Coherence estimate between a random and a periodic signal: Bias, variance, analytical critical values, and normalizing transforms

The present work deals with recent results on the sampling distribution of the magnitude-squared coherence (also called just coherence) estimate between a random (Gaussian) and a periodic signal, in order to obtain analytical critical values, alternative expressions for the probability density function (PDF) as well as the variance and bias of the estimate. A comparison with the more general case of coherence estimation when both signals are Gaussian was also provided. The results indicate that the smaller the true coherence (TC) values the closer both distributions become. The behaviour of variance and bias as a function of the number of data segments and the TC is similar for both coherence estimates. Additionally, the effect of a normalizing function (Fisher's z transform) in the coherence estimated between a random and a periodic signal was also evaluated and normality has been nearly achieved. However, the variance was less equalized in comparison with coherence estimate between two Gaussian signals.     

Effects and prevalence of responders after a multicomponent intervention on cardiometabolic risk factors in children and adolescents with overweight/obesity: Action for health study

ABSTRACT

This study aimed to verify the effect of a multicomponent intervention on cardiometabolic risk factors (CMRF), and to determine the prevalence of responders on CMRF among children and adolescents with overweight/obesity. This is a quasi-experimental study, developed with 35 children and adolescents with overweight/obesity (control group (CG) = 18; intervention group (IG) = 17), aged between 7 and 13 years. Participants in IG underwent a multicomponent intervention for 12 weeks. The following variables were evaluated: anthropometric measures, maturational stages and CMRF (body fatness, HOMA-IR, triglycerides, high-density and low-density lipoprotein) (HDL-C, LDL-C), total cholesterol (TC), aspartate aminotransferase (AST), alanine aminotransferase (ALT) and AST/ALT ratio. Mixed analysis of variance and the prevalence of responders were used for statistical analysis. There was a significant time x group interaction on body fatness (p < 0.001), HOMA-IR (p = 0.01), HDL-C (p < 0.001), LDL-C (p = 0.009) and TC (p < 0.001). The prevalence of responders for CMRF in IG and CG was respectively: body fatness (47%; 0%; p = 0.04), HOMA-IR (58.8%; 16.6%; p = 0.04); triglycerides (17.6%; 5.5%; p = 0.31); HDL-C (76.4%; 5.5%; p = 0.01), LDL-C (35.3%; 5%; p = 0.08), TC (64.7%; 5%; p = 0.01), AST (5.8%; 0%; p = 0.87), ALT (29.4%; 11.1%; p = 0.24) and AST/ALT ratio (24.4%; 22.2%; p = 0.67). Multicomponent intervention induced positive changes on CMRF along with a higher prevalence of positive adaptations in IG than the CG in some of the cardiometabolic outcomes assessed.     

Group identification in early adolescence: its relation with peer adjustment and its moderator effect on peer influence

This study was conducted to test whether group identification (importance of the group to the individual) covaried with individual-group similarity on problem behavior; and whether group identification moderated peer group influence on the individual's development of delinquent behavior across a 1-year period. The level of reciprocated nominations within the individual's self-nominated group was controlled for in all analyses. Participants were 190 sixth and seventh graders (during the first year of the study) from the north of Italy. Level of reciprocated nominations within the group, but not identification, was found to covary with individual-group behavioral similarity (group behavior interacted with reciprocity of group nominations in predicting individual behavior). Group identification, but not reciprocated nominations, was found to moderate peer group influence on the individual's change in delinquent behavior, across 1 year. The individual's peer status within the classroom, level of reciprocated nominations, and gender all were related to the individual's level of group identification. Results are discussed in terms of understanding peer group influence on the individual.     

