Stability of solitary wave solutions in the Lugiato–Lefever equation

We analyze the spectral and dynamical stability of solitary wave solutions to the Lugiato-Lefever equation (LLE) on $\mathbb{R}$. Our interest lies in solutions that arise through bifurcations from the phase-shifted bright soliton of the nonlinear Schrödinger equation (NLS). These solutions are highly nonlinear, localized, far-from-equilibrium waves, and are the physical relevant solutions to model Kerr frequency combs. We show that bifurcating solitary waves are spectrally stable when the phase angle satisfies $\theta\in(0,\pi)$, while unstable waves are found for angles $\theta\in(\pi,2\pi)$. Furthermore, we establish orbital asymptotical stability of spectrally stable solitary waves against localized perturbations. Our analysis exploits the Lyapunov-Schmidt reduction method, the instability index count developed for linear Hamiltonian systems, and resolvent estimates

Workplace Bullying: A Validation Study

Bullying in the workplace is a difficult construct to define. Research has largely used questionnaires developed based upon the inclusion of self-reported incidents rather than a theoretical model of the construct. This study utilized a six dimension model (emotional abuse, professional discredit and denigration, control and manipulation of information, control-abuse of working conditions, isolation, and devaluation of the role in the workplace). Items from the most frequently used bullying and incivility scales were presented to participants and factor analyzed to determine if the model could be reproduced. Convergent validity was assessed by examining the relationship with known correlates, job satisfaction and stress. The model was largely supported. No items from any scale loaded on the isolation dimension, indicating a need for the development of items that tap into the dimension. All subscales had adequate reliability and significantly negatively correlated with job satisfaction and significantly positively correlated with stress. Linear regression analyses indicated four dimensions of the scale (emotional abuse, discredit and denigration, control and manipulation of information, and devaluation of roles predicting stress) explained unique variance in perceived stress. Only the emotional abuse subscales and the devaluation of the role in the workplace category explained unique variance in job satisfaction. A solid measuring tool allows for internal assessment that would trigger interventio

Pinning in the extended Lugiato–Lefever equation

We consider a variant of the Lugiato-Lefever equation (LLE), which is a nonlinear Schrödinger equation on a one-dimensional torus with forcing and damping, to which we add a first-order derivative term with a potential $\varepsilon V(x)$. The potential breaks the translation invariance of LLE. Depending on the existence of zeroes of the effective potential $V_\text{eff}$, which is a suitably weighted and integrated version of $V$, we show that stationary solutions from $\varepsilon=0$ can be continued locally into the range $\varepsilon \ne 0$. Moreover, the extremal points of the $\varepsilon$-continued solutions are located near zeros of $V_\text{eff}$ . We therefore call this phenomenon pinning of stationary solutions. If we assume additionally that the starting stationary solution at $\varepsilon=0$ is spectrally stable with the simple zero eigenvalue due to translation invariance being the only eigenvalue on the imaginary axis, we can prove asymptotic stability or instability of its $\varepsilon$-continuation depending on the sign of $V\u27_\text{eff}$ at the zero of $V_\text{eff}$ and the sign of $\varepsilon$. The variant of the LLE arises in the description of optical frequency combs in a Kerr nonlinear ring-shaped microresonator which is pumped by two different continuous monochromatic light sources of different frequencies and different powers. Our analytical findings are illustrated by numerical simulations

Cardiac hybrid imaging

Computed tomography coronary angiography (CTCA) and myocardial perfusion imaging techniques (single photon emission computed tomography, SPECT, or positron emission tomography, PET) are established non-invasive modalities for the diagnosis of coronary artery disease (CAD). Cardiac hybrid imaging consists of the combination (or ‘fusion') of both modalities and allows obtaining complementary morphological (coronary anatomy, stenoses) and functional (myocardial perfusion) information in a single setting. However, hybrid cardiac imaging has also generated controversy with regard to which patients should undergo such integrated examinations for clinical effectiveness and minimization of costs and radiation dose. The feasibility and clinical value of hybrid imaging has been documented in small cohort studies and selected series of patients. Hybrid imaging appears to offer superior diagnostic and prognostic information compared with stand-alone or side-by-side interpretation of data sets. Particularly in patients with multivessel disease, the hybrid approach allows identification of flow-limiting coronary lesions and thereby provides useful information for the planning of revascularization procedures. Furthermore, integration of the detailed anatomical information from CTCA with the high molecular sensitivity of SPECT and PET may be useful to evaluate targeted molecular and cellular abnormalities in the future. While currently still restricted to specialized cardiac centres, the ongoing efforts to reduce radiation exposure and the increasing clinical interest will further pave the way for an increasing use of cardiac hybrid imaging in clinical practic

Relationship of organizational culture, teamwork and job satisfaction in interprofessional teams

BACKGROUND: Team effectiveness is often explained on the basis of input-process-output (IPO) models. According to these models a relationship between organizational culture (input = I), interprofessional teamwork (process = P) and job satisfaction (output = O) is postulated. The aim of this study was to examine the relationship between these three aspects using structural analysis. METHODS: A multi-center cross-sectional study with a survey of 272 employees was conducted in fifteen rehabilitation clinics with different indication fields in Germany. Structural equation modeling (SEM) was carried out using AMOS software version 20.0 (maximum-likelihood method). RESULTS: Of 661 questionnaires sent out to members of the health care teams in the medical rehabilitation clinics, 275 were returned (41.6 %). Three questionnaires were excluded (missing data greater than 30 %), yielding a total of 272 employees that could be analyzed. The confirmatory models were supported by the data. The results showed that 35 % of job satisfaction is predicted by a structural equation model that includes both organizational culture and teamwork. The comparison of this predictive IPO model (organizational culture (I), interprofessional teamwork (P), job satisfaction (O)) and the predictive IO model (organizational culture (I), job satisfaction (O)) showed that the effect of organizational culture is completely mediated by interprofessional teamwork. The global fit indices are a little better for the IO model (TLI: .967, CFI: .972, RMSEA .052) than for the IPO model (TLI: .934, CFI: .943, RMSEA: .61), but the prediction of job satisfaction is better in the IPO model (R(2) = 35 %) than in the IO model (R(2) = 24 %). CONCLUSIONS: Our study results underpin the importance of interprofessional teamwork in health care organizations. To enhance interprofessional teamwork, team interventions can be recommended and should be supported. Further studies investigating the organizational culture and its impact on interprofessional teamwork and team effectiveness in health care are important. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12913-015-0888-y) contains supplementary material, which is available to authorized users