The Union Wage Effect Re-Examined

La raison première de cet article provient d'une étude d'Ashenfelter et de Johnson (1972) dans laquelle ils énonçaient ce qui suit: 1° le modèle simple d'équation salariale, typiquement utilisée pour mesurer l'effet des syndicats sur les salaires, est inexact à cause de la présence de variables endogènes parmi les variables explicatives; 2° l'effet présumé des syndicats sur les salaires est de peu d'importance et sans signification quand il est obtenu à partir d'un modèle d'équation simultanée plus précis. Les résultats de notre étude confirment la première proposition, mais ils démontrent la fausseté de la seconde.Nous avons trouvé une preuve solide de dépendance réciproque entre le taux des salaires et deux de ses variables explicatives, soit la présence de syndicats et la qualité du travail. Cependant, le fait de tenir compte de cette double dépendance ne réduit pas l'effet présumé de l'existence des syndicats à néant. Au contraire, nous persistons à déceler que les salaires conventionnels ont un effet considérable etsignificatif. Les résultats de notre évaluation indiquent que le salaire moyen des travailleurs de la production dans les industries manufacturières est supérieur à 4.2 pour cent en regard d'une différence de 0.10 dans le degré de pénétration syndicale (celle-ci étant la proportion de tous les travailleurs de la production liés par une convention collective de travail). Les résultats que nous avons obtenus indiquent aussi une différence de 51 pour cent entre les salaires conventionnels et les autres, mais l'exactitude de cette estimation dépend, et cela d'une façon décisive, de l'exactitude avec laquelle nous pouvons établir le salaire moyen dans une industrie où il n'y a pas de syndicat. Parce que notre échantillon n'inclut pas de telles industries et ne contient en réalité que trois industries (sur 40) où le taux de syndicalisation est inférieur à 50 pour cent, nous avons peu de confiance dans notre estimation pour la différence d'ensemble.Les résultats d'une évaluation supplémentaire ont été obtenus dans un effort pour découvrir les raisons d'estimations disparates de l'effet du salaire conventionnel dans la présente étude et dans des études antérieures aux États-Unis et au Canada. Quoique ces résultats ne soient pas bien précis, il semble que les différences dans la spécification du modèle, les industries sélectionnées et l'ampleur de l'échantillon peuvent tous en être responsables. Cependant, les résultats auxquels nous sommes arrivés étaient solides dans toutes les expérimentations variées que nous avons tentées. Nous soupçonnons, bien que nous n'ayons pu le vérifier à partir des données dont nous disposions, que la cause principale de la disparité dans les estimations de l'effet du salaire conventionnel obtenues jusqu'ici réside dans les différents niveaux d'agrégation sur lesquels les diverses évaluations ont été fondées.In this paper, the authors extend the literature on union wage effect in two ways. They use aggregate industry data in a simultaneous-equations model to provide an estimate for the union wage effect in Canada which recognizes the endogenity of union coverages. And they suggest a possible cause for the difference in results obtained for the U.S. by Ashenfelter and Johnson, on the one hand, and Kahn on the other

The treatment of mixing in core helium burning models - I. Implications for asteroseismology

The detection of mixed oscillation modes offers a unique insight into the internal structure of core helium burning (CHeB) stars. The stellar structure during CHeB is very uncertain because the growth of the convective core, and/or the development of a semiconvection zone, is critically dependent on the treatment of convective boundaries. In this study we calculate a suite of stellar structure models and their non-radial pulsations to investigate why the predicted asymptotic g-mode $\ell = 1$ period spacing $\Delta\Pi_1$ is systematically lower than is inferred from Kepler field stars. We find that only models with large convective cores, such as those calculated with our newly proposed "maximal-overshoot" scheme, can match the average $\Delta\Pi_1$ reported. However, we also find another possible solution that is related to the method used to determine $\Delta\Pi_1$: mode trapping can raise the observationally inferred $\Delta\Pi_1$ well above its true value. Even after accounting for these two proposed resolutions to the discrepancy in average $\Delta\Pi_1$, models still predict more CHeB stars with low $\Delta\Pi_1$ ($< 270$ s) than are observed. We establish two possible remedies for this: i) there may be a difficulty in determining $\Delta\Pi_1$ for early CHeB stars (when $\Delta\Pi_1$ is lowest) because of the effect that the sharp composition profile at the hydrogen burning shell has on the pulsations, or ii) the mass of the helium core at the flash is higher than predicted. Our conclusions highlight the need for the reporting of selection effects in asteroseismic population studies in order to safely use this information to constrain stellar evolution theory.Comment: 24 pages. 24 figures. Published in MNRA

perms: Marginal likelihood estimation for binary Bayesian nonparametric models in Python and R

