The categorical limit of a sequence of dynamical systems

Modeling a sequence of design steps, or a sequence of parameter settings, yields a sequence of dynamical systems. In many cases, such a sequence is intended to approximate a certain limit case. However, formally defining that limit turns out to be subject to ambiguity. Depending on the interpretation of the sequence, i.e. depending on how the behaviors of the systems in the sequence are related, it may vary what the limit should be. Topologies, and in particular metrics, define limits uniquely, if they exist. Thus they select one interpretation implicitly and leave no room for other interpretations. In this paper, we define limits using category theory, and use the mentioned relations between system behaviors explicitly. This resolves the problem of ambiguity in a more controlled way. We introduce a category of prefix orders on executions and partial history preserving maps between them to describe both discrete and continuous branching time dynamics. We prove that in this category all projective limits exist, and illustrate how ambiguity in the definition of limits is resolved using an example. Moreover, we show how various problems with known topological approaches are now resolved, and how the construction of projective limits enables us to approximate continuous time dynamics as a sequence of discrete time systems.Comment: In Proceedings EXPRESS/SOS 2013, arXiv:1307.690

Internet-Based and other computerized psychological treatments for adults depression: A meta-analysis

Computerized and, more recently, Internet-based treatments for depression have been developed and tested in controlled trials. The aim of this meta-analysis was to summarize the effects of these treatments and investigate characteristics of studies that may be related to the effects. In particular, the authors were interested in the role of personal support when completing a computerized treatment. Following a literature search and coding, the authors included 12 studies, with a total of 2446 participants. Ten of the 12 studies were delivered via the Internet. The mean effect size of the 15 comparisons between Internet-based and other computerized psychological treatments vs. control groups at posttest was d = 0.41 (95% confidence interval [CI]: 0.29-0.54). However, this estimate was moderated by a significant difference between supported (d = 0.61; 95% CI: 0.45-0.77) and unsupported (d = 0.25; 95% CI: 0.14-0.35) treatments. The authors conclude that although more studies are needed, Internet and other computerized treatments hold promise as potentially evidence-based treatments of depression. Keywords: computerized treatment; depression; Internet-based; role of suppor

Psychological treatment of late-life depression:a meta-analysis of randomized controlled trials

SUMMARY Background Older meta-analyses of the effects of psychological treatments for depression in older adults have found that these treatments have large effects. However, these earlier meta-analyses also included non-randomized studies, and did not include newer high-quality randomized controlled trials. Methods We conducted a meta-analysis of randomized studies on psychological treatments for depression in older adults. Results Twenty-five studies were included, of which 17 compared a psychological intervention to a control condition (mainly waiting list and care-as-usual control groups). The quality of the included studies varied. Psychological treatments have moderate to large effects on depression in older adults (standardized mean effect size d¼0.72). Heterogeneity was very low. No differences were found between individual, group or bibliotherapy format, or between cognitive behavioral therapy and other types of psychological treatment. The effects were comparable in studies where depression was defined according to diagnostic criteria, and those in which depression was measured with self-rating questionnaires. Conclusion Although the quality of many studies was not optimal, the results of this meta-analysis support the results of earlier meta-analyses, which also included non-randomized studies. Psychological treatments are effective in the treatment of depression in older adults

Subklinische depressie: een klinisch relevante conditie?

0,1). conclusie De subklinische depressies hebben ernstige gevolgen, zij het iets minder ernstig dan depressieve stoornissen; psychologische behandeling ervan is effectief

Strong, Weak and Branching Bisimulation for Transition Systems and Markov Reward Chains: A Unifying Matrix Approach

We first study labeled transition systems with explicit successful termination. We establish the notions of strong, weak, and branching bisimulation in terms of boolean matrix theory, introducing thus a novel and powerful algebraic apparatus. Next we consider Markov reward chains which are standardly presented in real matrix theory. By interpreting the obtained matrix conditions for bisimulations in this setting, we automatically obtain the definitions of strong, weak, and branching bisimulation for Markov reward chains. The obtained strong and weak bisimulations are shown to coincide with some existing notions, while the obtained branching bisimulation is new, but its usefulness is questionable

Response shifts in mental health interventions: An illustration of longitudinal measurement invariance.

The efficacy of treatments for depression is often measured by comparing observed total scores on self-report inventories, in both clinical practice and research. However, the occurrence of response shifts (changes in subjects' values, or their standards for measurement) may limit the validity of such comparisons. As most psychological treatments for depression are aimed at changing patients' values and frame of reference, response shifts are likely to occur over the course of such treatments. In this article, we tested whether response shifts occurred over the course of treatment in an influential randomized clinical trial. Using confirmatory factor analysis, measurement models underlying item scores on the Beck Depression Inventory (Beck & Beamesderfer, 1974) of the National Institute of Mental Health Treatment of Depression Collaborative Research Program (Elkin, Parloff, Hadley, & Autry, 1985) were analyzed. Compared with before treatment, after-treatment item scores appeared to overestimate depressive symptomatology, measurement errors were smaller, and correlations between constructs were stronger. These findings indicate a response shift, in the sense that participants seem to get better at assessing their level of depressive symptomatology. Comparing measurement models of patients receiving psychotherapy and medication suggested that the aforementioned effects were more apparent in the psychotherapy groups. Consequently, comparisons of observed total scores on self-report inventories may yield confounded measures of treatment efficacy. © 2013 American Psychological Association

Predictors of psychological adjustment after bereavement.

Background: The impact of spousal bereavement on mental health varies among the widowed. More information is needed on factors influencing bereavement outcome. Method: We conducted a cross-sectional study on a sample of 216 widowed individuals. Initial non-response was high, with only 8% of all approached persons participating in the study. The influence of demographic and psychosocial predictors on four general outcome measures (depression, anxiety, somatization, and quality of life) and one loss-related outcome (complicated grief) was studied by means of backward linear regression analysis. Further analyses were performed to explore the possibility of a buffer effect. Results: Depressive symptomatology was best predicted by: age, duration of widowhood, perceived non-supportiveness, physical disorders, and mastery. The other outcome measures were predicted by the same predictors supplemented by gender and education. Mastery interacted with the number of physical disorders while perceived social support interacted with duration of widowhood and age. Conclusions: Enhancement of mastery should probably be one of the components of effective support for widowed individuals most vulnerable to psychiatric complications. The widowed could furthermore benefit from social support. Obviously, these suggestions need to be further examined in longitudinal research with more representative samples. © 2006 International Psychogeriatric Association