Tank experiments with borehole self-potential data

Despite their importance in the evaluation of petroleum and gas reservoirs, measurements of self-potential data under borehole conditions (well-logging) have found only minor applications in aquifer and waste-site characterization. This can be attributed to lower signals from the diffusion fronts in near-surface environments because measurements are made long after the drilling of the well, when concentration fronts are already disappearing. Proportionally higher signals arise from streaming potentials that prevent using simple interpretation models that assume signals from diffusion only. Our laboratory experiments found that dual-source self-potential signals can be described by a simple linear model, and that contributions (from diffusion and streaming potentials) can be isolated by slightly perturbing the borehole conditions. Perturbations are applied either by changing the concentration of the borehole-filling solution or its column height. Parameters useful for formation evaluation can be estimated from data measured during perturbations, namely, pore water resistivity, pressure drop across the borehole wall, and electrokinetic coupling parameter. These are important parameters to assess, respectively, water quality, aquifer lateral continuity, and interfacial properties of permeable formations.

What do medical students think about their quality of life? A qualitative study

Background: Medical education can affect medical students' physical and mental health as well as their quality of life. The aim of this study was to assess medical students' perceptions of their quality of life and its relationship with medical education. Methods: First-to sixth-year students from six Brazilian medical schools were interviewed using focus groups to explore what medical student's lives are like, factors related to increases and decreases of their quality of life during medical school, and how they deal with the difficulties in their training. Results: Students reported a variety of difficulties and crises during medical school. Factors that were reported to decrease their quality of life included competition, unprepared teachers, excessive activities, and medical school schedules that demanded exclusive dedication. Contact with pain, death and suffering and harsh social realities influence their quality of life, as well as frustrations with the program and insecurity regarding their professional future. The scarcity of time for studying, leisure activities, relationships, and rest was considered the main factor of influence. Among factors that increase quality of life are good teachers, classes with good didactic approaches, active learning methodologies, contact with patients, and efficient time management. Students also reported that meaningful relationships with family members, friends, or teachers increase their quality of life. Conclusion: Quality of teachers, curricula, healthy lifestyles related to eating habits, sleep, and physical activity modify medical students' quality of life. Lack of time due to medical school obligations was a major impact factor. Students affirm their quality of life is influenced by their medical school experiences, but they also reframe their difficulties, herein represented by their poor quality of life, understood as necessary and inherent to the process of becoming doctors.

Remarks on Parametric Surface Waves in a Nonlinear and Non-Ideally Excited Tank

We studied free surface oscillations of a fluid in a cylinder tank excited by an electric motor with limited power supply. We investigated the possibility of parametric resonance in this system, showing that the excitation mechanism can generate chaotic response. Numerical experiments are carried out to present the existence of several types of regular and chaotic attractors. For the first time powers (power of the motor, power consumed by the damping force under fluid free surface oscillations, and a total power) are calculated, investigated, and shown for different regimes, regular and chaotic ones for parametric resonance interactions. [DOI: 10.1115/1.4005844]