Unidirectional Models Research Articles

Living across borders: The everyday experiences of Moroccan and Brazilian transmigrants in Belgium

Abstract Based on research amongst Brazilian and Moroccan temporary residents of the cities of Brussels and Antwerp (Belgium), this article engages with the changes in and current methodological approaches to migration studies. By demonstrating how the trajectories of many contemporary migrants are marked by ongoing mobility, it further complicates previous linear and unidirectional models of migration to move beyond a classical and potentially deterministic model of studying migrant trajectories. The authors illustrate how many contemporary migrants come and go, not always being sure how long they will stay in the different stopovers on their trajectories, when they will stop migrating or where they will eventually settle. Because of the temporality of their residence, many of these so-called ‘transmigrants’ are not only faced with the same problems and challenges as other migrants, arriving newly in another country and rebuilding social networks, but are additionally confronted with a number of risks that are related to their mobile lifestyle. Although globalization and the porosity of nation state borders facilitate transmigration, they result in juridical and practical complexities, reflected in transmigrants’ everyday struggles. The authors explore these struggles and the difficulties and opportunities transmigrants encounter when they turn to their (transnational) networks to ask for support. Transmigrants’ social life is not only oriented towards their country of residence, but consists of complex networks beyond boundaries. Through visits, telephone calls and the use of social media, many transmigrants create, sustain and (re)discover transnational as well as local social networks. While many address their transnational networks to partly alleviate their needs, the development of local networks still appears as indispensable.

Reciprocal influence model of working alliance and therapeutic outcome over individual therapy course.

A reciprocal influence model of the working alliance and the therapeutic outcome was examined in a sample of clients (n = 638) seen by novice therapists. Past researchers have found a relation between the working alliance and symptom improvement and this relation has been interpreted as the alliance leading to such symptom change. The current study was an examination of whether the alliance does indeed lead to symptom change, or whether symptom change leads to subsequent alliance change, or whether each is related to the other in a reciprocal way over time. By modeling the longitudinal development of the working alliance and the symptomatic severity over the individual therapy course, we found support for the reciprocal model being superior to the unidirectional models. The ideas of relationship as strategy and relationship as outcome along with the reciprocal pattern revealed in the findings were discussed with respect to the theoretical and clinical implications. We also discussed the limitations of the study and provided suggestions for future research.

Understanding Psychosocial Mechanisms of the Influences of Acculturation on Physical Activity Participation among Ethnic Minorities in the United States

Culture has been studied as a factor that may account for physical activity disparities among different ethnicities in the U.S. Accordingly, acculturation has been one of the most prominent topics studied to explain mechanisms by which an individual or group may adopt a healthy or unhealthy lifestyle. Nevertheless, many studies lack the use of comprehensive theoretical frameworks, hence they are less informative for intervention design and implementation. This study was purposed to: 1) review important concepts of acculturation, and empirical findings regarding its association with physical activity participation, and 2) propose plausible syntheses of psychosocial theories of physical activity behavior and acculturative variables. The pros and cons of unidirectional and bidirectional models of acculturation were compared in terms of their theoretical plausibility as well as practicality. Acculturation has generally been found to be positively associated with leisure-time physical activity. Nevertheless, its impact on non leisure-time physical activity is still inconclusive. Lastly, we proposed that acculturation may affect physical activity participation through intrapersonal, interpersonal, and sociocultural streams of influence, adopting the typology of Flay et al.``s (2009) theory of triadic influence.

Exploring Seismic Response of Bridges with Bidirectional Coupled Modelling of Base Isolation Bearings System

Special bridges, curved, skew and long-span bridges need particular attentions in their analysis, modelling, seismic design, and construction to maintain structures performance at earthquake exposure up to the expectations. Typically, these bridges exhibit complex behaviour in which the flexural and torsional vibration motions are strongly coupled that promotes much solicitude about their behaviours under environmental dynamic loads such as earthquake. Application of passive control system has been shown to be effective to protect bridges under seismic excitation. The accurate description of the shear force deformation responses of the base isolation bearings under bidirectional earthquake excitation loading is major for analysis and design of base-isolated bridges since the using un-coupled modelling approach with two separate unidirectional models could not accurately describe the bidirectional coupled behaviour of the isolation bearing. A simplified lumped mass model of target bridges is used to investigate the seismic response under bidirectional excitation either harmonic or real earthquake ground motions; the Bouc–Wen model is used to capture coupling feature of the shear force deformation behaviour. The seismic response demands of the bridge model with bidirectional interaction modelling approach are compared with those without interaction. Numerical results show that the isolated bridge is significantly influenced by the bidirectional interaction of bearing forces.

