Hidden Markov mesh random field models in image analysis

This paper addresses the image modeling problem under the assumption that images can be represented by third-order, hidden Markov mesh random field models. The range of applications of the techniques described hereafter comprises the restoration of binary images, the modeling and compression of image data, as well as the segmentation of gray-level or multi-spectral images, and image sequences under the short-range motion hypothesis. We outline coherent approaches to both the problems of image modeling (pixel labeling) and estimation of model parameters (learning). We derive a real-time labeling algorithm-based on a maximum, marginal a posteriori probability criterion-for a hidden third-order Markov mesh random field model. Our algorithm achieves minimum time and space complexities simultaneously, and we describe what we believe to be the most appropriate data structures to implement it. Critical aspects of the computer simulation of a real-time implementation are discussed, down to the computer code level. We develop an (unsupervised) learning technique by which the model parameters can be estimated without ground truth information. We lay bare the conditions under which our approach can be made time-adaptive in order to be able to cope with short-range motion in dynamic image sequences. We present extensive experimental results for both static and dynamic images from a wide variety of sources. They comprise standard, infra-red and aerial images, as well as a sequence of ultrasound images of a fetus and a series of frames from a motion picture sequence. These experiments demonstrate that the method is subjectively relevant to the problems of image restoration, segmentation and modeling.     

Clinical correlates and repetition of self-harming behaviors among female adolescent victims of sexual abuse

This study investigated self-harming behaviors in 149 female adolescent victims of sexual abuse, first, by determining the rates of nine types of self-mutilating behavior at intake and nine months later and, second, by investigating comorbidity of clinical correlates associated with these behaviors. The adolescents were divided into three groups according to level of self-mutilating behavior and then compared on symptom self-reports; 62.1% of the adolescents engaged in at least one self-mutilating behavior. A graded relation was observed between level of self-mutilating behavior and rate, and total number of clinical disorders. At nine month follow-up, one in four teenagers still reported a moderate or high level of self-harm. The need for systematic assessment and intervention of self-mutilating behaviors is discussed.     

Work and mental health: the experience of the Quebec workforce between 1987 and 1998

This study examines the distribution of psychological distress in twelve occupational groups over the decade 1987-1998 in the Quebec workforce. Cross-sectional data from the three phases of the Quebec Health and Social Survey are used with n = 9,450 in 1987, n = 10,947 in 1992 and n = 10,960 in 1998, totalling 31,357 workers aged 15 and over. Occupations are classified according to the Canadian Socio-economic Classification of Occupations. Prevalence estimates for occupational groups are computed and logistic regression analyses are conducted controlling for gender, age and marital status. The results show that the prevalence of workers with psychological distress increased sharply between 1987 and 1992 and declined back in 1998 but still increased compared to 1987. However, only non-qualified white collars, semi-qualified blue collars and male non-qualified blue collars show a significant increment in psychological distress over time. Analysis of the differentials in the prevalence of psychological distress gives greater odds of distress for supervisors, semi-qualified white and blue collar workers compared to upper managers. The odds for occupations are stable over time, gender, age and marital status. The odds of female workers significantly decreased in the three phases. It appears that the restructuring of the work environment and the perturbations in the larger society promoted an increase of psychological distress within definite segments of the workforce. The specific contribution of occupation is limited but supervisors and occupations requiring lower qualifications are more at risk regarding mental health at work.     

On testing for multivariate ARCH effects in vector time series models

Using a spectral approach, the authors propose tests to detect multivariate ARCH effects in the residuals from a multivariate regression model. The tests are based on a comparison, via a quadratic norm, between the uniform density and a kernel‐based spectral density estimator of the squared residuals and cross products of residuals. The proposed tests are consistent under an arbitrary fixed alternative. The authors present a new application of the test due to Hosking (1980) which is seen to be a special case of their approach involving the truncated uniform kernel. However, they typically obtain more powerful procedures when using a different weighting. The authors consider especially the procedure of Robinson (1991) for choosing the smoothing parameter of the spectral density estimator. They also introduce a generalized version of the test for ARCH effects due to Ling & Li (1997). They investigate the finite‐sample performance of their tests and compare them to existing tests including those of Ling & Li (1997) and the residual‐based diagnostics of Tse (2002).Finally, they present a financial application.     

Passion and gambling: on the validation of the Gambling Passion Scale (GPS)

Vallerand and his colleagues (Vallerand & Blanchard, 1999; Vallerand, Blanchard, Koestner, & Gagné, 2001) have recently proposed a new concept of passion. According to these authors, passion refers to a strong inclination toward an activity that we like, find important, and in which we invest time. Vallerand et al. have identified two types of passion: obsessive and harmonious. Obsessive passion refers to an internal pressure that forces an individual to engage in the activity. Harmonious passion, on the other hand, refers to an internal force that leads an individual to choose freely to engage in an activity. While obsessive passion has been shown in some circumstances to lead to negative psychological and physical consequences, harmonious passion generally leads to positive psychological and physical consequences. The purpose of the present research was to validate a measure of passion toward gambling: the Gambling Passion Scale (GPS). The GPS consists of two subscales (obsessive passion and harmonious passion) comprising five items each. Results from two studies involving a total of 340 participants revealed satisfactory internal consistency and temporal stability indices, as well as a two-factor structure supported by exploratory and confirmatory factor analyses. Finally, a series of partial correlational analyses between the two subscales and scales assessing behavioral measures related to gambling supported the construct validity of the GPS. The present results suggest that the GPS is a useful scale for research on gambling.     

