Search results for "interval"

A Non-Stationary MIMO Vehicle-to-Vehicle Channel Model Derived from the Geometrical Street Model

2011

In this paper, we derive a non-stationary multiple-input multiple-output (MIMO) vehicle-to-vehicle (V2V) channel model from the geometrical street model. Single-bounce scattering is assumed for both fixed and moving scatterers. The high mobility of the transmitter, the receiver, and the surrounding vehicles results in time-variant angles-of-departure (AODs) and angles-of-arrival (AOAs). This fact makes the model non-stationary. Starting from the geometrical model, an analytical expression is derived for the channel gain taking into account the impact of fixed and moving scatterers. The statistical properties of the proposed channel model are studied. Analytical solutions are provided for th…

Soil biogeochemistry and microbial community dynamics in Pinus pinaster Ait. forests subjected to increased fire frequency.

2022

Fire frequency might increase in many fire-dominated ecosystems of the world due to the combined effects of global warming, land-use change and increased human pressures. Understanding how changes in fire frequency can affect the main soil biogeochemical dynamics, as well as the microbial community, in the long term is utmost important. Here we determined the effect of changes in fire frequency and other fire history characteristics on soil C and N dynamics and the main microbial groups (using soil fatty acid profiles), in Pinus pinaster forests from central Spain. Stands were chosen to differ in the number of fires (1 to 3) occurred between 1976 and 2018, in the time elapsed since the last…

New epicardial mapping electrode with warming/cooling function for experimental electrophysiology studies

2010

Cardiac electrical activity is influenced by temperature. In experimental models, the induction of hypothermia and/or hyperthermia has been used for the study of mechanisms of cardiac arrhythmia. A system that allows for localized, controlled induction, besides simultaneously recording electrical activity in the same induced area, needs to be developed ad hoc. This article describes the construction and application of a new system capable of locally modifying the epicardial temperature of isolated hearts and of carrying out cardiac mapping with sufficient spatial resolution. The system is based on a thermoelectric refrigerator and an array of 128 stainless steel unipolar electrodes in encap…

Transportation noise and gestational diabetes mellitus: A nationwide cohort study from Denmark

2020

Background: Few studies have investigated whether road traffic noise is associated with gestational diabetes mellitus (GDM), and have yielded inconsistent findings. We aimed to investigate whether maternal exposure to residential transportation noise, before and during pregnancy, was associated with GDM in a nationwide cohort. Methods: From the Danish population (2004–2017) we identified 629,254 pregnancies using the Danish Medical Birth Register. By linkage with the National Patient Registry, we identified 15,973 pregnancies complicated by GDM. Road traffic and railway noise (Lden) at the most and least exposed façades for all residential addresses from five years before pregnancy until bi…

Psychological therapies for adolescents with borderline personality disorder (BPD) or BPD features-A systematic review of randomized clinical trials …

2021

Objectives To review the effectiveness of psychological therapies for adolescents with borderline personality disorder (BPD) or BPD features. Methods We included randomized clinical trials on psychological therapies for adolescents with BPD and BPD features. Data were extracted and assessed for quality according to Cochrane guidelines, and summarized as mean difference (MD) with 95% confidence intervals (CI) for continuous data and as Odds ratios (OR) with 95% CI for dichotomous data. Risk of bias was assessed using Cochrane’s risk of bias tool for each domain. When possible, we pooled trials into meta-analyses, and used Trial Sequential Analysis (TSA) to control for random errors. Quality…

Handling the epistemic uncertainty in the selective maintenance problem

2020

Abstract Nowadays, both continuous and discontinuous operating systems require higher and higher reliability levels in order to avoid the occurrence of dangerous or even disastrous consequences. Accordingly, the definition of appropriate maintenance policies and the identification of components to be maintained during the planned system’s downtimes are fundamental to ensure the reliability maximization. Therefore, the present paper proposes a mathematical programming formulation of the selective maintenance problem with the aim to maximize the system’s reliability under an uncertain environment. Specifically, the aleatory model related to the components’ failure process is well known, where…

Population density and childhood leukaemia: results of the EUROCLUS study

1999

The EUROCLUS study assembled incidence data for 13,551 cases of childhood leukaemia (CL) diagnosed between 1980 and 1989 in 17 countries (or regions of countries). These were referenced by location at diagnosis to small census areas of which there were 25,723 in the study area. Population counts, surface area and, hence, population density were available for all these small areas. Previous analyses have shown limited extra-Poisson variation (EPV) of case counts within small areas; this is most pronounced in areas of intermediate population density (150-499 persons/km2). In this study, the data set was examined in more detail for evidence that variations in incidence and EPV of CL are associ…

Time estimation and aging: a comparison between young and elderly adults.

2001

Studies about effects of aging on the estimation of short temporal intervals are not conclusive. The aim of the present research was to evaluate age-related differences in the reproduction of a short interval (10 s) using a computerized method. The sample comprised thirteen young adults ( M = 26.15 years) and twelve elderly adults ( M = 79.1 years). Three parameters of time estimation were measured: estimated time, absolute error, and standard deviation. Results showed that time estimates performed by elderly participants were shorter than those of younger ones, although there were no significant differences between the two age groups in the percentage of absolute errors or standard deviat…

Non-parametric probabilistic forecasting of academic performance in Spanish high school using an epidemiological modelling approach

2013

Academic underachievement is a concern of paramount importance in Europe, and particularly in Spain, where around of 30% of the students in the last two courses in high school do not achieve the minimum knowledge academic requirement. In order to analyse this problem, we propose a mathematical model via a system of ordinary differential equations to study the dynamics of the academic performance in Spain. Our approach is based on the idea that both, good and bad study habits, are a mixture of personal decisions and influence of classmates. Moreover, in order to consider the uncertainty in the estimation of model parameters, a bootstrapping approach is employed. This technique permits to for…

2014

Depressed patients frequently report a subjective slowing of the passage of time. However, experimental demonstrations of altered time perception in depressed patients are not conclusive. We added a timed action task (time-to-contact estimation, TTC) and compared this indirect time perception task to the more direct classical methods of verbal time estimation, time production, and time reproduction. In the TTC estimation task, the deviations of the estimates from the veridical values (relative errors) revealed no differences between depressed patients (n = 22) and healthy controls (n = 22). Neither did the relative errors of the TTC estimates differ between groups. There was a weak trend to…