Explaining health care utilization for panic attacks using cusp catastrophe modeling

Despite increased health care utilization, patients with panic disorder continue to report unmet needs. The objective was to compare the fit of linear and Cusp Catastrophe Modeling in explaining changes in utilization of emergency, general and mental health settings, and self-treatments for panic symptoms. This community-based study surveyed 97 subjects with panic attacks drawn from a sample of randomly-selected adults from randomly-selected households. The stressor (splitting) variable used was Phobic Anxiety while predisposing variables included Family Health Care Utilization, Perceived Life Threat and Need For Treatment, and Treatment Experience. Outcomes consisted of the number of sites and self-treatments used for panic symptoms when first seeking care and during the 2 months prior to survey. Use of mental health sites and self-treatments demonstrated superior modeling with cusp catastrophe approaches using treatment experience as the predisposing variable, accounting for 47% and 38% of variances respectively, improving the fit by over 20% compared to the best linear models in both cases. Cusp catastrophe modeling accounted for more variance than all linear models when describing use of mental health settings and self-treatments. Cusp catastrophe may explain bimodal distributions in behavior, delays in behavior change, and sudden shifts in behavior in stressful situations.     

Cross-cultural generalizability of a cusp catastrophe model for binge drinking among college students

We examined whether a cusp catastrophe model for binge alcohol consumption by college students that was reported earlier (Smerz & Guastello, 2008) could generalize to another culture. Participants were 130 undergraduates enrolled in economics courses at a private urban Japanese university. They completed the same questionnaire items that were used in the previous US study. For some analyses, a stratified random subsample was taken from the earlier US data that was comparable in number, age, and gender proportions (N = 132). Results for the combined sample showed essentially the same results that were obtained from the US sample: Binge drinking can be modeled as a cusp catastrophe with two stable states of behavior - low to moderate consumption and binge level consumption. The two control parameters were peer influence (bifurcation) and attitude toward alcohol use (asymmetry). The nonlinear models (average R2 = .74) accounted for considerably more variance in binge drinking and other alcohol consumption indices than the comparison linear models (average r2 = .18 ). There were some subtle differences between the two samples of students, however.     

Long-range prediction of epileptic seizures with nonlinear dynamics

Patients with uncontrolled epilepsy have some significant problems with planning life routines, and thus one goal of the present study was to explore the viability of predicting seizures in time intervals of one week. The second goal was to utilize the principle of dynamic diseases and to assess the viability of a cusp catastrophe model for seizure onset that was proposed by Cerf (2006). A seizure history of 124 weeks from one adult male patient fit both the cusp and fold catastrophe models (R2 = .92 and .88 respectively) reasonably well using the pdf method and more accurately than counterpart linear models. Prediction of future states was possible, but somewhat compromised because of the nonstationary nature of the data and uncertainties regarding the control variables in the catastrophe models. Analyses of lag functions, however, revealed some surprising elements, suggesting that the precursory conditions for a seizure could be building up over a period of several weeks and that a self-correcting effect within the nervous system could have been occurring.     

Cusp catastrophe model for binge drinking in a college population

A cusp catastrophe model for binge drinking behavior was developed and tested with attitude toward alcohol consumption and peer influence as the two control parameters. Similar models were also developed for frequency and quantity of alcohol use. Participants were 1,247 students who completed the Long Form of the Core Alcohol and Drug Survey. The results were strongest for the binge drinking criterion (R(2) = .90), compared to a linear model (R(2) = .34) that is usually associated with the Theory of Planned Behavior or Theory of Reasoned Action. The results have numerous implications for the development of interventions and for future research.     

