8,193 research outputs found
The effect of the mail in voter registration form on voter turnout in the Commonwealth of Virginia
Over the years, many states have undertaken different approaches to increase voter registration and stimulate voter participation in the electoral process. One such approach was the Commonwealth of Virginia\u27s Voter Registration Extension Form, which was instituted in 1989. Using statewide voter registration statistics and a survey of state voter registrars, this paper attempts to measure the impact that this form had on voter registration and turnout in the electoral process from 1989 to 1994. This thesis finds that the registration extension form was reasonably successful in terms of increasing registration. Yet, easing registration requirements does not significantly increase voter turnout
Critical properties of loop percolation models with optimization constraints
We study loop percolation models in two and in three space dimensions, in
which configurations of occupied bonds are forced to form closed loop. We show
that the uncorrelated occupation of elementary plaquettes of the square and the
simple cubic lattice by elementary loops leads to a percolation transition that
is in the same universality class as the conventional bond percolation. In
contrast to this an optimization constraint for the loop configurations, which
then have to minimize a particular generic energy function, leads to a
percolation transition that constitutes a new universality class, for which we
report the critical exponents. Implication for the physics of solid-on-solid
and vortex glass models are discussed.Comment: 8 pages, 8 figure
Gastrointestinal Surface Changes: Interpretation Problems and Indexing Possibilities (A Review)
The purpose of this review on state-of-the-art and new perspectives on the use of scanning electron microscopy (SEM) in gastrointestinal pathology is to discuss the possibility of developing an index for quantitatively grading mucosal epithelial injury. This topic is reviewed within the framework of ulcer indices previously developed for gross lesions, where analogous problems exist, and in relation to the transmission electron microscope staging of epithelial cell pathology. If such an index could be developed it would increase objectivity and standardization of data analysis from laboratory to laboratory, and would allow for quantitative and statistical analysis of morphometric data. It is concluded that an index is possible based upon fields of injured cells rather than upon the grading of individual cell injury progression. An example of a useful SEM lesion index is presented. There are definite limitations to development of such an index, and guidelines are provided to help minimize some of the numerous complicating factors. These guidelines include comments on magnification, tissue contour, cell versus tissue analysis, morphometric considerations, sources of error, and other factors
Assessing the accuracy of δ<sup>18<\sup>O<sub>sw<?sub> estimates from corals: lessons from simple Monte Carlo simulations
EGU2008-A-04391
Paired measurements of δ18O and Sr/Ca in coral aragonite are routinely used for deriving estimates of δ18Osw and, by extension, sea surface salinity variations over the past centuries. However, in practice, the accuracy (or the error) of these estimates is often difficult to assess.
Here, we use simulated proxy data and Monte-Carlo simulations to investigate the accuracy of δ18Osw estimates from paired coral δ18O and Sr/Ca measurements. First, we estimate expected values of coral Sr/Ca and δ18O from instrumental or reanalysis data of sea surface temperature (SST) and sea surface salinity (SSS). We then add the typical analytical errors onto the expected Sr/Ca (δ18O) data as random numbers and compute δ18Osw+error from the noisy proxy data for a 1000 sample Monte Carlo. From this simple Monte Carlo simulation, the range of correlation coefficients between δ18Osw+error and expected δ18Osw is estimated. As expected, we find that this range mainly depends on the magnitude of the actual SSS variations at a given site, as well as on the slope of the δ18Osw-SSS relationship.
