A ring as a model of the main belt in planetary ephemerides

We assess the ability of a solid ring to model a global perturbation induced by several thousands of main-belt asteroids. The ring is first studied in an analytical framework that provides an estimate of all the ring's parameters excepting mass. In the second part, numerically estimated perturbations on the Earth-Mars, Earth-Venus, and Earth-Mercury distances induced by various subsets of the main-belt population are compared with perturbations induced by a ring. To account for large uncertainties in the asteroid masses, we obtain results from Monte Carlo experiments based on asteroid masses randomly generated according to available data and the statistical asteroid model. The radius of the ring is analytically estimated at 2.8 AU. A systematic comparison of the ring with subsets of the main belt shows that, after removing the 300 most perturbing asteroids, the total main-belt perturbation of the Earth-Mars distance reaches on average 246 m on the 1969-2010 time interval. A ring with appropriate mass is able to reduce this effect to 38 m. We show that, by removing from the main belt ~240 asteroids that are not necessarily the most perturbing ones, the corresponding total perturbation reaches on average 472 m, but the ring is able to reduce it down to a few meters, thus accounting for more than 99% of the total effect.Comment: 18 pages, accepted in A&

The Insider\u27s Advantage: CEO Experience and The Performance of Large Diversified Firms

Much upper echelons research focuses on the effect of CEO experience on firm performance outcomes. This paper extends this research stream using human and social capital theories as a framework to examine the effect of CEO experience on the performance of large diversified companies. Our analysis of 239 Fortune “500” companies finds that larger companies are more likely to select insiders and individuals who have more firm-specific experience to be their CEO. We also find that the selection of insiders and CEOs with more firm-specific experience is associated with significantly higher firm performance. These findings highlight the importance of the human and social capital possessed by company insiders, and shed additional light on the strategic leadership of large diversified companies and other complex organizations

TOPOFIT-DB, a database of protein structural alignments based on the TOPOFIT method

TOPOFIT-DB (T-DB) is a public web-based database of protein structural alignments based on the TOPOFIT method, providing a comprehensive resource for comparative analysis of protein structure families. The TOPOFIT method is based on the discovery of a saturation point on the alignment curve (topomax point) which presents an ability to objectively identify a border between common and variable parts in a protein structural family, providing additional insight into protein comparison and functional annotation. TOPOFIT also effectively detects non-sequential relations between protein structures. T-DB provides users with the convenient ability to retrieve and analyze structural neighbors for a protein; do one-to-all calculation of a user provided structure against the entire current PDB release with T-Server, and pair-wise comparison using the TOPOFIT method through the T-Pair web page. All outputs are reported in various web-based tables and graphics, with automated viewing of the structure-sequence alignments in the Friend software package for complete, detailed analysis. T-DB presents researchers with the opportunity for comprehensive studies of the variability in proteins and is publicly available at

Helping Leaders Grow Up: Vertical Leadership Development in Practice

This research reinforces arguments for the use of adult vertical development theory to transform traditional leadership development practices to prepare leaders for the volatile, uncertain, complex, and ambiguous (VUCA) world. Vertical leadership development strategies and practices were assessed in fifteen large organizations. Multiple factors impacted implementation of vertical development practices. The primary factor was the overall leadership development mindset (the organization’s learning strategy and its theory of individual change). Secondary factors include senior leader engagement, space for openness and vulnerability, capability and experience of practitioners, alignment in business processes, and expanded understanding of risk-taking. Our results illustrate that accelerating leadership capacity through the implementation of vertical development practices requires significant personal and organizational commitment

Helping Leaders Grow Up: Vertical Leadership Development in Practice

This research reinforces arguments for the use of adult vertical development theory to transform traditional leadership development practices to prepare leaders for the volatile, uncertain, complex, and ambiguous (VUCA) world. Vertical leadership development strategies and practices were assessed in fifteen large organizations. Multiple factors impacted implementation of vertical development practices. The primary factor was the overall leadership development mindset (the organization’s learning strategy and its theory of individual change). Secondary factors include senior leader engagement, space for openness and vulnerability, capability and experience of practitioners, alignment in business processes, and expanded understanding of risk-taking. Our results illustrate that accelerating leadership capacity through the implementation of vertical development practices requires significant personal and organizational commitment

Multiple solutions for asteroid orbits: Computational procedure and applications

We describe the Multiple Solutions Method, a one-dimensional sampling of the six-dimensional orbital confidence region that is widely applicable in the field of asteroid orbit determination. In many situations there is one predominant direction of uncertainty in an orbit determination or orbital prediction, i.e., a ``weak'' direction. The idea is to record Multiple Solutions by following this, typically curved, weak direction, or Line Of Variations (LOV). In this paper we describe the method and give new insights into the mathematics behind this tool. We pay particular attention to the problem of how to ensure that the coordinate systems are properly scaled so that the weak direction really reflects the intrinsic direction of greatest uncertainty. We also describe how the multiple solutions can be used even in the absence of a nominal orbit solution, which substantially broadens the realm of applications. There are numerous applications for multiple solutions; we discuss a few problems in asteroid orbit determination and prediction where we have had good success with the method. In particular, we show that multiple solutions can be used effectively for potential impact monitoring, preliminary orbit determination, asteroid identification, and for the recovery of lost asteroids

Tredegar Street Corridor Plan: A Step to Unifying the Richmond Riverfront

In order to understand the performance of a transportation network, the three concepts of mobility, connectivity, and accessibility must be evaluated. Each concept must be assessed separately and collectively to comprehend how people move about the network. The purpose of this professional plan is to evaluate and enhance these three concepts of Tredegar Street by the James River in Richmond, Virginia. The street is part of an extensive transportation network that consists of roads, trails, and bridges that connect to parks, workplaces, residential neighborhoods, and Downtown. Tredegar Street plays a vital role as a conveyer of multiple users utilizing various modes of transportation who are traveling between diverse destinations, and therefore, must perform sufficiently in order to continue that role. Evaluating the mobility, connectivity, and accessibility of Tredegar Street can further explain the network’s current assets and limitations while informing future opportunities and improvements. Through physical observations, a user survey, and technical research, Tredegar Street’s network was assessed and six goals to enhance the network’s performance were developed. These recommended goals focus on enhancing the mobility, connectivity, and accessibility of Tredegar Street’s network by using human-scaled approaches that reorient the street to the wants and needs of its current and potential users. If these recommendations are put into action, the Tredegar Street Corridor Plan: A Step to Unifying the Richmond Riverfront will make the area a safer and more comfortable environment for all ages, abilities, and racial/ethnic identities, regardless of their mode of transportation