Edgeworth Corrections for Realized Volatility

The quality of the asymptotic normality of realized volatility can be poor if sampling does not occur at very high frequencies. In this article we consider an alternative approximation to the finite sample distribution of realized volatility based on Edgeworth expansions. In particular, we show how confidence intervals for integrated volatility can be constructed using these Edgeworth expansions. The Monte Carlo study we conduct shows that the intervals based on the Edgeworth corrections have improved properties relatively to the conventional intervals based on the normal approximation. Contrary to the bootstrap, the Edgeworth approach is an analytical approach that is easily implemented, without requiring any resampling of one's data. A comparison between the bootstrap and the Edgeworth expansion shows that the bootstrap outperforms the Edgeworth corrected intervals. Thus, if we are willing to incur in the additional computational cost involved in computing bootstrap intervals, these are preferred over the Edgeworth intervals. Nevertheless, if we are not willing to incur in this additional cost, our results suggest that Edgeworth corrected intervals should replace the conventional intervals based on the first order normal approximation.     

Multivariate Kendall's tau for change‐point detection in copulas

Statistical procedures for the detection of a change in the dependence structure of a series of multivariate observations are studied in this work. The test statistics that are proposed are $L_1$ , $L_2$ , and $L_{\infty }$ distances computed from vectors of differences of Kendall's tau; two multivariate extensions of Kendall's measure of association are used. Since the distributions of these statistics under the null hypothesis of no change depend on the unknown underlying copula of the vectors, a procedure based on the multiplier central limit theorem is used for the computation of p‐values; the method is shown to be valid both asymptotically and for moderate sample sizes. Alternative versions of the tests that take into account possible breakpoints in the marginal distributions are also investigated. Monte Carlo simulations show that the tests are powerful under many scenarios of change‐point. In addition, two estimators of the time of change are proposed and their efficiency is carefully studied. The methodologies are illustrated on simulated series from the Canadian Regional Climate Model. The Canadian Journal of Statistics 41: 65–82; 2013 © 2012 Statistical Society of Canada     

Developing an Index to Measure Sub-municipal Level Urban Sprawl

The present study aims to develop an index composed of different spatial variables to measure the urban sprawl levels of a municipality located in Southern Spain. According to the findings, urban sprawl can be measured not only on the metropolitan level but also on a more detailed and precise level, such as sub-municipal. A group of experts chosen for their suitability in measuring urban sprawl select six spatial variables (population density, net residential density, coverage ratio, land use types, percentage of residential land use, and average year of construction). These variables are aggregated using Choquet integral, a technique that combines interactions between those variables providing greater coherence to the complexity that is inherent in the creation of composite sprawl indexes. This methodology has been demonstrated to be valid and appropriate in evaluating urban expansion at sub-municipal level, but can also be applied to other scales once it is clearly a phenomenon in which interaction between criteria exists. The resulting composite index allows the assignment of different levels of sprawl to the urban areas consistent with their morphology and landscape.     

Relational sociology,pragmatism, transactions and social fields

Starting from the idea that relational sociology has been founded on various and incompatible social ontologies, I argue that it is at risk of losing its raison d'être if we do not answer two fundamental practical and ontological questions: (1) Why do we need relational sociology? and (2) What do we study in relational sociology? In this respect, I propose a deep, transactional sociology partly and freely inspired by the work of J. Dewey which clearly detaches relational sociology from social determinism and co-determinism.     

Collaboration, (Dis)trust and Control in Brazilian Manufactured Public/Non-profit Partnerships

This study seeks to evaluate whether interorganizational trust and interpersonal trust influence the nature of state control in Brazilian public/non-profit partnerships (PNPs) by considering the social organization model with a non-profit partner that did not evolve organically from civil society as an equal and interdependent partner but instead was engineered by the state. We conducted qualitative research on two PNPs and analysed their historical trajectories through participant observation, documentary analysis and semi-structured interviews with the state and non-profit partners as well as other actors involved indirectly in the PNPs. Our findings call into question the assumption of current studies that trust tends to be built over time and reveal that PNPs embedded in state-dominant and low-social-capital contexts are more vulnerable to the effects of interpersonal trust. This vulnerability influences the volatile patterns of the PNPs’ trajectories and leads to strong informal state-partner control as reflected by PNP disruptions and lower levels of interorganizational trust.

