Evaporation and Accretion of Extrasolar Comets Following White Dwarf Kicks

Several lines of observational evidence suggest that white dwarfs receive small birth kicks due to anisotropic mass loss. If other stars possess extrasolar analogues to the Solar Oort cloud, the orbits of comets in such clouds will be scrambled by white dwarf natal kicks. Although most comets will be unbound, some will be placed on low angular momentum orbits vulnerable to sublimation or tidal disruption. The dusty debris from these comets will manifest itself as an IR excess temporarily visible around newborn white dwarfs; examples of such disks may already have been seen in the Helix Nebula, and around several other young white dwarfs. Future observations with the James Webb Space Telescope may distinguish this hypothesis from alternatives such as a dynamically excited Kuiper Belt analogue. Although competing hypotheses exist, the observation that $\gtrsim 15\%$ of young white dwarfs possess such disks, if interpreted as indeed being cometary in origin, provides indirect evidence that low mass gas giants (thought necessary to produce an Oort cloud) are common in the outer regions of extrasolar planetary systems. Hydrogen abundances in the atmospheres of older white dwarfs can, if sufficiently low, also be used to place constraints on the joint parameter space of natal kicks and exo-Oort cloud models.Comment: 22 pages, 13 figures, published in MNRAS. Changes made to match published versio

Public institutions and private transactions : the legal and regulatory environment for business private transactions in Brazil and Chile

Drawing on the new institutional economics, the authors examine the impact on businesses of Brazil's relatively complex, nontransparent legal and regulatory institutions and compare their costs with those of Chile's institutions, which are relatively simple. They examine four basic areas where legal and regulatory institutions could create critical obstacles to efficiency in the garment industries of Sao Paulo and Santiago: (a) the start-up of a new business (entry); (b) the regulation of business; (c) orders by customers of garment firms; and (d) sales with credit. They find that Chilean business transactions benefit from legal simplicity and more consistent enforcement than in Brazil, but that these perceived advantages are offset because of the differences between formal law and practice in Brazil. In two of these areas, Brazil has evolved some effective institutional substitutes to reduce the costs that would otherwise have been imposed by inefficient formal institutions. In the entry of new businesses, professions have evolved to transform the process of registering a new business from a potentially tortuous obstacle path into a fairly affordable one-stop process. In debt collection, information systems limit the need to resort to the formal legal system. Nevertheless, regulation raises the cost of transactions for Brazilian businesses. Costs are further raised by greater uncertainty and frequent renegotiation of orders.National Governance,Environmental Economics&Policies,Legal Products,Private Participation in Infrastructure,Small Scale Enterprise

Playing Around in Science: How Self-Directed Inquiry Benefits the Whole Child

Children of all ages who have the opportunities, time, and materials to explore science content in a self-directed manner will develop higher level understandings, and demonstrate more sophisticated approaches to science. A vast and growing body of research supports the academic benefits of self-directed or authentic scientific inquiry, which is defined as a line of questioning that belongs to the individual (Llewellyn, 2011; Akerson, Hanson, & Cullen, 2007; Cacciamani, 2010; Eick, Meadows, and Balkcom, 2005). Embedded within a child’s distinctive ownership of the inquiry process is a highly beneficial, yet often overlooked aspect, and that is the child’s choice to engage in play. Playing around in science presents children with opportunities to think creatively and divergently, to solve problems in innovative ways, and to develop a unique scientific identity. Llewellyn (2011) states that children learn about the world through exploration, “play, creativity, curiosity, and wonderment” (p. 63). Play in science extends far beyond promoting academic understandings. In fact, when a child engages in play activities while simultaneously undertaking inquiry processes, the child can also choose to participate in social/collaborative scientific endeavors. Furthermore, emotional development and connections can be made when children play around with science content. Also, since play activities typically involve movement, children are actively occupied in physical representations that can also make concepts concrete for better understanding. Play in science promotes comprehension, but it also provides opportunities for children to become socially, physically, emotionally, and even culturally involved. This article will discuss the benefits of play in science to the whole child as well as some of the obstacles that diminish or extinguish play behaviors and scientific exploration

Holistic Identity Development in STEAM

Holistic STEAM programs can benefit children by allowing them to develop an intersecting identity in STEAM disciplines, explore real-world issues more broadly, think critically and innovatively, solve problems using integrated approaches, and have confidence across multiple fields of study. Much of the current research situates identity development in single subjects such as science, math, or engineering. However, a broader conceptualization of identity in STEAM can influence the creation or progression of STEAM curriculum, environments, and programs to support the unique, organic construction of a child’s identity development across multipledisciplines. Suggestions for creating optimal conditions for holistic STEAM identity development include using an interactionist approach, developing meaningfully integrated and relevant real-world explorations, utilizing inquiry, interest, and play, and using a flexible curriculum that allows for divergence and creativity

Developing an Excel Decision Support System Using In-Transit Visibility to Decrease DoD Transportation Delays

The United States Air Force\u27s Air Mobility Command (AMC) is responsible for efficiently transporting military personnel and cargo throughout the world. Organizations throughout the transportation system search for ways to decrease cargo transportation time as part of their ongoing mission to provide timely airlift services to the DoD. As cargo is transported through the transportation system it is in one of two states; waiting at an air base for transportation or in some phase of the loading, transportation, or unloading process. The loading and unloading process has been streamlined throughout the transportation system to a point which leaves little room for significant improvement in terms of total transportation time. However, decreasing the average time pallets wait for a transportation aircraft, called the port hold time (PHT), is a difficult problem which is currently receiving attention. The DoD has invested in radio frequency identification (RFID) technology to provide in-transit visibility (ITV) of all cargo moving through the transportation system. In many ways ITV has made cargo transportation much more efficient but its capability to measure and characterize cargo flow through the system has not been fully exploited. The purpose of this research is to create a Microsoft Excel application which utilizes RFID data to quantify and analyze cargo velocity in the Iraqi theater. The transportation system is analyzed at the pallet level to reveal which specific air bases and transportation methods cause lengthy cargo delays. Pallet PHT data is processed and reported using Statistical Process Control (SPC) methods including control and Pareto charts