5,540 research outputs found
Generalized Multivariate Extreme Value Models for Explicit Route Choice Sets
This paper analyses a class of route choice models with closed-form
probability expressions, namely, Generalized Multivariate Extreme Value (GMEV)
models. A large group of these models emerge from different utility formulas
that combine systematic utility and random error terms. Twelve models are
captured in a single discrete choice framework. The additive utility formula
leads to the known logit family, being multinomial, path-size, paired
combinatorial and link-nested. For the multiplicative formulation only the
multinomial and path-size weibit models have been identified; this study also
identifies the paired combinatorial and link-nested variations, and generalizes
the path-size variant. Furthermore, a new traveller's decision rule based on
the multiplicative utility formula with a reference route is presented. Here
the traveller chooses exclusively based on the differences between routes. This
leads to four new GMEV models. We assess the models qualitatively based on a
generic structure of route utility with random foreseen travel times, for which
we empirically identify that the variance of utility should be different from
thus far assumed for multinomial probit and logit-kernel models. The expected
travellers' behaviour and model-behaviour under simple network changes are
analysed. Furthermore, all models are estimated and validated on an
illustrative network example with long distance and short distance
origin-destination pairs. The new multiplicative models based on differences
outperform the additive models in both tests
The effect of context on third parties and third-party support in the United States
The dissertation explores third parties from a contextual perspective, moving away from the traditional view of third party support as being merely the product of anti-party or anti-system sentiment. I study how context affects third party support in modern presidential elections, the development of third party voting in the 1800s through an empirical case study of Vermont from 1841-1854, and third party behavior in an electoral context that allows cross-endorsements (fusion balloting)
Conflict and the City: How Newspapers Deal with Local Political Conflict
While the study of the media and politics has become important to the discipline, little is know about how local political issues are depicted by newspapers. Building a theory derived from the communications and political science literature, the political and demographic environment of a city should shape the reporting of local political conflict in newspapers. Using an original data set, the results empirically confirm some aspects of the existing literature while offering new insights into the exact mechanisms behind the reporting of local political conflict
<i>In situ</i> investigation of controlled polymorphism in mechanochemistry at elevated temperatureâ
Mechanochemistry routinely provides solid forms (polymorphs) that are difficult to obtain by conventional solution-based methods, making it an exciting tool for crystal engineering. However, we are far from identifying the full scope of mechanochemical strategies available to access new and potentially useful solid forms. Using the model organic cocrystal system of nicotinamide (NA) and pimelic acid (PA), we demonstrate with variable temperature ball milling that ball milling seemingly decreases the temperature needed to induce polymorph conversion. Whereas Form I of the NA:PA cocrystal transforms into Form II at 90 °C under equilibrium conditions, the same transition occurs as low as 65 °C during ball milling: a ca 25 °C reduction of the transition temperature. Our results indicate that mechanical energy provides a powerful control parameter to access new solid forms under more readily accessible conditions. We expect this âthermo-mechanicalâ approach for driving polymorphic transformations to become an important tool for polymorph screening and manufacturing
The Effect of Cataract Surgery on Circadian Photoentrainment A Randomized Trial of Blue-Blocking versus Neutral Intraocular Lenses
PurposeCataract decreases blue light transmission. Because of the selective blue light sensitivity of the retinal ganglion cells governing circadian photoentrainment, cataract may interfere with normal sleepâwake regulation and cause sleep disturbances. The purpose was to investigate the effect of cataract surgery on circadian photoentrainment and to determine any difference between blue-blocking and neutral intraocular lenses (IOLs).DesignThe study was a single-center, investigator-driven, double-masked, block-randomized clinical trial.ParticipantsOne eye in 76 patients with bilateral age-related cataract eligible for cataract surgery was included.MethodsIntervention was cataract surgery by phacoemulsification. Patients were randomized to receive a blue-blocking or neutral IOL.Main Outcome MeasuresPrimary outcome was activation of intrinsic photosensitive ganglion cells using post-illumination pupil response (PIPR) to blue light from 10 to 30 seconds after light exposure as a surrogate measure. Secondary outcomes were circadian rhythm analysis using actigraphy and 24-hour salivary melatonin measurements. Finally, objective and subjective sleep quality were determined by actigraphy and the Pittsburgh Sleep Quality Index.ResultsThe blue light PIPR increased 2 days (17%) and 3 weeks (24%) after surgery (P < 0.001). The majority of circadian and sleep-specific actigraphy parameters did not change after surgery. A forward shift of the circadian rhythm by 22 minutes (PÂ = 0.004) for actigraphy and a tendency toward an earlier melatonin onset (PÂ = 0.095) were found. Peak salivary melatonin concentration increased after surgery (PÂ = 0.037). No difference was detected between blue-blocking and neutral IOLs, whereas low preoperative blue light transmission was inversely associated with an increase in PIPR (PÂ = 0.021) and sleep efficiency (PÂ = 0.048).ConclusionsCataract surgery increases photoreception by the photosensitive retinal ganglion cells. Because of inconsistency between the significant findings and the many parameters that were unchanged, we can conclude that cataract surgery does not adversely affect the circadian rhythm or sleep. Longer follow-up time and fellow eye surgery may reveal the significance of the subtle changes observed. We found no difference between blue-blocking and neutral IOLs, and, because of the minor effect of surgery in itself, an effect of IOL type seems highly unlikely
High immunogenicity of virus-like particles (VLPs) decorated with Aeromonas salmonicida VapA antigen in rainbow trout
The Gram-negative bacterium A. salmonicida is the causal agent of furunculosis and used to be one of the most loss-causing bacterial infections in the salmonid aquaculture industry with a mortality rate of about 90% until the 1990s, when an inactivated vaccine with mineral oil as adjuvant was successfully implemented to control the disease. However, the use of this vaccine is associated with inflammatory side effects in the peritoneal cavity as well as autoimmune reactions in Atlantic salmon, and incomplete protection has been reported in rainbow trout. We here aimed at developing and testing a recombinant alternative vaccine based on virus-like particles (VLPs) decorated with VapA, the key structural surface protein in the outer A-layer of A. salmonicida. The VLP carrier was based on either the capsid protein of a fish nodavirus, namely red grouper nervous necrotic virus (RGNNV) or the capsid protein of Acinetobacter phage AP205. The VapA and capsid proteins were expressed individually in E. coli and VapA was fused to auto-assembled VLPs using the SpyTag/SpyCatcher technology. Rainbow trout were vaccinated/immunized with the VapA-VLP vaccines by intraperitoneal injection and were challenged with A. salmonicida 7 weeks later. The VLP vaccines provided protection comparable to that of a bacterin-based vaccine and antibody response analysis demonstrated that vaccinated fish mounted a strong VapA-specific antibody response. To our knowledge, this is the first demonstration of the potential use of antigen-decorated VLPs for vaccination against a bacterial disease in salmonids
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