Identifying top relevant dates for implicit time sensitive queries

Despite a clear improvement of search and retrieval temporal applications, current search engines are still mostly unaware of the temporal dimension. Indeed, in most cases, systems are limited to offering the user the chance to restrict the search to a particular time period or to simply rely on an explicitly specified time span. If the user is not explicit in his/her search intents (e.g., “philip seymour hoffman”) search engines may likely fail to present an overall historic perspective of the topic. In most such cases, they are limited to retrieving the most recent results. One possible solution to this shortcoming is to understand the different time periods of the query. In this context, most state-of-the-art methodologies consider any occurrence of temporal expressions in web documents and other web data as equally relevant to an implicit time sensitive query. To approach this problem in a more adequate manner, we propose in this paper the detection of relevant temporal expressions to the query. Unlike previous metadata and query log-based approaches, we show how to achieve this goal based on information extracted from document content. However, instead of simply focusing on the detection of the most obvious date we are also interested in retrieving the set of dates that are relevant to the query. Towards this goal, we define a general similarity measure that makes use of co-occurrences of words and years based on corpus statistics and a classification methodology that is able to identify the set of top relevant dates for a given implicit time sensitive query, while filtering out the non-relevant ones. Through extensive experimental evaluation, we mean to demonstrate that our approach offers promising results in the field of temporal information retrieval (T-IR), as demonstrated by the experiments conducted over several baselines on web corpora collections.     

Effects of emphasising opposition and cooperation on collective movement behaviour during football small-sided games

ABSTRACT

Optimizing collective behaviour helps to increase performance in mutual tasks. In team sports settings, the small-sided games (SSG) have been used as key context tools to stress out the players’ awareness about their in-game required behaviours. Research has mostly described these behaviours when confronting teams have the same number of players, disregarding the frequent situations of low and high inequality. This study compared the players’ positioning dynamics when manipulating the number of opponents and teammates during professional and amateur football SSG. The participants played 4v3, 4v5 and 4v7 games, where one team was confronted with low-superiority, low- and high-inferiority situations, and their opponents with low-, medium- and high-cooperation situations. Positional data were used to calculate effective playing space and distances from each player to team centroid, opponent team centroid and nearest opponent. Outcomes suggested that increasing the number of opponents in professional teams resulted in moderate/large decrease in approximate entropy (ApEn) values to both distance to team and opponent team centroid (i.e., the variables present higher regularity/predictability pattern). In low-cooperation game scenarios, the ApEn in amateurs’ tactical variables presented a moderate/large increase. The professional teams presented an increase in the distance to nearest opponent with the increase of the cooperation level. Increasing the number of opponents was effective to overemphasise the need to use local information in the positioning decision-making process from professionals. Conversely, amateur still rely on external informational feedback. Increasing the cooperation promoted more regularity in spatial organisation in amateurs and emphasise their players’ local perceptions.     

Poor precompetitive sleep habits,nutrients’ deficiencies,inappropriate body composition and athletic performance in elite gymnasts

This study aimed to evaluate body composition, sleep, precompetitive anxiety and dietary intake on the elite female gymnasts’ performance prior to an international competition. Sixty-seven rhythmic gymnasts of high performance level were evaluated in relation to sport and training practice, body composition, sleep duration, daytime sleepiness by the Epworth Sleepiness Scale (ESS), sleep quality by the Pittsburgh Sleep Quality Index (PSQI), precompetitive anxiety by the Sport Competition Anxiety Test form A (SCAT-A) and detailed dietary intake just before an international competition. Most gymnasts (67.2%) suffered from mild daytime sleepiness, 77.6% presented poor sleep quality and 19.4% presented high levels of precompetitive anxiety. The majority of gymnasts reported low energy availability (EA) and low intakes of important vitamins including folate, vitamins D, E and K; and minerals, including calcium, iron, boron and magnesium (p?p?=?.001), sport practice (p?=?.024), number of daily training hours (p?=?.000), number of hours of training/week (p?=?.000), waist circumference (WC) (p?=?.008) and sleep duration (p?=?.005). However, it was negatively correlated with WC/hip circumference (p?=?.000), ESS (p?=?.000), PSQI (p?=?.042), SCAT-A (p?=?.002), protein g/kg (p?=?.028), EA (p?=?.002) and exercise energy expenditure (p?=?.000). High performance gymnasts presented poor sleep habits with consequences upon daytime sleepiness, sleep quality and low energy availability.