54,262 research outputs found
Refined shell elements for the analysis of functionally graded structures
The present paper considers the static analysis of plates and shells made of Functionally Graded Material (FGM), subjected to mechanical loads. Refined models based on the Carrera's Unified Formulation (CUF) are employed to account for grading material variation in the thickness direction. The governing equations are derived from the Principle of Virtual Displacement (PVD) in order to apply the Finite Element Method (FEM). A nine-nodes shell element with exact cylindrical geometry is considered. The shell can degenerate in the plate element by imposing an infinite radius of curvature. The Mixed Interpolation of Tensorial Components (MITC) technique is extended to the CUF in order to contrast the membrane and shear locking phenomenon. Different thickness ratios and orders of expansion for the displacement field are analyzed. The FEM results are compared with both benchmark solutions from literature and the results obtained using the Navier method that provides the analytical solution for simply-supported structures subjected to sinusoidal pressure loads. The shell element based on refined theories of the CUF turns out to be very efficient and its use is mandatory with respect to the classical models in the study of FGM structures
Maternal awareness of health promotion, parental and preschool childhood obesity
Aim: To investigate the association between parental and preschool childhood obesity, as well as maternal awareness of public health promotion on healthy eating with parental and preschool childhood obesity.
Methods: Data were collected by measuring the height and weight of two hundred randomly selected three-year old children and their parents. Details of the early feeding and dietary styles and level of health promotion awareness were assessed in faceto-face structured health interviews with the parents.
Results: There were statistically significant relationships between childhood obesity and parents’ obesity (r=0.2; p<0.001). A higher proportion of overweight and obese preschool children showed that their mothers lacked awareness of health promotion as compared to children with normally accepted weight (χ2 (6, n=200)=17.32, p=0.008). Maternal awareness of health promotion on healthy eating appeared to have a protective effect against overweight/obesity in three year old children (odds ratio=0.38, 95% CI=0.20 to 0.70). Furthermore, a higher proportion of overweight/obesity mothers had no awareness of health promotion as compared to mothers with normally accepted weight (χ 2 (4, n=200)=13.29, p=0.01). Maternal awareness of health promotion appeared to also have a protective effect against overweight/obesity in mothers (odds ratio=0.51, 95% CI=0.28 to 0.95).
Conclusions: This study showed the protective effect of maternal awareness of health promotion on maternal and preschool childhood obesity. Additionally, this study showed that overweight and obese preschool children had parents who were also overweight and obese.peer-reviewe
A symmetrical method to obtain shear moduli from microrheology
Passive microrheology typically deduces shear elastic loss and storage moduli
from displacement time series or mean-squared displacement (MSD) of thermally
fluctuating probe particles in equilibrium materials. Common data analysis
methods use either Kramers-Kronig (KK) transformations or functional fitting to
calculate frequency-dependent loss and storage moduli. We propose a new
analysis method for passive microrheology that avoids the limitations of both
of these approaches. In this method, we determine both real and imaginary
components of the complex, frequency-dependent response function as direct integral
transforms of the MSD of thermal particle motion. This procedure significantly
improves the high-frequency fidelity of relative to the use of
KK transformation, which has been shown to lead to artifacts in
. We test our method on both model data and experimental
data. Experiments were performed on solutions of worm-like micelles and dilute
collagen solutions. While the present method agrees well with established
KK-based methods at low frequencies, we demonstrate significant improvement at
high frequencies using our symmetric analysis method, up to almost the
fundamental Nyquist limit.Comment: 8 pages, 4 figure
ASSESSING CONSUMER PREFERENCES FOR ORGANIC, ECO-LABELED, AND REGULAR APPLES
We assess consumer choice of eco-labeled, organic, and regular apples, and identify sociodemographic characteristics affecting the choice among those three alternatives. Eco-labeled apples are less desirable than organic when food safety, the environment, and children's needs are considered. Characteristics that may be expected to positively affect the decision to buy eco-labeled apples relative to regular apples actually have the opposite effect with the inclusion of the organic alternative. When considering all three choices, the eco-labeled product is found to be an intermediate choice among consumers.Consumer/Household Economics,
Bio-logic: gene expression and the laws of combinatorial logic
