<1 lux) and after that in LL with gradual increase in light intensity each 21 days (<1 lux LL<1; 10 lux-LL10; 160 lux LL160; 450 lux LL450). In the fourth stage it was analyzed the motor activity of 16 animals in the first 10 days in LD. Motor activity was continuously recorded by passive infrared movement sensors connected to a computer and totaled in 5 min bins. The activity showed circadian and ultradian rhythms and activity peaks at phase transitions. The activity and the rest occurred in the light as well as in the dark phase, with activity mean greater in the light phase for most of the animals. The light intensity influenced the activity/rest rhythm in the first three stages and in the first stage the activity in 400 lux increased in four animals and decreases in two. In the second stage, the tau for 3 animals in LL470 was greater than 24 h; in LL<1 it was greater than 24 h for one and lower for two. In the third stage the tau decreased with the light intensity increase for animal 8. During the first days in the experimental room, the animals did not synchronize to the LD cycle with activity and rest occurring in both phases. The results indicate that the activity/rest rhythm of Kerodon rupestris can be affected by light intensity and that the synchronization to the LD cycle results from entrainment as well as masking probably as a consequence of the action of two or more oscillators with low coupling strength

Sincronização dos ritmos de atividade motora e temperatura central à disponibilidade de glicose em ratos

Food is essential for the survival of all animals. Its temporal availability is an important enviromental cue for the behavioral and physiological organization throughout the 24 hours of day in different species. Rats and mice, for example, show increased locomotion in the hours before food availability when it is presented in a recurrent manner, a behavior named foodanticipatory activity. Several lines of evidence indicate that this anticipation is mediated by a circadian oscillator. In this work, based on the hypothesis that pre- or post-ingestive humoral signals are involved in the entrainment process, we tested whether the daily intake of glucose is sufficient to induce anticipatory activity in rats. The rhythms of motor activity and central temperature were recorded in animals undergoing 10 days of temporal glucose (solution at 50%) or chow restriction in light-dark (LD) and constant darkness (DD). Animals under temporal glucose restriction increase motor activity and and central temperature in the hours preceding glucose availability and such aticipation is extremely similar to that observed in animals under temporal chow restriction. Glucose ingestion is, therefore, a sufficient temporal cue to induce anticipation in rats. It is possible that the increase in plasma glucose after food ingestion constitutes one of the signals involved in the behavioral entrainment process to food availability

Influência da auto seleção à luz no ritmo circadiano de atividade motora em Callithrix Jacchus

Marmosets, Callithrix jacchus, are strictly diurnal animals. The motor activity rhythmicity is generated by the circadian timing system and is modulated by environmental factors, mainly by photic stimuli that compose the light-dark cycle. Photic stimuli can reset the biological oscilators changing activity motor pattern, by a mechanism called entrainment. Otherwise, light can act directly on expressed rhythm, without act on the biological oscillators, promoting the masking. Thus, photic stimuli can synchronize the circadian activity rhythm (CAR) by two distinct mechanisms, acting isolated or at a combined way. Among the elements that can influence photic synchronization, the duration and time of photic exposure is pointed out. If in the natural environment the marmoset can choose places of different intensity illumination and is synchronized to light-dark cycle (LD), how the photic synchronization mechanism can be evaluated in laboratory by light self-selection? With objective to response this question, four adult male marmosets were studied at two conditions: with and without sleeping box. The animals were submitted to a LD cycle (12:12/ 350:2 lx) and constant light (LL: 350 lx) conditions in individual cages with an opaque sleeping box, that permitted the light self-selection. At the room, the temperature was 25.6 ºC (± 0.3 ºC) and humidity was 78.7 (± 5%). The motor activity was recorded at 5 min bins by infrared movement sensors installed at the top of the cages. The motor activity profile was distinct at the two conditions: without the sleeping box protection against light, the activity frequency was higher at CT 11-12 (ANOVA; F(3.23) = 62.27; p < 0.01). Also, the duration of the active phase (α) was prolonged of about 1 h (t test, p < 0.05) and the animals showed a significant delay on the activity onset and offset (t test, p < 0.05) and at the acrophase (confidence intervals of 5%) of CAR. In LL, the light continuous exposure prolonged the active phase and influenced the endogenous expression of the circadian activity rhythm period. From the result analysis, it is concluded that the light self-selection can modify several parameters of CAR in marmosets, allowing the study of the synchronization mechanism using the burrow model. Thus, without sleeping box there was a phase delay between the CAR and LD (entrainment) and an increase of activity near lights off (positive masking). Furthermore, in LL, the light continuous exposure modifies α and the endogenous expression of CAR. It is suggested that the light self-selection might be take into account at investigations that evaluate the biological rhythmicity in marmosets

