Pooling stated and revealed preference data in the presence of RP endogeneity

Pooled discrete choice models combine revealed preference (RP) data and stated preference (SP) data to exploit advantages of each. SP data is often treated with suspicion because consumers may respond differently in a hypothetical survey context than they do in the marketplace. However, models built on RP data can suffer from endogeneity bias when attributes that drive consumer choices are unobserved by the modeler and correlated with observed variables. Using a synthetic data experiment, we test the performance of pooled RP–SP models in recovering the preference parameters that generated the market data under conditions that choice modelers are likely to face, including (1) when there is potential for endogeneity problems in the RP data, such as omitted variable bias, and (2) when consumer willingness to pay for attributes may differ from the survey context to the market context. We identify situations where pooling RP and SP data does and does not mitigate each data source’s respective weaknesses. We also show that the likelihood ratio test, which has been widely used to determine whether pooling is statistically justifiable, (1) can fail to identify the case where SP context preference differences and RP endogeneity bias shift the parameter estimates of both models in the same direction and magnitude and (2) is unreliable when the product attributes are fixed within a small number of choice sets, which is typical of automotive RP data. Our findings offer new insights into when pooling data sources may or may not be advisable for accurately estimating market preference parameters, including consideration of the conditions and context under which the data were generated as well as the relative balance of information between data sources.This work was supported in part by a grant from the Link Foundation, a grant from the National Science Foundation # 1064241 , and a grant from Ford Motor Company. The opinions expressed are those of the authors and not necessarily those of the sponsors.Accepted manuscrip

Selective amplification of scars in a chaotic optical fiber

In this letter we propose an original mechanism to select scar modes through coherent gain amplification in a multimode D-shaped fiber. More precisely, we numerically demonstrate how scar modes can be amplified by positioning a gain region in the vicinity of specific points of a short periodic orbit known to give rise to scar modes

Quaternionic Madelung Transformation and Non-Abelian Fluid Dynamics

In the 1920's, Madelung noticed that if the complex Schroedinger wavefunction is expressed in polar form, then its modulus squared and the gradient of its phase may be interpreted as the hydrodynamic density and velocity, respectively, of a compressible fluid. In this paper, we generalize Madelung's transformation to the quaternionic Schroedinger equation. The non-abelian nature of the full SU(2) gauge group of this equation leads to a richer, more intricate set of fluid equations than those arising from complex quantum mechanics. We begin by describing the quaternionic version of Madelung's transformation, and identifying its ``hydrodynamic'' variables. In order to find Hamiltonian equations of motion for these, we first develop the canonical Poisson bracket and Hamiltonian for the quaternionic Schroedinger equation, and then apply Madelung's transformation to derive non-canonical Poisson brackets yielding the desired equations of motion. These are a particularly natural set of equations for a non-abelian fluid, and differ from those obtained by Bistrovic et al. only by a global gauge transformation. Because we have obtained these equations by a transformation of the quaternionic Schroedinger equation, and because many techniques for simulating complex quantum mechanics generalize straightforwardly to the quaternionic case, our observation leads to simple algorithms for the computer simulation of non-abelian fluids.Comment: 15 page

Archeological Survey Of The Proposed Loop 288 From IH 35E North Of Denton To IH35E At Vintage Boulevard South Of Denton, Denton County, Texas

This report documents the results of an archeological survey conducted on behalf of the Texas Department of Transportation, Dallas District, for proposed construction of a new segment of Loop 288 that would extend from IH 35E north of Denton to IH 35E at Vintage Boulevard south of Denton (CSJs 2250-02-013 and 2250-02-014). The road project involves construction of new location roadway for a distance of approximately eight miles. Archeological work was performed to comply with Section 106 of the National Historic Preservation Act and the Antiquities Code of Texas, under Texas Antiquities Permit 5660. AmaTerra Environmental, Inc. (AmaTerra) personnel conducted an intensive archeological survey of the project area from June 11 to June 17, 2010, to identify possible cultural resources within the Area of Potential Effect (APE). The project area was subject to 100 percent pedestrian survey wherever access to public and private properties was available. Survey included visual inspection of the landscape, 152 shovel test excavations, and excavation of eight backhoe trenches. No archeological sites were identified within the APE, and no artifacts were collected as this was a non-collection survey. Jon J. Dowling served as Project Archeologist and Rachel Feit acted as Principal Investigator. Approximately 224 person-hours were invested in the field investigation. No archeological resources were identified that meet eligibility requirements for designation as a State Archeological Landmark according to 13 Texas Administrative Code 26, or for listing in the National Register of Historic Places under 36 CFR 60.4. Additional work in connection with the proposed undertaking is not recommended. AmaTerra recommends that the proposed project should proceed to completion

