Transforming the child-care debate.

Criticizes L. B. Silverstein's (see record 1992-05293-001) article on child and maternal employment, which attacks what she perceives as the current agenda and misrepresents the nature and scope of current child-care research. N. Shpancer suggests that current child-care research is far from being confined by the myth of motherhood, and that it is largely aimed at exploring the factors contributing to quality care and those influencing both within-type and between-type differences. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Flow distribution in manifolded solar collectors with negligible buoyancy effects

To understand the influence of collector design parameters on the flow distribution among the solar collector absorber tubes, and as a first step to any detailed analysis of the influence of flow on heat transfer in the collector and on its consequent thermal performance, this study investigates the distribution of flow through a typical system consisting of two manifolds connected by a number of parallel riser tubes. No thermal effects, such as buoyancy, are taken into account. A discrete hydrodynamic model was developed for this system, and the resulting set of simultaneous nonlinear algebraic equations was solved numerically for 54 different combinations of the major independent variables. Quantitative flow distribution results are presented. In the investigated range, it was determined that the three parameters which have the major influence on flow distribution are, in the order of significance, the ratio of riser diameter to manifold diameter, the number of risers, and the length of the risers, with maldistribution increasing with the increase of the first two and with the decrease of the third one. To demonstrate the most dramatic influence, changing the value of d_r/d_i from 0.25 to 0.75 causes the peak riser flow excess above the average flow to increase 100-fold: from 5% for the first diameter ratio, to 500% for the second. Consistent with his finding, pressure changes in the system arising from inertia in the manifolds become larger than the frictional pressure changes in the risers when the riser tube length-to-diameter is decreased below about 75, causing large flow maldistribution. Predictions from the model are successfully compared with limited experimental data and with the closed-form solutions of two existing models.     

A preliminary study on the effects of acute ethanol ingestion on default mode network and temporal fractal properties of the brain

Object

To study the effect of acute alcohol intoxication on the functional connectivity of the default mode network (DMN) and temporal fractal properties of the healthy adult brain.

Materials and methods

Eleven healthy male volunteers were asked to drink 0.59 g/kg of ethanol. Resting state blood oxygen level dependent (rsBOLD) MRI scans were obtained before consumption, 60 min post-consumption and 90 min post-consumption. Before each rsBOLD scan, pointed-resolved spectroscopy (PRESS) ¹H-MRS (magnetic resonance spectroscopy) scans were acquired to measure ethanol levels in the right basal ganglia.

Results

Significant changes in DMN connectivity were found following alcohol consumption (p < 0.01). Both increased and decreased regional connectivity were found after 60 min, whereas mostly decreased connectivity was found after 90 min. The fractal behaviour of the rsBOLD signal, which is believed to help reveal complexity of small-scale neuronal circuitry, became more ordered after both 60 and 90 min of alcohol consumption (p < 0.01).

Conclusion

The DMN has been linked to personal identity and social behavior. As such, our preliminary findings may provide insight into the neuro-functional underpinnings of the cognitive and behavioral changes observed during acute alcohol intoxication. The reduced fractal dimension implies a change in function of small-scale neural networks towards less complex signaling.     

Colloid transport in porous media: impact of hyper-saline solutions

The transport of colloids suspended in natural saline solutions with a wide range of ionic strengths, up to that of Dead Sea brines (10^0.9 M) was explored. Migration of microspheres through saturated sand columns of different sizes was studied in laboratory experiments and simulated with mathematical models.Colloid transport was found to be related to the solution salinity as expected. The relative concentration of colloids at the columns outlet decreased (after 2-3 pore volumes) as the solution ionic strength increased until a critical value was reached (ionic strength > 10^−1.8 M) and then remained constant above this level of salinity.The colloids were found to be mobile even in the extremely saline brines of the Dead Sea. At such high ionic strength no energetic barrier to colloid attachment was presumed to exist and colloid deposition was expected to be a favorable process. However, even at these salinity levels, colloid attachment was not complete and the transport of ∼30% of the colloids through the 30-cm long columns was detected.To further explore the deposition of colloids on sand surfaces in Dead Sea brines, transport was studied using 7-cm long columns through which hundreds of pore volumes were introduced. The resulting breakthrough curves exhibited a bimodal shape whereby the relative concentration (C/C₀) of colloids at the outlet rose to a value of 0.8, and it remained relatively constant (for the ∼18 pore volumes during which the colloid suspension was flushed through the column) and then the relative concentration increased to a value of one. The bimodal nature of the breakthrough suggests different rates of colloid attachment. Colloid transport processes were successfully modeled using the limited entrapment model, which assumes that the colloid attachment rate is dependent on the concentration of the attached colloids. Application of this model provided confirmation of the colloid aggregation and their accelerated attachment during transport through soil in high salinity solution.     