Mecanismos de sincronia social no ritmo circadiano de atividade durante a coabitação em casais de saguis (Callithrix jacchus)

In marmosets, it was observed that the synchrony among circadian activity profiles of animals that cohabite in family groups is stronger than those of the same sex and age of different families. Inside the group, it is stronger between the younger ones than between them and their parents. However, the mechanisms involved in the social synchrony are unknown. With the aim to investigate the synchronization mechanisms involved in the synchrony between the circadian activity profiles during cohabitation in pairs of marmosets, the motor activity was continuously registered by the use of actmeters on three dyads. The pairs were maintained in two different conditions of illumination: light-dark cycle LD 12:12 (LD cohabitation I – 21 days), and thereafter in LL (~350 lux). Under LL, the pairs were submitted to four experimental situations: 1. Cohabitation (LLJ I – 24 days), 2. Removal of one member of the pair to another room with similar conditions (LLS I – 20 days), 3. Reintroduction of the separated member in the cage of the first situation (LLJ II – 30 days) and 4. Removal of a member from each pair to another experimental room (LLS II – 7 days), to evaluate the mechanisms of synchronization. Ultimately, the members of each pair were reintroduced in the cage and were kept in LD cycle 12:12 (LDJ II – 11 days). The rhythms of pairs free-ran in LL, with identical periods between the members of each pair during the two stages of cohabitation. In the stages in which the animals were separated, only the rhythms of two females free-ran in the first stage and of three animals in the second one. In those conditions, the rhythms of animals of each pair showed different endogenous periods. Besides, during cohabitation in LD and LL, the members of each pair showed a stable phase relationship in the beginning of the active phase, while in the stages in which the animals were separated it was noticed a breaking in the stability in the phase relationships between the circadian activity profiles, with an increase in the difference in the phase angles between them. During cohabitation, at the transition between LD and LL, all animals showed free-running rhythms anticipating progressively the beginning and the end of the active phase in a phase similar to the previous condition, showing signs of entrainment to the previous LD. While in the posterior stages this was observed in only three animals between: LLT I and LLS I, and LLT II and LLS II, evidencing signs of entrainment to social cues between the members of each pair. On the other hand, one animal delayed progressively between LLT I and LLS I, three animals delayed between LLS I and LLT II, and three animals between LLT II and LLS II, perhaps by entrainment to the animals maintained outdoors in the colony. Similar process was observed in four animals between LLS II and LDT II, indicating entrainment to LD. In the transition between LLS I and LLT II, signs of masking was observed in the rhythm of a female in response to the male and in another pair in the rhythm of the male in regard to that of the female. The general and maximum correlations in the circadian activity profiles were stronger during cohabitation in LD and LL than in the absence of social contact in LL, evidencing the social effect. The cohabiting pairs had higher values of the maximum correlation in LD and LL than when the profiles were correlated to animals of different cages, with same or different sexes. Similar results were observed in the general correlation. Therefore, it is suggested that cohabitation induces a strong synchrony between circadian activity profiles in marmosets, which involves entrainment and masking. Nevertheless, additional studies are necessary to evaluate the effect of social cues on the synchronization of the circadian rhythm in pairs of marmosets in the absence of external social cues in order to confirm this hypothesis.

Formulação e caracterização de pastas espumadas por incorporação de ar e estabilizantes minerais

Cementing operations may occur at various stages of the life cycle of an oil well since its construction until its definitive abandonment. There are some situations in which the interest zones are depleted or have low fracture pressure. In such cases, the adoption of lowdensity cement slurries is an efficient solution. To this end, there are basically three ways to reduce the density of cement slurries: using microspheres, water extending additives or foamed cement. The objective of this study is to formulate, to study and to characterize lowdensity foamed cement, using an air entrainment surfactant with vermiculite or diatomite as water extenders and stabilizers. The methodology consists on preparation and evaluation of the slurries under the American Petroleum Institute (API) and the Brazilian Association of Technical Standards (ABNT) guidelines. Based on calculated densities between 13 and 15 ppg (1.559 and 1.799 g/cm3), the slurries were prepared with fixed surfactant concentration, varying the concentrations of vermiculite and diatomite and were compared with the base slurries. The results of plastic viscosity, yield point and gel strength and the compressive strength for 24 h showed that the slurries presented suitable rheology and mechanical strength for cementing operations in oil wells, and had their densities reduced between 8.40 and 11.89 ppg (1.007 and 1.426 g/cm3). The conclusion is that is possible, under atmospheric conditions, to obtain light weighted foamed cement slurries with satisfactory rheological and mechanical properties by means of air entrainment and mineral additions with extenders and stabilizers effects. The slurries have great potential for cementing operations; applicability in deep wells, in low fracture gradient formations and in depleted zones and bring cost savings by reducing the cementing consumption