Estimation of multivariate probit models by exact maximum likelihood

In this paper, we develop a new numerical method to estimate a multivariate probit model. To this end, we derive a new decomposition of normal multivariate integrals that has two appealing properties. First, the decomposition may be written as the sum of normal multivariate integrals, in which the highest dimension of the integrands is reduced relative to the initial problem. Second, the domains of integration are bounded and delimited by the correlation coefficients. Application of a Gauss-Legendre quadrature rule to the exact likelihood function of lower dimension allows for a major reduction of computing time while simultaneously obtaining consistent and efficient estimates for both the slope and the scale parameters. A Monte Carlo study shows that the finite sample and asymptotic properties of our method compare extremely favorably to the maximum simulated likelihood estimator in terms of both bias and root mean squared error.Multivariate Probit Model, Simulated and Full Information Maximum Likelihood, Multivariate Normal Distribution, Simulations

Physicians' working practices : target income, altruistic objectives or a maximization problem ?

In traditional literature, a number of authors posit that physicians, like a consumer or a firm, adopt maximization behavior, while others claim that they are motivated by the attainment of a target income. These three approaches may seem contradictory, yet the present study aims to show that they are in fact complementary. This paper aims to highlight the overlapping of these approaches by using a theoretical model - the agent model. From this model, we deduce the income effect, the individualistic substitution effect, the monopolistic effect and their respective elasticities to detect target income behavior. We develop also two theoretical models of leisure and income renouncement to determine the priority which the physician gives to consumption and leisure. Unlike other models, our results show that about 20% of physicians prefer to reach an altruistic objective rather than a leisure or an target income. These last result implies a ranking of target priorities. Moreover, we observe that the Slutsky relation cannot be used to determine individualistic substitution, monopolistic substitution and income effects exactly when leisure is an inferior good. Nor can we confirm the adoption of a target income behavior when income and monopolistic elasticities are negative. Renouncement models indicate that between 60% and 67% of GPs have a clear consumption priority and that they accept a renouncement of their leisure in order to maintain their current level of income. Our results demonstrate that it would be necessary to introduce monopolistic power of physicians and their altruistic priority to test inducement demand.

Medicaid spending burden among beneficiaries with treatment-resistant depression.

AIM: To evaluate Medicaid spending and healthcare resource utilization (HRU) in treatment-resistant depression (TRD). MATERIALS & METHODS: TRD beneficiaries were identified from Medicaid claims databases (January 2010-March 2017) and matched 1:1 with major depressive disorder (MDD) beneficiaries without TRD (non-TRD-MDD) and randomly selected patients without MDD (non-MDD). Differences in HRU and per-patient-per-year costs were reported in incidence rate ratios (IRRs) and cost differences (CDs), respectively. RESULTS: TRD beneficiaries had higher HRU than 1:1 matched non-TRD-MDD (e.g., inpatient visits: IRR = 1.41) and non-MDD beneficiaries (N = 14,710 per cohort; e.g., inpatient visits: IRR = 3.42, p \u3c 0.01). TRD beneficiaries incurred greater costs versus non-TRD-MDD (CD = US$4382) and non-MDD beneficiaries (CD = US$8294; p \u3c 0.05). CONCLUSION: TRD is associated with higher HRU and costs versus non-TRD-MDD and non-MDD. TRD poses a significant burden to Medicaid

The effect of non-medical factors on variations in the performance of colonoscopy among different health care settings

Background: Previous studies in the literature have shown significant variations in colonoscopy performance, even when medical factors are taken into account. This study aimed to examine the role of non-medical factors (i.e. embodied in health care system design) as possible contributors to variations in colonoscopy performance. Methods: We used patient data from a multicenter observational study conducted between 2000 and 2002 in 21 centers across 11 western countries. Variability was captured through two performance outcomes (diagnostic yield and colonoscopy withdrawal time), jointly studied as dependent variables using a multilevel two-equation system. Results: Results showed that open-access systems and high-volume colonoscopy centers were independently associated with a higher likelihood of detecting significant lesions and higher withdrawal durations. Fee for service (FFS) payment was associated with shorter withdrawal durations, and had an indirect negative impact on the diagnostic yield. Teaching centers exhibited lower detection rates and higher withdrawal times. Conclusions: Our results suggest that gate-keeping colonoscopy is likely to miss patients with significant lesions and that developing specialized colonoscopy units is important to improve performance. Results also suggest that FFS may result in a lower quality of care in colonoscopy practice and highlight that longer withdrawal times do not necessarily mean higher quality in teaching-centers.Medical Practice Variation (MPV), performance, non-medical factors, panel two-equation linear-probit model, colonoscopy