The fiber break evolution process in a 2-D epoxy/glass multi-fiber array

Abstract The mechanical integrity of a structural composite is strongly affected by the strength and toughness of the fiber–matrix interface/interphase (Norwood, 1994), with interfacial shear strength (IFSS) being generally accepted as the best quantifying metric. The value of the IFSS is not directly measurable, but it can be approximated by several micromechanics based test methods with the value obtained being dependent on the choice of the model. The most popular of these test methods is the embedded single fiber fragmentation test (SFFT) which provides the experimental data needed to estimate the IFSS: (a) mean fragment length at saturation and (b) fiber strength at the critical fragment length. Because the IFSS is used in unidirectional composite models to predict strength and failure behavior, where the interaction between fibers can be important, the validity of extrapolating from test results based upon the repeated failure of a single isolated fiber has often been questioned. In this paper, the spatial distribution of fiber breaks in a 2-D array of glass fibers is compared with break locations observed from SFFT specimens. In both cases, the break locations in each fiber were found to evolve to a uniform distribution, thereby confirming that the ordered fragment lengths from the repeated fracture process conforms for both SFFT and multi-fiber fragmentation test (MFFT) specimens to a cumulative distribution function (CDF) derived by Whitworth (1887) and cited by others (Read, 1988; Pyke, 1988; Holst, 1980). The array break density was also observed to be less than the break density in isolated fibers, and break locations across array fibers were observed to be highly coordinated and mostly aligned.

Parenting stress and depressive symptoms in postpartum mothers: Bidirectional or unidirectional effects?

Despite the consistent link between parenting stress and postpartum depressive symptoms, few studies have explored the relationships longitudinally. The purpose of this study was to test bidirectional and unidirectional models of depressive symptoms and parenting stress. Uniquely, three specific domains of parenting stress were examined: parental distress, difficult child stress, and parent–child dysfunctional interaction (PCDI). One hundred and five women completed the Beck Depression Inventory and the Parenting Stress Index – Short Form at 3, 7, and 14 months after giving birth. Structural equation modeling revealed that total parenting stress predicted later depressive symptoms, however, there were different patterns between postpartum depressive symptoms and different types of parenting stress. A unidirectional model of parental distress predicting depressive symptoms best fit the data, with significant stability paths but non-significant cross-lagged paths. A unidirectional model of depressive symptoms predicted significant later difficult child stress. No model fit well with PCDI. Future research should continue to explore the specific nature of the associations of postpartum depression and different types of parenting stress on infant development and the infant–mother relationship.

Directionality of the associations between psychological empowerment and behavioural involvement: A longitudinal autoregressive cross‐lagged analysis

Many cross‐sectional studies have suggested that psychological empowerment (PE) – a higher‐order motivational construct – is related to employees' in‐role and extra‐role behavioural involvement (BI). The objective of this study was to assess the directionality of the longitudinal relationships between PE and employees' BI. Based on theories, three alternative causal directions are examined: two unidirectional models (PE → BI, BI → PE) and one reciprocal model including effects in both directions. A total of 818 health care workers completed self‐report questionnaires at three time points, equally spaced by a 1‐year lag. The results from autoregressive cross‐lagged fully latent structural equation models showed that on the construct level, PE significantly predicts subsequent BI, while the reverse causality was not supported. However, the exploration of relationships at the dimension level of PE suggests the existence of reverse and reciprocal relationship between some PE and BI dimensions. Consistent with previous longitudinal studies, levels of PE especially, but also BI, appeared to be very stable over time. Theoretical and practical implications are discussed.Practitioner points Psychological empowerment – as a global motivational state where all dimensions are present (meaning, competence, self‐determination, and impact) – appears to be a useful lever for lasting and pervasive effects on behavioural involvement. Organizational interventions could therefore prioritize the development of these critical cognitions to empower employees to subsequently perform in‐role and extra‐role behaviours. Encouraging behavioural involvement at the organizational level (e.g., asking an individual to participate and voice on organization issues) could alternatively be the best strategy to increase subsequent level of three PE cognitions (e.g., competence, self‐determination, and impact). The stability of the psychological empowerment and behavioural involvement constructs could indicate the importance of appropriate selection and work environment sustaining employees' empowerment.

