Adsorption dynamics of hydrophobically modified polymers at an air-water interface

The adsorption dynamics of a series of hydrophobically modified polymers, PAAαCn, at the air-water interface is studied by measuring the dynamic surface tension. The PAAαCn are composed of a poly(acrylic acid) backbone grafted with a percentage α of C8 or C12 alkyl moieties, at pH conditions where the PAA backbone is not charged. The observed adsorption dynamics is very slow and follows a logarithmic behavior at long times indicating the building of an energy barrier which grows over time. After comparison of our experimental results to models from the literature, a new model which accounts for both the deformation of the incoming polymer coils as well as the deformation of the adsorbed pseudo-brush is described. This model enables to fit very well the experimental data. The two fitting parameters give expected values for the monomer size and for the area per adsorbed polymer chain.This article is uploaded in "arXiv.org" https://arxiv.org/abs/1706.0710

Socioeconomic questionnaire and clinical assessment in the HELENA Cross-sectional Study: methodology

Rationale: Environmental factors such as dietary habits, breastfeeding, socioeconomic conditions and educational factors are strong influences on nutritional and puberty status, physical activity, food choices and their interactions. Several diseases of adulthood seem to be linked to, or to originate from, lifestyle in childhood and adolescence. Objective: The aims of this study are to describe birth parameters and socioeconomic factors and to assess clinical status in adolescents aged 13-16 years from 10 European countries participating in the Healthy Lifestyle in Europe by Nutrition in Adolescence (HELENA) Cross-Sectional Study (CSS). Methodology: A self-report questionnaire on the socioeconomic status, a parental questionnaire concerning neonatal period and also a case report form (CRF), in which clinical items during clinical examination (such as medical history, treatments, anthropometry, Tanner staging, blood pressure, heart rate) were assessed. To develop these documents, first a list of items was established, a search of existing documents was performed and the advice of local and international experts was taken. All documents (questionnaires and an operations manual) were discussed in plenary HELENA meetings; a final version of these documents was fixed, and the process of translation and back translation was performed. Results: The questionnaires and CRF were tested for validation in all 10 participant cities; 208 adolescents were enrolled during the pilot study. All items that caused problems or questions in one or more participating centers or were completed by < 85% of the adolescents were reviewed before the beginning of the HELENA-CSS. Conclusion: These final questionnaires and CRF will contribute to better understanding of the inequalities in nutrition, behavior and health in the European adolescent population. The experience and process should be useful for other multicenter studies

Influence of sex, age, pubertal maturation and body mass index on circulating white blood cell counts in healthy European adolescents—the HELENA study

Percentiles 10th, 25th, 50th, 75th and 90th are presented for circulating white blood cells (WBC), neutrophils, lymphocytes, monocytes, eosinophils and basophils in healthy European adolescents (12.5–17.5 years, n = 405, 48.9 % boys), considering age, sex, puberty and body mass index (BMI). CD3+ (mature T cells), CD4+ (T helper), CD8+ (T cytotoxic), CD16+56+ (natural killer), CD19+ (B cells), CD3+CD45RA+, CD4+CD45RA+, CD8+CD45RA+ (naïve), CD3+CD45RO+, CD4+CD45RO+ and CD8+CD45RO+ (memory) lymphocytes were also analysed by immunophenotyping. Girls presented higher WBC, neutrophil, CD3+CD45RO+ and CD4+CD45RO+ cell counts and CD3+/CD19+ ratio, and lower CD3+CD45RA+ and CD4+CD45RA+ counts than boys. Age was associated with higher neutrophil counts and CD3+/CD19+, and lower CD19+ counts; in boys, with lower CD3+CD45RA+, CD4+CD45RA+ and CD8+CD45RA+ counts as well; in girls, with higher WBC, CD3+CD45RO+ and CD4+CD45RO+ counts. Pubertal maturation in boys was associated with lower WBC and lymphocyte counts; in girls, with higher basophil, CD3+CD45RO+ and CD4+CD45RO+ values. BMI was associated with higher WBC counts; in boys, also with higher lymphocyte counts; in girls, with higher neutrophil, CD4+, CD3+CD45RO+ and CD4+CD45RO+ counts. Conclusion: Our study provides normative values for circulating immune cells in adolescents, highlighting the importance of considering sex, age, pubertal maturation and BMI when establishing reference ranges for WBC in paediatric populations

