343 research outputs found
Promises and Lies: Restoring Violated Trust
Trust is critical for organizations, effective management, and efficient negotiations, yet trust violations are common. Prior work has often assumed trust to be fragile—easily broken and difficult to repair. We investigate this proposition in a laboratory study and find that trust harmed by untrustworthy behavior can be effectively restored when individuals observe a consistent series of trustworthy actions. Trust harmed by the same untrustworthy actions and deception, however, never fully recovers—even when deceived participants receive a promise, an apology, and observe a consistent series of trustworthy actions. We also find that a promise to change behaviour can significantly speed the trust recovery process, but prior deception harms the effectiveness of a promise in accelerating trust recovery
Closed-Form Bayesian Inferences for the Logit Model via Polynomial Expansions
Articles in Marketing and choice literatures have demonstrated the need for
incorporating person-level heterogeneity into behavioral models (e.g., logit
models for multiple binary outcomes as studied here). However, the logit
likelihood extended with a population distribution of heterogeneity doesn't
yield closed-form inferences, and therefore numerical integration techniques
are relied upon (e.g., MCMC methods).
We present here an alternative, closed-form Bayesian inferences for the logit
model, which we obtain by approximating the logit likelihood via a polynomial
expansion, and then positing a distribution of heterogeneity from a flexible
family that is now conjugate and integrable. For problems where the response
coefficients are independent, choosing the Gamma distribution leads to rapidly
convergent closed-form expansions; if there are correlations among the
coefficients one can still obtain rapidly convergent closed-form expansions by
positing a distribution of heterogeneity from a Multivariate Gamma
distribution. The solution then comes from the moment generating function of
the Multivariate Gamma distribution or in general from the multivariate
heterogeneity distribution assumed.
Closed-form Bayesian inferences, derivatives (useful for elasticity
calculations), population distribution parameter estimates (useful for
summarization) and starting values (useful for complicated algorithms) are
hence directly available. Two simulation studies demonstrate the efficacy of
our approach.Comment: 30 pages, 2 figures, corrected some typos. Appears in Quantitative
Marketing and Economics vol 4 (2006), no. 2, 173--20
Maximal surface group representations in isometry groups of classical Hermitian symmetric spaces
Higgs bundles and non-abelian Hodge theory provide holomorphic methods with
which to study the moduli spaces of surface group representations in a
reductive Lie group G. In this paper we survey the case in which G is the
isometry group of a classical Hermitian symmetric space of non-compact type.
Using Morse theory on the moduli spaces of Higgs bundles, we compute the number
of connected components of the moduli space of representations with maximal
Toledo invariant.Comment: v2: added due credits to the work of Burger, Iozzi and Wienhard. v3:
corrected count of connected components for G=SU(p,q) (p \neq q); added due
credits to the work of Xia and Markman-Xia; minor corrections and
clarifications. 31 page
Adiabatic limit and the slow motion of vortices in a Chern-Simons-Schr\"odinger system
We study a nonlinear system of partial differential equations in which a
complex field (the Higgs field) evolves according to a nonlinear Schroedinger
equation, coupled to an electromagnetic field whose time evolution is
determined by a Chern-Simons term in the action. In two space dimensions, the
Chern-Simons dynamics is a Galileo invariant evolution for A, which is an
interesting alternative to the Lorentz invariant Maxwell evolution, and is
finding increasing numbers of applications in two dimensional condensed matter
field theory. The system we study, introduced by Manton, is a special case (for
constant external magnetic field, and a point interaction) of the effective
field theory of Zhang, Hansson and Kivelson arising in studies of the
fractional quantum Hall effect. From the mathematical perspective the system is
a natural gauge invariant generalization of the nonlinear Schroedinger
equation, which is also Galileo invariant and admits a self-dual structure with
a resulting large space of topological solitons (the moduli space of self-dual
Ginzburg-Landau vortices). We prove a theorem describing the adiabatic
approximation of this system by a Hamiltonian system on the moduli space. The
approximation holds for values of the Higgs self-coupling constant close to the
self-dual (Bogomolny) value of 1. The viability of the approximation scheme
depends upon the fact that self-dual vortices form a symplectic submanifold of
the phase space (modulo gauge invariance). The theorem provides a rigorous
description of slow vortex dynamics in the near self-dual limit.Comment: Minor typos corrected, one reference added and DOI give
Geometric transitions and integrable systems
We consider {\bf B}-model large duality for a new class of noncompact
Calabi-Yau spaces modeled on the neighborhood of a ruled surface in a
Calabi-Yau threefold. The closed string side of the transition is governed at
genus zero by an Hitchin integrable system on a genus Riemann surface
. The open string side is described by a holomorphic Chern-Simons
theory which reduces to a generalized matrix model in which the eigenvalues lie
on the compact Riemann surface . We show that the large planar
limit of the generalized matrix model is governed by the same Hitchin
system therefore proving genus zero large duality for this class of
transitions.Comment: 70 pages, 1 figure; version two: minor change
