27 research outputs found
Inverse-probability weighting and multiple imputation for evaluating selection bias in the estimation of childhood obesity prevalence using data from electronic health records
Background and objectives: Height and weight data from electronic health records are increasingly being used
to estimate the prevalence of childhood obesity. Here, we aim to assess the selection bias due to missing weight
and height data from electronic health records in children older than five.
Methods: Cohort study of 10,811 children born in Navarra (Spain) between 2002 and 2003, who were still living in
this region by December 2016. We examined the differences between measured and non-measured children older
than 5 years considering weight-associated variables (sex, rural or urban residence, family income and weight status
at 2–5 yrs). These variables were used to calculate stabilized weights for inverse-probability weighting and to conduct
multiple imputation for the missing data. We calculated complete data prevalence and adjusted prevalence considering
the missing data using inverse-probability weighting and multiple imputation for ages 6 to 14 and group ages 6 to 9 and
10 to 14.
Results: For 6–9 years, complete data, inverse-probability weighting and multiple imputation obesity age-adjusted
prevalence were 13.18% (95% CI: 12.54–13.85), 13.22% (95% CI: 12.57–13.89) and 13.02% (95% CI: 12.38–13.66) and
for 10–14 years 8.61% (95% CI: 8.06–9.18), 8.62% (95% CI: 8.06–9.20) and 8.24% (95% CI: 7.70–8.78), respectively.
Conclusions: Ages at which well-child visits are scheduled and for the 6 to 9 and 10 to 14 age groups, weight
status estimations are similar using complete data, multiple imputation and inverse-probability weighting. Readily
available electronic health record data may be a tool to monitor the weight status in children
Epigenetics in schizophrenia: a pilot study of global DNA methylation in different brain regions associated with higher cognitive functions
Attempts to discover genes that are involved in the pathogenesis of major psychiatric disorders have been frustrating and often fruitless. Concern is building about the need to understand the complex ways in which nature and nurture interact to produce mental illness. We analyze the epigenome in several brain regions from schizophrenic patients with severe cognitive impairment using high-resolution (450K) DNA methylation array. We identified 139 differentially methylated CpG sites included in known and novel candidate genes sequences as well as in and intergenic sequences which functions remain unknown. We found that altered DNA methylation is not restricted to a particular region, but includes others such as CpG shelves and gene bodies, indicating the presence of different DNA methylation signatures depending on the brain area analyzed. Our findings suggest that epimutations are not relatables between different tissues or even between tissues' regions, highlighting the need to adequately study brain samples to obtain reliable data concerning the epigenetics of schizophrenia
Epigenetics in schizophrenia: a pilot study of global DNA methylation in different brain regions associated with higher cognitive functions
Attempts to discover genes that are involved in the pathogenesis of major psychiatric disorders have been frustrating and often fruitless. Concern is building about the need to understand the complex ways in which nature and nurture interact to produce mental illness. We analyze the epigenome in several brain regions from schizophrenic patients with severe cognitive impairment using high-resolution (450K) DNA methylation array. We identified 139 differentially methylated CpG sites included in known and novel candidate genes sequences as well as in and intergenic sequences which functions remain unknown. We found that altered DNA methylation is not restricted to a particular region, but includes others such as CpG shelves and gene bodies, indicating the presence of different DNA methylation signatures depending on the brain area analyzed. Our findings suggest that epimutations are not relatables between different tissues or even between tissues' regions, highlighting the need to adequately study brain samples to obtain reliable data concerning the epigenetics of schizophrenia
Application of HPM to Solve Unsteady Squeezing Flow of a Second-Grade Fluid between Circular Plates
In this article, Homotopy Perturbation Method (HPM) is used to provide two approximate solutions to the nonlinear differential equation that describes the behaviour for the unsteady squeezing flow of a second grade fluid between circular plates. Comparing results between approximate and numerical solutions shows that our results are capable to provide an accurate solution and are extremely efficient
Classical Perturbation Method for the Solution of a Model of Diffusion and Reaction
In this paper, we employ perturbation method (PM) to solve nonlinear problems. As case study PM is employed to obtain approximate solutions for the nonlinear differential equation that models the diffusion and reaction in porous catalysts. We find that the square residual error (S.R.E) of our solutions is in the range and this requires only the third order approximation of PM, which shows the effectiveness of the method
Study of gold nanoparticles effect on thermal diffusivity of nanofluids based on various solvents by using thermal lens spectroscopy
Dual beam thermal lens technique is used to determine the
thermal diffusivity of different solvents in presence of gold nanoparticles.
In this technique an Ar+ laser (wavelength 514 nm, power 40 mW) and
intensity stabilized He-Ne laser were used as the heating source and probe
beam respectively. The experimental results showed that thermal diffusivity
values of the studied solvents (water, ethanol and ethylene glycol (EG))
were enhanced by the presence of gold nanoparticles
Study of gold nanoparticles effect on thermal diffusivity of nanofluids based on various solvents by using thermal lens spectroscopy
Photoacoustic Spectroscopy to determine
In order to compare the non radiative relaxation time
(NRRT) between standard protoporphyrin IX (PpIX) and protoporphyrin PpIX(1)
solution containing gold metallic nanoparticles, we measured the
photoacoustic spectroscopy (PAS) signal phase to determine, for each
solution, the NRRT by using the Rosencwaig-Gesho theory, modified to include
the effect of a finite non radiative deexcitation time. A NRRT average
value, obtained for each solution, is reported and compared with some NRRT
of triplet states reported in the literature for molecules with the same
tetrapyrrolic structure. In the study was used PpIX disodium salt (DS)
solution of 25% HCL. From each solution it was obtained its optical
absorption spectrum, by using a UV-Vis spectrophotometer. After this, in the
maximum observed optical absorption peak (404 nm), it was obtained the
Photoacoustic (PA) signal phase as a function of the light modulation
frequency, from 17 to 80 Hz. Our investigations are devoted to the
improvement of the thermal treatments of drugs for medical applications
Heat diffusion in the two layer system GaAs/GaSb joined by the fusion technique
Heat difusion is study in the two layer GaAs/GaSb system. Analysis of the thermal diffusivity of these systems demostrates the rol that the union plays in heat transport in these systems as a function of the temperature used in the joining process. The termal diffusivity measurementswere carried out by mean of the photoacoustic technique in a heat transmission configuration