Senior Inquiry: Diversity of the Human Experience

This collaboratively created poster summarizes, in graphic form, the Senior Inquiry students\u27 year-long course of study

Essential Role forSonic hedgehogduring Hair Follicle Morphogenesis

AbstractThe hair follicle is a source of epithelial stem cells and site of origin for several types of skin tumors. Although it is clear that follicles arise by way of a series of inductive tissue interactions, identification of the signaling molecules driving this process remains a major challenge in skin biology. In this study we report an obligatory role for the secreted morphogen Sonic hedgehog (Shh) during hair follicle development. Hair germs comprising epidermal placodes and associated dermal condensates were detected in both control andShh−/− embryos, but progression through subsequent stages of follicle development was blocked in mutant skin. The expression ofGli1andPtc1was reduced inShh−/− dermal condensates and they failed to evolve into hair follicle papillae, suggesting that the adjacent mesenchyme is a critical target for placode-derived Shh. Despite the profound inhibition of hair follicle morphogenesis, late-stage follicle differentiation markers were detected inShh−/− skin grafts, as well as cultured vibrissa explants treated with cyclopamine to block Shh signaling. Our findings reveal an essential role for Shh during hair follicle morphogenesis, where it is required for normal advancement beyond the hair germ stage of development

Putting downward pressure on natural gas prices: The impact of renewable energy and energy efficiency

Increased deployment of renewable energy (RE) and energy efficiency (EE) is expected to reduce natural gas demand and in turn place downward pressure on gas prices. A number of recent modeling studies include an evaluation of this effect. Based on data compiled from those studies summarized in this paper, each 1% reduction in national natural gas demand appears likely to lead to a long-term average wellhead gas price reduction of 0.75% to 2.5%, with some studies predicting even more sizable reductions. Reductions in wellhead prices will reduce wholesale and retail electricity rates, and will also reduce residential, commercial, and industrial gas bills. We further find that many of these studies appear to represent the potential impact of RE and EE on natural gas prices within the bounds of current knowledge, but that current knowledge of how to estimate this effect is extremely limited. While more research is therefore needed, existing studies suggest that it is not unreasonable to expect that any increase in consumer electricity costs attributable to RE and/or EE deployment may be substantially offset by the corresponding reduction in delivered natural gas prices. This effect represents a wealth transfer (from natural gas producers to consumers) rather than a net gain in social welfare, and is therefore not a standard motivation for policy intervention on economic grounds. Reducing gas prices and thereby redistributing wealth may still be of importance in policy circles, however, and may be viewed in those circles as a positive ancillary effect of RE and EE deployment

A Review of Wind Project Financing Structures in the USA

The rapid pace of wind power development in the U.S. over the last decade has outstripped the ability of most project developers to provide adequate equity capital and make efficient use of project-related tax benefits. In response, the sector has created novel project financing structures that feature varying combinations of equity capital from project developers and third-party tax-oriented investors, and in some cases commercial debt. While their origins stem from variations in the financial capacity and business objectives of wind project developers, as well as the risk tolerances and objectives of equity and debt providers, each structure is, at its core, designed to manage project risk and allocate federal tax incentives to those entities that can use them most efficiently. This article surveys the six principal financing structures through which most new utility-scale wind projects (excluding utility-owned projects) in the U.S. have been financed from 1999 to the present. These structures include simple balance-sheet finance, several varieties of all-equity special allocation partnership 'flip' structures, and two leveraged structures. In addition to describing each structure's mechanics, the article also discusses its rationale for use, the types of investors that find it appealing and why, and its relative frequency of use in the market. The article concludes with a generalized summary of how a developer might choose one structure over another

Factors driving wind power development in the United States

In the United States, there has been substantial recent growth in wind energy generating capacity, with growth averaging 24 percent annually during the past five years. About 1,700 MW of wind energy capacity was installed in 2001, while another 410 MW became operational in 2002. This year (2003) shows promise of significant growth with more than 1,500 MW planned. With this growth, an increasing number of states are experiencing investment in wind energy projects. Wind installations currently exist in about half of all U.S. states. This paper explores the key factors at play in the states that have achieved a substantial amount of wind energy investment. Some of the factors that are examined include policy drivers, such as renewable portfolio standards (RPS), federal and state financial incentives, and integrated resource planning; as well as market drivers, such as consumer demand for green power, natural gas price volatility, and wholesale market rules

Regioregularity and Single Polythiophene Chain Conformation

The regioregularity of a conjugated polymer can greatly affect bulk film morphologies and properties. However, it remains unclear how regioregularity affects the conformation of isolated individual chains where interchain interactions are absent. Here, the effect of the regioregularity on the conformations adopted by regioregular (<i>rr-</i>) and regiorandom (<i>rra-</i>) poly(3-hexylthiophene) (P3HT) chains was studied using single molecule fluorescence excitation polarization spectroscopy. While every <i>rr-</i>P3HT chain within an ensemble was found to fold into a highly ordered conformation, single <i>rra-</i>P3HT chains adopted a wide variety of conformations, ranging from highly ordered to isotropic. This distribution is likely due to variations in the positions of nonhead-to-tail linkages of the side-chains along the backbone of the different polymer chains. Molecular dynamics simulation on atomistic models of <i>rr-</i> and <i>rra-</i>P3HT chains supports the effect of regioregularity on the collapsed conformations. These results demonstrate that side-chains govern the morphology of P3HT, even at the single chain level