Relationship between self-reported dietary intake and physical activity levels among adolescents: The HELENA study

Background Evidence suggests possible synergetic effects of multiple lifestyle behaviors on health risks like obesity and other health outcomes. Therefore it is important to investigate associations between dietary and physical activity behavior, the two most important lifestyle behaviors influencing our energy balance and body composition. The objective of the present study is to describe the relationship between energy, nutrient and food intake and the physical activity level among a large group of European adolescents. Methods The study comprised a total of 2176 adolescents (46.2% male) from ten European cities participating in the HELENA (Healthy Lifestyle in Europe by Nutrition in Adolescence) study. Dietary intake and physical activity were assessed using validated 24-h dietary recalls and self-reported questionnaires respectively. Analyses of covariance (ANCOVA) were used to compare the energy and nutrient intake and the food consumption between groups of adolescents with different physical activity levels (1st to 3rd tertile). Results In both sexes no differences were found in energy intake between the levels of physical activity. The most active males showed a higher intake of polysaccharides, protein, water and vitamin C and a lower intake of saccharides compared to less active males. Females with the highest physical activity level consumed more polysaccharides compared to their least active peers. Male and female adolescents with the highest physical activity levels, consumed more fruit and milk products and less cheese compared to the least active adolescents. The most active males showed higher intakes of vegetables and meat, fish, eggs, meat substitutes and vegetarian products compared to the least active ones. The least active males reported the highest consumption of grain products and potatoes. Within the female group, significantly lower intakes of bread and cereal products and spreads were found for those reporting to spend most time in moderate to vigorous physical activity. The consumption of foods from the remaining food groups, did not differ between the physical activity levels in both sexes. Conclusion It can be concluded that dietary habits diverge between adolescents with different self-reported physical activity levels. For some food groups a difference in intake could be found, which were reflected in differences in some nutrient intakes. It can also be concluded that physically active adolescents are not always inclined to eat healthier diets than their less active peers.The HELENA study took place with the financial support of the European Community Sixth RTD Framework Programme (Contract FOOD-CT: 2005-007034). This work was also partially supported by the European Union, in the framework of the Public Health Programme (ALPHA project, Ref: 2006120), the Swedish Council for Working Life and Social Research (FAS), the Spanish Ministry of Education (EX-2007-1124, and EX-2008-0641), and the Spanish Ministry of Health, Maternal, Child Health and Development Network (number RD08/0072) (JPRL, LAM)

Evaluation of iron status in European adolescents through biochemical iron indicators: the HELENA Study

BACKGROUND/OBJECTIVES: To assess the iron status among European adolescents through selected biochemical parameters in a cross-sectional study performed in 10 European cities. SUBJECTS/METHODS: Iron status was defined utilising biochemical indicators. Iron depletion was defined as low serum ferritin (SF8.5 mg/l) plus iron depletion. Iron deficiency anaemia (IDA) was defined as ID with haemoglobin (Hb) below the WHO cutoff for age and sex: 12.0 g/dl for girls and for boys aged 12.5-14.99 years and 13.0 g/dl for boys aged ≥15 years. Enzyme linked immunosorbent assay was used as analytical method for SF, sTfR and C-reactive protein (CRP). Subjects with indication of inflammation (CRP >5 mg/l) were excluded from the analyses. A total of 940 adolescents aged 12.5-17.49 years (438 boys and 502 girls) were involved. RESULTS: The percentage of iron depletion was 17.6%, significantly higher in girls (21.0%) compared with boys (13.8%). The overall percentage of ID and IDA was 4.7 and 1.3%, respectively, with no significant differences between boys and girls. A correlation was observed between log (SF) and Hb (r = 0.36, P < 0.01), and between log (sTfR) and mean corpuscular haemoglobin (r = -0.30, P < 0.01). Iron body stores were estimated on the basis of log (sTfR/SF). A higher percentage of negative values of body iron was recorded in girls (16.5%) with respect to boys (8.3%), and body iron values tended to increase with age in boys, whereas the values remained stable in girls. CONCLUSIONS: To ensure adequate iron stores, specific attention should be given to girls at European level to ensure that their dietary intake of iron is adequate.status: publishe

