Asthma and physical activity in childhood

This thesis investigates the association between asthma and physical activity in children. Asthma is one of the most common chronic diseases in childhood and is caused by multiple factors, both genetic and environmental. Previous research has shown that obesity is a risk factor for developing asthma. This thesis focuses on the role of physical activity. The thesis describes several studies investigating asthma and physical activity in different directions and at different ages. Questionnaires, motion sensors (accelerometry) and lung function tests were used for this purpose. In conclusion, it can be stated that asthma and physical activity are not clearly associated

Photoluminescence from low temperature grown InAs/GaAs quantum dots

The authors investigated a set of self-assembled InAs/GaAs quantum dots (QDs) formed by mol. beam epitaxy at low temp. (LT, 250 DegC) and postgrowth annealing. A QD photoluminescence (PL) peak around 1.01 eV was obsd. The PL efficiency quickly quenches between 6 and 40 K due to the tunneling out of the QD into traps within the GaAs barrier. The PL efficiency increases by a factor of 45-280 when exciting below the GaAs band gap, directly into the InAs QD layer. This points towards good optical quality QDs, which are embedded in a LT-GaAs barrier with a high trapping efficiency. [on SciFinder (R)

Incorporating natural variation into IVF clinic league tables: The Expected Rank

Background. Rankings based on outcome are often used to present health care provider performance. These rankings do however not reflect that part of the variation in outcome between providers is caused by natural variation, and not by any differences in quality of care. The aim of this study is to compare standard methods for ranking with a novel method that takes into account natural variation. Methods. We used data on the number of treatment cycles and the number of pregnancies of 13 Dutch IVF clinics from 2004. We calculated the Expected Rank (ER), an estimate of the true rank of a provider, accounting for natural variation. We rescaled the ER to obtain the Percentile based on ER (PCER), that can be interpreted as the probability that a clinic is worse than a randomly selected other clinic. We also calculated a measure for rankability ρ, which is the part of variation between providers that is due to true differences (as opposed to natural variation). Results. The expected ranks ranged from 1.4 to 11.9 instead of the original ranks 1-13. The ER showed that some clinics performed very similar, which would be disregarded when using standard ranks. The PCER ranged from 7% to 88%. Rankability was substantial (ρ = 0.9). Conclusion. The Expected Rank provides a way to combine the attractiveness of a ranking, a single number and easy interpretation, with reliable analyses that does justice to the providers, and also allows individual comparisons

Formation of InAs quantum dot arrays on GaAs (100) by self-organized anisotropic strain engineering of a (In,Ga)As superlattice template

We demonstrate the formation of well-defined InAs quantum dot (QD) arrays by self-organized engineering of anisotropic strain in a (In,Ga)As/GaAs superlattice (SL). Due to the accumulation and improvement of the uniformity of the strain-field modulation along [011], formation of InAs QD arrays along [0-11] with 140 nm lateral periodicity is clearly observed on the SL template when the number of SL periods is larger than ten. By enhancing the In adatom surface migration length at low growth rates, clear arrays of single InAs QDs are obtained. The QD arrays exhibit strong photoluminescence efficiency that is not reduced compared to that from InAs QD layers on GaAs. Hence, ordering by self-organized anisotropic strain engineering maintains the high structural quality of InAs QD

Wavelength controlled multilayer-stacked linear InAs quantum dot arrays on InGaAsP/InP(100) by self-organized anisotropic strain engineering : a self-ordered quantum dot crystal

Multilayer-stacked linear InAs quantum dot (QD) arrays are created on InAs/InGaAsP superlattice templates formed by self-organized anisotropic strain engineering on InP (100) substrates in chemical beam epitaxy. Stacking of the QD arrays with identical emission wavelength in the 1.55 µm region at room temperature is achieved through the insertion of ultrathin GaAs interlayers beneath the QDs with increasing interlayer thickness in successive layers. The increment in the GaAs interlayer thickness compensates the QD size/wavelength increase during strain correlated stacking. This is the demonstration of a three-dimensionally self-ordered QD crystal with fully controlled structural and optical properties

