Association between breastfeeding and anthropometry and cardiovascular disease risk factor status in adolescence and young adulthood: the Young Hearts Project, Northern Ireland.

Objective: To examine the association between breastfeeding and blood pressure, anthropometry, and plasma lipid profile in both adolescence and young adulthood. Design: Longitudinal study of biological and behavioural risk factors for cardiovascular disease. Setting: The Young Hearts Project, Northern Ireland Subjects: School children aged 12 years and 15 years who participated in a cross-sectional study of lifestyle and health, and who were followed up as young adults aged 20 – 25 years. Results: There was no significant difference in height, weight, BMI, skin-fold thickness measurements, blood pressure or plasma lipid profile in adolescents who had been breastfed when compared to those who had not been breastfed. However, by the time these adolescents had reached adulthood, those who had been breastfed were significantly taller when compared to those who had not been breastfed (standing height, P=0.013; leg length (P=0.035)). Specifically, the breastfed group were on average taller by 1.7cm (95% CI 0.4, 3.0) and had longer legs by 1cm (95% CI 0.1, 1.9). There was no significant difference in other anthropometric measures, blood pressure or plasma lipid profile in adults who had been breastfed when compared to those who had not been breastfed. Conclusions: Compared with those who had not been breastfed, individuals who had been breastfed were taller in adulthood. Given the known association of increased adult height with improved life expectancy the results from this study support a beneficial effect of breastfeeding.

Artificial magnetic conductor surfaces and their application to low-profile high-gain planar antennas

Planar periodic metallic arrays behave as artificial magnetic conductor (AMC) surfaces when placed on a grounded dielectric substrate and they introduce a zero degrees reflection phase shift to incident waves. In this paper the AMC operation of single-layer arrays without vias is studied using a resonant cavity model and a new application to high-gain printed antennas is presented. A ray analysis is employed in order to give physical insight into the performance of AMCs and derive design guidelines. The bandwidth and center frequency of AMC surfaces are investigated using full-wave analysis and the qualitative predictions of the ray model are validated. Planar AMC surfaces are used for the first time as the ground plane in a high-gain microstrip patch antenna with a partially reflective surface as superstrate. A significant reduction of the antenna profile is achieved. A ray theory approach is employed in order to describe the functioning of the antenna and to predict the existence of quarter wavelength resonant cavities.

Low-profile resonant cavity antenna with artificial magnetic conductor ground plane

A planar artificial magnetic conductor (AMC) ground plane is proposed as a means to reduce the profile of a highly directive resonant cavity antenna. The structure is formed by a printed microstrip patch antenna and a superimposed partially reflective surface. The antenna profile is reduced to approximately half by virtue of employing the AMC ground plane. A ray theory model is used to qualitatively describe the functioning of the antenna and theoretically predict the existence of quarter wavelength resonant cavities.

Effect of Free-Fall Height in Water on Performance of Flowable Concrete

Concrete placed under water should be proportioned to flow readily into place with minimum materials separation. Unlike concrete cast for deep tremie seals, the use of concrete in repairs often necessitates some free fall of the mixture through water. Such placement conditions lead to greater risk of water erosion and segregation, and should be addressed in proportioning highly flowable underwater concrete. This paper evaluates the effect of free-fall height (FFH) of concrete through water on resulting in-place properties. Concrete was cast in blocks measuring 0.54 x 0.44 x 1 m with the initial FFH in water ranging between 0.25 and 0.60 m. In-place compressive and splitting tensile strengths, unit weight, and depth of washed-out and sedimentation materials were determined. In total, 24 highly flowable mixtures with slump flows greater than 500 mm were investigated. The evaluated mixtures were prepared with various hydraulic binders, including conventional Type 10 cement, a binary mixture with 10% of silica fume (SF), and a ternary binder incorporating 20% of fly ash (FA) and 6% of SF. The mixtures were proportioned with water-binder ratios (w/b) ranging between 0.41 and 0.47. Test results show that the increase of FFH of fresh concrete in water can greatly decrease the residual strength and significantly increase the thickness of washed out and sedimentation materials. The incorporation of 10% of SF, or 20% of FA and 6% of SF, and the reduction of the w/b from 0.47 to 0.41 can, however, lead to a significant increase in washout resistance and residual strength. A relationship between residual strength and the coupled factor of free-fall drop of concrete in water and washout resistance is established.

A Profile of Adolescent Cocaine Use in Northern Ireland.

Background: The image of cocaine as a 'party' drug used by more affluent members of society has begun to change as the levels of use of the drug rise amongst school aged young people. Methods: Cocaine use patterns amongst young people aged 13-16 years who were participating in the Belfast Youth Development Study, a longitudinal study of adolescent drug use was explored. Data was collected through an annual datasweep in participating schools. This paper includes data collected in years 3, 4 and 5 of the study. Results: The results show higher levels of cocaine use amongst this age group than reported in much of the existing harm reduction literature. Lifetime use was 3.8% at age 13-14 years, rising to 7.5% at 15-16 years. The profile indicated that adolescent cocaine users were more likely to be female, live in disrupted families and experience social deprivation which is similar to existing adolescent drug use profiles. There was also some evidence of experimental cocaine use amongst the sample. Conclusions: These findings provide further evidence for the development of age appropriate school focused harm reduction initiatives and continued monitoring of contemporary trends of use of cocaine amongst school aged young people.

Electromagnetic beam profile dynamics in collisional plasmas

The compression of a finite extent Gaussian laser pulse in collisional plasma is investigated. An analytical model is employed to describe the spatiotemporal evolution of a laser pulse propagating through the plasma medium. The pulse geometry is modeled via an appropriate ansatz which takes into account both beam radius (in space) and pulse width (in time). Compression and self-focusing are taken into account via appropriated group velocity dispersion and nonlinearity terms. The competition among the collisional nonlinearity in the plasma and the effect of divergence due to diffraction is pointed out and investigated numerically. Our results suggest that laser pulse compression and intensity localization is enhanced by plasma collisionality. In specific, a pulse width compression by an order of magnitude approximately is observed, for typical collisional laser plasma parameters, along with a significant increase in the intensity.