Bootstrap and Higher-Order Expansion Validity When Instruments May Be Weak

It is well-known that size-adjustments based on Edgeworth expansions for the t-statistic perform poorly when instruments are weakly correlated with the endogenous explanatory variable. This paper shows, however, that the lack of Edgeworth expansions and bootstrap validity are not tied to the weak instrument framework, but instead depends on which test statistic is examined. In particular, Edgeworth expansions are valid for the score and conditional likelihood ratio approaches, even when the instruments are uncorrelated with the endogenous explanatory variable. Furthermore, there is a belief that the bootstrap method fails when instruments are weak, since it replaces parameters with inconsistent estimators. Contrary to this notion, we provide a theoretical proof that guarantees the validity of the bootstrap for the score test, as well as the validity of the conditional bootstrap for many conditional tests. Monte Carlo simulations show that the bootstrap actually decreases size distortions in both cases.

Bootstrap and Higher-Order Expansion Validity When Instruments May Be Weak

It is well-known that size-adjustments based on Edgeworth expansions for the t-statistic perform poorly when instruments are weakly correlated with the endogenous explanatory variable. This paper shows, however, that the lack of Edgeworth expansions and bootstrap validity are not tied to the weak instrument framework, but instead depends on which test statistic is examined. In particular, Edgeworth expansions are valid for the score and conditional likelihood ratio approaches, even when the instruments are uncorrelated with the endogenous explanatory variable. Furthermore, there is a belief that the bootstrap method fails when instruments are weak, since it replaces parameters with inconsistent estimators. Contrary to this notion, we provide a theoretical proof that guarantees the validity of the bootstrap for the score test, as well as the validity of the conditional bootstrap for many conditional tests. Monte Carlo simulations show that the bootstrap actually decreases size distortions in both cases.

H-closed functions

summary:The notion of a Hausdorff function is generalized to the concept of H-closed function and the concept of an H-closed extension of a Hausdorff function is developed. Each Hausdorff function is shown to have an H-closed extension

Spaces whose Pseudocompact Subspaces are Closed Subsets

[EN] Every first countable pseudocompact Tychonoff space X has the property that every pseudocompact subspace of X is a closed subset of X (denoted herein by “FCC”). We study the property FCC and several closely related ones, and focus on the behavior of extension and other spaces which have one or more of these properties. Characterization, embedding and product theorems are obtained, and some examples are given which provide results such as the following. There exists a separable Moore space which has no regular, FCC extension space. There exists a compact Hausdorff Fréchet space which is not FCC. There exists a compact Hausdorff Fréchet space X such that X, but not X2, is FCC.The first author gratefully acknowledges partial research support from the National Science Foundation, Grant No. 2975010131. The third and fourth authors gratefully acknowledge partial research support from the University of Kansas and the sabbatical leave programs of their respective institutions, and in the case of the fourth author, from the Natural Sciences and Engineering Research Council of Canada.Dow, A.; Porter, JR.; Stephenson, R.; Grant Woods, R. (2004). Spaces whose Pseudocompact Subspaces are Closed Subsets. Applied General Topology. 5(2):243-264. doi:10.4995/agt.2004.1973.2432645

A Brief Centennial Bibliography Of Resources On The History Of The American Sociological Society/Association

Celebrating the centennial of the American Sociological Association provides the ritual occasion and reinforces the intellectual rationale for collectively exploring our professional and organizational roots. To guide us on our way, we have compiled a brief bibliography of relevant materials and exemplars that explicate the early history of the American Sociological Society and – to some degree – its subsequent evolution (the line separating “history” from “current events” is not always easily drawn). Practicing extreme parsimony, we have intentionally excluded literally thousands of otherwise important and instructive published works that focus primarily on specific departments of sociology, the ideas and accomplishments of individual sociologists, the development of sociological theories, the general intellectual history of the discipline as a whole, and myriad other matters of obvious historical and disciplinary interest. We hasten to add, however, that the structure and practical scope of a much more inclusive bibliography is now under consideration and is soon to be implemented. In the interim, we provide here a small down payment: a narrowly defined set of references for selected articles – and still fewer monographs – that specifically address, in various ways, the founding era and subsequent evolution of the American Sociological Society as a professional organization. To these citations, we add lists of relevant journals, abstracts, indexes and databases, and append the locations of archival deposits for the first ten presidents of the American Sociological Society, with the hope of encouraging ever more scholarship on the early history of the ASS/ASA per se. Corrections and suggested additions to this bibliography, focused specifically on the history of the ASS/ASA, are welcomed by the committee. [Submitted December 2004 by the Centennial Bibliography Project Committee]