Acoustic and perceptual evaluation of Mandarin tone productions before and after perceptual training
This is the publisher's version, also available electronically from http://scitation.aip.org/content/asa/journal/jasa/113/2/10.1121/1.1531176.Training American listeners to perceive Mandarin tones has been shown to be effective, with trainees’ identification improving by 21%. Improvement also generalized to new stimuli and new talkers, and was retained when tested six months after training [Y. Wang et al., J. Acoust. Soc. Am. 106, 3649–3658 (1999)]. The present study investigates whether the tonecontrasts gained perceptually transferred to production. Before their perception pretest and after their post-test, the trainees were recorded producing a list of Mandarin words. Their productions were first judged by native Mandarin listeners in an identification task. Identification of trainees’ post-test tone productions improved by 18% relative to their pretest productions, indicating significant tone production improvement after perceptual training. Acoustic analyses of the pre- and post-training productions further reveal the nature of the improvement, showing that post-training tone contours approximate native norms to a greater degree than pretraining tone contours. Furthermore, pitch height and pitch contour are not mastered in parallel, with the former being more resistant to improvement than the latter. These results are discussed in terms of the relationship between non-native tone perception and production as well as learning at the suprasegmental level
3,3′-Diindolylmethane Induces G1 Arrest and Apoptosis in Human Acute T-Cell Lymphoblastic Leukemia Cells
Certain bioactive food components, including indole-3-carbinol (I3C) and 3,3′-diindolylmethane (DIM) from cruciferous vegetables, have been shown to target cellular pathways regulating carcinogenesis. Previously, our laboratory showed that dietary I3C is an effective transplacental chemopreventive agent in a dibenzo[def,p]chrysene (DBC)-dependent model of murine T-cell lymphoblastic lymphoma. The primary objective of the present study was to extend our chemoprevention studies in mice to an analogous human neoplasm in cell culture. Therefore, we tested the hypothesis that I3C or DIM may be chemotherapeutic in human T-cell acute lymphoblastic leukemia (T-ALL) cells. Treatment of the T-ALL cell lines CCRF-CEM, CCRF-HSB2, SUP-T1 and Jurkat with DIM in vitro significantly reduced cell proliferation and viability at concentrations 8- to 25-fold lower than the parent compound I3C. DIM (7.5 µM) arrested CEM and HSB2 cells at the G1 phase of the cell cycle and 15 µM DIM significantly increased the percentage of apoptotic cells in all T-ALL lines. In CEM cells, DIM reduced protein expression of cyclin dependent kinases 4 and 6 (CDK4, CDK6) and D-type cyclin 3 (CCND3); DIM also significantly altered expression of eight transcripts related to human apoptosis (BCL2L10, CD40LG, HRK, TNF, TNFRSF1A, TNFRSF25, TNFSF8, TRAF4). Similar anticancer effects of DIM were observed in vivo. Dietary exposure to 100 ppm DIM significantly decreased the rate of growth of human CEM xenografts in immunodeficient SCID mice, reduced final tumor size by 44% and increased the apoptotic index compared to control-fed mice. Taken together, our results demonstrate a potential for therapeutic application of DIM in T-ALL
Coffee intake and CYP1A2*1F genotype predict breast volume in young women: implications for breast cancer
As breast volume may be associated with heart cancer risk, we studied the relationship between breast volume, CYP1A2*1F and coffee intake. Among healthy premenopausal non-hormone users, 3+ cups per day was associated with lower volume only in C-allele carriers (Pinteraction=0.02), which is consistent with reports that coffee protects only C-allele carriers against breast cancer
Cross-cultural validation of the Educational Needs Assessment Tool in RA in 7 European countries
<p>Abstract</p> <p>Background</p> <p>The Educational Needs Assessment Tool (the ENAT) is a 39-item patient questionnaire originally developed in the UK to assess educational needs of patients with rheumatoid arthritis (RA). The objective of this study was to assess the cross-cultural validity of the ENAT in 7 European countries.</p> <p>Methods</p> <p>The ENAT was translated into Dutch, Finnish, Norwegian, Portuguese, Spanish and Swedish versions by using Beaton's cross-cultural adaptation process, and was completed by a convenience sample of patients with RA in each country. The generated country-specific data were assessed for construct validity and were then pooled and assessed for cross-cultural invariance using Rasch analysis.</p> <p>Results</p> <p>Individual country-specific analysis showed adequate fit to the Rasch model after adjustment for local dependency within domains. When data from the different countries were pooled, the 39 items deviated significantly from Rasch model's expectations (X<sup>2 </sup>= 977.055, DF = 351, p = 0.000, PSI = 0.976). Again, most items within domains were found to be locally dependent, significantly affecting the fit. Consequently each domain was treated as a unit (i.e. testlet) and the ENAT was re-analysed as a seven-testlet scale resulting into a good fit to the Rasch model (X<sup>2 </sup>= 71.909; DF = 63; p = 0.207, PSI = 0.951). A test of strict unidimensionality confirmed that all domains contributed to measuring a single construct. Cross-cultural non-invariance was discounted by splitting domains for DIF maintaining an excellent fit to the Rasch model. This allowed calibration of the ENAT into an interval scale.</p> <p>Conclusion</p> <p>The ENAT is a simple tool, which is a valid measure of educational needs of people with RA. Adjustment for cross-cultural non-invariance is available if data from the 7 European countries are to be pooled or compared.</p
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