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Nonlinear wave propagation in large extra spatial dimensions (on and above d = 2) is investigated in the context of nonlinear electrodynamics theories that depend exclusively on the invariant F (= − (1 / 4) F μ ν F μ ν) . In this vein, we consider propagating waves under the influence of external uniform electric and magnetic fields. Features related to the blackbody radiation in the presence of a background constant electric field such as the generalization of the spectral energy density distribution and the Stefan–Boltzmann law are obtained. Interestingly enough, anisotropic contributions to the frequency spectrum appear in connection to the nonlinearity of the electromagnetic field. In addition, the long wavelength regime and Wien's displacement law in this situation are studied. The corresponding thermodynamics quantities at thermal equilibrium, such as energy, pressure, entropy, and heat capacity densities are contemplated as well. [ABSTRACT FROM AUTHOR]

A study of seasonal variation of metazoan parasite community of Pagrus pagrus was conducted between January and December 2012. Two hundred forty specimens of Pagrus pagrus were collected in four seasons (autumn and winter in dry season and spring and summer in rainy season) from off the state of Rio de Janeiro, Brazil. Twenty one species of metazoan parasites were found, with larvae of Hysterothylacium sp. being the dominant species. The highest values of prevalence and abundance was during the rainy season with peak prevalence of monogeneans and nematodes, period of action of the South Atlantic Central Waters (SACW) and reproductive activity of the host, suggesting that the sasonal variation in the parasites community was influenced for these phenomena.

The increasing pressure from agriculture and pasture activities over non-forest vegetation areas revealed the need of INPE to extend forest regular monitoring to non-forested areas. Non-forest vegetation consists of savannahs, shrub lands, grasslands or seasonal floodplains that occupy 279 thousand km2 (6,63 %) of Brazilian Amazon biome extension. Addressed ecosystem services of non-forest vegetation vary from climate, soil, carbon storage, biodiversity, water and fire regulation to cultural benefits and living of the population. The challenge in monitoring non-forest removal lies in climatic seasonality, high variability of phytophysiognomies and cloud coverage. In this work we developed a method to map non-forest vegetation from 2000 to 2021 in a pilot area enclosing five municipalities in Roraima and Amapá states. Considering the total area of 47 thousand km2, 58 % was originally forest and 37 % was non-forest vegetation. In 2020, soybean planted areas occupied 60 thousands hectares in these municipalities. We adapted PRODES protocol to non-forest features using visual interpretation of Landsat and SENTINEL-2 satellite images. Regional expertise supported the interpretation keys to distinguish non-forest removal from seasonal changes or other land use changes. A baseline map for 2000 is provided together with biannual and annual increments for 2002–2018 and 2019–2021, respectively. Results show removal of non-forested areas even overpassing deforestation in some municipalities. Accumulated non-forest removal was 3.133,06 km2 or 17,44 % of the non-forest area enclosed. This work consolidated the method to be applied in the Brazilian Amazon biome allowing a uniform historical mapping series of deforestation and non-forest removal. [ABSTRACT FROM AUTHOR]

In this paper, a new procedure and topology of magnetic metasurface lens are proposed for improving the performance of Resonant Wireless Power Transfer systems. Firstly, three subwavelength unit cells are optimized in order to get negative magnetic permeability in the same frequency, each one with a different refractive index, and they are experimentally characterized. Then, the Transformation Optics technique is applied in order to find the unit cell arrangements which lead to the magnetic field focusing in a given direction. For this purpose, two coordinate transformations are proposed, and the effective electric permittivity and permeability that generate these profiles are calculated. It is shown from simulations and measurements that the refractive index gradient produced by the radial disposition of the unit cells can lead to a magnetic field manipulation similar to the optical converging and diverging lenses. Both metamaterials lenses are built, and the calculation of the magnetic flux density as a function of the measured induced voltage in a probe coil verifies their effects on the magnetic field. Finally, their performance in a resonant wireless power transfer system is tested, and improvements in terms of efficiency and range are presented. The proposed design method and the lenses that were developed demonstrate that metasurface lenses can improve efficiency without reducing the range, once these lenses are positioned close to the transmitter coil. Besides that, this method can reduce the losses due to misalignment between coils once the field can be collimated in a specific direction. [ABSTRACT FROM AUTHOR]