Fertility in Populations and in Patients: Population studies on natural fertility and prediction of treatment outcome in anovulatory infertile patients

__Abstract__ In most western societies, reproductive behavior is nowadays controlled to a high degree: observed fertility patterns in a population -how many children do couples get and when do they get them- are the result of choices made by individuals rather than biological factors. This is in marked contrast with previous times, in which it was the biological destiny of women to have children - or to remain childless involuntarily. The driving force behind the change that has occurred is undoubtedly the availability of reliable contraception (Leridon, 1998), which has gone hand in hand with changes in social attitudes with respect to reproduction (e.g. secularization, emancipation of women (Blossfeld, 1995)). In many Western European societies, the number of children per woman has dropped below the natural replacement level (Von Cube, 1986), and everywhere couples who want to have children carefully plan when to have them. In many countries women delay childbearing to later age, the most pronounced example being the Netherlands in which the mean age at first childbirth has risen from 24.6 years in 1970 to 29.2 years in 2001. Since pregnancy chances decrease with age of the women (Schwartz and Mayaux, 1982) (van Noord-Zaadstra et al., 1991), postponement of the first child has led to an increase in incidence of subfertility (te Velde, 1991)

Effect of annealing on formation of self-assembled (In,Ga)As quantum wires on GaAs (100) by molecular beam epitaxy

The role of annealing for (In,Ga)As self-organized quantum wire (QWR) formation on GaAs (100) during growth of (In,Ga)As/GaAs superlattice (SL) structures is studied by X-ray diffraction (XRD), atomic force microscopy (AFM), and photoluminescence (PL) spectroscopy. XRD and AFM evidence that annealing after the supply of each layer of elongated (In,Ga)As quantum dots (QDs) in the SL is the crucial process for QWR formation. We conclude that during annealing, the shape anisotropy of the QDs is enhanced due to anisotropic mass transport and the QDs become connected along the [0-11] direction. Strain reduction by In desorption, revealed by XRD and PL, which accompanies this process, then results in well defined, uniform QWR arrays by repetition in SL growt

Sociedades justas: Una nueva visión para la equidad en la salud en la Región de las Américas después de la COVID19

Objective. Determine patterns of tuberculosis (TB) incidence indicators and number of deaths from TB within the framework of target 3.3 of the Sustainable Development Goals (SDGs) and their correlation with social determinants. Methods. Ecological study methodology was used, in which the population is the unit of analysis. Social determinants were analyzed using a negative binomial regression model and strength of association. Results. In the Americas, there was an average annual reduction in the TB incidence rate of 0.3% from 2009 to 2018; however, from 2015 to 2018, the rate increased, from 27.6 to 28.8 per 100,000 population. With regard to social determinants, the groups of countries with the lowest human development index (HDI) and gross domestic product (GDP) have a higher incidence of TB. TB risk in the country with the lowest HDI is six times that of the country with the highest HDI. Conclusions. At the current rate of reduction in the incidence rate and number of deaths from TB, the Region of the Americas will not meet the targets in the SDGs and in the End TB Strategy. Rapid implementation and expansion of interventions for TB prevention and control are required to attain the targets. This involves, among other actions, reducing access barriers to diagnosis and treatment and strengthening initiatives to address social determinants

Carrier dynamics of LT InAs/GaAs QDs using time resolved differential reflectivity

We present a Time Resolved Differential Reflectivity (TRDR) study of LT (low temperature grown) Stransky - Krastanov InAs/GaAs Quantum Dots (QDs) grown using molecular beam epitaxy. The photoluminescence (PL) spectrum shows a QD-peak around 1200nm. In the TRDR measurements we observe an initial fast decay (80ps) followed by a much slower decay of about 800ps. The strong temperature dependence of the PL-signal is not observed in the reflectivity signal. This leads us to conclude that the electrons are trapped at a fast rate by As antisite defects while the hole decay dynamics take place at a slower rate, which is also monitored in TRDR