A simple interpretation of the Fe2(-) photoelectron spectrum

The photoelectron spectrum of Fe2(-) can be simply interpreted in terms of electron detachment from the mildly bonding 4s sigma sup * sub u orbital of a (4s sigma sub s)(sup 2) (4s sigma sup * sub u)(sup 2) (3d)(sup 13) anion. This interpretation implies a (4s sigma sub g)(sup 2) (4s sigma sup * sub u)(sup1) (3d)(sup13) configuration for the ground state of Fe2, correlating with one ground state (4s2 3d6) and one excited state (4s1 3d7) Fe atom. A comparison of the bond length and vibrational frequency of Fe2 to values for transition metal dimers containing single 4s-4s bonds is suggestive of 3d-3d bonding in this molecule. The results of preliminary full-valence configuration interaction calculations provide stron support for the proposed Fe2 and Fe2(-) configurations

Satellite power system: Concept development and evaluation program. Volume 3: Power transmission and reception. Technical summary and assessment

Efforts in the DOE/NASA concept development and evaluation program are discussed for the solar power satellite power transmission and reception system. A technical summary is provided together with a summary of system assessment activities. System options and system definition drivers are described. Major system assessment activities were in support of the reference system definition, solid state system studies, critical technology supporting investigations, and various system and subsystem tradeoffs. These activities are described together with reference system updates and alternative concepts for each of the subsystem areas. Conclusions reached as a result of the numerous analytical and experimental evaluations are presented. Remaining issues for a possible follow-on program are identified

Leveraging Technology to Engage Parents at Scale: Evidence from a Randomized Controlled Trial

While leveraging parents has the potential to increase student performance, programs that do so are often costly to implement or they target younger children. We partner text-messaging technology with school information systems to automate the gathering and provision of information to parents at scale. In a field experiment across 22 middle and high schools, we used this technology to send automated text-message alerts to parents about their child’s missed assignments, grades and class absences. We pre-specified five primary outcomes. The intervention reduces course failures by 38% and increases class attendance by 17%. Students are more likely to be retained in the district. The positive effects are particularly large for students with below-average GPA and students in high school. There are no effects on standardized test scores however. We randomly chose either the mother or the father to receive the alerts, but there were no differential effects across these subgroups. As in previous research, the intervention appears to change parents’ beliefs about their child’s performance and increases parent monitoring. Our results show that this type of automated technology can improve student effort relatively cheaply and at scale

Measuring willingness to pay for reliable electricity:Evidence from Senegal

Low-quality electricity service constitutes a significant obstacle in achieving sustainable development. Governments in low-income countries and donors are increasingly seeking to invest in improving electricity service quality and reliability. Understanding households' and firms' willingness to pay (WTP) for quality improvements is key to designing investments in the electricity sector. In this paper, we provide new evidence on WTP for service quality improvements from a nationally-representative survey in Senegal. We find that households and firms are willing to pay a premium over current tariffs for high-quality electricity service without outages. However, WTP for marginal service improvements is significantly lower than WTP for uninterrupted service, suggesting that, for households and firms, any increase in electricity tariff must be accompanied by substantial quality improvements. We discuss the multi-round bidding game built in our data to emphasize the importance of design choices in eliciting the WTP and draw some policy implications

Modeling meander morphodynamics over self-formed heterogeneous floodplains

This work addresses the signatures embedded in the planform geometry of meandering rivers consequent to the formation of floodplain heterogeneities as the river bends migrate. Two geomorphic features are specifically considered: scroll bars produced by lateral accretion of point bars at convex banks and oxbow lake fills consequent to neck cutoffs. The sedimentary architecture of these geomorphic units depends on the type and amount of sediment, and controls bank erodibility as the river impinges on them, favoring or contrasting the river migration. The geometry of numerically generated planforms obtained for different scenarios of floodplain heterogeneity is compared to that of natural meandering paths. Half meander metrics and spatial distribution of channel curvatures are used to disclose the complexity embedded in meandering geometry. Fourier Analysis, Principal Component Analysis, Singular Spectrum Analysis and Multivariate Singular Spectrum Analysis are used to emphasize the subtle but crucial differences which may emerge between apparently similar configurations. A closer similarity between observed and simulated planforms is attained when fully coupling flow and sediment dynamics (fully-coupled models) and when considering self-formed heterogeneities that are less erodible than the surrounding floodplain