An investigation of co-movements among the growth rates of the G-7 countries

Early in 2000, after a decade of economic expansion, growth began to slow simultaneously in the large, advanced economies known as the Group of Seven (G-7)--Canada, France, Germany, Italy, Japan, the United Kingdom, and the United States. The general slide in GDP growth fueled speculation that a period was emerging in which broad movements in the economies of the industrialized countries would be more closely linked. Proponents of this view argued that greater trade in goods and financial markets was leading to a greater synchronization of national economies. A rise in the co-movement of GDP among countries would have important implications for the making of national economic policies. Governments, for example, would need to take closer account of forecasts for conditions abroad in formulating forecasts for their domestic economies. The authors find, first, that the degree to which enhanced trade and financial linkages might be expected to increase the co-movement, or correlation, of economic growth among countries is far from clear. Then, examining the period from 1970 to the first quarter of 2002, the authors find that, indeed, the estimated correlation of growth across the G-7 has been higher in the current downturn than during the expansion of the 1990s. Rather than signaling a future of permanently higher synchronization, however, the rise is shown to be typical of business cycles over the past thirty years. Furthermore, estimates of correlation have not yet reached the peaks attained after earlier recessions. Overall, despite many changes in the international economy, the evidence does not reveal the arrival of a permanently higher correlation of growth rates among the G-7.Group of Seven countries ; Economic development

Hierarchy in Knowledge Representations

This research was conducted at the Artificial Intelligence Laboratory of the Massachusetts Institute of Technology. Support for the Laboratory's artificial intelligence research is provided in part by the Advanced Research Projects Agency of the Department of Defense under Office of Naval Research contract number N00014-75-C-0643.This paper discusses a number of problems faced in communicating expertise and common sense to a computer, and the approaches taken by several current knowledge representation languages towards solving these problems. The main topic discussed is hierarchy. The importance of hierarchy is almost universally recognized. Hierarchy forms the backbone of many existing representation languages. We discuss several technical problems raised in constructing hierarchical and almost hierarchical systems as criteria and open problems.MIT Artificial Intelligence Laboratory Department of Defense Advanced Research Projects Agenc

The Use of Dependency Relationships in the Control of Reasoning

Research reported herein was conducted at the Artificial Intelligence Laboratory, a Massachusetts Institute of Technology research program supported in part by the Advanced Research Projects Agency of the Department of Defense and monitored by the Office of Naval Research under contract N00014-75-C-0643.Several recent problem-solving programs have indicated improved methods for controlling program actions. Some of these methods operate by analyzing the time-independent antecedent-consequent dependency relationships between the components of knowledge about the problem for solution. This paper is a revised version of a thesis proposal which indicates how a general system of automatically maintained dependency relationships can be used to effect many forms of control on reasoning in an antecedent reasoning framework.MIT Artificial Intelligence Laboratory Department of Defense Advanced Research Projects Agenc

Doctor of Philosophy

dissertationThe work presented here represents three separate research projects. Each explores different approaches to the same problem: how can artificial macromolecules be used to target specific intracellular sites in living organisms, and how may that technology be exploited to treat different disease states? Here, the copolymers based on pHPMA [poly N-(2-hydroxypropyl)methacrylamide)] were used to demonstrate cellular and subcellular targeting in a cancer model. Used as carriers for low molecular weight drugs, pHPMA copolymers may possess great potential for increasing the efficacy of drugs, while also decreasing side effects resulting from drug exposure to healthy tissues and cells. In the first project, antibody Fab’ fragments were dimerized using a multifunctionalized PEG (poly(ethylene glycol)) crosslinker to create a targeting module for pHPMA/drug carriers. The linker was semitrifunctional, able to crosslink 2 Fab’ antibody fragments, which could then be attached to an HPMA-doxorubicin anticancer drug carrier. Monoclonal antibody Fab’ fragments were chosen that target ovarian carcinoma cells. Using this strategy, the conjugates are selectively uptaken by cancer cells, whereby free doxorubicin is released. In the second project, HPMA copolymers were created with a terminal mitochondriotropic chemical moiety, TPP (triphenylphosphonium). Lipophilic cations are used to traffic low molecular weight drugs to mitochondria. Studies had reported that terminal TPP can also traffic high molecular weight, uncharged, linear macromolecules into mitochondria, and enable delivery to the cytosol via direct transduction through the plasma membrane. Semitelechelic TPP-HPMA copolymers were synthesized to determine if this effect could be applied to HPMA copolymer drug conjugates. In the third project, the flexibility of HPMA polymerization chemistry was exploited to create a large “library†or array of different HPMA copolymers with a wide range of chemical properties. Copolymers were made incorporating a variety of cationic, anionic, and hydrophobic sidechains. This array of copolymers was incubated and microinjected directly into the cytoplasm of living cells. The resulting uptake and/or intracellular distribution was observed using time-lapse confocal microscopy and flow cytometry. Using HPMA copolymers as a model, this work functioned as a general survey for cellular uptake, and the intracellular distribution/trafficking that can be expected when artificial macromolecules are internalized into living cells