Mental health care for youth: Predictors of use are not always the same as predictors of volume

This study identifies determinants of adolescents’ propensity to use outpatient mental care as well as factors predicting number of visits after contact with a provider was made. We examined three types of treatment outlets: day treatment program (DTP), mental health clinic (MHC), and private specialty services (PSS). Among youth, 1.6% visited DTP, 2.3% visited MHC, and 11.1% had PSS, with overlaps in services utilization. Results from multivariable logistic regressions indicate that most of the individual characteristics differentiated youth on odds of using MHC and PSS, but not DTP. Health status, alcohol dependence, drug dependence, and problematic conduct behaviors and having Medicaid increased the odds of using all three services. Censored regressions used to model number of visits among service users found that girls consistently used more visits than boys. The results suggest that policies that encourage seeking help to a mental care provider may be in instances different from those aimed at motivating retention in treatment.     

The Gap Concept as a Quality of Life Measure: Validation Study of the Child Quality of Life Systemic Inventory

The objective was to determine the interest and psychometric properties of a new QOL self-assessment questionnaire suitable for children 8–12 years old measuring alpha, beta and gamma changes: the “Inventaire Systémique de Qualité de vie pour Enfants” (ISQV-E^©). This was a cross-sectional validation study. 288 children have completed the ISQV-E. Other tools were used: The “Autoquestionnaire de Qualité de Vie Enfants Imagé” (AUQUEI), the State-Trait Anxiety Inventory for Children (STAIC), the Children’s Depression Inventory (CDI). The internal consistency of the four scores of the ISQV-E (state, goal, rank and gap) is satisfactory. All scores have their own specificity. The data show the convergent validity, sensitivity and applicability of the ISQV-E. On the other hand, no satisfactory factorial structure was found although a multidimensional theoretical perspective was applied. The feasibility of the ISQV-E seems clearly demonstrated and the value of this new tool seems evident in contexts of physical, psychological or social problems. The validation study was promising but certain points such as test–retest reliability remain to be studied.     

Physiological Daily Inhalation Rates for Health Risk Assessment in Overweight/Obese Children,Adults, and Elderly

Physiological daily inhalation rates reported in our previous study for normal‐weight subjects 2.6–96 years old were compared to inhalation data determined in free‐living overweight/obese individuals (n = 661) aged 5–96 years. Inhalation rates were also calculated in normal‐weight (n = 408), overweight (n = 225), and obese classes 1, 2, and 3 adults (n = 134) aged 20–96 years. These inhalation values were based on published indirect calorimetry measurements (n = 1,069) and disappearance rates of oral doses of water isotopes (i.e., ²H₂O and H₂¹⁸O) monitored by gas isotope ratio mass spectrometry usually in urine samples for an aggregate period of over 16,000 days. Ventilatory equivalents for overweight/obese subjects at rest and during their aggregate daytime activities (28.99 ± 6.03 L to 34.82 ± 8.22 L of air inhaled/L of oxygen consumed; mean ±  SD) were determined and used for calculations of inhalation rates. The interindividual variability factor calculated as the ratio of the highest 99th percentile to the lowest 1st percentile of daily inhalation rates is higher for absolute data expressed in m³/day (26.7) compared to those of data in m³/kg‐day (12.2) and m³/m²‐day (5.9). Higher absolute rates generally found in overweight/obese individuals compared to their normal‐weight counterparts suggest higher intakes of air pollutants (in μg/day) for the former compared to the latter during identical exposure concentrations and conditions. Highest absolute mean (24.57 m³/day) and 99th percentile (55.55 m³/day) values were found in obese class 2 adults. They inhale on average 8.21 m³ more air per day than normal‐weight adults.     

Children’s Deliberate Control of Facial Action Units Involved in Sad and Happy Expressions

Few attempts have been made since the pioneer work of Ekman et al. (1980) to examine the development of the deliberate control of facial action units in children. We are reporting here two studies concerned with this issue. In Study 1, we investigated children’s ability to activate facial action units involved in sadness and happiness expressions as well as combinations of these action units. In Study 2, we examined children’s ability to pose happiness and sadness with their face, without telling them which action unit to activate. The children who took part in this study were simply asked to portray happiness and sadness as convincingly as possible. The results of Study 1 indicate a strong developmental progression in children’s ability to produce elementary facial components of both emotions as well as in their ability to produce a combination of the elements in the case of happiness. In agreement with prior research in motor development, several non-target action units were also activated when children performed the task. Their occurrence persisted throughout childhood, indicating limitations in the finer motor control achieved by children across age. The results obtained in Study 2 paralleled those obtained in Study 1 in many respects, providing evidence that the children used the technique of deliberate action to pose the two target emotions.     

Optimal life-cycle fertility in a Barro-Becker economy

Parenthood postponement is a key demographic trend of the last three decades. In order to rationalize that stylized fact, we extend the canonical model by Barro and Becker (Econometrica 57:481–501, 1989) to include two—instead of one—reproduction periods. We examine how the cost structure of early and late children in terms of time and goods affects the optimal fertility timing. Then, we identify conditions that guarantee the existence and uniqueness of a stationary equilibrium with a stationary cohort size. Finally, we examine how the model can rationalize the observed postponement of births, and we highlight two plausible causes: (1) a general rise in the cost of children in terms of goods and (2) a decline in the degree of family altruism.