Copyright of Brazilian Journal of Biology is the property of Instituto Internacional de Ecologia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In its main definition, piezoelectrets are polymeric structures with electric charged internal cavities. The bipolar-trapped charges form macro-dipoles that can be mechanically deformed, thus presenting a high piezoelectric coefficient in the order of hundreds of pC/N. Such results outperform most of the traditional piezoelectric polymers. As piezoelectrets can be manufactured by different methods, some of the techniques allow the inner cavities to be geometrically controlled, therefore providing some degree of freedom in the piezoelectric behavior. This report provides a description of the most relevant methods, starting with a brief introduction of piezoelectret origin and reaching recent achievements in piezoelectret production, such as additive manufacturing (3D printing). Materials that are frequently employed in piezoelectret fabrication and methods for improving their characteristics are also presented. [ABSTRACT FROM AUTHOR]

Copyright of Archivos de Zootecnia is the property of Archivos de Zootecnia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Most aluminium (Al)‐accumulating species are found on soils with high Al saturation and low Ca availability (Ca poor). Callisthene fasciculata Mart. (Vochysiaceae), however, is an Al‐accumulating tree restricted to Ca‐rich soils with low Al saturation in the Brazilian Cerrado savanna. Here we tested its calcicole behaviour, and the possible role of organic acids in detoxification of Al during the early stages of plant development.We assessed growth, dry mass, nutrients, Al and organic acids in seedlings grown for 50 days on two contrasting Cerrado soils; one with high Ca concentrations and low Al saturation and the other with low Ca availability and high Al saturation.Relative to plants on Ca‐rich soil, plants on Ca‐poor soil had necrotic spots and bronzing of leaves. Roots and shoots contained reduced concentrations of P and Cu, but higher concentrations of Fe, Al and citrate. Despite lower concentrations in the soil, Ca and Mg increased in shoots. Shoot concentrations of oxalate were also higher.We confirmed C. fasciculata as an Al‐accumulating species with calcicole behaviour. The increased concentrations of organic acids in plants with higher Al accumulation suggest that high availability of soluble Al does not prevent occurrence of this species on soils with high Al saturation. Instead, the absence of C. fasciculata from Ca‐poor soils is probably due to imbalances in tissue Fe, Cu and Zn imposed by this soil type. [ABSTRACT FROM AUTHOR]

A study of the magnetic, electrical resistivity and hyperfine properties of polycrystalline La2RuO5 compounds is presented in this work. This compound forms in a monoclinic phase (space group P21/c). Magnetic susceptibility measurements yield an effective magnetic moment which is consistent with spin S = 1 of Ru ions, and a negative paramagnetic Curie temperature which indicates the presence of antiferromagnetic interactions. Below T ∼ 165 K, the magnetization shows a sudden decrease, precisely where the electrical resistivity shows a change in the activation energy. Room-temperature perturbed angular correlation spectrum is well fitted considering two electric-quadrupole components. The temperature dependences of electric-quadrupole frequencies and asymmetry parameters corroborate the occurrence of a phase transition at T ∼ 170 K. Moreover, below 170 K, magnetic-dipole interactions, which coexist with electric-quadrupole interactions, are observed at Ru sites. This is considered as a strong evidence for the preservation of S = 1 moment of Ru ions in the triclinic phase. The temperature dependence of the magnetic hyperfine field shows an unusual behavior, not consistent with the Brillouin function, and suggests a first-order magnetic transition, associated with either a structural transition or an orbital ordering induced by the Ru-Ru pair formation. [ABSTRACT FROM AUTHOR]