A comparison with real coral-based δ18Osw reconstructions from multiple sites indicates that correlations between reconstructed δ18Osw and instrumental SSS fall within the range of correlation coefficients predicted based on our Monte-Carlo simulation. Thus, our simple simulation exercise may help to assess the feasibility of δ18Osw and salinity reconstructions from corals in different climatic settings, provided that (i) some instrumental data of δ18Osw and/or SSS is available, and (ii) the slope of the
δ18Osw-SSS relationship is known
Non-uniqueness in conformal formulations of the Einstein constraints
Standard methods in non-linear analysis are used to show that there exists a
parabolic branching of solutions of the Lichnerowicz-York equation with an
unscaled source. We also apply these methods to the extended conformal thin
sandwich formulation and show that if the linearised system develops a kernel
solution for sufficiently large initial data then we obtain parabolic solution
curves for the conformal factor, lapse and shift identical to those found
numerically by Pfeiffer and York. The implications of these results for
constrained evolutions are discussed.Comment: Arguments clarified and typos corrected. Matches published versio
Explicit solution of the linearized Einstein equations in TT gauge for all multipoles
We write out the explicit form of the metric for a linearized gravitational
wave in the transverse-traceless gauge for any multipole, thus generalizing the
well-known quadrupole solution of Teukolsky. The solution is derived using the
generalized Regge-Wheeler-Zerilli formalism developed by Sarbach and Tiglio.Comment: 9 pages. Minor corrections, updated references. Final version to
appear in Class. Quantum Gra
The Impact of Honor Codes on Academic Cheating Within Liberal Arts Colleges
Many researchers study the subject of collegiate cheating by focusing on demographic characteristics of cheaters at schools of varying sizes. Other researchers examine whether collegiate honor codes can abate rampant cheating. A third group studies whether perceptions of what students believe to be cheating behaviors affects actual cheating. This paper incorporates previous research and develops a model of academic cheating based on three sets of incentives - moral, social and economic – and how they affect self-reported cheating behaviors at liberal arts colleges. An on-line survey was administered to students from three liberal arts colleges in spring 2008. The nearly 700 respondents provide a robust data set with nearly half of the respondents coming from institutions with honor codes in place. Econometric models using ordinary least squares highlight the determinants of cheating and whether honor codes are efficacious. The results will be useful in the national dialogue regarding college cheating
A model for global biomass burning in preindustrial time: LPJ-LMfire (v1.0)
Fire is the primary disturbance factor in many terrestrial ecosystems. Wildfire alters vegetation structure and composition, affects carbon storage and biogeochemical cycling, and results in the release of climatically relevant trace gases including CO2, CO, CH4, NOx, and aerosols. One way of assessing the impacts of global wildfire on centennial to multi-millennial timescales is to use process-based fire models linked to dynamic global vegetation models (DGVMs). Here we present an update to the LPJ-DGVM and a new fire module based on SPITFIRE that includes several improvements to the way in which fire occurrence, behaviour, and the effects of fire on vegetation are simulated. The new LPJ-LMfire model includes explicit calculation of natural ignitions, the representation of multi-day burning and coalescence of fires, and the calculation of rates of spread in different vegetation types. We describe a new representation of anthropogenic biomass burning under preindustrial conditions that distinguishes the different relationships between humans and fire among hunter-gatherers, pastoralists, and farmers. We evaluate our model simulations against remote-sensing-based estimates of burned area at regional and global scale. While wildfire in much of the modern world is largely influenced by anthropogenic suppression and ignitions, in those parts of the world where natural fire is still the dominant process (e.g. in remote areas of the boreal forest and subarctic), our results demonstrate a significant improvement in simulated burned area over the original SPITFIRE. The new fire model we present here is particularly suited for the investigation of climate–human–fire relationships on multi-millennial timescales prior to the Industrial Revolution
The Impact of Honor Codes and Perceptions of Cheating on Academic Cheating Behaviors, Especially for MBA Bound Undergraduates
Researchers studying academic dishonesty in college often focus on demographic characteristics of cheaters and discuss changes in cheating trends over time. To predict cheating behavior, some researchers examine the costs and benefits of academic cheating, while others view campus culture and the role which honor codes play in affecting behavior. This paper develops a model of academic cheating based on three sets of incentives - moral, social and economic—and how they affect cheating behaviors. An on-line survey comprising 61 questions was administered to students from three liberal arts colleges in the USA in spring 2008, yielding 700 responses, with half from colleges with honor codes. Econometric modelling indicates that students ultimately seeking MBA degrees, and those who lack a perception of what constitutes cheating, undertake more cheating, regardless of whether an honor code is in place. Additionally, unless an honor code is embraced by the college community, the existence of an honor code by itself will not reduce cheating
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