Shallow water asymptotic models for the propagation of internal waves

We are interested in asymptotic models for the propagation of internal waves at the interface between two shallow layers of immiscible fluid, under the rigid-lid assumption. We review and complete existing works in the literature, in order to offer a unified and comprehensive exposition. Anterior models such as the shallow water and Boussinesq systems, as well as unidirectional models of Camassa-Holm type, are shown to descend from a broad Green-Naghdi model, that we introduce and justify in the sense of consistency. Contrarily to earlier works, our Green-Naghdi model allows a non-flat topography, and horizontal dimension $d=2$. Its derivation follows directly from classical results concerning the one-layer case, and we believe such strategy may be used to construct interesting models in different regimes than the shallow-water/shallow-water studied in the present work.

Direct Effects of Tadalafil on Lower Urinary Tract Symptoms versus Indirect Effects Mediated through Erectile Dysfunction Symptom Improvement: Integrated Data Analyses from 4 Placebo Controlled Clinical Studies

Tadalafil has regulatory approval for the treatment of men with signs/symptoms of benign prostatic hyperplasia with and without erectile dysfunction. We assessed whether the effects of treatment with tadalafil for lower urinary tract symptoms/benign prostatic hyperplasia are independent of improvements in erectile dysfunction. Four separate analyses used integrated data from 4 randomized, double-blind, placebo controlled studies in men with lower urinary tract symptoms/benign prostatic hyperplasia with and without erectile dysfunction to test whether total I-PSS (International Prostate Symptom Score) improvement was due to improvement in IIEF-EF (International Index of Erectile Function-Erectile Function domain score). Unidirectional and bidirectional path analysis models determined direct and indirect treatment effects mediated by improvements in lower urinary tract symptoms/benign prostatic hyperplasia and erectile dysfunction symptoms. A total of 1,496 men, of whom 77% had erectile dysfunction, received at least 1 dose of tadalafil 5 mg once daily or placebo. The placebo adjusted treatment effect for men with erectile dysfunction was represented by a mean decrease of -2.3 (p <0.0001) in total I-PSS vs -2.2 (p = 0.0007) for men without erectile dysfunction. The correlation between change from baseline in total I-PSS and IIEF-EF was weak (r(2) = 0.08, p <0.0001). The unidirectional path analysis model suggested that the total treatment effect on total I-PSS score improvement (2.25) was derived from a direct treatment effect of 1.57 (70%, p <0.001) and an indirect treatment effect of 0.67 (30% via IIEF-EF improvement, p <0.001). Bidirectional path analysis showed that total I-PSS improvement was largely attributed to direct (92.5%, p <0.001) vs indirect (7.5%, p = 0.32) treatment effects via IIEF-EF improvement. Regardless of the analytical approach, self-reported erectile dysfunction status did not appreciably influence tadalafil treatment response in men with lower urinary tract symptoms/benign prostatic hyperplasia, supporting the dual action of tadalafil on lower urinary tract symptoms/benign prostatic hyperplasia and erectile dysfunction.

