Direct numerical simulation of gas transfer across the air-water interface driven by buoyant convection

A series of direct numerical simulations of mass transfer across the air-water interface driven by buoyancy-induced convection has been carried out to elucidate the physical mechanisms that play a role in the transfer of heat and atmospheric gases. The buoyant instability is caused by the presence of a thin layer of cold water situated on top of a body of warm water. In time, heat and atmospheric gases diff use into the uppermost part of the thermal boundary layer and are subsequently transported down into the bulk by falling sheets and plumes of cold water. Using a specifically-designed numerical code for the discretization of scalar convection and diffusion, it was possible to accurately resolve this buoyant instability induced transport of atmospheric gases into the bulk at a realistic Prandtl number (Pr = 6) and Schmidt numbers ranging from Sc = 20 to Sc = 500. The simulations presented here provided a detailed insight into instantaneous gas transfer processes. The falling plumes with highly gas-saturated fluid in their core were found to penetrate deep inside the bulk. With an initial temperature difference between the water surface and the bulk of slightly above 2 K peaks in the instantaneous heat flux in excess of 1600 W/m² were observed, proving the potential effectiveness of buoyant convective heat and gas transfer. Furthermore, the validity of the scaling law for the ratio of gas and heat transfer velocities K_L / H_L ∼ (Pr/Sc)^0:5 for the entire range of Schmidt numbers considered was confirmed. A good time-accurate approximation of K_L was found using surface information such as velocity fluctuations and convection cell size or surface divergence. A reasonable time-accuracy for the K_L estimation was obtained using the horizontal integral length scale and the root-mean-square of the horizontal velocity fluctuations in the upper part of the bulk.The German Research Foundation (DFG grant UH242/6-1). Additional funding by the Helmholtz Water Network

Intensive Parenting: Does it Have the Desired Impact on Child Outcomes?

Although parental involvement is generally thought to be beneficial for children, it is unclear whether the intensive level of parenting that has become commonplace results in improved child outcomes. Intensive parenting may involve the desire to anticipate and solve children’s problems as well as to enroll them in numerous, structured activities that might enhance their physical, cognitive, and social abilities. We surveyed 241 parents to assess intensive parenting beliefs, anticipatory problem solving (APS), enrollment in structured activities, and developmental outcomes of their children ages 2–5. Using structural equation modeling, we found that intensive parenting beliefs predicted more APS, which predicted greater enrollment in creative and physical activities. However, enrollment in structured activities did not predict children’s developmental outcomes. Although parents may believe that expensive and time-consuming activities are the keys to ensuring their children’s health, happiness, and success, this study does not support this assumption

Development and Validation of a Quantitative Measure of Intensive Parenting Attitudes

Intensive mothering (IM) attitudes have been considered the dominant discourse of motherhood, but have only been assessed qualitatively The goal of this study was to develop a quantitative scale to assess these ideologies, their construct validity, and their relationship to relevant constructs (i.e., work status and division of household labor). An on-line questionnaire was given to 595 mothers asking 56 questions assessing different aspects of IM attitudes as well as several validation measures. An Exploratory Factor Analysis on 315 randomly selected mothers yielded a 5 factor solution. A Confirmatory Factor Analysis on the remaining 280 mothers demonstrated good fit. The five factors expressed the ideas that 1) women are inherently better at parenting than men (Essentialism), 2) parenting should be fulfilling (Fulfillment), 3) children should be cognitively stimulated by parents (Stimulation), 4) mothering is difficult (Challenging), and 5) parents should prioritize the needs of the child (Child-Centered). Scales had adequate reliability and construct validity compared to the Parental Investment in Child scale, the Parenting Sense of Competence Scale, and Beliefs about Maternal Employment. The Essentialism, Fulfillment, and Challenging scales were positively related to having more responsibility for childcare and household chores. Stay-at-home mothers had higher scores on Essentialism and lower scores on Stimulation than both part-time and full-time working mothers supporting the notion that both working and non-working mothers have intensive parenting ideologies that are manifested in different ways

Virtual reality suturing task as an objective test for robotic experience assessment

BackgroundWe performed a pilot study using a single virtual-simulation suturing module as an objective measurement to determine functional use of the robotic system. This study will assist in designing a study for an objective, adjunctive test for use by a surgical proctor.MethodsAfter IRB approval, subjects were recruited at a robotic renal surgery course to perform two attempts of the "Tubes" module without warm-up using the Da Vinci® Surgical Skills Simulator™. The overall MScore (%) from the simulator was compared among various skill levels to provide construct validity. Correlation with MScore and number of robotic cases was performed and pre-determined skill groups were tested. Nine metrics that make up the overall score were also tested via paired t test and subsequent logistic regression to determine which skills differed among experienced and novice robotic surgeons.ResultsWe enrolled 38 subjects with experience ranging from 0- < 200 robotic cases. Median time to complete both tasks was less than 10 min. The MScore on the first attempt was correlated to the number of previous robotic cases (R(2) = 0.465; p = 0.003). MScore was different between novice and more experienced robotic surgeons on the first (44.7 vs. 63.9; p = 0.005) and second attempt (56.0 vs. 69.9; p = 0.037).ConclusionA single virtual simulator exercise can provide objective information in determining proficient use of the robotic surgical system

