Turbulence generation by a shock wave interacting with a random density inhomogeneity field

When a planar shock wave interacts with a random pattern of pre-shock density non-uniformities, it generates an anisotropic turbulent velocity/vorticity field. This turbulence plays an important role at the early stages of the mixing process in the compressed fluid. This situation emerges naturally in shock interaction with weakly inhomogeneous deuterium-wicked foam targets in Inertial Confinement Fusion (ICF) and with density clumps/clouds in astrophysics. We present an exact small-amplitude linear theory describing such interaction. It is based on the exact theory of time and space evolution of the perturbed quantities behind a corrugated shock front for a single-mode pre-shock non-uniformity. Appropriate mode averaging in 2D results in closed analytical expressions for the turbulent kinetic energy, degree of anisotropy of velocity and vorticity fields in the shocked fluid, shock amplification of the density non-uniformity, and sonic energy flux radiated downstream. These explicit formulas are further simplified in the important asymptotic limits of weak/strong shocks and highly compressible fluids. A comparison with the related problem of a shock interacting with a pre-shock isotropic vorticity field is also presented.Comment: This article corresponds to a presentation given at the Second International Conference and Advanced School "Turbulent Mixing and Beyond," held on 27 July - 07 August 2009 at the Abdus Salam International Centre for Theoretical Physics, Trieste, Italy. That Conference Proceeding will be published as a Topical Issue of the Physica Scripta IOP scienc

Formation of Ionization-Cone Structures in Active Galactic Nuclei: I. Stationary Model and Linear Stability Analysis

We discuss causes of the formation of the observed kinematics and morphology of cones of ionized matter in the neighborhood of the nuclei of Seyfert galaxies. The results of linear stability analysis of an optically thin conic jet where radiation cooling and gravity play an important part are reported. The allowance for radiation cooling is shown to result in strong damping of all acoustic modes and to have insignificant effect on unstable surface Kelvin--Helmholtz modes. In the case of waveguide--resonance internal gravity modes radiative cooling suppresses completely the instability of waves propagating away from the ejection source and, vice versa, reduces substantially the growth time scale of unstable sourceward propagating modes. The results obtained can be used to study ionization cones in Seyfert galaxies with radio jets. In particular, our analysis shows that surface Kelvin--Helmholtz modes and volume harmonics are capable of producing regular features observed in optical emission-line images of such galaxies.Comment: 13 pages, published in Astrophysical Bulleti

Infant screen exposure links to toddlers' inhibition, but not other EF constructs: a propensity score study

Technology is pervasive in homes of families with young children, despite evidence for negative associations between infant exposure to screen-based media and cognitive development that has led the American Academy of Pediatrics (AAP) to discourage parents from exposing children under the age of 18 months to any kind of screen time (AAP, 2016). Here, we apply a propensity score matching approach to estimate relations between electronic screen-based media use in infancy and executive function in early toddlerhood. In an international sample of 416 firstborn infants, parental report of regular exposure to screen-based media at 4 months predicted poorer performance on a test of inhibition at 14 months, but was unrelated to either cognitive flexibility or working memory at 14 months. Results of this study are therefore consistent with the view that early exposure to screen-based media adversely affects the development of executive function.Education and Child Studie

Beyond screen time: a synergistic approach to a more comprehensive assessment of family media exposure during early childhood

Digital media availability has surged over the past decade. Because of a lack of comprehensive measurement tools, this rapid growth in access to digital media is accompanied by a scarcity of research examining the family media context and sociocognitive outcomes. There is also little cross-cultural research in families with young children. Modern media are mobile, interactive, and often short in duration, making them difficult to remember when caregivers respond to surveys about media use. The Comprehensive Assessment of Family Media Exposure (CAFE) Consortium has developed a novel tool to measure household media use through a web-based questionnaire, time-use diary, and passive-sensing app installed on family mobile devices. The goal of developing a comprehensive assessment of family media exposure was to take into account the contextual factors of media use and improve upon the limitations of existing self-report measures, while creating a consistent, scalable, and cost-effective tool. The CAFE tool captures the content and context of early media exposure and addresses the limitations of prior media measurement approaches. Preliminary data collected using this measure have been integrated into a shared visualization platform. In this perspective article, we take a tools-of-the-trade approach (Oakes, 2010) to describe four challenges associated with measuring household media exposure in families with young children: measuring attitudes and practices; capturing content and context; measuring short bursts of mobile device usage; and integrating data to capture the complexity of household media usage. We illustrate how each of these challenges can be addressed with preliminary data collected with the CAFE tool and visualized on our dashboard. We conclude with future directions including plans to test reliability, validity, and generalizability of these measures

A novel observation of pubic osteomyelitis due to Streptococcus viridans after dental extraction: a case report

<p>Abstract</p> <p>Introduction</p> <p>Pubic osteomyelitis should be suspected in athletic individuals with sudden groin pain, painful restriction of hip movements and fever. It is an infrequent and confusing disorder, which is often heralded by atypical gait disturbance and diffuse pain in the pelvic girdle. The most common pathogen is <it>Staphylococcus aureus </it>but, on occasions, efforts to identify infectious agents sometimes prove negative. Pubic osteomyelitis due to <it>Streptococcus viridans </it>has not been reported previously in the literature.</p> <p>Case presentation</p> <p>We describe the case of a fit 24-year-old athlete, who had a wisdom tooth extracted 2 weeks prior to the presentation, which could have served as a port of entry and predisposed the patient to transient bacteraemia.</p> <p>Conclusion</p> <p><it>S. viridans </it>is well known for causing infective endocarditis of native damaged heart valves, but to the best of the authors' knowledge it has not been reported previously as a cause of pubic osteomyelitis. We believe that this case should alert physicians to the association between dental procedures and osteomyelitis of the pubis secondary to <it>S. viridans</it>.</p