Binary responses arise in a multitude of statistical problems, including binary classification, bioassay, current status data problems and sensitivity estimation. There has been an interest in such problems in the Bayesian nonparametrics community since the early 1970s, but inference given binary data is intractable for a wide range of modern simulation-based models, even when employing MCMC methods. Recently, Christensen (2023) introduced a novel simulation technique based on counting permutations, which can estimate both posterior distributions and marginal likelihoods for any model from which a random sample can be generated. However, the accompanying implementation of this technique struggles when the sample size is too large (n > 250). Here we present perms, a new implementation of said technique which is substantially faster and able to handle larger data problems than the original implementation. It is available both as an R package and a Python library. The basic usage of perms is illustrated via two simple examples: a tractable toy problem and a bioassay problem. A more complex example involving changepoint analysis is also considered. We also cover the details of the implementation and illustrate the computational speed gain of perms via a simple simulation study

Translating the fabrication of protein loaded poly(lactic-co-glycolic acid) nanoparticles from bench to scale-independent production using microfluidics

In the formulation of nanoparticles, poly(lactic-co-glycolic acid) (PLGA) is commonly employed due to its Food and Drug Administration and European Medicines Agency approval for human use, its ability to encapsulate a variety of moieties, its biocompatibility and biodegradability and its ability to offer a range of controlled release profiles. Common methods for the production of PLGA particles often adopt harsh solvents, surfactants/stabilisers and in general are multi-step and time-consuming processes. This limits the translation of these drug delivery systems from bench to bedside. To address this, we have applied microfluidic processes to develop a scale-independent platform for the manufacture, purification and monitoring of nanoparticles. Thereby, the influence of various microfluidic parameters on the physicochemical characteristics of the empty and the protein-loaded PLGA particles was evaluated in combination with the copolymer employed (PLGA 85:15, 75:25 or 50:50) and the type of protein loaded. Using this rapid production process, emulsifying/stabilising agents (such as polyvinyl alcohol) are not required. We also incorporate in-line purification systems and at-line particle size monitoring. Our results demonstrate the microfluidic control parameters that can be adopted to control particle size and the impact of PLGA copolymer type on the characteristics of the produced particles. With these nanoparticles, protein encapsulation efficiency varies from 8 to 50% and is controlled by the copolymer of choice and the production parameters employed; higher flow rates, combined with medium flow rate ratios (3:1), should be adopted to promote higher protein loading (% wt/wt). In conclusion, herein, we outline the process controls for the fabrication of PLGA polymeric nanoparticles incorporating proteins in a rapid and scalable manufacturing process. [Figure not available: see fulltext.]

Analysis of the internal heat losses in a thermoelectric generator

A 3D thermoelectric numerical model is used to investigate different internal heat loss mechanisms for a thermoelectric generator with bismuth telluride p- and n-legs. The model considers all thermoelectric effects, temperature dependent material parameters and simultaneous convective, conductive and radiative heat losses, including surface to surface radiation. For radiative heat losses it is shown that for the temperatures considered here, surface to ambient radiation is a good approximation of the heat loss. For conductive heat transfer the module efficiency is shown to be comparable to the case of radiative losses. Finally, heat losses due to internal natural convection in the module is shown to be negligible for the millimetre sized modules considered here. The combined case of radiative and conductive heat transfer resulted in the lowest efficiency. The optimized load resistance is found to decrease for increased heat loss. The leg dimensions are varied for all heat losses cases and it is shown that the ideal way to construct a TEG module with minimal heat losses and maximum efficiency is to either use a good insulating material between the legs or evacuate the module completely, and use small and wide legs closely spaced.Comment: 11 pages, 9 figure

Effects of Graded Levels of Dietary Lasalocid on Performance of Holstein Cows During Early Lactation

Thirty-six multiparous Holstein cows were assigned to one of three dietary levels of lasalocid· 0, 180, or 360 mg/hd/d in a completely randomized design Cows were assigned to treatments I wk postcalving and remained on treatment until II wk postcalving Basal diets were composed of ground corn, alfalfa hay, alfalfa haylage, corn silage, and soybean meal, fortified with vitamins and minerals as needed. All ingredients were ground and fed as a total mixed ration Daily rations were fed in two equal portions at 0500 and I 700 h at a rate to allow a 5- 10% refusal. Daily measurements included milk production and dry matter intake (OM 1). Milk composition (fat, protein, and somatic ii cells) was analyzed twice per week on Tuesdays and Fridays. Cow body weight (BW) and visual body condition were measured weekly. Production during previous lactation was used as a covariate in analyzing the data. Although milk production was not affected by dietary treatment, lasalocid tended to increase daily milk production by approximately 2.5 kg/d (P 13) at both the 180 and 360 mg/hd/d levels Percent milk fat and protein were not afl\u27ected by dietary lasalocid (P 84 and 78, respectively). Somatic cell count of the milk was not affected by dietary lasalocid (/\u27 17). Dietary lasalocid reduced DMI by approximately I 5 kg/d at both the 180 and 360 mg/hdld levels (P .02). At the 180 and 360 mg/hdld levels, lasalocid increased amount of milk produced per kg of DM consumed by 16 kg (I\u27 08). either BW (P 89) nor body condition (P = 90) were affected by dietary lasalocid at either level. No effect of treatments was observed on blood metabolites Glucose, nonesterified fatty acids, P-hydroxybutyrate, and cholesterol all tell within the normal ranges of blood serum