Quantum computers can search rapidly by using almost any transformation

A quantum computer has a clear advantage over a classical computer for exhaustive search. The quantum mechanical algorithm for exhaustive search was originally derived by using subtle properties of a particular quantum mechanical operation called the Walsh-Hadamard (W-H) transform. This paper shows that this algorithm can be implemented by replacing the W-H transform by almost any quantum mechanical operation. This leads to several new applications where it improves the number of steps by a square-root. It also broadens the scope for implementation since it demonstrates quantum mechanical algorithms that can readily adapt to available technology.Comment: This paper is an adapted version of quant-ph/9711043. It has been modified to make it more readable for physicists. 9 pages, postscrip

Helping or Hovering? The Effects of Helicopter Parenting on College Students’ Well-Being

Parental involvement is related to many positive child outcomes, but if not developmentally appropriate, it can be associated with higher levels of child anxiety and depression. Few studies have examined the effects of over-controlling parenting, or “helicopter parenting,” in college students. Some studies have found that college students of over-controlling parents report feeling less satisfied with family life and have lower levels of psychological well-being. This study examined self-determination theory as the potential underlying mechanism explaining this relationship. College students (N = 297) completed measures of helicopter parenting, autonomy supportive parenting, depression, anxiety, satisfaction with life, and basic psychological needs satisfaction. Students who reported having over-controlling parents reported significantly higher levels of depression and less satisfaction with life. Furthermore, the negative effects of helicopter parenting on college students’ well-being were largely explained by the perceived violation of students’ basic psychological needs for autonomy and competence

Probing impulsive strain propagation with x-ray pulses

Pump-probe time-resolved x-ray diffraction of allowed and nearly forbidden reflections in InSb is used to follow the propagation of a coherent acoustic pulse generated by ultrafast laser-excitation. The surface and bulk components of the strain could be simultaneously measured due to the large x-ray penetration depth. Comparison of the experimental data with dynamical diffraction simulations suggests that the conventional model for impulsively generated strain underestimates the partitioning of energy into coherent modes.Comment: 4 pages, 2 figures, LaTeX, eps. Accepted for publication in Phys. Rev. Lett. http://prl.aps.or

Fluxes and gas transfer rates of the biogenic trace gas DMS derived from atmospheric gradients

Author Posting. © American Geophysical Union, 2004. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 109 (2004): C08S10, doi:10.1029/2003JC001795.Gas transfer rates were determined from vertical profile measurements of atmospheric dimethylsulfide (DMS) gradients over the equatorial Pacific Ocean obtained during the GasEx-2001 cruise. A quadratic relationship between gas transfer velocity and wind speed was derived from the DMS flux measurements; this relationship was in close agreement with a parameterization derived from relaxed eddy accumulation measurements of DMS over the northeastern Pacific Ocean. However, the GasEx-2001 relationship results in gas transfer rates that are a factor 2 higher than gas transfer rates calculated from a parameterization that is based on coincident eddy correlation measurements of CO2 flux. The measurement precision of both the profiling and eddy correlation techniques applied during GasEx-2001 is comparable; the two gas transfer data sets are in agreement within their uncertainty. Differences in the number of samples and the wind speed range over which CO2 and DMS fluxes were measured are likely causes for the observed discrepancy.Funding for this work came from the Netherlands Organization for Scientific Research (NWO) and from the NOP project 951203: ‘‘Micrometeorology of air/sea fluxes of carbon dioxide. This work was supported by the Global Carbon Cycle project of the NOAA Office of Global Programs grant NA17RJ1223, National Science Foundation grant OCE-9986724, and NSF grant ATM-0120569

Surface Tension of Seawater

New measurements and a reference correlation for the surface tension of seawater at atmospheric pressure are presented in this paper. Surface tension of seawater was measured across a salinity range of 20 ⩽ S ⩽ 131 g/kg and a temperature range of 1 ⩽ t ⩽ 92 °C at atmospheric pressure using the Wilhelmy plate method. The uncertainty within measurements varied from 0.18 to 0.37 mN/m with the average uncertainty being 0.22 mN/m. The experimental procedures were validated with tests conducted on ACS reagent grade water and aqueous sodium chloride solutions. Literature data and present measurements were evaluated and a reference correlation was developed expressing surface tension of seawater as a function of temperature and salinity. The average absolute percentage deviation between measurements and the correlation was 0.19% while the maximum deviation was 0.60%.Center for Clean Water and Clean Energy at MIT and KFUPM (Project R13-CW-10