Nonlinear models for the adoption and diffusion of innovations for industrial energy conservation

Four different theoretical models for explaining the diffusion of innovation were compared for 13 energy-related innovations--the Theory of Planned Behavior, the S-curve for Diffusion of Innovations, the power law distribution, and the cusp catastrophe. The substantive concern was to explore the roles of facilitative and obstructive factors in diffusing industrial and commercial innovations. Participants were 102 industrial plant and facilities managers from sites that were among the top users of electrical energy and natural gas in the United States. They completed a survey that contained measurements of positive attitudes toward innovation, organizational resistance to innovation, and the extent to which they had investigated or adopted each of the target innovations. Seven of the 13 innovations exhibited strong cusp catastrophe models (via nonlinear regression, average R2 = .91) compared to linear alternative models (average R2 = .31) for those innovations; the S-curve for diffusion was regarded as a simplified version of the cusp. One innovation was characterized best by a power law distribution (R2 = .94), and the remaining five were characterized best by a linear model that was based on the Theory of Planned Behavior (R2 = .41). Different underlying dynamics for the various innovations were implied by these results.     

Familial aggregation of early-onset myocardial infarction

Although ischemic heart disease tends to cluster in families, previous studies have reported a modest (2-fold increased risk) to strong (10-fold increased risk) contribution of family history to the explanation of disease occurrence. The authors assessed the familial aggregation of early-onset myocardial infarction in 11,307 adults aged <65 years who participated in the Third National Health and Nutrition Examination Survey. Logistic regression was used to obtain odds ratios (ORs) and 95% confidence intervals (CIs). A parental history was more common in those with (n = 237) than in those without (n = 11,070) a myocardial infarction (19.8 vs. 7.9%, p < or = 0.01). Adults with a parental history were also more likely to have multiple risk factors for cardiovascular disease (OR for four or five risk factors compared with none: 2.9, 95% CI: 1.4, 6.3). After multivariate adjustment, the likelihood of myocardial infarction was more than three times greater among adults with a parental history than among those without (95% CI: 1.7, 6.7). A maternal history of myocardial infarction was strongly associated (OR = 6.1, 95% CI: 2.1, 17.4) with an increased likelihood of myocardial infarction, and a paternal history was associated with a 3-fold (95% CI: 1.5, 6.3) increased likelihood of myocardial infarction after adjustment for cardiovascular disease risk factors. These results suggest a familial aggregation of early-onset myocardial infarction and show that family history is strongly associated with cardiovascular disease risk factors.     

A Cusp Catastrophe Model for Adolescent Alcohol Use: An Empirical Test

The current study was designed to assess the usefulness of a cusp catastrophe model in predicting adolescent alcohol use. The model suggests that dispositions should be viewed as a normal parameter in a cusp catastrophe model and situational pressure serves as a splitting parameter. This conceptualization predicts that as situational pressure increases a bimodal distribution in the underlying behavior should result. Statistical analyses revealed that the cusp model was a better predictor of alcohol use than the alternative linear models. These findings suggest that the modeling of situational pressure variables should be reexamined from within this new framework.     

Self-Organization and Leadership Emergence: A Cross-Cultural Replication

Project examined the cross-cultural generalizability of a model for leadership emergence based on the rugged landscape self-organization and the swallowtail catastrophe. Twelve groups of eight Chilean university students played the Island Commission game and rated each other on leadership behavior at the end of the one-hour activity. Analysis confirmed the replication of dynamical structure and critical points obtained previously from a U.S. sample.     

光滑试样表面疲劳裂纹演化的数值仿真

考虑裂纹形核，扩展，合并以及晶界的作用等因素，对光滑圆试样表面疲劳裂纹的演化进行了数值模拟。结果表明，疲劳裂纹系统的演化是由无序向有序转化的过程，演化诱致突变。这一过程与实验观察到的结果一致。疲劳裂纹系统的演化终态具有很大的分散性，主要表现为裂纹路径的随机性和突变寿命的分散性。样本的随机性是造成上述分散性的外因，系统对裂纹位形的敏感性是内因。     

CATASTROPHE FRACTURE OF THIN-WALL PRESSURE TUBES

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Is research publication a catastrophic phenomenon among medical faculty?