Abstract: Background: The preschool years are a period of great developmental achievements, which impact critically on a child's interactive skills. Having valid and reliable measures to assess interactive behaviour at this stage is therefore crucial. The aim of this study was to describe the adaptation and validation of the child coding of the Coding System for Mother–Child Interactions and discuss its applications and implications in future research and practice. Methods: Two hundred twenty Portuguese preschoolers and their mothers were videotaped during a structured task. Child and mother interactive behaviours were coded based on the task. Maternal reports on the child's temperament and emotional and behaviour problems were also collected, along with family psychosocial information. Results: Interrater agreement was confirmed. The use of child Cooperation, Enthusiasm, and Negativity as subscales was supported by their correlations across tasks. Moreover, these subscales were correlated with each other, which supports the use of a global child interactive behaviour score. Convergent validity with a measure of emotional and behavioural problems (Child Behaviour Checklist 1 ½–5) was established, as well as divergent validity with a measure of temperament (Children's Behaviour Questionnaire–Short Form). Regarding associations with family variables, child interactive behaviour was only associated with maternal behaviour. Conclusions: Findings suggest that this coding system is a valid and reliable measure for assessing child interactive behaviour in preschool age children. It therefore represents an important alternative to this area of research and practice, with reduced costs and with more flexible training requirements. Attention should be given in future research to expanding this work to clinical populations and different age groups. [ABSTRACT FROM AUTHOR]

Metazoan parasite assemblages of Pagrus pagrus inhabiting the southwestern Atlantic were analysed with the aim of identifying the existence of different stocks and to comparatively assess the value of different parasite guilds as indicators of zoogeographical regions. A total of 186 fish was examined. Samples were obtained from three Brazilian and one Argentine localities, distributed in three different biogeographic districts of the Argentine Zoogeographical Province. Pagrus pagrus harboured 26 metazoan parasite species distributed in three guilds, ectoparasites (10 species), long-lived larval endoparasites and short-lived gastrointestinal endoparasites (eight species each). Prevalence and abundance values of the former two guilds allowed analysing them comparatively to assess their value as biological indicators of both host population structure and zoogeography. Results of analyses on long-lived parasites evidenced the existence of three stocks, one in the regions of Rio de Janeiro and Sao Paulo, other in southern Brazil (Rio Grande do Sul) and a third in northern Argentina (Mar del Plata), responding to the differential environmental conditions characteristic of three zoogeographical ecoregions. Ectoparasite assemblages exhibited significant differences between all pairs of samples, including those considered as a single stock according to data on persistent parasites. Assemblages of long-lived larval parasites are considered as better indicators for stock assessment purposes than ectoparasites, whose population parameters were variable temporally and heterogeneous at small spatial scales. The distributional variability of persistent parasites of P. pagrus along large scales provides valuable information to help defining robust biogeographical patterns, applicable to stock identification and fishery management of this species. [ABSTRACT FROM AUTHOR]

The pretreatment of lignocellulosic residues has been extensively studied as a method to disrupt the cellulose–hemicelluloses–lignin complex in biomass to access the sugars in their respective components. In this work, we carried out a study using sulfuric acid pretreatment of sugarcane bagasse by varying the following operational parameters: solid loading (10–30% of bagasse relative to the volume of the sulfuric acid solution), sulfuric acid concentration (0.5–2.5% relative to the dry mass of bagasse), reaction time (5–25 min), and temperature (135–195°C). The obtained solids from each pretreatment condition were submitted to enzymatic hydrolysis under the same process conditions: 0.232 g of Celluclast 1.5 L and 0.052 g of Novozym 188 per g of pretreated sugarcane bagasse, 72 h of hydrolysis, and 200 rpm of agitation at 50°C. Using central composite rotational design configuration in the experiments and analysis of variance, the results indicate that the conditions that produced larger quantities of glucose by enzymatic hydrolysis (0.35 g glucose/g pulp) with minimum amounts of degradation products were as follows: 20% solids loading, 15 min of reaction time, 1.5% sulfuric acid, and a minimum temperature of reaction of 170°C. [ABSTRACT FROM AUTHOR]