How to improve influenza vaccine coverage of healthcare personnel

Abstract Influenza causes substantial morbidity and mortality worldwide each year. Healthcare-associated influenza is a frequent event. Health care personnel (HCP) may be the source for infecting patients and may propagate nosocomial outbreaks. All HCP should receive a dose of influenza vaccine each year to protect themselves and others. This commentary will discuss the study recently published in the IJHPR by Nutman and Yoeli which assessed the beliefs and attitudes of HCP in an Israel hospital regarding influenza and the influenza vaccine. Unfortunately, as noted by Nutman and Yoeli in this issue many HCP in Israel choose not to receive influenza immunization and many harbor misconceptions regarding their risk for influenza as well as the benefits of influenza vaccine. We also discuss proven methods to increase acceptance by HCP for receiving an annual influenza vaccine

Worrying in the wings? Negative emotional birth memories in mothers and fathers show similar associations with perinatal mood disturbance and delivery mode

Abstract: Negative birth experiences can lead to symptoms of post-traumatic stress disorder in new mothers but have received much less attention in new fathers. A sample of 314 first-time expectant couples rated their symptoms of anxiety and depression in the third trimester and at 4-month post birth (227 vaginal delivery, 87 caesarean section), when they also completed the emotional memories subscale of the BirthMARQ (Foley et al. BMC Pregnancy Childbirth, 14, 211, 2014). We first examined mode of delivery (vaginal birth versus caesarean section) as a predictor of mothers’ and fathers’ BirthMARQ scores. Next, we used actor-partner interdependence model (APIM) to investigate intra- and interpersonal associations between birth experiences and maternal/paternal latent factors for antenatal and postnatal depression/anxiety. Reports of negative birth experiences were more common for mothers than fathers and for parents of babies born by caesarean section than by vaginal delivery. Within-couple agreement was moderately strong and, for both parents at both time-points, individual differences in negative birth memories were associated with symptoms of depression and anxiety. Negative birth memories also played a mediating role in the association between birth via caesarean section and reduced postnatal maternal wellbeing. Given the striking similarities between mothers and fathers in links between birth experiences and wellbeing, our findings highlight the need for partner-inclusive intervention strategies

Association of circulating angiotensin converting enzyme activity with respiratory muscle function in infants

<p>Abstract</p> <p>Background</p> <p>Angiotensin converting enzyme (ACE) gene contains a polymorphism, consisting of either the presence (I) or absence (D) of a 287 base pair fragment. Deletion (D) is associated with increased circulating ACE (cACE) activity. It has been suggested that the D-allele of ACE genotype is associated with power-oriented performance and that cACE activity is correlated with muscle strength. Respiratory muscle function may be similarly influenced. Respiratory muscle strength in infants can be assessed specifically by measurement of the maximum inspiratory pressure during crying (Pi_max). Pressure-time index of the respiratory muscles (PTImus) is a non-invasive method, which assesses the load to capacity ratio of the respiratory muscles.</p> <p>The objective of this study was to determine whether increased cACE activity in infants could be related to greater respiratory muscle strength and to investigate the potential association of cACE with PTImus measurements as well as the association of ACE genotypes with cACE activity and respiratory muscle strength in this population.</p> <p>Methods</p> <p>Serum ACE activity was assayed by using a UV-kinetic method. ACE genotyping was performed by polymerase chain reaction amplification, using DNA from peripheral blood. PTImus was calculated as (Pi_mean/Pi_max) × (Ti/Ttot), where Pi_meanwas the mean inspiratory pressure estimated from airway pressure, generated 100 milliseconds after an occlusion (P_0.1), Pi_maxwas the maximum inspiratory pressure and Ti/Ttot was the ratio of the inspiratory time to the total respiratory cycle time. Pi_maxwas the largest pressure generated during brief airway occlusions performed at the end of a spontaneous crying effort.</p> <p>Results</p> <p>A hundred and ten infants were studied. Infants with D/D genotype had significantly higher serum ACE activity than infants with I/I or I/D genotypes. cACE activity was significantly related to Pi_maxand inversely related to PTImus. No association between ACE genotypes and Pdi_maxmeasurements was found.</p> <p>Conclusions</p> <p>These results suggest that a relation in cACE activity and respiratory muscle function may exist in infants. In addition, an association between ACE genotypes and cACE activity, but not respiratory muscle strength, was demonstrated.</p

‘Can I be a kinky ace?’: How asexual people negotiate their experiences of kinks and fetishes

Prior research has found that asexual people may fantasise or participate in activities typically conceptualised as ‘sexual’. These behaviours may be considered paradoxical when an asexual person is conceptualised as someone who does not experience sexual attraction or desire. This research aimed to explore how kinks and fetishes are conceptualised, experienced, and negotiated by asexual individuals. Forty-eight participants were recruited to take part in an online qualitative survey. Thematic analysis resulted in three themes. In “Am I asexual?”: (How) can you be a kinky ace?, we discuss the sense of dissonance which some participants reported in negotiating what was seemingly the paradox between their self-identity as asexual and their exploration of kinks and fetishes. In the second theme, Between me and me’ and make believe: Kinks and fetishes as solo and imaginary, we report on how kinks, fetishes, and fantasies were often understood in a solitary context and as either undesirable – or impossible – to live out. In the final theme, Kink as a sensual enhancement in relationships, we highlight how participants positioned kinks and fetishes as an agent for intimacy. These findings expand our knowledge of how asexual people negotiate kinks and fetishes and capture the complexities of asexual identities