Concentrating solar thermal power as a viable alternative in China's electricity supply

Study of low-carbon and pollution renewable alternatives for China revealed that concentrating solar thermal (CST) electric power generation was underemphasized in China's renewable energy plan. The analysis shows the competitive viability of CST: (1) China has the key prerequisites to make CST power generation economical including high-quality insolation and appropriate land, (2) CST's proven history, scale, and dispatchability makes it a good utility-scale power option, especially in the economically underdeveloped Western regions, (3) while CST power is currently more expensive than coal-fired electricity on a nominal basis, when costs of externalities are accounted for, CST, at 11.4 US cents/kWh, can become 57% cheaper than scrubbed coal and 29% cheaper than nuclear power, (4) CST power continues dropping in cost due to economies of scale and technological improvements and can potentially realize a levelized electricity cost of around 4 cents/kWh within ten years, (5) it would significantly rise in competitiveness if and when China completes the extensive smart grid for connecting its solar-abundant western regions with the high-demand eastern regions, (6) CST has the potential to positively impact Western China's economy, but proper policy and deal structure must be in place to ensure that the local community shares the benefit.     

Energy resources and use: The present (2008) situation and possible sustainable paths to the future

Recent estimates and forecasts of the oil, gas, and coal resources and their reserve/production ratio, nuclear and renewable energy potential, and energy uses are surveyed. A brief discussion of the status and prospects of fossil, nuclear and renewable energy use, and of power generation (including hydrogen, fuel cells, micropower systems, and the futuristic concept of generating power in space for terrestrial use) is given. Ways to resolve the problem of the availability, cost, and sustainability of energy resources alongside the rapidly rising demand are discussed. The author's view of the promising energy R&D areas, their potential, foreseen improvements and their time scale, and last year's trends in government funding, are presented.     

Optimal insulation of solar heating system pipes and tanks

A compact and time-effective insulation design procedure for solar heating system piping and water-filled thermal storage tanks was developed. Recognizing the particular sensitivity of solar systems to cost, the economic aspect of the problem was treated by a comprehensive present-value life-cycle cost analysis. In the development of the method, a numerical sensitivity analysis was performed to determine the relative effects of all relevant independent variables (within their pertinent ranges) on piping and tank heat transfer coefficient values. For the acceptable error limits of ± 14% for pipes and ± 19% for tanks, it was found that one may assume that only the nominal pipe diameter (or tank diameter), the thermal conductivity of the insulation, and the insulation's thickness have an effect on the overall heat transfer coefficient. Based on this result, design graphs and tables are presented which can be used to determine the optimal insulation thickness and type, total annual heat losses, present-value annual costs of insulation and lost heat, and overall insulation R-values. The use of the method is illustrated by calculating all the above quantities for all piping and storage tanks for the University of Pennsylvania SolaRow House. The present method provided insulation thicknesses slightly greater than those obtained by the ETI technique.A major conclusion of the study is that the cost of insulation in solar systems is not insignificant (e.g., ~15% in SolaRow), and that heat losses through insulation could amount to an important percentage of the useful solar energy collected (e.g., 24% in SolaRow). This re-emphasizes the need for a careful design of insulation in solar systems.     

The energy situation and its sustainable development strategy in China

The paper briefly summarizes China’s energy situation and sustainable development strategy as they were by 2009. The energy consumption in 2009 is reported to be 3.1 billion tons standard coal equivalent, 1/7 of the world total, 6.3% higher than in the year 2008, and its share of world CO₂ emissions increased rapidly to 20.3% in 2006. These trends are most likely to continue with China’s plan to accomplish its social and economy development goals. To address these problems and also respond to increasing world pressure for reduction of greenhouse gas emissions, the Chinese government plans and has legislated promotion of energy conservation, efficiency, renewable energy technologies and use, and reduction of energy-related environmental impacts to reduce energy intensity by 20% during the 2006-2010 period, and to reduce the CO₂ emission/GDP ratio by 40-45% by 2020 relative to 2005. China is facing severe energy-related challenges that conflict resources shortages with the planned rapid economic development, energy use with the related environmental pollution, and new technology with the old production/consumption patterns. It is recognized that energy development must, however, follow a sustainable path to coordinate economy growth, social development, and environmental protection.