Copula selection models for non-Gaussian responses that are missing not at random

Missing not at random (MNAR) data poses key challenges for statistical inference because the model of interest is typically not identifiable without imposing further (e.g., distributional) assumptions. Sample selection models have been routinely used for handling MNAR by jointly modelling the outcome and selection variables assuming that these follow a bivariate normal distribution. Recent studies have advocated parametric selection model approaches, for example estimated by multiple imputation and maximum likelihood, that are more robust to departures from the normality assumption. However, the proposed methods have been mostly restricted to a specific joint distribution (e.g., bivariate t-distribution). This paper discusses a flexible copula-based selection approach (which accommodates a wide range of non-Gaussian outcome distributions and offers great flexibility in the choice of functional form specifications for both the outcome and selection equations) and proposes a flexible imputation procedure that generates plausible imputed values from the copula selection model. A simulation study characterises the relative performance of the copula model compared with the most commonly used selection models for estimating average treatment effects with MNAR data. We illustrate the methods in the REFLUX study, which evaluates the causal effect of laparoscopic surgery compared to usual medical management on long-term quality of life in patients with reflux disease. We provide software code for implementing the proposed copula framework using the R package GJRM

Picture Power? The Contribution of Visuals and Text to Partisan Selective Exposure

Today’s high-choice media environment allows citizens to select news in line with their political preferences and avoid content counter to their priors. So far, however, selective exposure research has exclusively studied news selection based on textual cues, ignoring the recent proliferation of visual media. This study aimed to identify the contribution of visuals alongside text in selective exposure to pro-attitudinal, counter-attitudinal and balanced content. Using two experiments, we created a social media-style newsfeed with news items comprising matching and non-matching images and headlines about the contested issues of immigration and gun control in the U.S. By comparing selection behavior of participants with opposing prior attitudes on these topics, we pulled apart the contribution of images and headlines to selective exposure. Findings show that headlines play a far greater role in guiding selection, with the influence of images being minimal. The additional influence of partisan source cues is also considered

Vestiges of an orb-weaving ancestor? The “biogenetic law” and ontogenetic changes in the webs and building behavior of the black widow spider Latrodectus geometricus (Araneae Theridiidae)

Young juveniles of L. geometricus fit the strong trend for “ontogeny to repeat phylogeny” previously documented in other web-building spiders; younger spiders were less likely to build the derived silk retreats that occur at the edges of webs of adults. Younger individuals also consistently builtç more highly organized webs, with radial lines that converge on a central, horizontal disc and that support regularly spaced, sticky “gumfoot” lines. Some details of how radial and gumfoot lines were built suggest that the radial and gumfoot lines and the behavior involved in their construction may be homologous with traits associated with radii and sticky spirals in aranoid orb webs. The numerous convergences between the webs and building behavior of young L. geometricus and the highly modified webs and building behavior of genera of the orb weaving families Theridiosomatidae (Wendilgarda) and Anapidae (Comaroma), which have independently replaced orbs with webs designed to capture prey on surfaces near the web, suggest a new hypothesis for how gumfoot theridiid webs may have evolved from orbs.Smithsonian Tropical Research InstituteUniversidad de Costa RicaUCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Biologí

Incidence of hypohidration in athletes and sedentary male adults with intellectual disability

El presente estudio descriptivo de tipo transversal se diseñó para determinar el nivel de hidratación de deportistas con discapacidad intelectual y su comparación con adultos sedentarios con la misma discapacidad. Participaron 22 deportistas federados que realizan el mismo programa de entrenamiento además de 22 adultos sedentarios ajustados en sexo, edad y cociente de inteligencia. Los parámetros ensayados fueron la densidad urinaria determinada mediante refractómetro así como la ingesta diaria de líquido adlibitum. Este protocolo fue aprobado por un Comité de Ética Institucional. Tan solo 6 deportistas (21,6%) presentaron valores de euhidratación frente a 9 (40,9%) de los participantes sedentarios incluidos en el grupo control. Las únicas diferencias significativas respecto a la ingesta de líquidos se estableció precisamente entre deportistas y sedentarios con euhidratación. Se concluye que los deportistas con discapacidad intelectual se encuentran en riesgo de deshidratación que podría explicarse, al menos en parte, por una insuficiente ingesta hídricaThe current study was designed to determine hydration status of well-trained, male athletes with ID. A secondary purpose was to compare these results with hydration status of sedentary young adults with ID. A total of 22 athletes with ID volunteered for this cross-sectional, descriptive study. The control group included 22, age, sex and IQ-matched sedentary adults with ID. Main outcome measurements were urine specific gravity (USG) and daily fluid intake for three consecutive days. With regard to athletes with ID, it was found that 5 participants (21,7%) stayed significantly hypohydrated, 12 athletes (52,2%) appeared hypohydrated and 6 participants (26,1%) stayed euhydrated. In fact, a significantly lower percentage of athletes was euhydrated when compared to sedentary matched adults with ID (26,1vs.40,9%;χ2=5,67;p<001). In conclusion, athletes with ID are at increased risk of dehydration that may be explained, at least in part, given that ad-libitum fluid consumption was insufficien