DAX1 transcription factor is a key determinant of adrenogonadal development, acting as a repressor of SF1 targets in steroidogenesis. It was recently demonstrated that DAX1 regulates pluripotency and differentiation in murine embryonic stem cells. In this study, we investigated DAX1 expression in adrenocortical tumors (ACTs) and correlated it with SF1 expression and clinical parameters. DAX1 and SF1 protein expression were assessed in 104 ACTs from 34 children (25 clinically benign and 9 malignant) and 70 adults (40 adenomas and 30 carcinomas). DAX1 gene expression was studied in 49 ACTs by quantitative real-time PCR. A strong DAX1 protein expression was demonstrated in 74 % (25 out of 34) and 24 % (17 out of 70) of pediatric and adult ACTs, respectively (X2 = 10.1, p = 0.002). In the pediatric group, ACTs with a strong DAX1 expression were diagnosed at earlier ages than ACTs with weak expression [median 1.2 (range, 0.5-4.5) vs. 2.2 (0.9-9.4), p = 0.038]. DAX1 expression was not associated with functional status in ACTs. Interestingly, a positive correlation was observed between DAX1 and SF1 protein expression in both pediatric and adult ACTs (r = 0.55 for each group separately; p < 0.0001). In addition, DAX1 gene expression was significantly correlated with SF1 gene expression (p < 0.0001, r = 0.54). In conclusion, DAX1 strong protein expression was more frequent in pediatric than in adult ACTs. Additionally, DAX1 and SF1 expression positively correlated in ACTs, suggesting that these transcription factors might cooperate in adrenocortical tumorigenesis. [ABSTRACT FROM AUTHOR]

This study is an empirical approach to understand the determinants of renewable energy (RES) investment in European Union (EU-27) through panel data study over the period 1995 to 2011. Random effect panel data modelling technique was used to understand the variables that affect solar and wind energy investments in EU-27. Results suggest that the strong regulation perception plays negative role in the solar energy investment, and lower sunshine hours lead to higher wind investment. [ABSTRACT FROM AUTHOR]

Dogs' teeth with apical periodontitis were treated endodontically, Dakin's solution being used in an experimental group as the irrigation solution, and camphorated paramono-chlorophenol as an intracanal dressing. For a second group of teeth, the irrigation solution used was physiologic saline, dry cotton only being placed into the pulpal chamber to take the place of an intracanal dressing. In a second visit, overinstrumentation and a new application of the same kind of dressing were performed, the root canals being then filled with gutta-percha cones and zinc oxide-eugenol cement. Other specimens were treated, in one visit, where physiologic saline or Dakin's solution were the irrigation solutions. The animals were sacrificed 6 months after the obturation of the root canals. Histologic exams showed better results for the experimental group where Dakin's solution and camphorated paramonochlorophenol had been used, with signs of repair characterized by newly formed cementum and bone tissue, as well as a marked reduction in size of the periapical lesions. No differences were seen in the results with physiologic saline or Dakin's solution as irrigants. [ABSTRACT FROM AUTHOR]

