Small-amplitude perturbations of shape for a nearly spherical bubble in an inviscid straining flow (steady shapes and oscillatory motion)

The method of domain perturbations is used to study the problem of a nearly spherical bubble in an inviscid, axisymmetric straining flow. Steady-state shapes and axisymmetric oscillatory motions are considered. The steady-state solutions suggest the existence of a limit point at a critical Weber number, beyond which no solution exists on the steady-state solution branch which includes the spherical equilibrium state in the absence of flow (e.g. the critical value of 1.73 is estimated from the third-order solution). In addition, the first-order steady-state shape exhibits a maximum radius at θ = 1/6π which clearly indicates the barrel-like shape that was found earlier via numerical finite-deformation theories for higher Weber numbers. The oscillatory motion of a nearly spherical bubble is considered in two different ways. First, a small perturbation to a spherical base state is studied with the ad hoc assumption that the steady-state shape is spherical for the complete Weber-number range of interest. This analysis shows that the frequency of oscillation decreases as Weber number increases, and that a spherical bubble shape is unstable if Weber number is larger than 4.62. Secondly, the correct steady-state shape up to O(W) is included to obtain a rigorous asymptotic formula for the frequency change at small Weber number. This asymptotic analysis also shows that the frequency decreases as Weber number increases; for example, in the case of the principal mode (n = 2), ω^2 = ω_0^0(1−0.31W), where ω_0 is the oscillation frequency of a bubble in a quiescent fluid

Bubble dynamics in time-periodic straining flows

The dynamics and breakup of a bubble in an axisymmetric, time-periodic straining flow has been investigated via analysis of an approximate dynamic model and also by time-dependent numerical solutions of the full fluid mechanics problem. The analyses reveal that in the neighbourhood of a stable steady solution, an O(ϵ1/3) time-dependent change of bubble shape can be obtained from an O(ε) resonant forcing. Furthermore, the probability of bubble breakup at subcritical Weber numbers can be maximized by choosing an optimal forcing frequency for a fixed forcing amplitude

Underrepresentation of Hispanic Bilingual Students in Gifted and Talented Programs: The Role of Teacher Expectations

There is currently an underrepresentation of Hispanic and bilingual students in Gifted and Talented (GT) programs. The present study examines the role of teachers’ expectations and preconceptions of what constitutes a gifted student as possible contributing factors to the underrepresentation of Hispanic and bilingual students in GT programs. Participants will include approximately 100 pre-service teachers and currently practicing teachers in the community. Measures will include a demographic survey, vignettes for identifying giftedness which describe bilingual and monolingual potential gifted students across three ethnic groups, and a survey about student qualities that includes both quantitative and qualitative items. Results and implications will be discussed

Fission fragment angular distribution measurements of U-235 and U-238 at CERN n_TOF facility

Neutron-induced fission cross sections of U-238 and U-235 are used as standards in the fast neutron region up to 200 MeV. A high accuracy of the standards is relevant to experimentally determine other neutron reaction cross sections. Therefore, the detection efficiency should be corrected by using the angular distribution of the fission fragments (FFAD), which are barely known above 20 MeV. In addition, the angular distribution of the fragments produced in the fission of highly excited and deformed nuclei is an important observable to investigate the nuclear fission process. In order to measure the FFAD of neutron-induced reactions, a fission detection setup based on parallel-plate avalanche counters (PPACs) has been developed and successfully used at the CERN-n_TOF facility. In this work, we present the preliminary results on the analysis of new U-235(n,f) and U-238(n,f) data in the extended energy range up to 200 MeV compared to the existing experimental data.Postprint (published version

Treatment of bimodality in proficiency test of pH in bioethanol matrix

The pH value in bioethanol is a quality control parameter related to its acidity and to the corrosiveness of vehicle engines when it is used as fuel. In order to verify the comparability and reliability of the measurement of pH in bioethanol matrix among some experienced chemical laboratories, reference material (RM) of bioethanol developed by Inmetro - the Brazilian National Metrology Institute - was used in a proficiency testing (PT) scheme. There was a difference of more than one unit in the value of the pH measured due to the type of internal filling electrolytic solutions (potassium chloride, KCl or lithium chloride, LiCl) from the commercial pH combination electrodes used by the participant laboratories. Therefore, bimodal distribution has occurred from the data of this PT scheme. This work aims to present the possibilities that a PT scheme provider can use to overcome the bimodality problem. Data from the PT of pH in bioethanol were treated by two different statistical approaches: kernel density model and the mixture of distributions. Application of these statistical treatments improved the initial diagnoses of PT provider, by solving bimodality problem and contributing for a better performance evaluation in measuring pH of bioethanol.Comment: 20 pages, 6 figures, Accepted for publication in Accreditation and Quality Assurance (ACQUAL

The impact of home care nursing in puerpera dificulties

BACKGROUND: The birth of the first child forwards the new mother to an individual, family and social reset in order to deal with self-caring and parenting skills. Many women in postpartum period report having to deal often with new doubts and/or problems. OBJECTIVE: Identify the main difficulties reported by mothers during puerperium time. Compare those mentioned difficulties, between control group and study group. METHODS: Quasi-experimental design - Control group and study group with 200 primiparous women (100 women in each group). Participants in the study group were submited to at least two home visits during the postpartum period. RESULTS: Chi-square test revealed statistically significant differences between groups, for participants who did not report difficulties (p=0.021). A larger number of mothers in the experimental group did not mention difficulties (38%), compared to those belonging to the control group (23%). The three main difficulties were found: Understanding child's cry - 53% in the control group and 45% in study group; Child feeding - 29% in the control group and 21% in study group; “Psychological changes” are referred by both groups in thirdly. Chi-square test shows differences between groups in this variable (p=0.037) - Control group 27% and study group 15%. CONCLUSIONS: This investigation demonstrated the relationship between home visit and expressed difficulties: a higher number of participants followed during puerperium did not mention difficulties. For those who mentioned difficulties also the groups show different regarding the difficulty in dealing with the psychological changes. More mothers from control group mentioned this problem

The Role of Psychological Adjustment in the Decision-Making Process for Voluntary Termination of Pregnancy

BACKGROUND: This study's objective was to evaluate the role of psychological adjustment in the decision-making process to have an abortion and explore individual variables that might influence this decision. METHODS: In this cross-sectional study, we sequentially enrolled 150 women who made the decision to voluntarily terminate a pregnancy in Maternity Dr. Alfredo da Costa, in Lisbon, Portugal, between September 2008 and June 2009. The instruments were the Depression, Anxiety and Stress Scale (DASS), Satisfaction with Social Support Scale (SSSS), Emotional Assessment Scale (EAS), Decision Conflict Scale (DCS), and Beliefs and Values Questionnaire (BVQ). We analyzed the data using Student's T-tests, MANOVA, ANOVA, Tukey's post-hoc tests and CATPCA. Statistically significant effects were accepted for p<0.05. RESULTS: The participants found the decision difficult and emotionally demanding, although they also identified it as a low conflict decision. The prevailing emotions were sadness, fear and stress; but despite these feelings, the participants remained psychologically adjusted in the moment they decided to have an abortion. The resolution to terminate the pregnancy was essentially shared with supportive people and it was mostly motivated by socio-economic issues. The different beliefs and values found in this sample, and their possible associations are discussed. CONCLUSION: Despite high levels of stress, the women were psychologically adjusted at the time of making the decision to terminate the pregnancy. However, opposing what has been previously reported, the women presented high levels of sadness and fear, showing that this decision was hard to make, triggering disruptive emotions