Childhood Stomach Pains May Foretell Adult Anxiety Disorders

Back to table of contents Previous article Next article Clinical and Research NewsFull AccessChildhood Stomach Pains May Foretell Adult Anxiety DisordersJoan Arehart-TreichelJoan Arehart-TreichelSearch for more papers by this authorPublished Online:10 Sep 2013https://doi.org/10.1176/appi.pn.2013.9b1AbstractA study linking abdominal pain in childhood with anxiety disorders in adolescence and early adulthood suggests that such pain and anxiety have common origins.Sergiy BykhunenkoWho would have thought that childhood functional abdominal pain—that is, periodic abdominal pain that cannot be attributed to organic disease— might presage anxiety and depression later in life?Yet that is what data from a new study indicate.The study was headed by Lynn Walker, Ph.D., a professor of pediatrics and director of the Division of Adolescent Health at Vanderbilt University. The findings were published online August 12 in Pediatrics.Walker and colleagues studied 332 children who had received extensive medical evaluations and were found to have functional abdominal pain, as well as 147 age-matched children from the same area who did not experience such pain.The subjects were reassessed during adolescence and early adulthood to determine whether they experienced anxiety disorders or depressive disorders.The researchers found that 51 percent of the subjects who had experienced chronic abdominal pain as youngsters met criteria for an anxiety disorder at some point during the follow-up period, and 30 percent currently met criteria for an anxiety disorder.In contrast, only 20 percent of controls met criteria for an anxiety disorder at some point, and just 12 percent met criteria for a current anxiety disorder.Regarding depressive disorders, the lifetime risk among the subjects was significantly higher in the abdominal-pain group than in controls—40 percent versus 16 percent—but current depressive disorders were rare at follow-up and did not differ significantly between the two groups. The reason for this latter finding, the researchers suggested, may be that depression follows a more episodic course than anxiety disorders, and therefore they “did not detect increased risk at the single snapshot evaluation conducted in adolescence or early adulthood.”Thus it appears that functional abdominal pain in childhood predicts a long-term increased risk for developing anxiety disorders and possibly depressive disorders as well.The findings have implications for psychiatrists, Walker told Psychiatric News, highlighting that “a biopsychosocial approach is most effective in the treatment of chronic or recurrent pain. Psychiatrists are important members of the multidisciplinary team as they can identify and treat psychosocial issues that may be missed in a medical evaluation that focuses primarily on ruling out disease. Psychiatrists can be particularly helpful,” he added, “in explaining to patients that the relationship between anxiety and pain is not necessarily cause-effect, but rather that anxiety and pain interact with each other in a vicious cycle. By reducing anxiety, we can begin to break that cycle.”“This is an important study conducted by an outstanding group of researchers,” John Campo, M.D., chair of psychiatry at Ohio State University, said during an interview. Campo published seminal research on the subject in the July 2001 Pediatrics.“A cross-sectional relationship between functional abdominal pain and anxiety has been noted in multiple studies in children, adolescents, and adults, but the nature of this observed ‘comorbidity’ is unclear. Though unidirectional causal models (i.e., functional abdominal pain causes the associated anxiety or vice versa) have been entertained, this study’s findings that functional abdominal pain and anxiety are associated longitudinally into adulthood offers some support for the notion that functional abdominal pain and anxiety may share common risk factors or perhaps even be manifestations of a common disorder.”Yet another reason to believe that functional abdominal pain is closely related to anxiety, and perhaps to depression, was the discovery that anxiety and depression are implicated in irritable bowel syndrome and that antidepressants can help some irritable bowel syndrome patients (Psychiatric News, September 21, 2007).The study was funded by the National Institutes of Health, the Vanderbilt Kennedy Center, and the Vanderbilt Digestive Disease Research Center. ■An abstract of “Functional Abdominal Pain in Childhood and Long-Term Vulnerability to Anxiety Disorders” is posted at http://pediatrics.aappublications.org/content/early/2013/08/07/peds.2012-2191.abstract. ISSUES NewArchived

The progression of severe behavior disorder in young children with intellectual and developmental disabilities

Behavior disorders, such as self-injurious, stereotypic, and aggressive behavior are common among individuals with intellectual or developmental disabilities. While we have learned much about those behaviors over the past few decades, longitudinal research that looks at developmental trajectory has been rare. This study was designed to examine the trajectory of these three forms of severe behavior disorders over a one year time period. The behaviors were measured on two dimensions: frequency of occurrence and severity. Participants were 160 infants and toddlers at risk for developmental delays in Lima, Peru. Using structural equation modeling, we found that the frequency of self-injury and stereotypic behavior and the severity of aggressive behavior remained stable over the 12-month period. Uni-directional structural models fit the data best for self-injurious and aggressive behavior (with frequency being a leading indicator of future severity of self-injury and severity being a leading indicator of future frequency for aggression). For stereotypic behavior, a cross-lagged autoregressive model fit the data best, with both dimensions of frequency and severity involved as leading indicators of each other. These models did not vary significantly across diagnostic groups, suggesting that toddlers exhibiting behavior disorders may be assisted with interventions that target the specific frequencies or severities of behaviors, regardless of diagnostic category.