Landscapes are amongst the main responsible factors for the attractiveness of tourist destinations, while, at the same time, they are degraded as a result of environmentally unsustainable practices of the touristic activity. Facing this context, this paper has as its goal to investigate the visual quality of tourist landscapes of the Ponta Negra Beach (Natal/RN) and to contribute to its use in a sustainable way. In order to achieve that, it has been used the systemic method as theoretical support and a set of indicators of visual quality of the landscape as methodology. It has been observed that, in addition to the Morro do Careca dune, other physical aspects contribute to the visual quality of the Ponta Negra landscape, such as the shape of the coast as a bay. The urbanistic and environmental legislation of Natal is another element that contributes to the protection of the Ponta Negra landscape. It has been detected as detractors the artificialization caused by the insertion of physical structures that reduce the naturality of the beach, the hydric pollution caused by sewers running into the gallery of rain waters and the sound pollution that takes place as a result of the noise generated by CD and DVD peddlers. The indicators of naturality and diversity showed that these characteristics take place mainly in the surroundings of the Morro do Careca. At last, it is stresses the importance of the sustainable tourism perspective as a strategy that guarantees the protection of natural landscapes and the very maintenance of the tourist activity. [ABSTRACT FROM AUTHOR]

We derive the Bondi-Sachs 4-momentum conservation laws that regulate the emission of gravitational waves in non-axisymmetric Robinson-Trautman spacetimes. Although Robinson-Trautman spacetimes describe the exterior vacuum gravitational field of a bounded system radiating gravitational waves, the Robinson-Trautman metrics do not satisfy the appropriate Bondi- Sachs boundary conditions formulated for radiating systems. We therefore derive the transformations between Robinson-Trautman and Bondi-Sachs coordinates which allow us to obtain some of the basic Bondi-Sachs physical quantities, namely the news functions and the Bondi-Sachs energy-momentum fluxes of the gravitational waves. These quantities are fundamental to the description of the radiative transfer processes involved in the generation and emission of gravitational waves by the system. The Bondi-Sachs 4-momentum conservation laws are covariant under the transformations of the Bondi- Metzner-Sachs group. The section of this paper containing the derivation of the coordinate transformations extends the work of von der Gonna and Kramer done for the case of axisymmetric Robinson-Trautman spacetimes. We discuss some possible applications of the conservation laws in numerical simulations of black hole systems emitting gravitational waves, and also future research of Bondi-Sachs conservation laws for twisting Robinson-Trautmantype spacetimes. [ABSTRACT FROM AUTHOR]

We examine the dynamics of the gravitational collapse in a 4-dim Lorentzian brane embedded in a 5-dim bulk with an extra timelike dimension. By considering the collapse of pure dust on the brane we derive a bouncing FLRW interior solution and match it with a corrected Schwarzschild exterior geometry. In the physical domain considered for the parameters of the solution, the analytical extension is built, exhibiting an exterior event horizon and a Cauchy horizon, analogous to the Reissner-Nordstrom solution. For such an exterior geometry we examine the effects of the bulk-brane corrections in the Hawking radiation. In this scenario the model extends Bekenstein's black hole geometrical thermodynamics for quasi-extremal configurations, with an extra work term in the laws associated with variations of the brane tension. We also propose a simple statistical mechanics model for the entropy of the bouncing collapsed matter by quantizing its fluctuations and constructing the associated partition function. This entropy differs from the geometrical entropy by an additive constant proportional to the area of the extremal black hole and satisfies an analogous first law of thermodynamics. A possible connection between both entropies is discussed. [ABSTRACT FROM AUTHOR]

Few studies were dedicated to study the role of contextual factors, such as the socioeconomic status and urban or rural residence in emotional distress of infertile couples. This study aimed to explore the impact of contextual factors on emotional distress, either directly or by affecting the importance of parenthood in one's life, which in turn affects emotional distress. In this cross-sectional study, 70 couples recruited during hormonal stimulation phase prior to in vitro fertilisation completed clinical and sociodemographic forms and self-report questionnaires assessing representations about the importance of parenthood and emotional distress. Path analysis using structural equation modelling was used to examine direct and indirect effects among variables. Results indicated that socioeconomic status and place of residence had an impact in emotional distress by affecting the representations about the importance of parenthood in one's life. Gender differences were found regarding model paths, suggesting that the social context may have a stronger influence on women's emotional distress than on their partners’ distress. When delineating psychological interventions, health care providers should consider that cultural values about children and parenthood contribute to shape the infertility experience. [ABSTRACT FROM PUBLISHER]

