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This paper examines the stability of egocentric networks as reported over time using a novel touchscreen-based participant-aided sociogram. Past work has noted the instability of nominated network alters, with a large proportion leaving and reappearing between interview observations. To explain this instability of networks over time, researchers often look to structural embeddedness, namely the notion that alters are connected to other alters within egocentric networks. Recent research has also asked whether the interview situation itself may play a role in conditioning respondents to what might be the appropriate size and shape of a social network, and thereby which alters ought to be nominated or not. We report on change in these networks across three waves and assess whether this change appears to be the result of natural churn in the network or whether changes might be the result of factors in the interview itself, particularly anchoring and motivated underreporting. Our results indicate little change in average network size across waves, particularly for indirect tie nominations. Slight, significant changes were noted between waves one and two particularly among those with the largest networks. Almost no significant differences were observed between waves two and three, either in terms of network size, composition, or density. Data come from three waves of a Chicago-based panel study of young men who have sex with men.
The interaction of an acoustic wave with a stratified fluid can drive strong streaming flows owing to the baroclinic production of fluctuating vorticity, as recently demonstrated by Chini et al. (J. Fluid Mech., 744, 2014, pp. 329–351). In the present investigation, a set of wave/mean-flow interaction equations is derived that governs the coupled dynamics of a standing acoustic-wave mode of characteristic (small) amplitude
and the streaming flow it drives in a thin channel with walls maintained at differing temperatures. Unlike classical Rayleigh streaming, the resulting mean flow arises at
rather than at
. Consequently, fully two-way coupling between the waves and the mean flow is possible: the streaming is sufficiently strong to induce
rearrangements of the imposed background temperature and density fields, which modifies the spatial structure and frequency of the acoustic mode on the streaming time scale. A novel Wentzel–Kramers–Brillouin–Jeffreys analysis is developed to average over the fast wave dynamics, enabling the coupled system to be integrated strictly on the slow time scale of the streaming flow. Analytical solutions of the reduced system are derived for weak wave forcing and are shown to reproduce results from prior direct numerical simulations (DNS) of the compressible Navier–Stokes and heat equations with remarkable accuracy. Moreover, numerical simulations of the reduced system are performed in the regime of strong wave/mean-flow coupling for a fraction of the computational cost of the corresponding DNS. These simulations shed light on the potential for baroclinic acoustic streaming to be used as an effective means to enhance heat transfer.
The physics of compressible turbulence in high energy density (HED) plasmas is an unchartered experimental area. Simulations of compressible and radiative flows relevant for astrophysics rely mainly on subscale parameters. Therefore, we plan to perform turbulent hydrodynamics experiments in HED plasmas (TurboHEDP) in order to improve our understanding of such important phenomena for interest in both communities: laser plasma physics and astrophysics. We will focus on the physics of supernovae remnants which are complex structures subject to fluid instabilities such as the Rayleigh–Taylor and Kelvin–Helmholtz instabilities. The advent of megajoule laser facilities, like the National Ignition Facility and the Laser Megajoule, creates novel opportunities in laboratory astrophysics, as it provides unique platforms to study turbulent mixing flows in HED plasmas. Indeed, the physics requires accelerating targets over larger distances and longer time periods than previously achieved. In a preparatory phase, scaling from experiments at lower laser energies is used to guarantee the performance of future MJ experiments. This subscale experiments allow us to develop experimental skills and numerical tools in this new field of research, and are stepping stones to achieve our objectives on larger laser facilities. We review first in this paper recent advances in high energy density experiments devoted to laboratory astrophysics. Then we describe the necessary steps forward to commission an experimental platform devoted to turbulent hydrodynamics on a megajoule laser facility. Recent novel experimental results acquired on LULI2000, as well as supporting radiative hydrodynamics simulations, are presented. Together with the development of LiF detectors as transformative X-ray diagnostics, these preliminary results are promising on the way to achieve micrometric spatial resolution in turbulent HED physics experiments in the near future.
