Suchergebnisse

Protecting the health, safety, and performance of exploration-class mission crews against the physiological deconditioning resulting from long-term weightlessness during transit and long-term reduced gravity during surface operations will require effective, multi-system countermeasures. Artificial gravity, which would replace terrestrial gravity with inertial forces generated by rotating the transit vehicle or by short-radius human centrifuge devices within the transit vehicle or surface habitat, has long been considered a potential solution. However, despite its attractiveness as an efficient, multi-system countermeasure and its potential for improving the environment and simplifying operational activities, much still needs to be learned regarding the human response to rotating environments before artificial gravity can be successfully implemented. This book reviews the principle and rationale for using artificial gravity during space missions, and describes the current options proposed, including a short-radius centrifuge contained within a spacecraft. In Artificial Gravity, experts provide recommendations on the research needed to assess whether or not short-radius centrifuge workouts can help limit deconditioning of physiological systems. "Aided by an exquisite group of experts, Gilles Clement and Angie Bukley have managed to put together THE new, comprehensive reference book on artificial gravity. This book will be an essential resource for students, scientists, and program planners alike."--Oliver Angerer, European Space Agency "Drs. Gilles Clement and Angie Bukley have provided a unique book that looks at the practicability of artificial gravity, and have invited respected experts in the space flight community to contribute to this discourse. Like the early 1960 studies of artificial gravity, their book charts the future, guiding both seasoned investigators and students with the tools necessary for understanding the complex problems of artificial gravity and the effect of that environment on biological systems."--Millard F. Reschke, NASA, The Johnson Space Center

In Off Center: The Republican Revolution and the Erosion of American Democracy, Jacob Hacker and Paul Pierson—political science professors from Yale and Berkeley, respectively—direct our attention to one of the central mysteries of our time: how Republican elected officials have turned themselves into distinctly less amusing and way less lovable versions of Wile E. Coyote. How is it that the national Republican Party has been able to govern from the far right even while the public opposes it on issue after issue? Enacting policies that have no visible means of public support (indeed, that engender widespread public opposition), the Republicans, by every known law of political physics, should have long since dropped to earth. Though the party "has strayed dramatically from the moderate middle of public opinion," write Hacker and Pierson, "the normal mechanisms of democratic accountability have not been able to bring them back."

Meyerson reviews Off Center: The Republican Revolution and The Erosion of American Democracy by Jacob S. Hacker and Paul Pierson.

Prospects for Indonesia's President Wahid's continued hold on power, in light of impeachment proceedings and economic and political problems.

It is well known that the problem of the cosmological constant appears in a new light in unimodular gravity. In particular, the zero-momentum piece of the potential does not automatically produce a corresponding cosmological constant. Here we show that quantum corrections do not renormalize the classical value of this observable ; This work has been partially supported by the European Union FP7 ITN INVISIBLES (Marie Curie Actions, PITN- GA-2011- 289442, and HPRN-CT-200-00148) as well as by FPA2012-31880 (MICINN, Spain), FPA2011-24568 (MICINN, Spain), S2009ESP-1473 (CA Madrid), and COST Action MP1210 (The String Theory Universe). The authors acknowledge the support of the Spanish MINECO Centro de Excelencia Severo Ochoa Program under Grant No. SEV-2012-0249

This paper examines the effects of zero trade on the estimation of the gravity model using both simulated and real data with a panel structure, which is different from the more conventional cross-sectional structure. We begin by showing that the usual log-linear estimation method can result in highly deceptive inference when some observations are zero. As an alternative approach, we suggest using the Poisson fixed effects estimator. This approach eliminates the problems of zero trade and is shown to perform well in small samples.

"The gravity model in economics was until relatively recently an intellectual orphan, unconnected to the rich family of economic theory. This review is a tale of the orphan's reunion with its heritage and the benefits that have flowed from it. Gravity has long been one of the most successful empirical models in economics. Incorporating the theoretical foundations of gravity into recent practice has led to a richer and more accurate estimation and interpretation of the spatial relations described by gravity. Recent developments are reviewed here and suggestions are made for promising future research"--National Bureau of Economic Research web site