We examine numerically the post-merger regime of two nonspining holes in non-head-on collisions in the realm of nonaxisymmetric Robinson-Trautman spacetimes. Characteristic initial data for the system are constructed and evolved via the Robinson-Trautman equation. The numerical integration is performed using a Galerkin spectral method which is sufficiently stable to reach the final configuration of the remnant black hole, when the gravitational wave emission ceases. The initial data contains three independent parameters, the ratio mass a of the individual colliding black holes, their initial premerger infalling velocity and the incidence angle of collision pQ. The remnant black hole is characterized by ils final boost parameter, rest mass and scattering angle. The motion of the remnant black hole is restricted to the plane determined by the directions of the two initial colliding black holes, characterizing a planar collision. The net momentum fluxes carried out by gravitational waves are confined to this plane. We evaluate the efficiency of mass-energy extraction, the total energy and momentum carried out by gravitational waves and the momentum distribution of the remnant black hole for a large domain of initial data parameters. Our analysis is based on the Bondi-Sachs four-momentum conservation laws. The process of mass-energy extraction is shown to be less efficient as the initial data departs from the head-on configuration. Head-on collisions (&b.rho;0 = 0") and orthogonal collisions (&b.rho;0 = 90° ) constitute, respectively, upper and lower bounds to the power emission and to the efficiency of mass-energy extraction. On the contrary, head-on collisions and orthogonal collisions constitute, respectively, lower and upper bounds for the momentum of the remnant. Distinct regimes of gravitational wave emission (bursts or quiescent emission) are characterized by the analysis of the time behavior of the gravitational wave power as a function of a. In particular, the net gravitational wave flux is nonzero for equal-mass colliding black holes in non-head-on collisions. The momentum extraction and the patterns of the momentum fluxes, as a function of the incidence angle, are examined. The relation between the incidence angle and the scattering angle closely approximates a relation for the inelastic collision of classical particles in Newtonian dynamics. [ABSTRACT FROM AUTHOR]

We examined the psychosocial adjustment of 35 Portuguese couples who conceived through Assisted Reproductive Technologies (ART) and 31 couples with a spontaneous conception during their transition to parenthood (pregnancy and 4 months postpartum). Couples completed self-report questionnaires regarding their perceptions of pregnancy and parenthood, psychological distress, quality of life, marital relationship, and parenting stress. Compared with parents who conceived spontaneously, parents who conceived through ART perceived pregnancy as being more risky and demanding, reported a decrease in their psychological quality of life, and ART fathers only perceived themselves as being more competent than fathers who conceived spontaneously. Healthcare professionals should be aware of need of couples in their efforts to adapt to the individual and relational challenges associated with the transition to parenthood. © 2010 Wiley Periodicals, Inc. Res Nurs Health 33:207-220, 2010 [ABSTRACT FROM AUTHOR]

The dynamics of gravitational collapse is examined in the realm of string-based formalism of D-branes which encompasses general relativity as a low energy limit. A complete analytical solution is given to the spherically symmetric collapse of a pure dust star, including its matching with a corrected Schwarzschild exterior space–time. The collapse forms a black hole (an exterior event horizon) enclosing not a singularity but perpetually bouncing matter in the infinite chain of space–time maximal analytical extensions inside the outer event horizon. This chain of analytical extensions has a structure analogous to that of the Reissner–Nordstrom solution. The interior trapped bouncing matter has the possibility of being expelled by disruptive nonlinear resonance mechanisms. [ABSTRACT FROM AUTHOR]

