2,148 research outputs found
Estimating the maximum rise in temperature according to climate models using abstract interpretation
Current climate models are complex computer programs that are typically iterated time-step by time-step to predict the next set of values of the climate-related variables. Since these iterative methods are necessarily computed only for a fixed number of iterations, they are unable to answer the natural question whether there is a limit to the rise of global temperature. In order to answer that question we propose to combine climate models with software verification techniques that can find invariant conditions for the set of program variables. In particular, we apply the constraint database approach to software verification to find that the rise in global temperature is bounded according to the common Java Climate Model that implements the Wigely/Raper Upwelling-Diffusion Energy Balance Model climate model
Cost of lifetime immunosuppression coverage for kidney transplant recipients.
On January 1, 2000, Medicare extended the coverage of immunosuppression medications from 3 years to life for elderly and disabled kidney transplant recipients. This research estimates the impact of extending this lifetime coverage to all kidney transplant recipients on Medicare\u27s cash flows. The study finds that extending coverage to all kidney transplant recipients would have increased Medicare\u27s net cash outflows if the coverage were extended for patients of all income levels. There is evidence that extending coverage to only patients in the lowest income quartile could have resulted in a net cost savings to Medicare
Benchmarking the Returns to Venture
We describe a new index of the current and historical returns to venture-type capital. The conceptual basis for the index is the value of a continuously reinvested value-weighted portfolio of all venture-backed and similar pre-public companies. It provides a metric for private equity comparable to the S&P 500 for public equity. We build the index from valuations revealed in episodic transactions in the companies' shares - private placements of new rounds of equity funding, IPOs, acquisitions, and liquidations. Our approach to dealing with the episodic nature of the data is similar to the one used in constructing indexes of real-estate value from transaction data for individual properties. We have extended earlier sources of data to deal with selection bias - we tracked down unfavorable valuations that were less likely to be reported in the earlier data. We also use econometric techniques to handle the remaining selection bias. The resulting index has important uses in marking venture portfolios to market and in assessing the performance of venture investments.
The Incentives to Start New Companies: Evidence from Venture Capital
The standard venture-capital contract rewards entrepreneurs only for creating successful companies that go public or are acquired on favorable terms. As a result, entrepreneurs receive no help from venture capital in avoiding the huge idiosyncratic risk of the typical venture-backed startup. Entrepreneurs earned an average of 1 million at the outset rather than face that risk. The standard financial contract provides entrepreneurs capital supplied by passive investors and rewards entrepreneurs for successful outcomes. We track the division of value for a sample of the great majority of U.S. venture-funded companies over the period form 1987 through 2005. Venture capitalists received an average of $5 million in fee revenue from each company they backed. The outside investors in venture capital received a financial return substantially above that of publicly traded companies, but that the excess is mostly a reward for bearing risk. The pure excess return measured by the alpha of the Capital Asset Pricing Model is positive but may reflect only random variation.
A Partial Taxonomy of Substitutability and Interchangeability
Substitutability, interchangeability and related concepts in Constraint
Programming were introduced approximately twenty years ago and have given rise
to considerable subsequent research. We survey this work, classify, and relate
the different concepts, and indicate directions for future work, in particular
with respect to making connections with research into symmetry breaking. This
paper is a condensed version of a larger work in progress.Comment: 18 pages, The 10th International Workshop on Symmetry in Constraint
Satisfaction Problems (SymCon'10
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