In this paper, we present a model characterizing the interaction of a radiative shock (RS) with a solid material, as described in a recent paper (Koenig et al., Phys. Plasmas, 24, 082707 (2017)), the new model is then related to recent experiments performed on the GEKKO XII laser facility. The RS generated in a xenon gas cell propagates towards a solid obstacle that is ablated by radiation coming from the shock front and the radiative precursor, mimicking processes occurring in astrophysical phenomena. The model presented here calculates the dynamics of the obstacle expansion, which depends on several parameters, notably the geometry and the temperature of the shock. All parameters required for the model have been obtained from experiments. Good agreement between experimental data and the model is found when spherical geometry is taken into account. As a consequence, this model is a useful and easy tool to infer parameters from experimental data (such as the shock temperature), and also to design future experiments.
Previous research suggests that the experience of abuse and neglect in childhood has negative implications for physical health in adulthood. Using data from the Minnesota Longitudinal Study of Risk and Adaptation (N = 115), the present research examined the predictive significance of childhood physical abuse, sexual abuse, and physical/cognitive neglect for multilevel assessments of physical health at midlife (age 37–39 years), including biomarkers of cardiometabolic risk, self-reports of quality of health, and a number of health problems. Analyses revealed that childhood physical/cognitive neglect, but not physical or sexual abuse, predicted all three health outcomes in middle adulthood, even when controlling for demographic risk factors and adult health maintenance behaviors. We discuss possible explanations for the unique significance of neglect in this study and suggest future research that could clarify previous findings regarding the differential impact of different types of abuse and neglect on adult health.
Despite significant needs, patients with chronic obstructive pulmonary disease (COPD) make limited use of palliative care, in part because the current models of palliative care do not address their key concerns.
Our aim was to develop a tailored model of palliative care for patients with COPD and their family caregivers.
Based on information gathered within a program of studies (qualitative research exploring experiences, a cohort study examining service use), an expert advisory committee evaluated and integrated data, developed responses, formulated principles to inform care, and made recommendations for practice. The informing studies were conducted in two Australian states: Victoria and South Australia.
A series of principles underpinning the model were developed, including that it must be: (1) focused on patient and caregiver; (2) equitable, enabling access to components of palliative care for a group with significant needs; (3) accessible; and (4) less resource-intensive than expansion of usual palliative care service delivery. The recommended conceptual model was to have the following features: (a) entry to palliative care occurs routinely triggered by clinical transitions in care; (b) care is embedded in routine ambulatory respiratory care, ensuring that it is regarded as “usual” care by patients and clinicians alike; (c) the tasks include screening for physical and psychological symptoms, social and community support, provision of information, and discussions around goals and preferences for care; and (d) transition to usual palliative care services is facilitated as the patient nears death.
Significance of results:
Our proposed innovative and conceptual model for provision of palliative care requires future formal testing using rigorous mixed-methods approaches to determine if theoretical propositions translate into effectiveness, feasibility, and benefits (including economic benefits). There is reason to consider adaptation of the model for the palliative care of patients with other nonmalignant conditions.
In this paper, we examine wood charcoal assemblages that were recovered from ash layers in Terminal Classic (A.D. 800–950) burials at the Maya site of Rio Bee to understand the use of fuel wood in funerary rites. Compared to charcoal deposits from domestic and non-funerary contexts, the spectrum of wood taxa used in the burial deposits is unique, which suggests specific fire-related practices. Members of the Sapotaceae family and Cordiasp. dominated all contexts and were clearly primary fuels. In contrast, the use of pine (Pinus sp.), which does not grow locally today, was limited to ritual practices. In addition, it seems that a deliberate effort was made to maximize the taxonomic richness of the fuel wood used in burials. Funerary charcoal deposits appear to have been carefully and intentionally “composed” for burning during funerary rites. We propose that this practice materialized the relationship between fire, ash, and the cycles of life and death, which are often symbolized by plant life cycles in the worldview of ancient Maya societies. This study also emphasizes the contribution of anthracological (wood charcoal) analysis to the reconstruction of human behavior and the importance of systematic paleoethnobotanical sampling in funerary contexts.