The phase space dynamics of preinflationary closed Friedmann-Robertson-Walker (FRW) models is examined in a string-inspired bulk-brane scenario. Friedmann equations on the brane contain correction terms arising from the brane-bulk interaction that implement nonsingular metastable bounces in the early evolution of the universe. The matter content of the model is a massive inflaton field plus dust and/or radiation. In narrow windows of the parameter space, labeled by an integer n ≥ 2, nonlinear resonance phenomena destroy KAM tori that trap the inflaton, leading to a graceful entrance to inflation. As a consequence nonlinear resonance imposes constraints on the physical parameters, and in the initial configurations of the models so that inflation may be realized. [ABSTRACT FROM AUTHOR]

We analyze the head-on collision of two boosted Schwarzschild black holes and the mass-energy loss of the system by gravitational wave emission, in the realm of Robinson-Trautman (RT) spacetimes. The characteristic initial data for the problem are constructed, and evolved by RT equation integrated by numerical codes based on the Galerkin method. The emission of gravitational waves is typical bremsstrahlung at early times and the final configuration is that of a boosted black hole with larger (Bondi) rest mass and smaller velocity parameter. The efficiency Δ of the process of energy extraction by gravitational radiation is evaluated and satisfies a nonextensive distribution with entropic index q ≃ 1/2. The final momentum of the remnant black hole has a maximum which depends on the ratio of the masses of the initial black holes. [ABSTRACT FROM AUTHOR]

Nonlinear resonance is ubiquitous in nature. Resonance is relevant to understanding phenomena in quite distinct areas such as music, cellular structure, and astrophysics, and in the very early universe. In order to see the crucial role played by resonance in cosmology, we assume that closed FRW universes with a massive inflaton field evolve according to the field equations that contain additional terms arising from high energy corrections to cosmological scenarios. As a consequence, nonsingular bounces in the early evolution of the universe are produced. We have shown that in narrow windows of the parameter space of the models, nonlinear resonance phenomena of KAM tori occur and lead to the destruction of those tori that trap the inflaton, resulting in the escape of the universe into inflation. These resonance windows are labeled by an integer n ≥ 2; n is related to the ratio of the frequencies in the scale factor/scalar field degrees of freedom. [ABSTRACT FROM AUTHOR]

In this paper, we examine the efficiency of gravitational bremsstrahlung production in the process of head-on collision of two boosted Schwarzschild black holes. We construct initial data for the characteristic initial value problem in Robinson–Trautman space–times, which represent two instantaneously stationary Schwarzschild black holes in motion toward each other with the same velocity. The Robinson–Trautman equation is integrated for these initial data using a numerical code based on the Galerkin method. The resulting final configuration is a boosted black hole with Bondi mass greater than the sum of the individual masses of the individual initial black holes. Two relevant aspects of the process are presented. The first relates the efficiency Δ of the energy extraction by gravitational wave emission to the mass of the final black hole. This relation is fitted by a distribution function of nonextensive thermostatistics with entropic parameter q ≃ 1/2; the result extends and validates analysis based on the linearized theory of gravitational wave emission. The second aspect is a typical bremsstrahlung angular pattern in the early period of emission at the wave zone, a consequence of the deceleration of the black holes as they coalesce; this pattern evolves to a quadrupole form for later times. [ABSTRACT FROM AUTHOR]

We show that gravitational wave emission, both in the linear approximation and in the full nonlinear regime of general relativity, gives a hint of black hole thermodynamic processes by which a black hole evolves emitting part of its perturbation in the form of gravitational waves and absorbing the remnant, reaching a final configuration with a larger entropy. The partition of energy in this process is constrained by the maximum entropy principle, and the final entropy obtained numerically is given as a distribution function of the efficiency of the process. The distribution function is in the realm of nonextensive thermostatistics with entropic index q ≃ 1/2, a result that is validated analytically by the linear approximation. [ABSTRACT FROM AUTHOR]

In this paper we explore one of the most important features of the Galerkin method, which is to achieve high accuracy with a relatively modest computational effort, in the dynamics of Robinson–Trautman spacetimes. [ABSTRACT FROM AUTHOR]