Search results for "Mathematica"
showing 10 items of 7971 documents
The calculation of the first positive Lyapunov exponent in sleep EEG data
1993
To help determine if the EEG is quasiperiodic or chaotic we performed a new analysis by calculating the first positive Lyapunov exponent L1 from sleep EEG data. Lyapunov exponents measure the mean exponential expansion or contraction of a flow in phase space. L1 is zero for periodic as well as quasiperiodic processes, but positive in case of chaotic processes expressing the sensitive dependence on initial conditions. We calculated L1 for sleep EEG segments of 15 healthy male subjects corresponding to sleep stages I, II, III, IV and REM (according to Rechtschaffen and Kales). Our investigations support the assumption that EEG signals are neither quasiperiodic waves nor simple noise. Moreover…
Effects of neuromuscular function and split step on reaction speed in simulated tennis response
2013
The purpose of this study was to examine whether split step (small hop before step) would be more beneficial than no-split condition in simulated tennis response situation. In addition, it was studied if movement time of the response is related to separately measured force production capabilities and reflex sensitivity of the players. Nine skilled male tennis players participated in this study. Subjects stood on a force plate and reacted to a light signal and moved to appointed direction as fast as possible. With split step the participants were 13.1% faster (P <0.05) than without split step from the start to the distal end of the so called close range movement continuum (2.70 m). This was …
Self-care appraisal in nursing assistant students: Adaptation, validation and psychometric properties of the Spanish ASAS
2021
The core implication of nursing professionals’ labor is promoting self-care and foster well-being among healthcare service users. The beginning of the healing process starts with the provider, and self-care habits are needed to positively impact on patients’ care outcomes at different spheres. Overall, current literature supports the idea that nurses’ personal self-care should be a necessary skill to be expected in their professional role. In this regard, the Appraisal of Self-care Agency Scale (ASAS) is a worldwide known instrument aimed at assessing the ability to engage in self-care. However, it has never been tested in the Spanish context before, and much less in nursing practitioners o…
Population-based validation of a German version of the Brief Resilience Scale.
2017
Smith and colleagues developed the Brief Resilience Scale (BRS) to assess the individual ability to recover from stress despite significant adversity. This study aimed to validate the German version of the BRS. We used data from a population-based (sample 1: n = 1.481) and a representative (sample 2: n = 1.128) sample of participants from the German general population (age ≥ 18) to assess reliability and validity. Confirmatory factor analyses (CFA) were conducted to compare one- and two-factorial models from previous studies with a method-factor model which especially accounts for the wording of the items. Reliability was analyzed. Convergent validity was measured by correlating BRS scores …
The anisotropy of personal space.
2019
Violations of personal space are associated with discomfort. However, the exact function linking the magnitude of discomfort to interpersonal distance has not yet been specified. In this study, we explore whether interpersonal distance and discomfort are isotropic with respect to uncomfortably far or close distances. We also extend previous findings with regard to intrusions into personal space as well as maintenance of distances outside of personal space. We presented subjects with 15 interpersonal distances ranging from 40 to 250 cm and obtained verbal and joystick-based ratings of discomfort. Whereas discomfort rose immediately when personal space was entered, the gradient was less steep…
Body composition assessment for the definition of cardiometabolic risk.
2013
Obesity is associated with a major prevalence of cardiovascular risk factors and high risk of cardiovascular events and contributes to the increase in cardiovascular morbidity and mortality worldwide. Beyond the fat mass per se, the pattern of fat distribution has a profound influence on cardiometabolic risk. The increase in abdominal adipose tissue confers an independent risk, while the amount of gluteofemoral body fat is thought to be protective. Changes in the capacity of different depots to store and release fatty acids and to produce adipocytokines are important determinants of fat distribution and its metabolic consequences. Because of the complexity of the assessment of body fat with…
The Construct of Sexual Openness for Females in Steady Intimate Relationships
2017
The analysis of open-minded attitudes towards sexuality in general requires a construct based on attitudinal dimensions. Although several existing studies involve sexual attitudes, they differ substantially and standardized conceptual work is missing. Thus, the authors introduce the latent variable sexual openness to develop a construct based on self-oriented attitudes towards different sexual topics. Available survey data of female German students in a steady relationship allowed providing a first empirical test for the applicability of this construct. Five subdimensions are acknowledged central for sexual openness: sexual practices, masturbation, bisexuality, permissiveness, and pornograp…
Factorial Structure of Web-Credibility in a population of Italian Internet Users. A pilot study
2009
Recent studies by Fogg and his colleagues have defined a new psychological construct called Web credibility. It describes the principal dimensions which lead people to believe (or not) online information. In this framework, the factorial structure of Web credibility was explored in a sample of 152 Italian students of psychology who were Internet users, using a questionnaire. A consistent four-factorial structure emphasized crucial aspects of Web credibility, namely, Inaccuracy, Efficiency, Social Validation, and Commercial Features. Such results seem in line with Fogg's theoretical model; however, further research is required to identify dimensions of this construct.
Nonlinear analysis of sleep EEG data in schizophrenia: calculation of the principal Lyapunov exponent
1995
The generating mechanism of the electroencephalogram (EEG) points to the hypothesis that EEG signals derive from a nonlinear dynamic system. Hence, the unpredictability of the EEG might be considered as a phenomenon exhibiting its chaotic character. The essential property of chaotic dynamics is the so-called sensitive dependence on initial conditions. This property can be quantified by calculating the system's first positive Lyapunov exponent, L1. We calculated L1 for sleep EEG segments of 13 schizophrenic patients and 13 control subjects that corresponded to sleep stages I, II, III, IV and REM (rapid eye movement), as defined by Rechtschaffen and Kales, for the lead positions Cz and Pz. Du…
Preattentive and attentive responses to changes in small numerosities of tones in adult humans
2016
The brain hosts a primitive number sense to non-symbolically represent numerosities of objects or events. Small exact numerosities (~4 or less) can be individuated in parallel. In contrast, large numerosities (more than ~4) can only be approximated. However, whether small numerosities can be approximated without their parallel individuation remains unclear. Parallel individuation is suggested to be an attentive process and numerical approximation an automatic process. We, therefore, tested whether small numerosities can be represented preattentively. We recorded adult humans׳ event-related potentials (ERPs) and behavioral responses to 300-ms sequences of six tones (each of either 440 Hz or …