615 research outputs found
Body composition obtained from the body mass index
BACKGROUND: Since obesity and related diseases are now considered epidemic, new
and more accurate formulas for epidemiological studies are of interest to the
scientific community. Several equations have been proposed to estimate the body
composition simply from anthropometric measurements. However, with time, the body
composition of the populations studied changes in relation to their food habits
and lifestyle, and, therefore, the equations must be regularly updated and
corrected.
AIM OF THE STUDY: The aim of the study was to develop new equations to determine
the body composition among the Italian population using the body mass index and
independently by variables such as age and body structure.
METHODS: Bioelectrical impedance and anthropometric analysis of 764 Italian
Caucasian subjects (342 females and 422 males), 11 to 80 years of age, were
analysed. Females and males were analysed separately. Multiple regression
analyses were performed in order to estimate the body composition of the
subjects. The estimated masses were then compared with the measured masses using
Bland and Altman plots. We also calculated the differences between the estimated
and measured masses, reported as % of the body weight, for the 95, 85 and 75
degrees percentile of the female and male groups. Finally we compared our
formulas with the Watson equations, which are used to estimate the total body
water.
RESULTS: All body masses estimated were positively correlated to the measured
values. Moreover, at any percentile analysed, our formulas resulted more precise
than the Watson formula. Equations: Females: FM = 1.9337 BMI - 26.422; FFM = BW -
FM; BCM = 0.3655 FFM + 4.865; TBW = 0.5863 FFM + 7.1732; Males: FM = 1.407 BMI -
21.389; FFM = BW - FM; BCM = 0.4485 FFM + 3.3534; TBW = 0.6997 + 1.4567.
CONCLUSIONS: Although an inevitable inaccuracy must be expected in
epidemiological studies, our equations are adequate to analyze the body
composition state and changes occurring among the Italian population by simply
considering weight and height
Eye movements during long-term pictorial recall
We investigated eye movements during long-term pictorial recall. Participants performed a perceptual encoding task, in which they memorized 16 stimuli that were displayed in different areas on a computer screen. After the encoding phase the participants had to recall and visualize the images and answer to specific questions about visual details of the stimuli. One week later the participants repeated the pictorial recall task. Interestingly, not only in the immediate recall task but also 1week later participants looked longer at the areas where the stimuli were encoded. The major contribution of this study is that memory for pictorial objects, including their spatial location, is stable and robust over tim
In-Situ Component-Based TPA for Time-Variant Dynamic Systems: A State-Space Formulation
In this chapter, a methodology to calculate equivalent forces by taking into account the possible time-varying dynamic behavior of the components under analysis is presented. This methodology is based on the use of the state-space realization of the in-situ component-based TPA method. To take into account possible time-varying dynamic behavior of the systems under study, a local linear parameter varying (LPV) model identification approach is used. This approach enables the computation of state-space models representative of the components at each time instant by interpolating a given set of linear time-invariant (LTI) state-space models representative of the dynamics of the components under study for fixed operating conditions. By exploiting a numerical example, it is found that when dealing with structures presenting time-varying behavior, accurate equivalent forces can be computed in time domain by using the approaches presented in this chapter. Furthermore, it is clearly demonstrated that ignoring the time dependency of the dynamic behavior of mechanical systems can lead to an important deterioration of the results
Effects of Losartan and Irbesartan administration on brain angiotensinogen mRNA levels
Losartan,
2-n-butyl-4-chloro-5-hydroxymethyl-1-[(2'(1H-tetrazol-5-yl)-biphenil-4-yl)methyl]
imidazole, and Irbesartan,
2-n-butyl-3-[(2'-(1H-tetrazol-5-yl)-biphenyl-4-yl)methyl]-1,3-diaza-spiro[4,4]non
-1-en-4-one, are two angiotensin AT1 receptor antagonists largely used in human
health care as antihypertensive agents. Their ability to cross the blood-brain
barrier and to influence the central renin-angiotensin system are widely
investigated, but how this brain system responds to the subchronic and chronic
block of the angiotensin AT1 receptor is still unknown. Normotensive rats were
intragastrically implanted for 7- and 30-day administration, with a dose of 3 and
30 mg/kg body weight. Treatments were shown to influence, in a dose-, time- and
brain-area-dependent manner, angiotensinogen mRNA levels in scanned areas. This
study showed a general up-regulation of angiotensinogen mRNA expression after 7
days and a widespread down-regulation or basal level of expression after a 30-day
administration of two angiotensin AT1 receptor antagonists
Diaphragmatic Breathing Reduces Exercise-Induced Oxidative Stress
Diaphragmatic breathing is relaxing and therapeutic, reduces stress, and is a fundamental procedure of Pranayama Yoga, Zen, transcendental meditation and other meditation practices. Analysis of oxidative stress levels in people who meditate indicated that meditation correlates with lower oxidative stress levels, lower cortisol levels and higher melatonin levels. It is known that cortisol inhibits enzymes responsible for the antioxidant activity of cells and that melatonin is a strong antioxidant; therefore, in this study, we investigated the effects of diaphragmatic breathing on exercise-induced oxidative stress and the putative role of cortisol and melatonin hormones in this stress pathway. We monitored 16 athletes during an exhaustive training session. After the exercise, athletes were divided in two equivalent groups of eight subjects. Subjects of the studied group spent 1 h relaxing performing diaphragmatic breathing and concentrating on their breath in a quiet place. The other eight subjects, representing the control group, spent the same time sitting in an equivalent quite place. Results demonstrate that relaxation induced by diaphragmatic breathing increases the antioxidant defense status in athletes after exhaustive exercise. These effects correlate with the concomitant decrease in cortisol and the increase in melatonin. The consequence is a lower level of oxidative stress, which suggests that an appropriate diaphragmatic breathing could protect athletes from long-term adverse effects of free radicals
Imagery-related eye movements in 3D space depend on individual differences in visual object imagery.