Engineering xylose metabolism in Thraustochytrid T18

Thraustochytrids spp are oleaginous marine protists with significant potential for biofuel production at industrial levels; however, the cost of feedstocks has been a major challenge in making this process economical. On a quest for cheaper and renewable feedstocks, we investigated the ability of Thraustochytrid strain T18 to grow in the presence of xylose and demonstrated its ability to produce xylitol. However, genome sequencing and in vivo enzymatic assays revealed the presence of a xylose isomerase which indicates there are two xylose metabolism pathways in Thraustochytrid T18: a xylose reductase/xylitol dehydrogenase pathway as well as an isomerase pathway. Characterization of the two native pathways suggested that xylitol production is a bottleneck to T18 xylose metabolism. Through various strain improvement strategies, including over-expression of the endogenous xylose isomerase and heterologous xylulose kinases, we enhanced xylose usage while reducing xylitol production by \u3e50% and 80%, respectively, compared to wild-type. Highest levels of xylose metabolism were obtained through selection of strains possessing multiple copies of the transgenes. The xylose usage of the best xylose metabolizing isolate was further validated through fermentation. These newly engineered strains pave the way to using T18 for biofuel production using hemicellulosic feedstock

A global review of green turtle diet: sea surface temperature as a potential driver of omnivory levels

To better understand dietary requirements, trophic shifts, and trophic interactions of the threatened green turtle (Chelonia mydas), we conducted a comprehensive global review and literature tabulation (177 studies) reporting diets of individuals & 25 cm carapace length. We analysed those studies involving natural sites and healthy animals that reported relative proportions of all diet components (67 studies, 89 datasets at 75 sites, 13 geographic sub-regions, 3 oceans). We compared diets by sub-region and foraging site relative to four diet components, i.e., seagrass, macroalgae, terrestrial plants (including mangroves) and animal matter. To assess sea surface temperature (SST) as an environmental driver, values were extracted from satellite data (single year) and site-specific observations (study durations) and examined relative to diet composition. Satellite data indicated that at warmer sites with temperatures & 25 °C (≥ 6 months annually), diet was predominantly herbivorous (mean = 92.97%; SE = 9.85; n = 69 datasets). At higher latitude sites and in cold-water currents with SST & 20 °C (≥ 6 months annually), dietary animal matter featured prominently (mean = 51.47%; SE = 4.84; n = 20 datasets). Site-specific observations indicated that SST had a small but significant effect on contributions of animal matter (r2 = 0.17, P =  & 0.001) and seagrass (r2 = 0.24, P =  & 0.001) but not macroalgae and terrestrial plants. Our study presents the first quantitative evidence at a global scale that temperature may be an important driver of omnivory, providing a new perspective on variations in green turtle diet, especially in light of global warming and climate change

Green turtle diet is dominated by seagrass in the Western Indian Ocean except amongst gravid females

Green turtles (Chelonia mydas) are key herbivores of tropical and subtropical neritic habitats and play a major role in structuring seagrass meadows. We present the first detailed assessment of green turtle diet in the Western Indian Ocean using the gut contents of salvaged animals from three atolls in the Republic of Seychelles separated from each other by 400-825 km: Cosmoledo (adults, n=12), Farquhar (adults, n=33; immature, n=1) collected in 1982-1983; and Desroches (immatures, n=8) in 2016-2018. We report the first comparison of the diets of gravid females (n=17), males (n=26) and non-breeding females (n=2) at sites providing both foraging and breeding habitat. Seagrass (mostly Thalassodendron ciliatum) dominated the diet, accounting for 95% of the mean gut content biomass for males and non-breeding females but only 58% for gravid females, alongside relatively large amounts of substrate (14%) and macroalgae (13%). Satellite tracking of post-nesting green turtles from Chagos Archipelago in 2016 located foraging sites at Farquhar Atoll that coincided with capture locations of 26 of the 33 adult turtles sampled there in 1983. In situ surveys of those sites in 2018 revealed extensive nearly monospecific beds of T. ciliatum. The prominence of seagrass in the diet of green turtles and connectivity between foraging and nesting habitats throughout the region illustrate the need to conserve and monitor seagrass habitats of the Western Indian Ocean especially in the context of changing green turtle population densities

The role of the Eurasian wheat belt to regional and global food security

Food security remains to be a major societal concern. In the light of the current expectations of population growth, world food production has to be massively increased to sustain the associated food demand rise. While agricultural productivity was rising during recent decades in the US, Europe and also in some developing countries, the corresponding growth rates lately appeared to be slowing down. In fact, the only world region with a significant amount of arable land, which currently is not under cultivation and which at the same time is, moreover, experiencing rising productivity figures, is the so called 'Eurasian wheat belt', comprising of Russia, Ukraine, Kazakhstan and the Central Asian countries, namely Uzbekistan, Tajikistan, Turkmenistan, and Kirgizstan. In this light, the Joint Research Centre and the Directorate-General for Agriculture and Rural Development organized a thematic workshop, held during 20 – 22 May 2014 in Istanbul/Turkey, set up to bring experts on the matter together and to discuss to what extent these countries could play a role for regional and international food security. Following the workshop analysis and discussion, this report provides a comprehensive technical overview of the wheat production, and the main factors to achieve full production potential across the Eurasian wheat belt with regards to national, regional and global issues of cereal supply and food security in evolving global markets. It reviews key horizontal issues, such as land policy, credit and finance, privatization, farm structures, social consequences of transition, environmental challenges, against the backdrop of agrarian reforms implemented during the transition period. In addition the report explores production potential and corresponding institutional and policy restrictions in a series of Eurasian countries. Finally, the report closes with expert opined policy-relevant conclusions as a basis for policy suggestions and recommendations.JRC.J.4-Agriculture and Life Sciences in the Econom