A note on the Estimation of a Gamma-Variance Process: Learning from a Failure

This paper confirms that, as originally reported in Seneta (Journal of Applied Probability 41:177–187, 2004, p. 183), it is impossible to replicate Madan et al. (European Finance Review 2:135–156, 1998) results using log daily returns on S&P 500 Index from January 1992 to September 1994. This failure leads to a close investigation of the computational problems associated with finding maximum likelihood estimates of the parameters of the popular VG model. Both standard econometric software, such as R, low level programming languages, such as Matlab\(^{\textregistered }\), and non-standard optimization software, such as Ezgrad described in Tucci (Journal of Economic Dynamics and Control 26:1739–1764, 2002), are used. The complexity of the log-likelihood function is studied. It is shown that it looks very complicated, with many local optima, and may be incredibly sensitive to very small changes in the sample used. Adding or removing a single observation may cause huge changes both in the maximum of the log-likelihood function and in the estimated parameter values. An intuitive procedure which works nicely both when implemented in R and in Matlab\(^{\textregistered }\) is presented.     

Identification of Myocardial Insulin Resistance by Using Liver Tests: A Simple Approach for Clinical Practice

Background: We report that myocardial insulin resistance (mIR) occurs in around 60% of patients with type 2 diabetes (T2D) and was associated with higher cardiovascular risk in comparison with patients with insulin-sensitive myocardium (mIS). These two phenotypes (mIR vs. mIS) can only be assessed using time-consuming and expensive methods. The aim of the present study is to search a simple and reliable surrogate to identify both phenotypes. Methods: Forty-seven patients with T2D underwent myocardial [18F]FDG PET/CT at baseline and after a hyperinsulinemic–euglycemic clamp (HEC) to determine mIR were prospectively recruited. Biochemical assessments were performed before and after the HEC. Baseline hepatic steatosis index and index of hepatic fibrosis (FIB-4) were calculated. Furthermore, liver stiffness measurement was performed using transient elastography. Results: The best model to predict the presence of mIR was the combination of transaminases, protein levels, FIB-4 score and HOMA (AUC = 0.95; sensibility: 0.81; specificity: 0.95). We observed significantly higher levels of fibrosis in patients with mIR than in those with mIS (p = 0.034). In addition, we found that patients with mIR presented a reduced glucose uptake by the liver in comparison with patients with mIS. Conclusions: The combination of HOMA, protein, transaminases and FIB-4 is a simple and reliable tool for identifying mIR in patients with T2D. This information will be useful to improve the stratification of cardiovascular risk in T2D.     

Microbial risk and removal--a utility perspective.

In this paper the results of a sampling programme, undertaken as part of the EU MicroRisk project, are described. This project was undertaken to ascertain the occurrence of pathogens and indicators in the River Thames and their subsequent removal through a treatment works. Appropriate physico-chemical surrogates, as determined by statistical correlation are proposed for the microorganisms identified in the raw water. This study shows that under normal raw water conditions the treatment works is able to remove microbial contamination with a significant margin of safety.     

Effluent quality from 200 on-site sewage systems: design values for guidelines.

The quality of effluent from an on-site sewage treatment system is a critical factor in designing the disposal area and, hence, ensuring the sustained performance of the system. Contaminant concentrations in effluent are typically specified in regulatory guidelines or standards; however, the accuracy of these guideline values are brought into question due to the poor performance of septic tanks and the high failure rates of disposal systems reported here and elsewhere. Results from studies of septic tank effluent quality indicated that the effluent is of poorer quality than currently suggested by guidelines. Aerated wastewater treatment systems were found to perform to accreditation guidelines; however, insufficient nutrient data is presently available to assess nutrient loads. It is proposed that the 80th percentile of system performance be adopted as the design value for sizing effluent disposal areas to minimise failure associated with overloading. For septic tanks this equates to 660 mg L(-1) SS, 330 mg L(-1) BOD, 250 mg L(-1) TN and 36 mg L(-1) TP.     

Influence of ripening stage and maceration length on the contribution of grape skins,seeds and stems to phenolic composition and astringency in wine-simulated macerations

This paper studies the influence of ripening stage and maceration time (1–23 days) on the contribution of each cluster grape components to phenolic composition and astringency in wine-simulated macerations. In general terms, proanthocyanidin extraction from skins, stems and especially from seeds increased with maceration time. The ripening stage also had a major influence on tannin extraction and astringency. The tannin contribution from skins and stems increased with ripening but the contribution from the seeds decreased. The contribution to astringency from all cluster components was clearly higher when the grapes were unripened. The mean degree of polymerization of the tannins from skin and seed components was unaffected by ripening and maceration length.     

Attention to Science/Environment News Positively Predicts and Attention to Political News Negatively Predicts Global Warming Risk Perceptions and Policy Support

Contemporary science and environmental news coverage of global warming increasingly portrays scientific consensus. Political news coverage of global warming, however, typically portrays controversy. We hypothesize that attention to science and environmental news is associated with beliefs more consistent with the global warming science and higher risk perceptions, and that the opposite is true of attention to political news. Furthermore, we hypothesize that science‐based beliefs and risk perceptions are positively associated with support for policies aiming at reducing global warming. These hypotheses were confirmed by survey data from a nationally representative sample of adults (N = 2,164). These findings support and extend the cognitive mediation model of news learning and have important practical ramifications.     

The Legnaro ion microprobe in low current experiments

The focused ion microprobe of the Laboratori Nazionali di Legnaro has been recently employed in experiments requiring very low beam current. This article will discuss the performance of our apparatus in this application, the drawbacks which showed up and the appropriate solutions. We present IBIC observations of grain boundaries in polycrystalline silicon solar cells and IBIC and IBIL measurements on CVD diamond samples. The modifications introduced in the experimental setup are outlined. We emphasise the problems typical of these measurements and propose the interposition of thin gold foils in the beam line, as a way to handle very different current intensities. We study the effects of these foils on beam quality and their effectiveness in reducing the current. A new designed system for easy interchange of foils and related collimators is described, which will be inserted upstream in the beam line.     

Results and consequences of frequent quality control of quantitative clinical 1H-MR-spectroscopy

BACKGROUND: The cut-off point of serum C-reactive protein to differentiate the mild from the severe form of acute pancreatitis is still debated; data concerning the C-reactive protein pattern in assessing the severity of acute biliary pancreatitis are lacking. AIM: To define the best cut-off point in differentiating the severe from the mild form of acute biliary pancreatitis. PATIENTS: Fifty patients with acute biliary pancreatitis: 34 patients with mild pancreatitis and 16 with the severe form of the disease were studied. METHODS: Serum C-reactive protein concentrations were assessed in all patients upon admission and for the following 5 days. RESULTS: No significant difference in serum C-reactive protein levels was found in the first 2 days in patients with mild pancreatitis compared to those with the severe form of the disease. Using a cut-off point of 11 mg/dl, the sensitivity of serum C-reactive protein in assessing the severity of acute pancreatitis during the first two days of the study was 9% and 57%, the specificity, 93% and 81%, and the accuracy 71% and 74%, respectively. CONCLUSIONS: Serum determination of C-reactive protein in the first 48 hours of the disease is not a reliable marker of the severity of acute biliary pancreatitis.