     

Securing Aquaculture‐Related Resources through Social Interaction in the Pampanga River Delta,Philippines: An Ethnogeographic Perspective on the Strengths and Pitfalls of Social Capital

Social relationships play a pivotal role in agricultural systems because they influence the economic behavior of stakeholders, but sociological studies aimed at understanding these links have until now not focused much on aquaculture. Here we examine how social capital among communities of the Pampanga River delta in the Philippines plays out in the conduct of aquatic livestock breeding, harvesting, and trading, and how it either facilitates or restrains the transformation of individual livelihoods. Relying on a mixed method of field surveys, participant observation, and questionnaires, we construct an ethnographic portrayal of how the main categories of stakeholder involved in aquaculture (from livestock producers to traders via landless gleaners) elaborate strategies to access or control aquaculture‐related resources. We show that the bonding and bridging efforts to construct social capital are strongly embedded in the cultural matrix, and that they are limited by environmental constraints (ecosystem carrying capacity, exposure to natural hazards) and shaped by historical legacies. The resulting pattern of social interactions is overall successful at buffering the negative impact of external forcing factors such as environmental hazards and global market crashes, but we also show how the different outcomes of social exchange are nonetheless unevenly distributed across the spectrum of stakeholders.     

Association between sarcopenia and erectile dysfunction in males with type II diabetes mellitus

Background: The prevalence rates for both sarcopenia and erectile dysfunction (ED) gradually increase in middle-aged and elderly diabetic male population and they impair physical functioning, sexual functioning, and quality of life. The aim of the present study was to evaluate the sarcopenia in patients with diabetic ED.

Methods: The study included 98 male patients with type II diabetes mellitus (DM) aged 18–80?years. Blood chemistry and hormone levels were obtained. The International Index of Erectile Function (IIEF-5) questionnaire was administered to the patients. The patients were divided into three groups according to the IIEF-5 score; a score of 5–10 points indicated severe ED, a score of 11–20 indicated moderate ED, and a score of 21–25 points indicated no ED. The muscle mass, handgrip strength, timed up and go test, upper mid-arm circumference, calf circumference, and body mass index were obtained. The statistical analysis was performed using MedCalc Statistical Software version 12.7.7. All parameters were compared between the three groups.

Results: Of 98 patients included in the study, 84 patients had severe sarcopenia, 13 had moderate sarcopenia, while only one patient had normal muscle mass. The mean age was 56.59?±?11.46?years. When patients were divided into three groups according to IIEF-5 score, 38 had severe ED, 39 had moderate ED, and 21 had no ED. There was a significant difference between the three groups in terms of handgrip strength, timed up and go test scores, upper mid-arm circumference, and calf circumference (p?Conclusions: Although muscle mass remains unchanged, muscle strength and physical performance decrease in diabetic ED patients. Diabetic patients with severe and moderate ED have lower muscle strength and physical performance.     

Do downward private transfers enhance maternal labor supply? Evidence from around Europe

Using data on 2,317 mother–daughter pairs from 10 European countries, we investigate the impact of downward time and monetary transfers on the career choices of transfer-receiving young mothers. For Europe as a whole, we find a strong positive effect of grandchild care on the labor force participation and the degree of labor market involvement of the young mother, but no impact of monetary transfers on either of these decisions. Both recipients and donors with better endowments are more likely to participate in a monetary transaction, while mothers with lower level of human capital are more likely to provide time transfers to their better endowed daughters.     

What motivates adolescent bystanders to intervene when immigrant youth are bullied?

Pathways to bystander responses were examined in both generalized and bias-based bullying incidents involving immigrant-origin victims. Participants were 168 (M_age = 14.54, 57% female) adolescents of immigrant (37.5%) and nonimmigrant backgrounds, who responded to their likelihood of intervening on behalf of either an Arab or Latine victim. Models tested whether contact with immigrants and one's desires for social contact with immigrant-origin peers mediated the effects of individual (shared immigrant background, and discriminatory tendencies) and situational (inclusive peer norms) intergroup factors on active bystander responses. Findings indicated that desires for social contact reliably mediated effects across both victims; however, contact with immigrant peers was only associated with responses to Latine victims. Implications for how to promote bystander intervention are discussed.