Interactions between corticosterone phenotype, environmental stressor pervasiveness and irruptive movement-related survival in the cane toad

© 2018. Published by The Company of Biologists Ltd Animals use irruptive movement to avoid exposure to stochastic and pervasive environmental stressors that impact fitness. Beneficial irruptive movements transfer individuals from high-stress areas (conferring low fitness) to alternative localities that may improve survival or reproduction. However, being stochastic, environmental stressors can limit an animal’s preparatory capacity to enhance irruptive movement performance. Thus individuals must rely on pre-existing, or rapidly induced, physiological and behavioural responses. Rapid elevation of glucocorticoid hormones in response to environmental stressors are widely implicated in adjusting physiological and behaviour processes that could influence irruptive movement capacity. However, there remains little direct evidence demonstrating that corticosterone-regulated movement performance or interaction with pervasiveness of environmental stress, confers adaptive movement outcomes. Here, we compared how movement-related survival of cane toads (Rhinella marina) varied with three different experimental corticosterone phenotypes across four increments of increasing environmental stressor pervasiveness (i.e. distance from water in a semi-arid landscape). Our results indicated that toads with phenotypically increased corticosterone levels attained higher movement-related survival compared with individuals with control or lowered corticosterone phenotypes. However, the effects of corticosterone phenotypes on movement-related survival to some extent co-varied with stressor pervasiveness. Thus, our study demonstrates how the interplay between an individual’s corticosterone phenotype and movement capacity alongside the arising costs of movement and the pervasiveness of the environmental stressor can affect survival outcomes

Driven Morse Oscillator: Model for Multi-photon Dissociation of Nitrogen Oxide

Within a one-dimensional semi-classical model with a Morse potential the possibility of infrared multi-photon dissociation of vibrationally excited nitrogen oxide was studied. The dissociation thresholds of typical driving forces and couplings were found to be similar, which indicates that the results were robust to variations of the potential and of the definition of dissociation rate. PACS: 42.50.Hz, 33.80.WzComment: old paper, 8 pages 6 eps file

Classical and quantum decay of one dimensional finite wells with oscillating walls

To study the time decay laws (tdl) of quasibounded hamiltonian systems we have considered two finite potential wells with oscillating walls filled by non interacting particles. We show that the tdl can be qualitatively different for different movement of the oscillating wall at classical level according to the characteristic of trapped periodic orbits. However, the quantum dynamics do not show such differences.Comment: RevTeX, 15 pages, 14 PostScript figures, submitted to Phys. Rev.

DNA alkylation and interstrand cross-linking by treosulfan

The anti-tumour drug treosulfan (L-threitol 1,4-bismethanesulphonate, Ovastat) is a prodrug for epoxy compounds by converting non-enzymatically to L-diepoxybutane via the corresponding monoepoxide under physiological conditions. The present study supports the hypothesis that this conversion of treosulfan is required for cytotoxicity in vitro. DNA alkylation and interstrand cross-linking of plasmid DNA is observed after treosulfan treatment, but this is again produced via the epoxide species. Alkylation occurs at guanine bases with a sequence selectivity similar to other alkylating agents such as the nitrogen mustards. In treosulfan-treated K562 cells, cross-links form slowly, reaching a peak at approximately 24 h. Incubation of K562 cells with preformed epoxides shows faster and more efficient DNA cross-linking. © 1999 Cancer Research Campaig

A Phenomenological Exploration of Beginning Counselor Educators’ Experiences Developing a Research Agenda

Hermeneutic, phenomenological methodology was used to explore experiences developing a research agenda for five beginning counselor educators. Through in-depth, open-ended interviews, experiences included (a) balance, (b) isolation, and (c) evaluation while references to trusting relationships were manifest across all themes. Recommendations for counselor educators spanning the profession are provided

Reaction rate calculations via transmission coefficients

The transmission coefficient of a wavepacket traversing a potential barrier can be determined by steady state calculations carried out in imaginary time instead of by real time dynamical calculations. The general argument is verified for the Eckart barrier potential by a comparison of transmission coefficients calculated from real and imaginary time solutions of the Schroedinger equation. The correspondence demonstrated here allows a formulation for the reaction rate that avoids difficulties due to both rare events and explicitly time dependent calculations. 5 refs., 2 figs