Nanocrystalline cellulose (NCC) solid films obtained from evaporated aqueous
heterogeneous mixtures retain the self-assembled chiral nematic order formed in
the suspension. These semi-translucent films are iridescent and reflect or
transmit circularly polarized visible light (400-700nm) due to the chiral
properties of the self-assembled nanostructure. This effect occurs at different
wavelengths depending on the pitch of the helical structure. In this paper, NCC
films have been fabricated from different recipes to produce various helix
pitches. The corresponding red-shift in the optical wavelength has been obtained
by means of Spectrophotometry measurements. Preliminary experiments have been
performed to investigate optical polarization effects as function of angles of
incidence using ellipsometry. Finally, laser micromachining results on NCC films
may suggest feasibility for integration as tunable light polarizer
Agricultural intensification has been a major factor in the loss of global biodiversity. Still, agricultural landscapes provide important habitat for many bird species, particularly in the Central Valley of California, USA, where >90% of the natural wildlife habitat has been lost. As wildlife professionals increasingly work with agricultural producers to promote ‘wildlife-friendly’ farming, it is important to understand the relative value of specific crops and field management practices to birds. The value to wintering waterbirds of seven treatments (crop and management practice combinations) across two crops (corn and winter wheat) was assessed at Staten Island in the Sacramento–San Joaquin River Delta of the Central Valley. Significant variation in the relative abundance of waterbirds was found among management practices, and post-harvest flooding and chopping and rolling (mulching) of corn were most beneficial to waterbirds. As expected, most waterbirds were common in flooded treatments, but geese, cranes and long-legged waders also were numerous in some dry treatments. Our data suggest that a greater waterbird species richness and abundance can be achieved by maintaining a mosaic of dry and flooded crop types, varying water depths and continuing the chop-and-roll practice for flooded corn. The observed benefits of particular crops and field management practices in this study should aid in the development of incentive-based programs to improve the habitat value of other working lands both within, and outside, the Delta.
A trend toward greater body size in dizygotic (DZ) than in monozygotic (MZ) twins has been suggested by some but not all studies, and this difference may also vary by age. We analyzed zygosity differences in mean values and variances of height and body mass index (BMI) among male and female twins from infancy to old age. Data were derived from an international database of 54 twin cohorts participating in the COllaborative project of Development of Anthropometrical measures in Twins (CODATwins), and included 842,951 height and BMI measurements from twins aged 1 to 102 years. The results showed that DZ twins were consistently taller than MZ twins, with differences of up to 2.0 cm in childhood and adolescence and up to 0.9 cm in adulthood. Similarly, a greater mean BMI of up to 0.3 kg/m2 in childhood and adolescence and up to 0.2 kg/m2 in adulthood was observed in DZ twins, although the pattern was less consistent. DZ twins presented up to 1.7% greater height and 1.9% greater BMI than MZ twins; these percentage differences were largest in middle and late childhood and decreased with age in both sexes. The variance of height was similar in MZ and DZ twins at most ages. In contrast, the variance of BMI was significantly higher in DZ than in MZ twins, particularly in childhood. In conclusion, DZ twins were generally taller and had greater BMI than MZ twins, but the differences decreased with age in both sexes.
Drillholes made by naticid and muricid gastropods are frequently used in evolutionary and ecological studies because they provide direct, preservable evidence of predation. The muricid Ecphora is common in many Neogene Atlantic Coastal Plain assemblages in the United States, but is frequently ignored in studies of naticid predation. We used a combination of Pliocene fossil, modern beach, and experimentally derived samples to evaluate the hypothesis that Ecphora was an important source of drillholes in infaunal bivalve prey shared with naticids. We focused on the large, thick-shelled venerid, Mercenaria, which is commonly drilled by naticids today. Laboratory experiments, modern beach samples, and the published literature confirm that naticids preferentially drill near the umbo (significant clumping of holes), show a significant correlation between prey size and predator size (estimated by outer borehole diameter), and prefer Mercenaria <50 mm antero-posterior width when other prey are present. Fossil samples containing Ecphora (with or without other large muricids) show no drillhole site stereotypy (no significant clumping, greater variability in placement), no significant predator: prey size correlation, drilled prey shells larger than the largest modern naticids could produce in an experimental setting, and drillholes larger in diameter than those estimated for the largest Pliocene naticids, thus supporting our hypothesis. Substantial overlap in the placement of holes drilled by naticids and muricids, however, made identifying predators from drillhole position problematic. The lack of overlapping ranges of prey shell thickness between fossil and other samples precluded the use of drillhole morphology to establish predator identity (e.g., ratio of inner borehole diameter to outer borehole diameter, drillhole angle). Whereas the difficulty in determining predator identity from drillholes limits the types of analyses that can be reliably performed in mixed-predator assemblages, recognizing Ecphora as a prominent drilling predator creates the opportunity to investigate previously unrecognized questions.
