Search results for " MODELS"

A comparison of semiparametric approaches to evaluate composite endpoints in heart failure trials

2021

In heart failure trials efficacy is usually proven by a composite endpoint including cardiovascular death (CVD) and recurrent heart failure hospitalisations (HFH), evaluated with time-to-first-event analysis based on a Cox model. As a considerable fraction of events is ignored that way, recurrent event[for full text, please go to the a.m. URL]

GAMLSS for high-variability data: an application to liver fibrosis case

2020

In this paper, we propose management of the problem caused by overdispersed data by applying the generalized additive model for location, scale and shape framework (GAMLSS) as introduced by Rigby and Stasinopoulos (2005). The idea of using a GAMLSS approach for handling our problem comes from the idea of Aitkin (1996) consisting in the use of an EM maximum likelihood estimation algorithm (Dempster, Laird, and Rubin, 1977) to deal with overdispersed generalized linear models (GLM). As in the GLM case, the algorithm is initially derived as a form of Gaussian quadrature assuming a normal mixing distribution. The GAMLSS specification allows the extension of the Aitkin algorithm to probability d…

Contributed discussion on article by Pratola

2016

The author should be commended for his outstanding contribution to the literature on Bayesian regression tree models. The author introduces three innovative sampling approaches which allow for efficient traversal of the model space. In this response, we add a fourth alternative.

A Calvin Bestiary

2017

This paper compares a number of mathematical models for the Calvin cycle of photosynthesis and presents theorems on the existence and stability of steady states of these models. Results on five-variable models in the literature are surveyed. Next a number of larger models related to one introduced by Pettersson and Ryde-Pettersson are discussed. The mathematical nature of this model is clarified, showing that it is naturally defined as a system of differential-algebraic equations. It is proved that there are choices of parameters for which this model admits more than one positive steady state. This is done by analysing the limit where the storage of sugars from the cycle as starch is shut d…

A core cochlear phenotype in USH1 mouse mutants implicates fibrous links of the hair bundle in its cohesion, orientation and differential growth

2008

The planar polarity and staircase-like pattern of the hair bundle are essential to the mechanoelectrical transduction function of inner ear sensory cells. Mutations in genes encoding myosin VIIa, harmonin, cadherin 23,protocadherin 15 or sans cause Usher syndrome type I (USH1, characterized by congenital deafness, vestibular dysfunction and retinitis pigmentosa leading to blindness) in humans and hair bundle disorganization in mice. Whether the USH1 proteins are involved in common hair bundle morphogenetic processes is unknown. Here, we show that mouse models for the five USH1 genetic forms share hair bundle morphological defects. Hair bundle fragmentation and misorientation (25-52° mean ki…

Cornering (3+1) sterile neutrino schemes

2001

Using the most recent atmospheric neutrino data, as well as short-baseline, long-baseline and tritium $\beta$-decay data we show that the joint interpretation of the LSND, solar and atmospheric neutrino anomalies in (3+1) sterile neutrino schemes is severely disfavored, in contrast to the theoretically favored (2+2) schemes.

A methodology for optimisation of solar dish-Stirling systems size, based on the local frequency distribution of direct normal irradiance

2021

Abstract In geographical areas where direct solar irradiation levels are relatively high, concentrated solar energy systems are one of the most promising green energy technologies. Dish-Stirling systems are those that achieve the highest levels of solar-to-electric conversion efficiency, and yet they are still among the least common commercially available technologies. This paper focuses on a strategy aimed at promoting greater diffusion of dish-Stirling systems, which involves optimizing the size of the collector aperture area based on the hourly frequency distributions of beam irradiance and defining a new incentive scheme with a feed-in tariff that is variable with the installed costs of…

Stochastic Models and Escapes Times of Financial Markets

2005

Effective target arrangement in a deterministic scale-free graph

2010

We study the random walk problem on a deterministic scale-free network, in the presence of a set of static, identical targets; due to the strong inhomogeneity of the underlying structure the mean first-passage time (MFPT), meant as a measure of transport efficiency, is expected to depend sensitively on the position of targets. We consider several spatial arrangements for targets and we calculate, mainly rigorously, the related MFPT, where the average is taken over all possible starting points and over all possible paths. For all the cases studied, the MFPT asymptotically scales like N^{theta}, being N the volume of the substrate and theta ranging from (1 - log 2/log3), for central target(s)…

Stochastic analysis of motorcycle dynamics

2011

Off-road and racing motorcycles require a particular setup of the suspensions to improve the comfort and the safety of the rider, maintaining a continuous contact between the road and the motorcycle (by means of the tires). Further, because of the ground roughness, in the case of offroad motorcycle, suspensions usually experience extreme and erratic excursions (suspension stroke) in performing their function. In this regard, the adoption of nonlinear devices can, perhaps, limit both the acceleration experienced by the sprung mass and the excursions of the suspensions. This leads to the consideration of asymmetric nonlinearly-behaving suspensions. This option, however, induces the difficulty…