Studies seeking to predict publication rates among faculty have found contradictory results. The purpose of this study was to determine whether short- or long-term research publications among family medicine faculty were better accounted for using cusp catastrophe modeling (CCM) rather than linear modeling. This secondary analysis of annual research publications used data collected from family medicine faculty in a university department. To predict the number of research publications, two service variables -- national service and administrative responsibility -- were used. There were three bifurcation variables: Scholarly Activity, Professional Status, and 'proportion of studies asprincipal investigator'. Research publications at two and five years were modeled using CCM as well as two linear models. Based upon the amount of variance explained, while linear models accounted for more variance in publications at -year intervals, CCM was superior at explaining publications for all three bifurcation variables at -year intervals. Entering all of the bifurcation variables into the models found that CCM explained more of the -year publication variance with Scholarly Activity and national service as significant predictors. In conclusion, short-term career planning needs to consider its irregular cusp behavior and to minimize the possible impact of bifurcation factors.     

A Cusp Catastrophe Analysis of Changes to Adolescent Smoking Behaviour in Response to Smoking Prevention Programs

The efficacy of smoking prevention programs aimed at adolescent smoking behaviour is widely debated in the health psychology literature. In general, however, these are not seen to be particularly effective in eliminating this acknowledged health risk behaviour. Even when positive results are presented, they frequently assume a linear association between exposure to some prevention or other and the dynamics of subsequent smoking behaviour change. Clair (1998) demonstrated that for alcohol consumption behaviour in adolescents, at least, this was not necessarily so. A nonlinear model, and in Clair's particular case, a Cusp Catastrophe Model (CCM) provided a better fit for the data than did any of a number of simple or interactive linear models. The present paper reports the use of precisely the same analysis for change in adolescent smoking behaviour following exposure to one or other of three smoking prevention programs of different orientations. While changes to adolescent smoking behaviour were evident following intervention, the reported analyses suggested that unlike alcohol consumption behaviour, CCM's were not necessarily the best nonlinear representation of the data.     

Two mechanisms of ductile fracture: void by void growth versus multiple void interaction

Two distinct mechanisms of crack initiation and advance by void growth have been identified in the literature on the mechanics of ductile fracture. One is the interaction a single void with the crack tip characterizing initiation and the subsequent void by void advance of the tip. This mechanism is represented by the early model of Rice and Johnson and the subsequent more detailed numerical computations of McMeeking and coworkers on a single void interacting with a crack tip. The second mechanism involves the simultaneous interaction of multiple voids on the plane ahead of the crack tip both during initiation and in subsequent crack growth. This mechanism is revealed by models with an embedded fracture process zone, such as those developed by Tvergaard and Hutchinson. While both mechanisms are based on void nucleation, growth and coalescence, the inferences from them with regard to crack growth initiation and growth are quantitatively different. The present paper provides a formulation and numerical analysis of a two-dimensional plane strain model with multiple discrete voids located ahead of a pre-existing crack tip. At initial void volume fractions that are sufficiently low, initiation and growth is approximately represented by the void by void mechanism. At somewhat higher initial void volume fractions, a transition in behavior occurs whereby many voids ahead of the tip grow at comparable rates and their interaction determines initiation toughness and crack growth resistance. The study demonstrates that improvements to be expected in fracture toughness by reducing the population of second phase particles responsible for nucleating voids cannot be understood in terms of trends of one mechanism alone. The transition from one mechanism to the other must be taken into account.     

Piezomagnetic and piezoelectric poling effects on mode I and II crack initiation behavior of magnetoelectroelastic materials