A Brief Centennial Bibliography Of Resources On The History Of The American Sociological Society/Association

Celebrating the centennial of the American Sociological Association provides the ritual occasion and reinforces the intellectual rationale for collectively exploring our professional and organizational roots. To guide us on our way, we have compiled a brief bibliography of relevant materials and exemplars that explicate the early history of the American Sociological Society and – to some degree – its subsequent evolution (the line separating “history” from “current events” is not always easily drawn). Practicing extreme parsimony, we have intentionally excluded literally thousands of otherwise important and instructive published works that focus primarily on specific departments of sociology, the ideas and accomplishments of individual sociologists, the development of sociological theories, the general intellectual history of the discipline as a whole, and myriad other matters of obvious historical and disciplinary interest. We hasten to add, however, that the structure and practical scope of a much more inclusive bibliography is now under consideration and is soon to be implemented. In the interim, we provide here a small down payment: a narrowly defined set of references for selected articles – and still fewer monographs – that specifically address, in various ways, the founding era and subsequent evolution of the American Sociological Society as a professional organization. To these citations, we add lists of relevant journals, abstracts, indexes and databases, and append the locations of archival deposits for the first ten presidents of the American Sociological Society, with the hope of encouraging ever more scholarship on the early history of the ASS/ASA per se. Corrections and suggested additions to this bibliography, focused specifically on the history of the ASS/ASA, are welcomed by the committee. [Submitted December 2004 by the Centennial Bibliography Project Committee]

Exploring a Gemcitabine-Glucose Hybrid as a Glycoconjugate Prodrug

Nucleoside analogues are established treatments for cancer and viral infection. Gemcitabine is a commonly employed nucleoside analogue displaying anticancer properties against a range of tumor types but is rapidly inactivated in vivo. Efforts to bolster its pharmaceutical profile include investigating prodrug forms. Herein, we explore the synthesis of a novel glucose-gemcitabine glycoconjugate, targeting uptake via glucose transport. We select a redox-reactive disulfide linker for conjugation of gemcitabine (through N4-cytosine) with glucose. Evaluation of this glycoconjugate reveals increased toxicity against androgen insensitive PC3 prostate cancer cells compared to LNCaP (which have lower levels of glucose transporter GLUT1). These preliminary results suggest that glycoconjugation of nucleosides may be an effective approach to targeting cells which display increased uptake and metabolism of glucose

Airborne sampling of aerosol particles: Comparison between surface sampling at Christmas Island and P-3 sampling during PEM-Tropics B

Bulk aerosol sampling of soluble ionic compounds from the NASA Wallops Island P-3 aircraft and a tower on Christmas Island during PEM-Tropics B provides an opportunity to assess the magnitude of particle losses in the University of New Hampshire airborne bulk aerosol sampling system. We find that most aerosol-associated ions decrease strongly with height above the sea surface, making direct comparisons between mixing ratios at 30 m on the tower and the lowest flight level of the P-3 (150 m) open to interpretation. Theoretical considerations suggest that vertical gradients of sea-salt aerosol particles should show exponential decreases with height. Observed gradients of Na+ and Mg2+, combining the tower observations with P-3 samples collected below 1 km, are well described by exponential decreases (r values of 0.88 and 0.87, respectively), though the curve fit underestimates average mixing ratios at the surface by 25%. Cascade impactor samples collected on the tower show that \u3e99% of the Na+ and Mg2+mass is on supermicron particles, 65% is in the 1–6 micron range, and just 20% resides on particles with diameters larger than 9 microns. These results indicate that our airborne aerosol sampling probes must be passing particles up to at least 6 microns with high efficiency. We also observed that nss SO42− and NH4+, which are dominantly on accumulation mode particles, tended to decrease between 150 and 1000 m, but they were often considerably higher at the lowest P-3 sampling altitudes than at the tower. This finding is presently not well understood

Habitat categorisation and mapping of a seabird reserve: Ilhéu da Praia, Azores

The removal of invasive species and mitigation of habitat loss are vital conservation tools for species such as seabirds. We surveyed habitats across the entirety of a small seabird islet reserve, Ilhéu da Praia, in the Azores, two decades on from mammalian eradication and floral restoration. Here, we present a fine-scale map, to a 12 metre resolution, representing the first full habitat survey of this islet. This resource can serve as a baseline for monitoring future habitat changes to this internationally important seabird islet. Following restoration efforts in the 1990s, the islet’s dominant habitats are meadow, grassland dominated by Festuca petraea, or a combination of the two. We also report a novel observation of both Band-rumped Hydrobates castro and Monteiro’s H. monteiroi Storm Petrels breeding in the cavities of Tamarix africana, an invasive tree species