Consistency of compact and extended models of glucose-insulin homeostasis: The role of variable pancreatic reserve

Published compact and extended models of the glucose-insulin physiologic control system are compared, in order to understand why a specific functional form of the compact model proved to be necessary for a satisfactory representation of acute perturbation experiments such as the Intra Venous Glucose Tolerance Test (IVGTT). A spectrum of IVGTT’s of virtual subjects ranging from normal to IFG to IGT to frank T2DM were simulated using an extended model incorporating the population-of-controllers paradigm originally hypothesized by Grodsky, and proven to be able to capture a wide array of experimental results from heterogeneous perturbation procedures. The simulated IVGTT’s were then fitted with the Single-Delay Model (SDM), a compact model with only six free parameters, previously shown to be very effective in delivering precise estimates of insulin sensitivity and secretion during an IVGTT. Comparison of the generating, extended-model parameter values with the obtained compact model estimates shows that the functional form of the nonlinear insulin-secretion term, empirically found to be necessary for the compact model to satisfactorily fit clinical observations, captures the pancreatic reserve level of the simulated virtual patients. This result supports the validity of the compact model as a meaningful analysis tool for the clinical assessment of insulin sensitivity

Oscillatory dynamics in nanocavities with noninstantaneous Kerr response

We investigate the impact of a finite response time of Kerr nonlinearities over the onset of spontaneous oscillations (self-pulsing) occurring in a nanocavity. The complete characterization of the underlying Hopf bifurcation in the full parameter space allows us to show the existence of a critical value of the response time and to envisage different regimes of competition with bistability. The transition from a stable oscillatory state to chaos is found to occur only in cavities which are detuned far off-resonance, which turns out to be mutually exclusive with the region where the cavity can operate as a bistable switch

Neurophysiological correlates of embodiment and motivational factors during the perception of virtual architectural environments

The recent efforts aimed at providing neuroscientific explanations of how people perceive and experience architectural environments have largely justified the initial belief in the value of neuroscience for architecture. However, a systematic development of a coherent theoretical and experimental framework is missing. To investigate the neurophysiological reactions related to the appreciation of ambiances, we recorded the electroencephalographic (EEG) signals in an immersive virtual reality during the appreciation of interior designs. Such data have been analyzed according to the working hypothesis that appreciated environments involve embodied simulation mechanisms and circuits mediating approaching stimuli. EEG recordings of 12 healthy subjects have been performed during the perception of three-dimensional interiors that have been simulated in a CAVE system and judged according to dimensions of familiarity, novelty, comfort, pleasantness, arousal and presence. A correlation analysis on personal judgments returned that scores of novelty, pleasantness and comfort are positively correlated, while familiarity and novelty are in negative way. Statistical spectral maps reveal that pleasant, novel and comfortable interiors produce a de-synchronization of the mu rhythm over left sensorimotor areas. Interiors judged more pleasant and less familiar generate an activation of left frontal areas (theta and alpha bands), along an involvement of areas devoted to spatial navigation. An increase in comfort returns an enhancement of the theta frontal midline activity. Cerebral activations underlying appreciation of architecture could involve different mechanisms regulating corporeal, emotional and cognitive reactions. Therefore, it might be suggested that people's experience of architectural environments is intrinsically structured by the possibilities for action

Decision support for medical disasters: Evaluation of the IMPRESS system in the live Palermo demo

Abstract Background In medical disasters, coordination, information flows, and decision making are crucial for response and management. Different factors contribute to thwart the response efforts. Some are due to the coordination of the many agencies active in disaster response. Support tools for gathering and analysing data may support task assignment, resource allocation, and acquisition as well as training at different decision levels (in the field and in command-rooms). Validation of Decision Support Systems (DSS) in simulated contexts, simulating real situations, becomes mandatory. In the framework of testing and validation of the IMPRESS project (and of its INCIMOB and INCIMAG tools), one scenario was planned in Palermo, a city of 700,000 inhabitants in the Mediterranean Area of Southern Italy, simulating the sudden liberation of high concentrations of toxic compounds from a fire in Palermo harbor. Emergency Agencies, a real and a simulated Hospital and operators in the field used the system during the response phase. A group of 20 external Observers participated for evaluation purposes. During a joint debriefing session, ad-hoc questionnaires were administered. IMPRESS was useful in improving the execution of important functions during the DEMO; Users agreed about the advantages of the use of IMPRESS tools for conducting crisis activities. INCIMOB use resulted more problematic from an operational point of view. Shortcomings were detected and criticisms were raised due mainly to the lack of training and direct voice communication. Evaluation of DSS in Emergency medicine can benefit from live exercises to highlight weaknesses in both the response system and decision support

Prognostic implications of atrial fibrillation in patients with stable coronary artery disease: a systematic review and meta-analysis of adjusted observational studies

Atrial fibrillation (AF) is the most common cardiac arrhythmia encountered in clinical practice. Despite the frequent coexistence with coronary artery disease (CAD), the prognostic independent implication of AF in patients with stable CAD remains controversial. Our aim was to perform a pairwise meta-analysis of adjusted observational studies comparing cardiovascular outcomes in patients with stable CAD with and without concomitant AF, in search of AF-specific prognostic implications. We performed random effect meta-analysis of binary outcome events in studies comparing stable CAD patients with versus without AF providing risk estimates adjusted for confounding variables. Literature search was performed in PubMed/MEDLINE and Google Scholar. Death was the primary endpoint of the analysis, while myocardial infarction, coronary revascularization and stroke secondary endpoints. 5 studies were included in the meta-analysis, encompassing a total of 30230 stable CAD patients (2844 with AF, 27386 without AF). Stable CAD patients with AF presented an independent increased risk of death (HR 1.39, 95% CI: 1.17–1.66) and stroke (HR 1.88, 95% CI: 1.45–2.45) compared to those without AF. Instead, risk of myocardial infarction (HR 0.90, 95% CI: 0.66–1.22) and coronary revascularization (HR 0.96, 95% CI: 0.79–1.16) did not differ in stable CAD patients with and without the arrhythmia. In patients with stable CAD, AF exerts an independent negative prognostic effect, increasing the risk of death and stroke. However, the small number of eligible studies included in this analysis highlights the astonishing lack of data regarding prognostic implications of concomitant AF in patients with stable CAD