Original article can be found at: http://www.mitpressjournals.org/ Copyright MIT Press DOI: 10.1162/artl.2008.14.1.121At the heart of the development of fertilized eggs into fully formed organisms and the adaptation of cells to changed conditions are genetic regulatory networks (GRNs). In higher multi-cellular organisms, signal selection and multiplexing is performed at the cis-regulatory domains of genes, where combinations of transcription factors (TFs) regulate the rates at which the genes are transcribed into mRNA. To be able to act as activators or repressors of gene transcription, TFs must first bind to target sequences on the regulatory domains. Two TFs that act in concert may bind entirely independently of each other, but more often binding of the first one will alter the affinity of the other for its binding site. This paper presents a systematic investigation into the effect of TF binding dependencies on the predicted regulatory function of this “bio-logic”. Four extreme scenarios, commonly used to classify enzyme activation and inhibition patterns, for the binding of two TFs were explored: independent (the TFs bind without affecting each other’s affinities), competitive (the TFs compete for the same binding site), ordered (the TFs bind in a compulsory order), and joint binding (the TFs either bind as a preformed complex, or binding of one is virtually impossible in the absence of the other). The conclusions are: 1) the laws of combinatorial logic hold only for systems with independently binding TFs; 2) systems formed according to the other scenarios can mimic the functions of their Boolean logical counterparts, but cannot be combined or decomposed in the same way; and 3) the continuously scaled output of systems consisting of competitively binding activators and repressors can be more robustly controlled than that of single TF or (quasi-) logical multi-TF systems. Keywords: Transcription regulation, Genetic regulatory networks, Enzyme kinetics, Combinatorial logic, Non-Boolean continuous logic, Modelling.Peer reviewe
Primordial Gravitational Waves Enhancement
We reconsider the enhancement of primordial gravitational waves that arises
from a quantum gravitational model of inflation. A distinctive feature of this
model is that the end of inflation witnesses a brief phase during which the
Hubble parameter oscillates in sign, changing the usual Hubble friction to
anti-friction. An earlier analysis of this model was based on numerically
evolving the graviton mode functions after guessing their initial conditions
near the end of inflation. The current study is based on an equation which
directly evolves the normalized square of the magnitude. We are also able to
make a very reliable estimate for the initial condition using a rapidly
converging expansion for the sub-horizon regime. Results are obtained for the
energy density per logarithmic wave number as a fraction of the critical
density. These results exhibit how the enhanced signal depends upon the number
of oscillatory periods; they also show the resonant effects associated with
particular wave numbers.Comment: 25 pages, 14 figure
Reversibility of Red blood Cell deformation
The ability of cells to undergo reversible shape changes is often crucial to
their survival. For Red Blood Cells (RBCs), irreversible alteration of the cell
shape and flexibility often causes anemia. Here we show theoretically that RBCs
may react irreversibly to mechanical perturbations because of tensile stress in
their cytoskeleton. The transient polymerization of protein fibers inside the
cell seen in sickle cell anemia or a transient external force can trigger the
formation of a cytoskeleton-free membrane protrusion of micrometer dimensions.
The complex relaxation kinetics of the cell shape is shown to be responsible
for selecting the final state once the perturbation is removed, thereby
controlling the reversibility of the deformation. In some case, tubular
protrusion are expected to relax via a peculiar "pearling instability".Comment: 4 pages, 3 figure
Foeniculum vulgare Essential Oils: Chemical Composition, Antioxidant and Antimicrobial Activities
The essential oils from Foeniculum vulgare commercial aerial parts and fruits were isolated by hydrodistillation, with different distillation times (30 min, I h, 2 h and 3 h), and analyzed by GC and GC-MS. The antioxidant ability was estimated using four distinct methods. Antibacterial activity was determined by the agar diffusion method. Remarkable differences, and worrying from the quality and safety point of view, were detected in the essential oils. trans-Anethole (31-36%), alpha-pinene (14-20%) and limonene (11-13%) were the main components of the essentials oil isolated from F. vulgare dried aerial parts, whereas methyl chavicol (= estragole) (79-88%) was dominant in the fruit oils. With the DPPH method the plant oils showed better antioxidant activity than the fruits oils. With the TBARS method and at higher concentrations, fennel essential oils showed a pro-oxidant activity. None of the oils showed a hydroxyl radical scavenging capacity >50%, but they showed an ability to inhibit 5-lipoxygenase. The essential oils showed a very low antimicrobial activity. In general, the essential oils isolated during 2 h were as effective, from the biological activity point of view, as those isolated during 3 h.info:eu-repo/semantics/publishedVersio
Experimental evidence of replica symmetry breaking in random lasers
Spin-glass theory is one of the leading paradigms of complex physics and
describes condensed matter, neural networks and biological systems, ultracold
atoms, random photonics, and many other research fields. According to this
theory, identical systems under identical conditions may reach different states
and provide different values for observable quantities. This effect is known as
Replica Symmetry Breaking and is revealed by the shape of the probability
distribution function of an order parameter named the Parisi overlap. However,
a direct experimental evidence in any field of research is still missing. Here
we investigate pulse-to-pulse fluctuations in random lasers, we introduce and
measure the analogue of the Parisi overlap in independent experimental
realizations of the same disordered sample, and we find that the distribution
function yields evidence of a transition to a glassy light phase compatible
with a replica symmetry breaking.Comment: 10 pages, 5 figure
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