26,225 research outputs found
Altruistic Behavior and Habit Formation
This paper examines whether altruistic behavior is habit forming. We take advantage of a data set that includes a rich set of information concerning individuals’ donations of cash and time as adults as well as information about whether they were involved with charitable activities when they were young. The basic premise is that if altruistic behavior when young is a good predictor of such behavior in adulthood, then this is consistent with the notion that altruistic behavior is habit forming. Using U.S. data, we examine both donations of money and time, and find that engaging in charitable behavior when young is a strong predictor of adult altruistic behavior, ceteris paribus. A major issue in the interpretation of this result is that the correlation between youthful and adult altruistic behavior may be due to some third variable that affects both. While it is impossible to rule out such a possibility, we are able to control for family influences that likely could affect lifetime attitudes toward altruism. We find that, even taking this factor into account, altruistic behavior as a youth plays a significant role in explaining adult behavior. This result applies to donations of money and time to a variety of types of non-profit organizations.altruistic behavior, donations, nonprofit fundraising
Advanced composites wing study program. Volume 1: Executive summary
The effort necessary to achieve a state of production readiness for the design and manufacturing of advanced composite wing structure is outlined. Technical assessment and program options are also reviewed for the wing study results
Housing Tenure, Uncertainty, and Taxation
Modern empirical work on the choice between renting and owning focuses on the concept of the "user cost" of housing, which integrates into a single measure the various components of housing costs. The standard approach implicitly assumes that households know the user cost of housing with certainty. However, the ex post user cost measure exhibits substantial variability over time, and it is highly unlikely that individuals believe themselves able to forecast these fluctuations with certainty. In this paper, we construct and estimate a model of the tenure choice that explicitly allows for the effects of uncertainty. The results suggest that previous work which ignored uncertainty may have overstated the effects of the income tax system upon the tenure choice.
Relationship between fish size and otolith length for 63 species of fishes from the Eastern North Pacific Ocean
Otoliths commonly are used to determine the taxon, age, and size of fishes. This information is useful for population management, predator-prey studies, and archaeological research. The relationship between the length of a fish and the length of its otoliths remains unknown for many species of marine fishes in the Pacific Ocean. Therefore, the relationships between fish length and fish weight, and between otolith length and fish length, were developed for 63 species of fishes caught in the eastern North Pacific Ocean. We also summarized similar relationships for 46 eastern North Pacific fish species reported in the literature. The relationship between fish length and otolith length was linear, and most of the variability was explained by a simple least-squares regression (r 2 > 0.700 for 45 of 63 species). The relationship between otolith length and fish length was not significantly different between left and right otoliths for all but one fish species. Images of otoliths from 77 taxa are included to assist in the identification of species. (PDF file contains 38 pages.
Time-lapse embryo imaging and morphokinetic profiling: towards a general characterisation of embryogenesis
In vitro fertilisation is an effective method of assisted reproductive technology in both humans and certain non-human animal species. In most species, specifically, in humans and livestock, high in vitro fertilisation success rates are achieved via the transfer of embryos with the highest implantation and subsequent developmental potential. In order to reduce the risk of multiple gestation, which could be a result of the transfer of several embryos per cycle, restrictive transfer policies and methods to improve single embryo selection have been implemented. A non-invasive alternative to standard microscopic observation of post-fertilisation embryo morphology and development is time-lapse technology; this enables continuous, uninterrupted observation of embryo development from fertilisation to transfer. Today, there are several time-lapse devices that are commercially available for clinical use, and methods in which time-lapse could be used to improve embryology are continually being assessed. Here we review the use of time-lapse technology in the characterisation of embryogenesis and its role in embryo selection. Furthermore, the prospect of using this technology to identify aneuploidy in human embryos, as well as the use of time-lapse to improve embryological procedures in agriculturally important species such as the pig and cow are discussed
The range of the tangential Cauchy-Riemann system on a CR embedded manifold
We prove that every compact, pseudoconvex, orientable, CR manifold of \C^n,
bounds a complex manifold in the sense. In particular, the
tangential Cauchy-Riemann system has closed range
The Self-Dual String and Anomalies in the M5-brane
We study the anomalies of a charge self-dual string solution in the
Coulomb branch of M5-branes. Cancellation of these anomalies allows us to
determine the anomaly of the zero-modes on the self-dual string and their
scaling with and . The dimensional reduction of the five-brane
anomalous couplings then lead to certain anomalous couplings for D-branes.Comment: 13 pages, Harvmac, refs adde
Non-Commutative Instantons and the Seiberg-Witten Map
We present several results concerning non-commutative instantons and the
Seiberg-Witten map. Using a simple ansatz we find a large new class of
instanton solutions in arbitrary even dimensional non-commutative Yang-Mills
theory. These include the two dimensional ``shift operator'' solutions and the
four dimensional Nekrasov-Schwarz instantons as special cases. We also study
how the Seiberg-Witten map acts on these instanton solutions. The infinitesimal
Seiberg-Witten map is shown to take a very simple form in operator language,
and this result is used to give a commutative description of non-commutative
instantons. The instanton is found to be singular in commutative variables.Comment: 26 pages, AMS-LaTeX. v2: the formula for the commutative description
of the Nekrasov-Schwarz instanton corrected (sec. 4). v3: minor correction
On a three-body confinement force in hadron spectroscopy
Recently it has been argued that a three-body colour confinement interaction
can affect the stability condition of a three-quark system and the spectrum of
a tetraquark described by any constituent quark model. Here we discuss the role
of a three-body colour confinement interaction in a simple quark model and
present some of its implications for the spectra of baryons, tetraquarks and
six-quark systems.Comment: 19 pages (RevTeX), addition of new material regarding the NN
interaction, more accurate discussion of the baryonic case, accepted for
publication in Phys. Rev.
Genetic distance predicts trait differentiation at the subpopulation but not the individual level in eelgrass, Zostera marina.
Ecological studies often assume that genetically similar individuals will be more similar in phenotypic traits, such that genetic diversity can serve as a proxy for trait diversity. Here, we explicitly test the relationship between genetic relatedness and trait distance using 40 eelgrass (Zostera marina) genotypes from five sites within Bodega Harbor, CA. We measured traits related to nutrient uptake, morphology, biomass and growth, photosynthesis, and chemical deterrents for all genotypes. We used these trait measurements to calculate a multivariate pairwise trait distance for all possible genotype combinations. We then estimated pairwise relatedness from 11 microsatellite markers. We found significant trait variation among genotypes for nearly every measured trait; however, there was no evidence of a significant correlation between pairwise genetic relatedness and multivariate trait distance among individuals. However, at the subpopulation level (sites within a harbor), genetic (FST) and trait differentiation were positively correlated. Our work suggests that pairwise relatedness estimated from neutral marker loci is a poor proxy for trait differentiation between individual genotypes. It remains to be seen whether genomewide measures of genetic differentiation or easily measured "master" traits (like body size) might provide good predictions of overall trait differentiation
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