The ferrite and ferroelectric phase of magnetoelectroelastic (MEE) material can be selected and processed to control the macroscopic behavior of electron devices using continuum mechanics models. Once macro- and/or microdefects appear, the highly intensified magnetic and electric energy localization could alter the response significantly to change the design performance. Alignment of poling directions of piezomagnetic and piezoelectric materials can add to the complexity of the MEE material behavior to which this study will be concerned with.Appropriate balance of distortional and dilatational energy density is no longer obvious when a material possesses anisotropy and/or nonhomogeneity. An excess of the former could result in unwanted geometric change while the latter may lead to unexpected fracture initiation. Such information can be evaluated quantitatively from the stationary values of the energy density function dW/dV. The maxima and minima have been known to coincide, respectively, with possible locations of permanent shape change and crack initiation regardless of material and loading type. The direction of poling with respect to a line crack and the material microstructure described by the constitutive coefficients will be specified explicitly with reference to the applied magnetic field, electric field and mechanical stress, both normal and shear. The crack initiation load and direction could be predicted by finding the direction for which the volume change is the largest. In contrast to intuition, change in poling directions can influence the cracking behavior of MEE dramatically. This will be demonstrated by the numerical results for the BaTiO₃–CoFe₂O₄ composite having different volume fractions where BaTiO₃ and CoFe₂O₄ are, respectively, the inclusion and matrix.To be emphasized is that mode I and II crack behavior will not have the same definition as that in classical fracture mechanics where load and crack extension symmetry would coincide. A striking result is found for a mode II crack. By keeping the magnetic poling fixed, a reversal of electric poling changed the crack initiation angle from θ₀=+80° to θ₀=−80° using the line extending ahead of the crack as the reference. This effect is also sensitive to the distance from the crack tip. Displayed and discussed are results for r/a=10⁻⁴ and 10⁻¹. Because the theory of magnetoelectroelasticity used in the analysis is based on the assumption of equilibrium where the influence of material microstructure is homogenized, the local space and temporal effects must be interpreted accordingly. Among them are the maximum values of (dW/dV)_max and (dW/dV)_min which refer to as possible sites of yielding and fracture. Since time and size are homogenized, it is implicitly understood that there is more time for yielding as compared to fracture being a more sudden process. This renders a higher dW/dV in contrast to that for fracture. Put it differently, a lower dW/dV with a shorter time for release could be more detrimental.     

Catastrophe fracture of thin-wall pressure tubes

Catastrophe theory was used to investigate the fracture behavior of thin-wall cylindrical tubes subjected to internal explosive pressure. Based on the energy theory and catastrophe theory, a cusp catastrophe model for the fracture was established, and a critical condition associated with the model is given. Contributed by YANG Gui-tong Biographies: WEI De-min (1955-); YANG Gui-tong (1931-)     

Initiation of damage with implicit gradient-enhanced damage models

Through a mixed local and nonlocal formulation, a continuous transition from a local to a nonlocal behavior is obtained. Initially driven by the local action, the damage driving quantity at a material point in non-damaged materials is later influenced by the nonlocal effect only if the occurrence of damage is effectively found in the surroundings. Qualitative resemblance is hence expected in the prediction of damage initiation by the non-regularized and regularized damage models. Numerical simulations with simple tests and comparisons with existing nonlocal damage models show the qualitative improvement of the mixed formulation in the prediction of damage initiation for 1D and 2D damaged structures.     

Interfacial stress analysis and prediction of debonding for a thin plate bonded to a curved substrate

This paper focuses on the analytical and numerical modeling of the interface between a rigid substrate with simple constant curvature and a thin bonded plate. The interfacial behavior is modeled by independent cohesive laws in the normal and tangential directions, coupled with a mixed-mode fracture criterion. The newly developed analytical model determines the interfacial shear and normal stress distributions as functions of the substrate curvature, during the various behavioral stages of the interface prior to the initiation of debonding. The model is also able to predict the debonding load and the effective bond length. In the numerical model the interface is modeled by zero-thickness node-to-segment contact elements, in which both the geometrical relationships between the nodes of the discretized problem and the interface constitutive laws are suitably defined. Numerical results and comparisons between the predictions of the two models are presented.     

Diffusion models for innovation: s-curves, networks, power laws, catastrophes, and entropy

This article considers models for the diffusion of innovation would be most relevant to the dynamics of early 21st century technologies. The article presents an overview of diffusion models and examines the adoption S-curve, network theories, difference models, influence models, geographical models, a cusp catastrophe model, and self-organizing dynamics that emanate from principles of network configuration and principles of heat diffusion. The diffusion dynamics that are relevant to information technologies and energy-efficient technologies are compared. Finally, principles of nonlinear dynamics for innovation diffusion that could be used to rehabilitate the global economic situation are discussed.