Wetting phenomenon in the liquid-vapor phase coexistence of a partially miscible Lennard-Jones binary mixture

We have carried out extensive equilibrium molecular dynamics (MD) simulations to study the structure and the interfacial properties in the liquid-vapor (LV) phase coexistence of partially miscible binary Lennard-Jones (LJ) mixtures. By analyzing the structural properties as a function of the miscibility parameter, $\alpha$, we found that at relatively low temperatures the system separates forming a liquid A-liquid B interface in coexistence with the vapor phase. At higher temperatures and, $0<\alpha\leq 0.5$, we found a temperature range, $T^{*}_{w}(\alpha) \leq T^{*} < T^{*}_{cons}(\alpha)$, where the liquid phases are wet by the vapor phase. Here, $T^{*}_{w}(\alpha)$ represents the wetting transition temperature (WTT) and $T^{*}_{cons}(\alpha)$ is the consolute temperature of the mixture. However, for $0.5< \alpha < 1$, no wetting phenomenon occurs. For the particular value, $\alpha=0.25$, we analyzed quantitatively the $T^{*}$ versus $\rho^{*}$, and $P^{*}$ versus $T^{*}$ phase diagrams and found, $T^{*}_{c}\simeq 1.25$, and $T^{*}_{cons}\simeq1.25$. We also studied quantitatively, as a function of temperature, the surface tension and the adsorption of molecules at the liquid-liquid interface. It was found that the adsorption shows a jump from a finite negative value up to minus infinity, when the vapor wets the liquid phases, suggesting that the wetting transition (WT) is of first order. The calculated phase diagram together with the wetting phenomenon strongly suggest the existence of a tricritical point. These results agree well with some experiments carried out in fluid binary mixtures.Comment: Enlarged version that include results of more extensive simulations. A total of 24 LaTeX pages that include 12 encapsulated poscript figures. To appear in PRE, Vol. 70, issue Sept. 1st (2004

Young children's research: children aged 4-8 years finding solutions at home and at school

Children's research capacities have become increasingly recognised by adults, yet children remain excluded from the academy, with reports of their research participation generally located in adults' agenda. Such practice restricts children's freedom to make choices in matters affecting them, underestimates children’s capabilities and denies children particular rights. The present paper reports on one aspect of a small-scale critical ethnographic study adopting a constructivist grounded approach to conceptualise ways in which children's naturalistic behaviours may be perceived as research. The study builds on multi-disciplinary theoretical perspectives, embracing 'new' sociology, psychology, economics, philosophy and early childhood education and care (ECEC). Research questions include: 'What is the nature of ECEC research?' and 'Do children’s enquiries count as research?' Initially, data were collected from the academy: professional researchers (n=14) confirmed 'finding solutions' as a research behaviour and indicated children aged 4-8 years, their practitioners and primary carers as 'theoretical sampling'. Consequently, multi-modal case studies were constructed with children (n=138) and their practitioners (n=17) in three ‘good’ schools, with selected children and their primary carers also participating at home. This paper reports on data emerging from children aged 4-8 years at school (n=17) and at home (n=5). Outcomes indicate that participating children found diverse solutions to diverse problems, some of which they set themselves. Some solutions engaged children in high order thinking, whilst others did not; selecting resources and trialing activities engaged children in 'finding solutions'. Conversely, when children's time, provocations and activities were directed by adults, the quality of their solutions was limited, they focused on pleasing adults and their motivation to propose solutions decreased. In this study, professional researchers recognised 'finding solutions' as research behaviour and children aged 4-8 years naturalistically presented with capacities for finding solutions; however, the children's encounters with adults affected the solutions they found

Imprint of past and present environmental conditions on microbiology and biogeochemistry of coastal Quaternary sediments

To date, North Sea tidal-flat sediments have been intensively studied down to a depth of 5 m below seafloor (mbsf). However, little is known about the biogeochemistry, microbial abundance, and activity of sulfate reducers as well as methanogens in deeper layers. In this study, two 20 m-long cores were retrieved from the tidal-flat area of Spiekeroog Island, NW Germany. The drill sites were selected with a close distance of 900 m allowing to compare two depositional settings: first, a paleo-channel filled with Holocene sediments and second, a mainly Pleistocene sedimentary succession. Analyzing these cores, we wanted to test to which degree the paleo-environmental imprint is superimposed by present processes. &lt;br&gt;&lt;br&gt; In general, the numbers of bacterial 16S rRNA genes are one to two orders of magnitude higher than those of &lt;i&gt;Archaea&lt;/i&gt;. The abundances of key genes for sulfate reduction and methanogenesis (&lt;i&gt;dsr&lt;/i&gt;A and &lt;i&gt;mcr&lt;/i&gt;A) correspond to the sulfate and methane profiles. A co-variance of these key genes at sulfate-methane interfaces and enhanced ex situ AOM rates suggest that anaerobic oxidation of methane may occur in these layers. Microbial and biogeochemical profiles are vertically stretched relative to 5 m-deep cores from shallower sediments in the same study area, but still appear compressed compared to deep sea sediments. Our interdisciplinary analysis shows that the microbial abundances and metabolic rates are elevated in the Holocene compared to Pleistocene sediments. However, this is mainly due to present environmental conditions such as pore water flow and organic matter availability. The paleo-environmental imprint is still visible but superimposed by these processes

Structure of isobaric analog states in 91Nb populated by the 90Zr(a,t) reaction

Decay via proton emission of isobaric analog states (IAS's) in $^{91}{Nb}$ was studied using the $^{90}{Zr}(\alpha,t)$ reaction at $E_\alpha$=180 MeV. This study provides information about the damping mechanism of these states. Decay to the ground state and low-lying phonon states in $^{90}{Zr}$ was observed. The experimental data are compared with theoretical predictions wherein the IAS `single-particle' proton escape widths are calculated in a continuum RPA approach. The branching ratios for decay to the phonon states are explained using a simple model.Comment: 3 figures. submitted to Phys. Lett.