During recall of visual information people tend to move their eyes even though there is nothing to see. Previous studies indicated that such eye movements are related to the spatial location of previously seen items on 2D screens, but they also showed that eye movement behavior varies significantly across individuals. The reason for these differences remains unclear. In the present study we used immersive virtual reality to investigate how individual tendencies to process and represent visual information contribute to eye fixation patterns in visual imagery of previously inspected objects in three-dimensional (3D) space. We show that participants also look back to relevant locations when they are free to move in 3D space. Furthermore, we found that looking back to relevant locations depends on individual differences in visual object imagery abilities. We suggest that object visualizers rely less on spatial information because they tend to process and represent the visual information in terms of color and shape rather than in terms of spatial layout. This finding indicates that eye movements during imagery are subject to individual strategies, and the immersive setting in 3D space made individual differences more likely to unfold
On the use of Lagrange Multiplier State-Space Substructuring in dynamic substructuring analysis
In this article, the formulation of Lagrange Multiplier State-Space
Substructuring (LM-SSS) is presented and extended to directly compute coupled
displacement and velocity state-space models. The LM-SSS method is applied to
couple and decouple state-space models established in the modal domain.
Moreover, it is used together with tailored postprocessing procedures to
eliminate the redundant states originated from the coupling and decoupling
operations. This specific formulation of the LM-SSS approach made it possible
to develop a tailored coupling form, named Unconstrained Coupling Form (UCF).
UCF just requires the computation of a nullspace and does not rely on the
selection of a subspace from a nullspace. By exploiting a numerical example,
LM-SSS was compared with the Lagrange Multiplier Frequency Based Substructuring
(LMFBS) approach, which is currently widely recognized as a reference approach.
This was done both in terms of: a)coupled FRFs derived by coupling the
state-space models of two substructures and b) decoupled FRFs derived by
decoupling the state-space model of a component from the coupled model. LM-SSS
showed to be suitable to compute minimal order coupled models and UCF turned
out to have similar performance as other coupling forms already presented to
the scientific community. As for the decoupling task, the FRFs derived from the
LM-SSS approach perfectly matched those obtained by LM-FBS. Moreover, it was
also demonstrated that the elimination of the redundant states originated from
the decoupling operation was correctly performed. The approaches discussed were
exploited on an experimental substructuring application. LM-SSS resulted to be
a reliable SSS technique to perform coupling and decoupling operations with
state-space models estimated from measured FRFs as well as to provide accurate
minimal-order models
Learning by teaching in immersive virtual reality – Absorption tendency increases learning outcomes
We investigated the learning outcome of teaching an agent via immersive virtual reality (IVR) in two experiments. In Experiment 1, we compared IVR to a less immersive desktop setting and a control condition (writing a summary). Learning outcomes of participants who had explained the topic to an agent via IVR were better. However, this was only the case for participants who scored high on absorption tendency. In Experiment 2, we investigated whether including social cues in the task instructions enhances learning in participants explaining a topic to an agent. Instruction manipulation affected learning as a function of absorption tendency: Low-absorption participants benefitted most from being instructed to imagine they were helping a student peer pass an upcoming test, while high-absorption participants benefitted more when they were to explain the text to a virtual agent. The findings highlight the crucial role of personality traits in learning by teaching in IVR
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