Simple noise-reduction method based on nonlinear forecasting.

Nonparametric detrending or noise reduction methods are often employed to separate trends from noisy time series when no satisfactory models exist to fit the data. However, conventional noise reduction methods depend on subjective choices of smoothing parameters. Here we present a simple multivariate noise reduction method based on available nonlinear forecasting techniques. These are in turn based on state-space reconstruction for which a strong theoretical justification exists for their use in nonparametric forecasting. The noise reduction method presented here is conceptually similar to Schreiber's noise reduction method using state-space reconstruction. However, we show that Schreiber's method has a minor flaw that can be overcome with forecasting. Furthermore, our method contains a simple but nontrivial extension to multivariate time series. We apply the method to multivariate time series generated from the Van der Pol oscillator, the Lorenz equations, the Hindmarsh-Rose model of neuronal spiking activity, and to two other univariate real-world data sets. It is demonstrated that noise reduction heuristics can be objectively optimized with in-sample forecasting errors that correlate well with actual noise reduction errors.

Symmetric and Asymmetric Tendencies in Stable Complex Systems.

A commonly used approach to study stability in a complex system is by analyzing the Jacobian matrix at an equilibrium point of a dynamical system. The equilibrium point is stable if all eigenvalues have negative real parts. Here, by obtaining eigenvalue bounds of the Jacobian, we show that stable complex systems will favor mutualistic and competitive relationships that are asymmetrical (non-reciprocative) and trophic relationships that are symmetrical (reciprocative). Additionally, we define a measure called the interdependence diversity that quantifies how distributed the dependencies are between the dynamical variables in the system. We find that increasing interdependence diversity has a destabilizing effect on the equilibrium point, and the effect is greater for trophic relationships than for mutualistic and competitive relationships. These predictions are consistent with empirical observations in ecology. More importantly, our findings suggest stabilization algorithms that can apply very generally to a variety of complex systems.

Predictors of acute diverticulitis severity: A systematic review.

BACKGROUND: Diverticulitis is a common condition with a broad spectrum of disease severity. A scoring system has been proposed for diagnosing diverticulitis, and a number of scoring systems exist for predicting prognosis associated with severe complications of diverticulitis such as peritonitis. However, predicting disease severity has not received as much attention. Therefore, the aim of this review was to identify the factors that are predictive of severe acute diverticulitis. METHODS: A systematic literature search was performed using Medline, PubMed, EMBASE, and the Cochrane Library to identify papers that evaluated factors predictive of severe diverticulitis. Severe diverticulitis was defined as complicated diverticulitis (associated with haemorrhage, abscess, phlegmon, perforation, purulent/faecal peritonitis, stricture, fistula, or small-bowel obstruction) or diverticulitis that resulted in prolonged hospital admission, surgical intervention or death. RESULTS: Twenty one articles were included. Studies were categorised into those that identified patient characteristics (n = 12), medications (n = 5), biochemical markers (n = 8) or imaging (n = 3) as predictors. Predictors for severe diverticulitis included first episode of diverticulitis, co-morbidities (Charlson score ≥ 3), non-steroidal anti-inflammatory drug use, steroid use, a high CRP on admission and severe disease on radiological imaging. Age and gender were not associated with disease severity. CONCLUSION: A number of predictors exist for identifying severe diverticulitis, and CT remains the gold standard for diagnosing complicated disease. Patients who present with identified risk factors for severe disease warrant early imaging, closer in-patient observation and a lower threshold for early surgical intervention. Patients without these factors may be suitable for outpatient-based treatment.

Efficacy of general practitioners with specialty interests for surgical procedures.

BACKGROUND: General practitioners with specialty interests (GPwSIs) have been an emerging entity in the last decade or so and aim to improve patient's access to specialist level care in the primary care setting. This is achieved by them providing equivalent quality and outcomes to secondary consultant-led services, while not necessarily providing the same breadth of clinical care as them. In this systematic review, we attempt to address their efficacy for surgical procedures and specialties. METHODS: PRISMA guidelines were followed and an electronic literature search was performed independently by two authors using predefined search terms across EMBASE, Ovid MedLine, PubMed, PSYCINFO and the Cochrane Library databases. A total of 817 articles were reviewed after which only six were included for the systematic review. RESULTS: Of the six articles selected, three studies analysed efficacy of GPwSIs with regard to surgical excision of skin lesions. One study looked at the economic evaluation of a GPwSI-led dermatology service in primary care and included GPwSIs carrying out skin excisions. The remaining two included studies were from the same institution and evaluated hernia repairs at a single centre general practitioner practice. CONCLUSION: There is generally, a paucity of evidence looking at the efficacy of GPwSIs for surgical procedures. While they seem to provide an acceptable standard of specialist care in the primary care setting, they do not appear to save money. However, they provide an alternative workforce and the improved access to care that results from it may offset their higher costs.