Social environment and food and beverage intake in European adolescents: The Helena study

[Background] The family environment influences food consumption and behaviours, which impact adolescent’s eating habits, diet and health. Young individuals who frequently eat family meals are less likely to develop risk- and behaviour-related outcomes as obesity.[Aim] To assess the relationship between the family meal environment and food and macronutrient consumption in European adolescents.[Methods] 1,703 adolescents aged 12.5-17.5 years (46.5% male) from the European HELENA cross-sectional study were selected. Sociodemographic variables and dietary intake using two non-consecutive self-reported 24-hour dietary recalls were collected from all the included participants. The relationship between family meals’ environment and food and macronutrient consumption was analized using analysis of covariance.[Results] Adolescents who used to take their main meals with their family were associated with high consumption of healthy foods and beverages (i.e. vegetables, fruit, milk, water) and low consumption of energy dense food and beverages as chocolate, savoury snacks, sugar or juices compared with those who used to eat alone, with friends or other people (p < 0.05).[Conclusion] The company/people with whom adolescents consume their meal have an important influence on the adolescent’s consumption of different types of food (especially at lunch). Family’s environment during meals has been associated with a high consumption of healthy foods.This work was carried out as part of the HELENA study (www.helenastudy.com/). We gratefully acknowledge the financial support of the European Community sixth RTD Framework Programme (Contract FOOD-CT-2005-007034). Also, we gratefully acknowledge the Ministry of Science and Innovation (MICINN) and the European Region Development Fund (Fondo Europeo de Desarrollo Regional, FEDER) for their financial support.Peer reviewe

Electron temperature anisotropy associated to field-aligned currents in the Earth's magnetosphere inferred from Rosetta MIP-RPC observations during 2009 flyby

International audienceA new approach is proposed for data interpretation of the Mutual Impedance Probe (MIP) instrument from the Rosetta Plasma Consortium (RPC) during the 2009 Earth's fly-by gravity assist through the magnetosphere, from dusk to dawn regions. The spacecraft trajectory of +/-8 Re (Earth's radius) was crossing several structures of field aligned currents (FACs) and radiations belts on both legs of the closest approach (CA, 2.450 km altitude). As routinely revealed by several pioneering space missions, natural and forced electrostatic wave emissions called Fq's were observed over +/- 3 Re at around CA using a dedicated mode of the MIP instrument. These emissions are lying between consecutive harmonics of the electron-cyclotron frequency, and their wavelength is perpendicular to the magnetic field-lines. Provided that the Fq's wavelengths projected along the MIP antenna might be estimated, it is shown that the local value of the Larmor radius can be deduced, hence the electron temperature component perpendicular to the magnetic field is subsequently derived. On the other hand, during the time of Fq's observations, the presence of VLF hiss emissions usually observed in these regions, gives us the possibility to determine the electron temperature anisotropy associated to the electrostatic electron anisotropy instability according to the theoretical model proposed by Gary and Cairns (JGR, vol.104,1999). Significant dynamic constraints revealed by crossing successive series of FACs tubes are shown being controlled by this anisotropy, and the fact that the magnetic pressure is significantly larger than the thermal pressure suggests that the FACs lobes are non-force free

The small-scale turbulent structure of the high latitude ionosphere - Arcad-Aureol-3 observations

International audienceThe small-scale structure of the high-latitude topside ionosphere is investigated through electric-field and electron-density measurements made by the Arcad-Aureol-3 satellite. The frequency range is between 12.5 and 200 Hz, which, under the hypothesis of zero frequency turbulence, corresponds to spatial wavelengths between 40 and 640 m. Two different groups of regions are identified, in which different types of turbulence are observed: the arc region of the auroral zone, where intense sporadic turbulence events occur, which are associated with precipitations, parallel current, and velocity shears; and the polar cap, diffuse auroral zone and subauroral region, where the turbulence is less intense and often associated with density gradients. The frequency spectra of the electric and density fluctuations generally have a power law shape. The distribution of the spectral indices is different in each type of turbulence, with smaller and less dispersed values in the E x B turbulence than in shear-associated turbulence