Bayesian model averaging over tree-based dependence structures for multivariate extremes

Describing the complex dependence structure of extreme phenomena is particularly challenging. To tackle this issue we develop a novel statistical algorithm that describes extremal dependence taking advantage of the inherent hierarchical dependence structure of the max-stable nested logistic distribution and that identifies possible clusters of extreme variables using reversible jump Markov chain Monte Carlo techniques. Parsimonious representations are achieved when clusters of extreme variables are found to be completely independent. Moreover, we significantly decrease the computational complexity of full likelihood inference by deriving a recursive formula for the nested logistic model likelihood. The algorithm performance is verified through extensive simulation experiments which also compare different likelihood procedures. The new methodology is used to investigate the dependence relationships between extreme concentration of multiple pollutants in California and how these pollutants are related to extreme weather conditions. Overall, we show that our approach allows for the representation of complex extremal dependence structures and has valid applications in multivariate data analysis, such as air pollution monitoring, where it can guide policymaking

Narrowing the Tax Gap Through Presumptive Taxation

This Article highlights the primary tax enforcement problem in the United States, that of noncompliant small and medium-sized businesses (" SMBs"), and it explores the possibility of a radical solution: shifting away from the current system, which attempts to tax the actual income of each business, and toward a system that taxes only a rough approximation (or probabilistic estimate) of business income. This sort of presumptive tax approach has been used for years in developing economies, where the problem of SMB noncompliance is even worse than in the U.S. This Article argues that the time has come to at least consider various ways of taxing SMBs in the U.S. on a presumptive basis as well. The particular regime that the Article spends the most time developing is a type of modified gross receipts (MGR) tax of the sort that is used in some developing economies. Under our version of the MGR approach, SMB taxpayers would be taxed on a rough estimate of their annual income using (a) their reported gross receipts and (b) presumed profit ratios based on historical line-of-business profit margins. Whether such a regime would make sense depends on a number of key unanswered questions, including how narrowly and accurately such historical line-of-business profit percentages can be drawn and at what cost. We also discuss whether such a regime should be mandatory or optional; and, if mandatory, whether it should be only a mandatory minimum (like the alternative minimum tax) or both a minimum and maximum. Moving to an MGR approach to taxing SMB income would require a major change in the Internal Revenue Code. As a more modest alternative, the Article also considers instead having the IRS begin to use presumptive-tax principles as part of their audit strategies. If the Service could credibly commit to applying some form of presumptive/probabilistic tax system in its auditing decisions (perhaps as part of the Discriminate Index Function), and if taxpayers reacted rationally to such an audit policy, the results could be similar to an optional presumptive business income tax

Optical mapping of neuronal activity during seizures in zebrafish

Mapping neuronal activity during the onset and propagation of epileptic seizures can provide a better understanding of the mechanisms underlying this pathology and improve our approaches to the development of new drugs. Recently, zebrafish has become an important model for studying epilepsy both in basic research and in drug discovery. Here, we employed a transgenic line with pan-neuronal expression of the genetically-encoded calcium indicator GCaMP6s to measure neuronal activity in zebrafish larvae during seizures induced by pentylenetretrazole (PTZ). With this approach, we mapped neuronal activity in different areas of the larval brain, demonstrating the high sensitivity of this method to different levels of alteration, as induced by increasing PTZ concentrations, and the rescuing effect of an anti-epileptic drug. We also present simultaneous measurements of brain and locomotor activity, as well as a high-throughput assay, demonstrating that GCaMP measurements can complement behavioural assays for the detection of subclinical epileptic seizures, thus enabling future investigations on human hypomorphic mutations and more effective drug screening methods. Notably, the methodology described here can be easily applied to the study of many human neuropathologies modelled in zebrafish, allowing a simple and yet detailed investigation of brain activity alterations associated with the pathological phenotype

Survival and death causes in 251 systemic sclerosis patients from a single Italian center

Objective: To investigate survival in Italian systemic sclerosis (SSc) patients from a tertiary center, reporting death causes. Materials and methods: We analyzed the charts of 251 SSc patients prospectively enrolled in our Rheumatology Unit from 2000 to 2008. Baseline characteristics were recorded. In 2008 the vital status and the causes of death were assessed. Overall and subgroup survival were analyzed by the Kaplan-Meier method and the log-rank test. Results: In 2008, 82% of patients were alive, 8% were known to have died and 10% were lost to follow-up. Overall 5- and 8-year survival were 94.8% and 77.1%, respectively. Patients with an age greater than the median value of the cohort (χ2=4.4; p=0.036), diffuse cutaneous SSc (χ2=3.9; p=0.048), digital ulcers (χ2=6; p=0.015), articular (χ2=5.3; p=0.021), lung (χ2=5.6; p=0.018) and heart involvement (χ2=9.3; p=0.002) had a poorer survival than patients without these features. The majority of SSc-related deaths (60%) were secondary to interstitial lung disease and heart involvement (both 33.3%); 50% of non-SSc-related deaths were due to cancer. Conclusions: Our study reports an improvement in survival of Italian SSc patients during the last decade with respect to the previous ones. Moreover, a reduction in deaths from renal involvement and an increase in deaths from interstitial lung disease were recorded in Italian SSc patients. Our data are consistent with those from recent survival studies carried out on SSc patients from other geographic areas

Effect of Diet and Essential Oils on the Fatty Acid Composition, Oxidative Stability and Microbiological Profile of Marchigiana Burgers

The objective of this study is to evaluate the effects of including linseed (L) or linseed plus vitamin E (LE) in the diet of Marchigiana young bulls on the oxidative stability, color measurements, microbiological profile and fatty acid composition (FA) of burgers treated with and without a blend of essential oils (Rosmarinus officinalis and Origanum vulgare var. hirtum) (EOs). For this aim, the burgers were analysed for pH, thiobarbituric-acid-reactive substance (TBARS) content, Ferric Reducing/Antioxidant Power Assay (FRAP), vitamin E and colour measurements (L, a*, b) at 3, 6, 9, 12 days of storage: the TBARs were the highest in group L compared to C and LE after 12 days of storage (0.98, 0.73, and 0.63 mg MDA/kg, respectively). The TBARS content was also influenced by the use of EO compared to burgers not treated with EO (p < 0.05). The vitamin E content was influenced by the diet (p < 0.01), but not by the EO. The meat of the L group showed the lowest value of redness (a*) compared to C and LE (p < 0.01), while the use of EO did not affect colour parameters. The microbiological profile of the burgers showed a lower Pseudomonas count for L and LE at T0 (2.82 ± 0.30 and 2.30 ± 0.52 Log CFU/g, respectively) compared to C (3.90 ± 0.38 Log CFU/g), while the EO did not influence the microbiological profile. The FA composition was analysed at 0 and 12 days. The burgers from the LE group showed the highest value of polyunsaturated FA compared to the L and C groups (p < 0.05). Our findings suggest that the inclusion of vitamin E in a concentrate rich in polyunsaturated fatty acids is useful to limit intramuscular fat oxidation and to preserve the colour stability of burgers from young Marchigiana bulls enriched with healthy fatty acids. Moreover, linseed and vitamin E had a positive effect on microbial loads and growth dynamics, containing microbial development through time