The dynamics of apparent horizons in Robinson-Trautman spacetimes

We present an alternative scheme of finding apparent horizons based on spectral methods applied to Robinson-Trautman spacetimes. We have considered distinct initial data such as representing the spheroids of matter and the head-on collision of two non-rotating black holes. The evolution of the apparent horizon is presented. We have obtained in some cases a mass gap between the final Bondi and apparent horizon masses, whose implications were briefly commented in the light of the thermodynamics of black holes.Comment: 9 pages, 7 figure

Cross-cultural adaptation and validation of the Nursing Student Satisfaction Scale for use with Brazilian nursing students

Objective: to cross-culturally adapt and validate the Nursing Student Satisfaction Scale (NSSS) for use with nursing students in the Brazilian context. Method: this was a quantitative exploratory and descriptive study using a cross-sectional design conducted with 123 undergraduate nursing students studying at a public university in the south of Brazil. The cross-cultural adaptation was performed according to international guidelines. Validation for use in a Brazilian context was performed using factor analysis and Cronbach's alpha. Results: based on the expert committee assessment and pre-test, face and content validity were considered satisfactory. Factor analysis resulted in three constructs: curriculum and teaching; professional social interaction, and learning environment. The internal consistency of the instrument was satisfactory: the value of Cronbach's alpha coefficient was 0.93 for the instrument as a whole, and between 0.88 and 0.89 for the constructs. Conclusion: the Brazilian version of the Nursing Student Satisfaction Scale was shown to be reliable and validated for the evaluation of student satisfaction with undergraduate nursing programs, considering the aspects teaching activities, curriculum, professional social interaction, and learning environment

High occurrence of giardiasis in children living on a 'landless farm workers' settlement in Araras, São Paulo, Brazil

Enteric parasitosis remains an important public health problem in many areas around the world including in Brazil, and it is frequently associated with poverty and lack of sanitation facilities. Research carried out over the course of a year revealed that 96.6% (28/29) of children randomly selected from a 'landless farm workers' settlement in Araras, São Paulo, aged 4 - 15 years, presented Giardia intestinalis cysts. After referral to the neighborhood Health Office, all the children received tinidazole, given as a single dose of 50 mg/kg and 12 months later, new fecal samples were collected and analyzed. Despite the low adherence to the study, a high percentage (64.3% - 9/14) of the children remained positive for the parasite. This study showed a high positivity of giardiasis in child residents of the settlement, even after treatment; adults were not sensitized to the study and did not collected and/or deliver children fecal samples. The precarious living conditions are consistent with a high susceptibility to parasitic diseases, suggesting that the treatment of the infected individuals without identifying and eradicating the means of contamination is simply a palliative measure

Lower Richness of Small Wild Mammal Species and Chagas Disease Risk

A new epidemiological scenario involving the oral transmission of Chagas disease, mainly in the Amazon basin, requires innovative control measures. Geospatial analyses of the Trypanosoma cruzi transmission cycle in the wild mammals have been scarce. We applied interpolation and map algebra methods to evaluate mammalian fauna variables related to small wild mammals and the T. cruzi infection pattern in dogs to identify hotspot areas of transmission. We also evaluated the use of dogs as sentinels of epidemiological risk of Chagas disease. Dogs (n = 649) were examined by two parasitological and three distinct serological assays. kDNA amplification was performed in patent infections, although the infection was mainly sub-patent in dogs. The distribution of T. cruzi infection in dogs was not homogeneous, ranging from 11–89% in different localities. The interpolation method and map algebra were employed to test the associations between the lower richness in mammal species and the risk of exposure of dogs to T. cruzi infection. Geospatial analysis indicated that the reduction of the mammal fauna (richness and abundance) was associated with higher parasitemia in small wild mammals and higher exposure of dogs to infection. A Generalized Linear Model (GLM) demonstrated that species richness and positive hemocultures in wild mammals were associated with T. cruzi infection in dogs. Domestic canine infection rates differed significantly between areas with and without Chagas disease outbreaks (Chi-squared test). Geospatial analysis by interpolation and map algebra methods proved to be a powerful tool in the evaluation of areas of T. cruzi transmission. Dog infection was shown to not only be an efficient indicator of reduction of wild mammalian fauna richness but to also act as a signal for the presence of small wild mammals with high parasitemia. The lower richness of small mammal species is discussed as a risk factor for the re-emergence of Chagas disease

Properties of Graphene: A Theoretical Perspective

In this review, we provide an in-depth description of the physics of monolayer and bilayer graphene from a theorist's perspective. We discuss the physical properties of graphene in an external magnetic field, reflecting the chiral nature of the quasiparticles near the Dirac point with a Landau level at zero energy. We address the unique integer quantum Hall effects, the role of electron correlations, and the recent observation of the fractional quantum Hall effect in the monolayer graphene. The quantum Hall effect in bilayer graphene is fundamentally different from that of a monolayer, reflecting the unique band structure of this system. The theory of transport in the absence of an external magnetic field is discussed in detail, along with the role of disorder studied in various theoretical models. We highlight the differences and similarities between monolayer and bilayer graphene, and focus on thermodynamic properties such as the compressibility, the plasmon spectra, the weak localization correction, quantum Hall effect, and optical properties. Confinement of electrons in graphene is nontrivial due to Klein tunneling. We review various theoretical and experimental studies of quantum confined structures made from graphene. The band structure of graphene nanoribbons and the role of the sublattice symmetry, edge geometry and the size of the nanoribbon on the electronic and magnetic properties are very active areas of research, and a detailed review of these topics is presented. Also, the effects of substrate interactions, adsorbed atoms, lattice defects and doping on the band structure of finite-sized graphene systems are discussed. We also include a brief description of graphane -- gapped material obtained from graphene by attaching hydrogen atoms to each carbon atom in the lattice.Comment: 189 pages. submitted in Advances in Physic