More than teacher directed or child initiated: Preschool curriculum type, parent involvement, and children's outcomes in the child-parent centers.

This study investigated the contributions of curriculum approach and parent involvement to the short- and long-term effects of preschool participation in the Title I Chicago Child-Parent Centers. Data came from the complete cohort of 989 low-income children (93% African American) in the Chicago Longitudinal Study, who attended preschool in the 20 Child-Parent Centers in 1983-1985 and kindergarten in 1985-1986. We found that implementation of an instructional approach rated high by Head Teachers in teacher-directed and child-initiated activities was most consistently associated with children’s outcomes, including school readiness at kindergarten entry, reading achievement in third and eighth grades, and avoidance of grade retention. Parent involvement in school activities, as rated by teachers and by parents, was independently associated with child outcomes from school readiness at kindergarten entry to eighth grade reading achievement and grade retention above and beyond the influence of curriculum approach. Findings indicate that instructional approaches that blend a teacher-directed focus with child-initiated activities and parental school involvement are origins of the long-term effects of participation in the Child-Parent Centers

Health related quality of life after extremely preterm birth: a matched controlled cohort study

<p>Abstract</p> <p>Background</p> <p>The majority of infants born before the last trimester now grow up. However, knowledge on subsequent health related quality of life (HRQoL) is scarce. We therefore aimed to compare HRQoL in children born extremely preterm with control children born at term. Furthermore, we assessed HRQoL in relation to perinatal and neonatal morbidity and to current clinical and sociodemographic characteristics.</p> <p>Method</p> <p><it>The Child Health Questionnaire </it>(CHQ-PF50) and a general questionnaire were applied in a population based cohort of 10 year old children born at gestational age ≤ 28 weeks or with birth weight ≤ 1000 grams in Western Norway in 1991-92 and in term-born controls, individually matched for gender and time of birth. The McNemar test and paired t-tests were used to explore group differences between preterms and matched controls. Paired regression models and analyses of interaction (SPSS mixed linear model) were used to explore potential effects of sociodemographic and clinical characteristics on HRQoL in the two groups.</p> <p>Results</p> <p>All 35 eligible preterm children participated. None had major impairments. Learning and/or attention problems were present in 71% of preterms and 20% of controls (odds ratio (OR): 7.0; 95% confidence interval (CI): 2.2 to 27.6). Insufficient professional support was described by 36% of preterm vs. 3% of control parents (OR: infinite; CI: 2.7 to infinite). Preterms scored lower on eight CHQ-PF50 sub-scales and the two summary scores, boys accounting for most of the deficits in areas of behavior, psychosocial functioning and parental burden. HRQoL was associated with learning and/or attention problems in both preterm and control children, significantly more so in preterms in areas related to health and parental burden. Within the preterm group, HRQoL was mostly unrelated to perinatal and neonatal morbidity.</p> <p>Conclusions</p> <p>HRQoL for children born extremely preterm, and particularly for boys, was described by parents to be inferior to that of children born at term, and sufficiently poor to affect the daily life of the children and their families. Learning and/or attention problems were reported for a majority of preterms, strongly influencing their HRQoL.</p

Explaining the Adjustment of Adolescents With Type 1 Diabetes: Role of diabetes-specific and psychosocial factors

OBJECTIVE - The aim of this study was to explain adjustment (diabetes-related quality of life, general well-being, and psychopathology) in adolescents with type 1 diabetes by testing the direct, mediating, and moderating effects of diabetes-specific and psychosocial factors, using an adapted version of the Disability-Stress-Coping model of Wallander and Varni. RESEARCH DESIGN AND METHODS - A total of 437 adolescents (54.5% girls; age range 11-19 years) with type 1 diabetes (mean ± SD diabetes duration 6.13 ± 3.78 years) were recruited from 25 hospitals in the Netherlands. Questionnaires were completed by the adolescents and their family members. Metabolic control was assessed by measuring A1C in all participants in one laboratory. RESULTS - Diabetes stress mediated between A1C and adjustment, after controlling for protective factors, and explained an additional 16% variance in quality of life and a 15% variance in general well-being, whereas a 19% additional variance in psychopathology was explained by both diabetes-related and general stress. No moderating effects were identified after controlling for the main effects of all risk and protective factors in the model. CONCLUSIONS - Both diabetes-related and general stress are critical predictors of the adjustment of adolescents with type 1 diabetes. Protective factors such as self-worth and social support may mediate the effects of generic stress and thus should be encouraged. Diabetes-related stress has the potential to displace the effects of protective factors and thus may play a critical role in the development of maladjustment in adolescents with type 1 diabetes. © 2009 by the American Diabetes Association