Actual causation and the art of modeling

We look more carefully at the modeling of causality using structural equations. It is clear that the structural equations can have a major impact on the conclusions we draw about causality. In particular, the choice of variables and their values can also have a significant impact on causality. These choices are, to some extent, subjective. We consider what counts as an appropriate choice. More generally, we consider what makes a model an appropriate model, especially if we want to take defaults into account, as was argued is necessary in recent work.Comment: In Heuristics, Probability and Causality: A Tribute to Judea Pearl (editors, R. Dechter, H. Geffner, and J. Y. Halpern), College Publications, 2010, pp. 383-40

Shock Wave Development in the Collapse of a Cloud of Bubbles

A numerical simulation of the collapse of a cloud of bubbles has been used to demonstrate the development of an inwardly propagating shock wave which grows rapidly in magnitude. The fully non-linear nonbarotropic homogeneous flow equations are coupled with single bubble dynamics and solved by a stable numerical scheme. The computational results demonstrate the structure of the shock wave as well as its strengthening effect due to the coupling of the single bubble dynamics with the global dynamics of the flow through the pressure and velocity fields. This appears to confirm the speculation of Morch and his co-workers that such shock formation is an important part of cloud collapse

Potential Supply and Demand for Apple and Cherry-Apple Hard Cider Markets in Michigan, and Constraints to Market Development

The current research explores the potential to develop a cherry-apple hard cider market as a potential means to increase demand for and the value of Michigan fruit grower's product. Factors affecting both the development of hard cider markets in Michigan and cherry-apple hard cider were explored. Research results show that the potential value of Michigan hard cider market is relatively small but significant, estimated at ranging between $580,000 and$2,900,000 per year. Microbrews would be primary actors to promote HC market. They are willing and able to dabble in it, promote it. But they are constrained by need for license and this impedes participation of many who would be otherwise interested. Some microbrews uninterested in state-wide push because they feel it will focus on sweet product that they are uninterested in producing. This position is reflective of a seeming contraction inherent in current enthusiasm over the potential of the market, as figures recent market growth is largely fueled by the current trendiness of "malternatives" as a beverage category, while the maintenance of the market, and the interests of some microbrewers and other purveyors is primarily derived from the traditional image of hard cider, with "traditional" vs. "trendy" hard cider products reflecting significant taste differences. Hard cider is also potentially an important product for wineries. There is a high sales potential for a Michigan-brewed hard cider product, however producing a hard cider that is produced exclusively from Michigan-grown fruit could be more difficult due to supply limitations, logistical constraints, and cost. Constraints to growth of hard cider industry include licensing requirements, taxation issues, primary ingredient sourcing and transport, and fluctuating prices, particularly for cherry juice. The research showed high potential for hard cider that blends cherries (and many other fruits) with apple, however such a product would be rotated with current hard cider, not added as a new product in most cases. Its demand increasing potential still exists, however, even if offered as a substitute to hard cider, due to its novelty and variety.Demand and Price Analysis,

Potential Demand for Apple Hard Cider in Michigan

This paper reports the results of market place and consumer research for hard apple cider. The objectives of the research were to determine potential demand for and constraints to the supply of hard apple cider in Michigan. The research was undertaken using on-site and focus group interviews of managers of microbrews, brew-pubs, restaurants and retailers. The research revealed much enthusiasm over HC market potential among purveyors interviewed, particularly among microbrewers, brew-pubs, and specialty retailers. Respondents estimated the potential value of Michigan hard cider market to be relatively small but significant-from 1-5% of purveyors' alcohol sales, and as high as 20% in some cases. Potential hard cider consumers are diverse and include 1) traditional microbrew connoisseurs, 2) young, adventurous drinkers who are driving the "malternative" trend, and 3) the "significant others" and other companions of microbrew connoisseurs who seek an alternative to the heavier beers served in microbrews. While microbrew connoisseurs are likely to gravitate toward a more traditional, drier cider, "malternative" drinkers and the "significant others" are likely to prefer a sweeter product. Compared to other respondents, microbrews showed particular enthusiasm for producing and marketing hard cider. While microbrews and brewpubs would market the product on tap, restaurants and retailers will more likely market a bottled product. The primary impediment to consumer acceptance of the product is a lack of familiarity, and numerous promotional efforts that could overcome these constraints were suggested. Demand for hard cider is likely to be somewhat seasonal, however there are numerous hard cider themes and products that might serve to mitigate this seasonality. While strong enthusiasm for the marketability of a Michigan-brewed product was expressed by respondents, an organic or "all-natural" product was not felt to have potential due to both demand and supply constraints. The primary constraints to supply of hard cider in general are the cost and availability of ingredients, as well as regulatory and taxation issues.Demand and Price Analysis,

The role of stereotactic radiosurgery in the multimodal management of growth hormone–secreting pituitary adenomas

Growth hormone (GH)–secreting pituitary adenomas represent a common source of GH excess in patients with acromegaly. Whereas surgical extirpation of the culprit lesion is considered first-line treatment, as many as 19% of patients develop recurrent symptoms due to regrowth of previously resected adenomatous tissue or to continued growth of the surgically inaccessible tumor. Although medical therapies that suppress GH production can be effective in the management of primary and recurrent acromegaly, these therapies are not curative, and lifelong treatment is required for hormonal control. Stereotactic radiosurgery has emerged as an effective adjunctive treatment modality, and is an appealing alternative to conventional fractionated radiation therapy. The authors reviewed the growing body of literature concerning the role of radiosurgical procedures in the treatment armamentarium of acromegaly, and identified more than 1350 patients across 45 case series. In this review, the authors report that radiosurgery offers true hormonal normalization in 17% to 82% of patients and tumor growth control in 37% to 100% of cases across all series, while minimizing adverse complications. As a result, stereotactic radiosurgery represents a safe and effective treatment option in the multimodal management of primary or recurrent acromegaly secondary to GH-secreting pituitary adenomas

Growth or Glamour? Fundamentals and Systematic Risk in Stock Returns

The cash flows of growth stocks are particularly sensitive to temporary movements in aggregate stock prices (driven by movements in the equity risk premium), while the cash flows of value stocks are particularly sensitive to permanent movements in aggregate stock prices (driven by market-wide shocks to cash flows. ) Thus the high betas of growth stocks with the market's discount-rate shocks, and of value stocks with the market's cash-flow shocks, are determined by the cash-flow fundamentals of growth and value companies. Growth stocks are not merely "glamour stocks" whose systematic risks are purely driven by investor sentiment. More generally, accounting measures of firm-level risk have predictive power for firms' betas with market-wide cash flows, and this predictive power arises from the behavior of firms' cash flows. The systematic risks of stocks with similar accounting characteristics are primarily driven by the systematic risks of their fundamentals.

Growth or Glamour? Fundamentals and Systematic Risk in Stock Returns

The cash flows of growth stocks are particularly sensitive to temporary movements in aggregate stock prices (driven by movements in the equity risk premium), while the cash flows of value stocks are particularly sensitive to permanent movements in aggregate stock prices (driven by market-wide shocks to cash flows.) Thus the high betas of growth stocks with the market's discount-rate shocks, and of value stocks with the market's cash-flow shocks, are determined by the cash-flow fundamentals of growth and value companies. Growth stocks are not merely "glamour stocks" whose systematic risks are purely driven by investor sentiment. More generally, accounting measures of firm-level risk have predictive power for firms' betas with market-wide cash flows, and this predictive power arises from the behavior of firms' cash flows. The systematic risks of stocks with similar accounting characteristics are primarily driven by the systematic risks of their fundamentals.