Detecting Reflected Light from Close-In Extrasolar Giant Planets with the Kepler Photometer

NASA's Kepler Mission promises to detect transiting Earth-sized planets in the habitable zones of solar-like stars. In addition, it will be poised to detect the reflected light component from close-in extrasolar giant planets (CEGPs) similar to 51 Peg b. Here we use the DIARAD/SOHO time series along with models for the reflected light signatures of CEGPs to evaluate Kepler's ability to detect such planets. We examine the detectability as a function of stellar brightness, stellar rotation period, planetary orbital inclination angle, and planetary orbital period, and then estimate the total number of CEGPs that Kepler will detect over its four year mission. The analysis shows that intrinsic stellar variability of solar-like stars is a major obstacle to detecting the reflected light from CEGPs. Monte Carlo trials are used to estimate the detection threshold required to limit the total number of expected false alarms to no more than one for a survey of 100,000 stellar light curves. Kepler will likely detect 100-760 51 Peg b-like planets by reflected light with orbital periods up to 7 days.Comment: 43 pages, 6 figures, 9 tables, accepted for publication by ApJ May 200

Bayesian neural networks for detecting epistasis in genetic association studies

Background: Discovering causal genetic variants from large genetic association studies poses many difficult challenges. Assessing which genetic markers are involved in determining trait status is a computationally demanding task, especially in the presence of gene-gene interactions. Results: A non-parametric Bayesian approach in the form of a Bayesian neural network is proposed for use in analyzing genetic association studies. Demonstrations on synthetic and real data reveal they are able to efficiently and accurately determine which variants are involved in determining case-control status. By using graphics processing units (GPUs) the time needed to build these models is decreased by several orders of magnitude. In comparison with commonly used approaches for detecting interactions, Bayesian neural networks perform very well across a broad spectrum of possible genetic relationships. Conclusions: The proposed framework is shown to be a powerful method for detecting causal SNPs while being computationally efficient enough to handle large datasets. Electronic supplementary material The online version of this article (doi:10.1186/s12859-014-0368-0) contains supplementary material, which is available to authorized users

Evidence supporting the recent origin and species status of the Timberline Sparrow

The Timberline Sparrow (Spizella taverneri), although originally described as a species, is currently classified as a subspecies of the more widespread Brewer\u27s Sparrow (S. breweri). We investigated the taxonomic status and recent evolutionary history of these species by comparison of both morphological and molecular characters. Morphometric comparisons using 6 external and 18 skeletal measurements show that S. taverneri specimens from two widely separated populations (Yukon and southwestern Alberta, Canada) are indistinguishable with respect to size yet are significantly larger (by 3%) than representatives of several breweri populations. Analysis of 1,413 base pairs of mitochondrial DNA (mtDNA) for 10 breweri and 5 taverneri samples representing widely scattered breeding populations revealed a maximum divergence among any breweri-taverneri pair of 0.21% and an overall average of 0.13%. In contrast, the average (± SE) pairwise distance among the other Spizella species is 5.7 ± 0.5%. We discovered that breweri and taverneri could be distinguished on the basis of a single, fixed nucleotide difference. Of an additional 11 taverneri and 8 breweri surveyed for this diagnostic site, a single bird (morphologically a taverneri) from northwest British Columbia did not sort to type. Overall, 18 of 18 breweri and 15 of 16 taverneri were diagnosable. We interpret these results to suggest that gene flow does not currently occur between these two forms and that each is on an independent, albeit recently derived, evolutionary course. The molecular data are consistent with theoretical expectations of a Late Pleistocene speciation event. We believe that for passerine birds, this is the first empirical validation of this widely accepted evolutionary model. The data presented corroborate plumage, vocal, and ecological evidence suggesting that these taxa are distinct. As such, we suggest that Spizella taverneri be recognized as a species