Equilibria in unidirectional spatial models

This paper (a) characterizes the unique Nash equilibrium of the unidirectional Hotelling–Downs game in which firms maximize their market shares, for any distribution of the consumers, and (b) analyzes equilibrium behavior in the variation of the game in which each firm aims to secure a larger market share than its competitor. In the first case, firms employ identical mixed strategies and each of them serves (in expected terms) a fraction (1/e) of the market and in both cases no firm ever locates in a position to the left of the first quartile of the consumers’ distribution.

Finite volume methods for unidirectional dispersive wave models

SUMMARYWe extend the framework of the finite volume method to dispersive unidirectional water wave propagation in one space dimension. In particular, we consider a KdV–BBM‐type equation. Explicit and implicit–explicit Runge–Kutta‐type methods are used for time discretizations. The fully discrete schemes are validated by direct comparisons to analytic solutions. Invariants' conservation properties are also studied. Main applications include important nonlinear phenomena such as dispersive shock wave formation, solitary waves, and their various interactions. Copyright © 2012 John Wiley &amp; Sons, Ltd.

Comparison of kinetic models for analysis of pyruvate‐to‐lactate exchange by hyperpolarized 13C NMR

The activity of specific enzyme-catalyzed reactions may be detected in vivo by (13) C NMR of hyperpolarized (HP) substrates. The signals from HP substrates and products, acquired over time, have been fitted to a number of different mathematical models to determine fluxes, but these models have not been critically compared. In this study, two-pool and three-pool first-order models were constructed to measure flux through lactate dehydrogenase in isolated glioblastoma cells by NMR detection of lactate and pyruvate following the addition of HP [1-(13) C]pyruvate. Mass spectrometry (MS) was used to independently monitor (13) C enrichment in intra- and extracellular lactate. Six models were evaluated using time-dependent pyruvate C2 and lactate C1 HP NMR data acquired by the use of selective excitation pulses, plus (13) C enrichment data from intracellular and extracellular lactate measured by MS. A three-pool bidirectional model provided the most accurate description of pyruvate metabolism in these cells. With computed values for T(1) of pyruvate and lactate, as well as the effect of pulsing, the initial flux through lactate dehydrogenase was well determined by both the two-pool bidirectional and unidirectional models when only HP data were available. The three-pool model was necessary to fit the combined data from both MS and HP, but the simpler two-pool exchange model was sufficient to determine the (13) C lactate concentration when the lactate appearance was measured only by HP.

Affective mediators of intergroup contact: A three-wave longitudinal study in South Africa.

Intergroup contact (especially cross-group friendship) is firmly established as a powerful strategy for combating group-based prejudice (Pettigrew & Tropp, 2006). Great advances have been made in understanding how contact reduces prejudice (Brown & Hewstone, 2005), highlighting the importance of affective mediators (Pettigrew & Tropp, 2008). The present study, a 3-wave longitudinal study undertaken among minority-status Colored high school children in South Africa (N = 465), explored the full mediation of the effects of cross-group friendships on positive outgroup attitudes, perceived outgroup variability, and negative action tendencies via positive (affective empathy) and negative (intergroup anxiety) affective mediators simultaneously. The target group was the majority-status White South African outgroup. As predicted, a bidirectional model described the relationship between contact, mediators, and prejudice significantly better over time than either autoregressive or unidirectional longitudinal models. However, full longitudinal mediation was only found in the direction from Time 1 contact to Time 3 prejudice (via Time 2 mediators), supporting the underlying tenet of the contact hypothesis. Specifically, cross-group friendships were positively associated with positive outgroup attitudes (via affective empathy) and perceived outgroup variability (via intergroup anxiety and affective empathy) and were negatively associated with negative action tendencies (via affective empathy). Following Pettigrew and Tropp (2008), we compared two alternative hypotheses regarding the relationship between intergroup anxiety and affective empathy over time. Time 1 intergroup anxiety was indirectly negatively associated with Time 3 affective empathy, via Time 2 cross-group friendships. We discuss the theoretical and empirical contributions of this study and make suggestions for future research.

