3D rainbow phononic crystals for extended vibration attenuation bands

We hereby report for the first time on the design, manufacturing and testing of a three-dimensional (3D) nearly-periodic, locally resonant phononic crystal (PnC). Most of the research effort on PnCs and metamaterials has been focused on the enhanced dynamic properties arising from their periodic design. Lately, additive manufacturing techniques have made a number of designs with intrinsically complex geometries feasible to produce. These recent developments have led to innovative solutions for broadband vibration attenuation, with a multitude of potential engineering applications. The recently introduced concept of rainbow metamaterials and PnCs has shown a significant potential for further expanding the spectrum of vibration attenuation in such structures by introducing a gradient profile for the considered unit cells. Given the above, it is expected that designing non-periodic PnCs will attract significant attention from scientists and engineers in the years to come. The proposed nearly-periodic design is based on cuboid blocks connected by curved beams, with internal voids in the blocks being implemented to adjust the local masses and generate a 3D rainbow PnC. Results show that the proposed approach can produce lightweight PnCs of a simple, manufacturable design exhibiting attenuation bandwidths more than two times larger than the equivalent periodic designs of equal mass

Bullying among medical and nonmedical students at a university in Eastern Saudi Arabia

Background: Many medical students, junior doctors, and other health-care professionals have been affected by the negative experience of bullying. Research is scarce on bullying experienced by medical and nonmedical students in Saudi Arabia unlike what is found in Western countries. It is unclear whether being a nonmedical student modifies the risk of being bullied. Materials and Methods: A cross-sectional study included 400 university students using convenient sampling. The sample comprised 295 students who responded and were stratified into medical (n = 176) and nonmedical (n = 119) groups. Statistical Package for the Social Sciences (SPSS) version 22.0 was used to analyze our data. Normality was measured using the Kolmogorov–Smirnov test. Statistical significance was tested using chi-square test for categorical variables, and t-test for continuous variables. Results: Almost half of the respondents were found to have experienced some bullying, victimization, or other harassment during their medical education. The most common forms of bullying were verbal abuse and undue pressure to produce work (43.8%; n = 77). Nonmedical students experienced more bullying than medical students and were more likely to be female, single, and younger in age. The number of medical students subjected to sexual harassment (1.7%; n = 3) was higher than nonmedical students (0.8%; n = 1). Physical violence was more towards nonmedical (4.2%; n = 5) than medical students (1.1%, n = 2). The rates of bullying continue to be associated with anxiety and depression. Conclusions: Our data suggest similar bullying rates in the developed world but higher than previously reported in a Saudi study. Bullying or harassment affects both medical and nonmedical students and is associated with high levels of anxiety and depression

Approaching the biology of human parental attachment: Brain imaging, oxytocin and coordinated assessments of mothers and fathers

Brain networks that govern parental response to infant signals have been studied with imaging techniques over the last 15 years. The complex interaction of thoughts and behaviors required for sensitive parenting of offspring enable formation of each individual’s first social bonds and critically shape infants’ behavior. This review concentrates on magnetic resonance imaging experiments which directly examine the brain systems involved in parental responses to infant cues. First, we introduce themes in the literature on parental brain circuits studied to date. Next, we present a thorough chronological review of state-of-the-art fMRI studies that probe the parental brain with a range of baby audio and visual stimuli. We also highlight the putative role of oxytocin and effects of psychopathology, as well as the most recent work on the paternal brain. Taken together, a new model emerges in which we propose that cortico-limbic networks interact to support parental brain responses to infants for arousal/salience/motivation/reward, reflexive/instrumental caring, emotion response/regulation and integrative/complex cognitive processing. Maternal sensitivity and the quality of caregiving behavior are likely determined by the responsiveness of these circuits toward long-term influence of early-life experiences on offspring. The function of these circuits is modifiable by current and early-life experiences, hormonal and other factors. Known deviation from the range of normal function in these systems is particularly associated with (maternal) mental illnesses – commonly, depression and anxiety, but also schizophrenia and bipolar disorder. Finally, we discuss the limits and extent to which brain imaging may broaden our understanding of the parental brain, and consider a current model and future directions that may have profound implications for intervention long term outcomes in families across risk and resilience profiles