Interior perfect fluid scalar-tensor solution

We present a new exact perfect fluid interior solution for a particular scalar-tensor theory. The solution is regular everywhere and has a well defined boundary where the fluid pressure vanishes. The metric and the dilaton field match continuously the external solution.Comment: 8 pages, 3 figures, LaTe

Using Gamma Functions in the Mathematical Formulation of the Impact Crater Size-Age Frequency Distribution on Earth and Mars

A review of a mathematical formulation that describes the number of impact craters as function of diameter and time of formation is presented, where the use of Gamma functions is emphasized. The application of this formalism for the description of the impact crater data of Planets Earth and Mars is also discussed

Influence of Student Problem Behavior and Teacher Tolerance on Student Grades

The current study examines the influence of student problem behavior (as rated by teachers), teacher disposition to tolerate problem behavior, and interaction effects on student grade point average, reading grades, and math grades. The sample includes 3rd through 5th grade students (N = 12,993) and their classroom teachers (N = 562) from 45 schools. Multilevel models, with students nested within classrooms, test the influence of student problem behavior and teacher tolerance on student grades. Results imply that problem behavior negatively influences grades for students at each grade level, controlling for standardized academic achievement and other student and classroom-level covariates. Results also indicate that low teacher tolerance predicts higher current student grades in some analyses. Finally, tests for interactions of teacher tolerance with student problem behavior indicate that 5th grade students rated as having extreme problem behaviors receive lower grades in classrooms with more tolerant teachers, and higher grades in classrooms with less tolerant teachers

Exact solutions of Brans-Dicke wormholes in the presence of matter

A fundamental ingredient in wormhole physics is the presence of exotic matter, which involves the violation of the null energy condition. Although a plethora of wormhole solutions have been explored in the literature, it is useful to find geometries that minimize the usage of exotic matter. In this work, we find exact wormhole solutions in Brans-Dicke theory where the normal matter threading the wormhole satisfies the null energy condition throughout the geometry. Thus, the latter implies that it is the effective stress-energy tensor containing the scalar field, that plays the role of exotic matter, that is responsible for sustaining the wormhole geometry. More specifically, we consider a zero redshift function and a particular choice for the scalar field and determine the remaining quantities, namely, the stress-energy tensor components and the shape function. The solution found is not asymptotically flat, so that this interior wormhole spacetime needs to be matched to an exterior vacuum solution.Comment: 7 pages, 3 figure

Considerations for Sustainable Biomass Production – Assessing the Nutritional Status of Oak Dominated Stands

AbstractAnthropogenic induced climate change, geopolitical concerns and availability of mainly fossil sources fuelling our current energy system have led to a shift towards renewable and regional energy systems such as solid biomass from agriculture and forestry. A shift from traditional forest management towards more intensive biomass extraction scenarios with shorter rotation periods may implies higher rates of nutrient extractions. Here we present results from a macronutrient assessment in traditionally managed oak dominated stands considered as potential source for solid biofuel extraction

A phenomenological study of the experiences of welfare-to-work mothers in selecting child care

In this phenomenological study, 10 low-income working single mothers were interviewed. The in-depth interviews focused on issues related to selection of child care. The overarching theme was the demanding nature of being a low-income single mother. Eight of the mothers were never-married and this contributed to no contact between them and the children\u27s fathers or the children and their fathers. Despite the demands they experienced these women were aware of their growth and gratification in being a mother. The mothers experienced contextual constraints and related issues that contributed to the child care selection process. These themes included; (a) the constraints related to the choices available to the mothers, (b) resources the mothers used in making child care choices, (c) concerns about child care and previous experiences, and (d) characteristics of child care that contributed to the mothers\u27 satisfaction with the care they arranged. Policy implications include the mothers\u27 needs for financial support and access to quality child care programs with staff trained to work effectively with these families