Organizational Reputation: A Review

The idea of organizational reputation is intuitive and simple in its common usage. However, it is surprisingly complex when employed and investigated in management research, as evidenced by the multiple definitions, conceptualizations, and operationalizations that have emerged across studies. The authors see the past decade as a formative phase of the research, characterized by attempts to bring theoretical coherence and rigor to the subject area. In their review of the management literature, the authors focus on this formative period in particular. They attempt to inspire and guide management researchers by clarifying what organizational reputation is. In particular, they identify three dominant conceptualizations, namely, that reputation consists of familiarity with the organization, beliefs about what to expect from the organization in the future, and impressions about the organization’s favorability. The final part of the review is an overview of recent empirical findings in the management literature pertaining to the effects or causes of organizational reputation. The authors conclude by drawing attention to some important directions for future research, including the needs to investigate organizational reputation as multidimensional and dynamic and to model its antecedents and effects as more complex than the unidirectional models typically proposed.

Collaborative Leadership Effects on School Improvement: Integrating Unidirectional- and Reciprocal-Effects Models

Abstract Researchers have persisted in framing leadership as the driver for change and performance improvement in schools despite convincing theoretical commentary that proposes leadership as a process of reciprocal interaction. Although conceptualizing leadership as a reciprocal process offers leverage for understanding leadership effects on learning, methodological constraints have limited empirical tests of this model. This report focuses on understanding the contribution that collaborative leadership and school capacity for improvement make to growth in student learning in elementary school mathematics. We compare unidirectional and reciprocal-effects models focusing on change in leadership and learning in 195 elementary schools over a 4-year period. The results support the efficacy of a reciprocal-effects model that conceptualizes leadership within a changing, mutually reinforcing system of organizational relationships.

The Complexity of Theories on Rural Development in Europe: An Analysis of the Paradigmatic Case of Almería (South‐east Spain)

AbstractIn recent decades several theories on rural development have been expounded in an attempt to explain some experiences of regional economic growth or to provide recommendations on rural development policies. The objective of this article is to revise this open debate and attempt to introduce more concerns about the delimitation of theories and the mosaic of rural areas in Europe. In this context the present article analyses the paradigmatic development of Almería (south‐east Spain) based primarily on agriculture in a process categorised as an economic miracle. Some authors have attempted to explain this success by mechanisms associated with the endogenous development approach. Nevertheless, this study reveals that Almería's development experience can be categorised as a miscellaneous one, and a mixture of development approaches should therefore be considered as opposed to unidirectional models. This also shows the importance of keeping open the debate on the impact of agrarian activity on rural development.

Factors Underlying Organizations' Successful Press Release Publication in Newspapers: Additional PR Elements for the Evolving “Press Agentry” and “Public Information” Models

This study tests 71 PR elements and tools regarding publishing success of 373 press releases in light of PR's two major, unidirectional models: press agentry and public information. Thirteen PR agencies and 12 subject areas were analyzed. A formula was developed to pinpoint the successful PR elements in 575 published news items emanating from these press releases. The main elements underlying publication success were importance of the item, its novelty and its practical usefulness; text composition and timely transfer to the journalist; and original source of the item. Overall, the public information model had the higher average success rate. The study's ramifications for organizations' overall communication strategy are also discussed.

Tension-type Headache and Migraine in Multiple Sclerosis

We review the evidence for a link between multiple sclerosis (MS) and two of the most common primary headache disorders: tension-type headache and migraine. We argue that the association between migraine and MS is biologically plausible and is confirmed by most studies. We discuss possible explanations for the association. First, we consider the possibility that the association is spurious. Next, we consider unidirectional causal models in which one of the conditions increases the risk of the other. A bidirectional model would suggest that each disease predisposes to the other. Alternatively, genetic or environmental risk factors shared by each condition may account for the association between them. We also address the question of whether coexisting migraine or tension-type headache in a patient with MS affects the symptom profile, clinical course, and radiographic characteristics of MS.