For over 100 years, the genetics of human anthropometric traits has attracted scientific interest. In particular, height and body mass index (BMI, calculated as kg/m2) have been under intensive genetic research. However, it is still largely unknown whether and how heritability estimates vary between human populations. Opportunities to address this question have increased recently because of the establishment of many new twin cohorts and the increasing accumulation of data in established twin cohorts. We started a new research project to analyze systematically (1) the variation of heritability estimates of height, BMI and their trajectories over the life course between birth cohorts, ethnicities and countries, and (2) to study the effects of birth-related factors, education and smoking on these anthropometric traits and whether these effects vary between twin cohorts. We identified 67 twin projects, including both monozygotic (MZ) and dizygotic (DZ) twins, using various sources. We asked for individual level data on height and weight including repeated measurements, birth related traits, background variables, education and smoking. By the end of 2014, 48 projects participated. Together, we have 893,458 height and weight measures (52% females) from 434,723 twin individuals, including 201,192 complete twin pairs (40% monozygotic, 40% same-sex dizygotic and 20% opposite-sex dizygotic) representing 22 countries. This project demonstrates that large-scale international twin studies are feasible and can promote the use of existing data for novel research purposes.
Hantavirus cardiopulmonary syndrome (HCPS) is a viral zoonosis that may result in cardiogenic shock and respiratory failure with significant associated mortality. Hantavirus infection has been identified throughout much of North, Central, and South America. In the United States 586 cases of HCPS have been reported through December 2012 with a case-fatality rate of 35%. Half of these cases have been in the Four Corners area in the southwest. The incidence is even greater in South America, particularly in Argentina, Brazil, Chile, and Paraguay. In Chile alone, 795 cases have been reported through December 2012, with a case-fatality rate of 35%.
HCPS is caused by an infection with a hantavirus. There have been over 20 New World hantaviruses identified since their discovery in 1993. The New World hantaviruses differ from the Old World hantaviruses that cause hemorrhagic fever with renal syndrome (HFRS) and are found primarily in Asia and Europe. The most common hantavirus causing HCPS in Canada and the United States is Sin Nombre virus (SNV). Other hantaviruses that cause significant disease in Central and South America include Andes virus (ANDV) in Chile and Argentina, Choclo virus in Panama, and Laguna Negra virus in Paraguay. The hantaviruses are small single-stranded negative-sense RNA viruses that belong to the family Bunyaviridae, a family known to include other viruses that cause significant zoonotic illnesses.
The impact of longitudinal psychiatric comorbidity, parenting and social characteristics on attention-deficit hyperactivity disorder (ADHD) medication use is still poorly understood.
To assess the baseline and longitudinal influences of behavioural and environmental factors on ADHD medication use.
Survival regressions with time-dependent covariates were used to model data from a population-based longitudinal birth cohort. The sample (n = 1920) was assessed from age 5 months to 10 years. Measures of children's psychiatric symptoms, parenting practices and social characteristics available at baseline and during follow-up were used to identify individual and family-level features associated with subsequent use of ADHD medication.
Use of ADHD medication ranged from 0.2 to 8.6% between ages 3.5 to 10 years. Hyperactivity–inattention was the strongest predictor of medication use (hazard ratio (HR) = 2.75, 95% CI 2.35–3.22). Among all social variables examined, low maternal education increased the likelihood of medication use (HR = 2.09, 95% CI 1.38–3.18) whereas immigrant status lowered this likelihood (HR = 0.40, 95% CI 0.17–0.92).
Beyond ADHD symptoms, the likelihood of receiving ADHD medication is predicted by social variables and not by psychiatric comorbidity or by parenting. This emphasises the need to improve global interventions by offering the same therapeutic opportunities (including medication) as those received by the rest of the population to some subgroups (i.e. immigrants) and by diminishing possible unnecessary prescriptions.