7,461 research outputs found
Relativistic deuteron structure function at large Q^2
The deuteron deep inelastic unpolarized structure function F_2^D is
calculated using the Wilson operator product expansion method. The long
distance behaviour, related to the deuteron bound state properties, is
evaluated using the Bethe-Salpeter equation with one particle on mass shell.
The calculation of the ratio F_2^D/F_2^N is compared with other convolution
models showing important deviations in the region of large x. The implications
in the evaluation of the neutron structure function from combined data on
deuterons and protons are discussed.Comment: 7 pages, 1 ps figure, RevTeX source, 1 tar.gz file. Submited to
Physical Letter
Preface of the "Symposium on dynamical systems applied to robotics"
[Excerpt] Robotics has been evolving in last years, considering the different fields that can be tackled. This is an important and diversified domain, which is normally solved using bio-inspired or model-based approaches.
In this symposia, we focus on the use of the dynamical systems theory to address any related problems in the
robotics domain. Dynamical systems exhibit some properties which makes them well suited to real-time robotic
applications, such as movement generation for legged; modular and wheeled platforms; balance control; grasping; reaching, etc. [...](undefined
The association of problematic eating behaviours with food quality and body mass index at 7 years of age
Background/objectives: There is scarce evidence of how certain eating behaviours compromise the compliance with dietary guidelines and weight status in school-aged children. This study aims to evaluate the association of children’s problematic eating behaviours with food quality and body mass index at 7 years of age.
Subjects/methods: Participants were children aged 7 years old from a population-based cohort study from Porto, Portugal-Generation XXI. Children’s quantity and speed of ingestion, food refusal at the table and food rewards requesting were evaluated by caregiver’s perception. Food consumption was evaluated by a food frequency questionnaire and compared with age-appropriate guidelines. Children’s weight status was assessed by objective measurements and parent’s perceptions. Associations were estimated by logistic regressions (odds ratio (OR), 95% confidence intervals (95% CI)) adjusted for maternal age, education, smoking during pregnancy, birth type, child’s sex, weight-for-gestational age and sports (n = 3801).
Results: Children eating small amounts of food, refusing to eat at the table with the rest of the family during meals and asking for food rewards showed a higher consumption of energy-dense foods (OR = 1.51; 95% CI:1.23–1.86; OR = 1.58; 95% CI:1.16–2.16; OR = 1.56; 95% CI:1.14–2.12) and presented higher odds of consuming fruit and vegetables below recommendations (OR = 1.41; 95% CI:1.22–1.64; OR = 1.20; 95% CI:1.00–1.45; OR = 1.28; 95% CI:1.05–1.55). Children displaying these eating behaviours were less likely to be overweight/obese, hence their parents were less likely to show concern with their weight. Including food quality as covariate in the final models with obesity status did not change the associations.
Conclusions: Problematic eating behaviours were associated with poorer food quality (more energy-dense foods and low fruit and vegetables), but food quality does not seem to explain the association with obesity status. Parents were less likely to be concerned about their child’s weight if the child ate slowly or poorly, and accordingly the odds of them being overweight or obese were lower.Generation XXI was funded by the Health Operational Programme—Saúde XXI, Community Support Framework III and the Regional Department of Ministry of Health. This study was supported through FEDER from the Operational Programme Factors of Competitiveness (COMPETE) and through national funding from the Foundation for Science and Technology (FCT; Portuguese Ministry of Education and Science) under the project PTDC/SAU-EPI/121532/2010 (FCOMP-01-0124-FEDER-021177) and through the Investigator Programme (IF/01350/2015–Andreia Oliveira and IF/01060/2015–Ana Cristina Santos). It also had support from the Calouste Gulbenkian Foundation
A brainstem-like modulation approach for gait transition in a quadruped robot
The ability to traverse a wide variety of terrains
while walking is basically a requirement for performing useful
tasks in our human centric world.
In this article, we propose a bio-inspired robotic controller
able to generate locomotion and to easily switch between different
type of gaits. In order to improve the robot stability and
response while locomoting, we adjust both the duty factor and
the interlimb phase relationships, according to the velocities.
We extend previous work, by applying nonlinear oscillators
to generate the rhythmic locomotor movements for a
quadruped robot, similarly to the biological counterparts. The
generated trajectories are modulated by a drive signal, that
modifies the oscillator frequency, amplitude and the coupling
parameters among the oscillators, proportionally to the drive
signal strength. By increasing the drive signal, locomotion
can be elicited and velocity increased while switching to the
appropriate gaits. This drive signal can be specified according
to sensory information or set a priori.
The implementation of the central pattern generator network
and the activity modulation layer is shown in simulation and
in an AIBO robot
Evidence for entanglement at high temperatures in an engineered molecular magnet
The molecular compound
[Fe(-oxo)(CHN)(CO)]
was designed and synthesized for the first time and its structure was
determined using single-crystal X-ray diffraction. The magnetic susceptibility
of this compound was measured from 2 to 300 K. The analysis of the
susceptibility data using protocols developed for other spin singlet
ground-state systems indicates that the quantum entanglement would remain at
temperatures up to 732 K, significantly above the highest entanglement
temperature reported to date. The large gap between the ground state and the
first-excited state (282 K) suggests that the spin system may be somewhat
immune to decohering mechanisms. Our measurements strongly suggest that
molecular magnets are promising candidate platforms for quantum information
processing
The motion of two masses coupled to a massive spring
We discuss the classical motion of a spring of arbitrary mass coupled to two
arbitrary massive blocks attached at its ends. A general approach to the
problem is presented and some general results are obtained. Examples for which
a simple elastic function can be inferred are discussed and the normal modes
and normal frequencies obtained. An approximation procedure to the evaluation
of the normel frequencies in the case of uniform elastic function and mass
density is also discussed.Comment: Standard Latex file plus three eps figure
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