Insights on Hydrothermal‐Magmatic Interactions and Eruptive Processes at Poás Volcano (Costa Rica) From High‐Frequency Gas Monitoring and Drone Measurements

n/

Colouration in amphibians as a reflection of nutritional status : the case of tree frogs in Costa Rica

Colouration has been considered a cue for mating success in many species; ornaments in males often are related to carotenoid mobilization towards feathers and/or skin and can signal general health and nutrition status. However, there are several factors that can also link with status, such as physiological blood parameters and body condition, but there is not substantial evidence which supports the existence of these relationships and interactions in anurans. This study evaluated how body score and blood values interact with colouration in free-range Agalychnis callidryas and Agalychnis annae males. We found significant associations between body condition and plasmatic proteins and haematocrit, as well as between body condition and colour values from the chromaticity diagram. We also demonstrated that there is a significant relation between the glucose and plasmatic protein values that were reflected in the ventral colours of the animals, and haematocrit inversely affected most of those colour values. Significant differences were found between species as well as between populations of A. callidryas, suggesting that despite colour variation, there are also biochemical differences within animals from the same species located in different regions. These data provide information on underlying factors for colouration of male tree frogs in nature, provide insights about the dynamics of several nutrients in the amphibian model and how this could affect the reproductive output of the animals

Comparison of breast and bowel cancer screening uptake patterns in a common cohort of South Asian women in England

Background: Inequalities in uptake of cancer screening by ethnic minority populations are well documented in a number of international studies. However, most studies to date have explored screening uptake for a single cancer only. This paper compares breast and bowel cancer screening uptake for a cohort of South Asian women invited to undertake both, and similarly investigates these women's breast cancer screening behaviour over a period of fifteen years. Methods: Screening data for rounds 1, 2 and 5 (1989-2004) of the NHS breast cancer screening programme and for round 1 of the NHS bowel screening pilot (2000-2002) were obtained for women aged 50-69 resident in the English bowel screening pilot site, Coventry and Warwickshire, who had been invited to undertake breast and bowel cancer screening in the period 2000-2002. Breast and bowel cancer screening uptake levels were calculated and compared using the chi-squared test. Results: 72,566 women were invited to breast and bowel cancer screening after exclusions. Of these, 3,539 were South Asian and 69,027 non-Asian; 18,730 had been invited to mammography over the previous fifteen years (rounds 1 to 5). South Asian women were significantly less likely to undertake both breast and bowel cancer screening; 29.9% (n = 1,057) compared to 59.4% (n = 40,969) for non-Asians (p < 0.001). Women in both groups who consistently chose to undertake breast cancer screening in rounds 1, 2 and 5 were more likely to complete round 1 bowel cancer screening. However, the likelihood of completion of bowel cancer screening was still significantly lower for South Asians; 49.5% vs. 82.3% for non-Asians, p < 0.001. South Asian women who undertook breast cancer screening in only one round were no more likely to complete bowel cancer screening than those who decided against breast cancer screening in all three rounds. In contrast, similar women in the non-Asian population had an increased likelihood of completing the new bowel cancer screening test. The likelihood of continued uptake of mammography after undertaking screening in round 1 differed between South Asian religio-linguistic groups. Noticeably, women in the Muslim population were less likely to continue to participate in mammography than those in other South Asian groups. Conclusions: Culturally appropriate targeted interventions are required to reduce observed disparities in cancer screening uptakes

Catastrophizing mediates the relationship between the personal belief in a just world and pain outcomes among chronic pain support group attendees

Health-related research suggests the belief in a just world can act as a personal resource that protects against the adverse effects of pain and illness. However, currently, little is known about how this belief, particularly in relation to one’s own life, might influence pain. Consistent with the suggestions of previous research, the present study undertook a secondary data analysis to investigate pain catastrophizing as a mediator of the relationship between the personal just world belief and chronic pain outcomes in a sample of chronic pain support group attendees. Partially supporting the hypotheses, catastrophizing was negatively correlated with the personal just world belief and mediated the relationship between this belief and pain and disability, but not distress. Suggestions for future research and intervention development are made