Saharan dust electrification perceived by a triangle of atmospheric electricity stations in Southern Portugal

Atmospheric Electric Potential Gradient (PG) measurements were carried out in three sites forming a triangular array in Southern Portugal. The campaign was performed during the summer, characterized by Saharan dust outbreaks; 16th-17th July 2014 dust event is considered. Short time-scale oscillations of the PG at two of the stations and a mid time-scale suppression of the PG in the three stations are found. Results are interpreted as evidencing long-range dust electrification; attributed to the air-Earth electrical current creating a bipolar charge distribution inside of the dust layer. The relevance of using arrays of sensors, instead of single sited, is highlighted

Childhood obesity and reduction of hours of sleep: results from cross-sectional study

Childhood obesity is a prevalent condition in modern societies which can negatively impact people's health during life. Although there are several factors contributing to obesity, sleep duration has been pointed out as an important risk factor. This study, held in the district of Porto, Portugal, aimed to analyze the association between sleep duration and the nutritional status of school-aged children studying in Portugal. 1396 students from 35 and 3 public and private schools, respectively, were contacted, of which 829 participated in this study (9.2 +/- 0.38 years old; 50.3% male; 49.7% female). Age, sex, sleep duration, height, weight and body composition were registered trough a questionnaire. According to the obtained z-score for Body Mass Index (BMI), 22.9% of the children were overweight and 15.2% were obese. The mean of sleep duration was 9.7 +/- 1.08 hours and z-score for BMI was 0.78 +/- 1.21, demonstrating a statistically significant (p<0.01) weak negative correlation (r=-0.15) between sleep duration and z-score of BMI. Results were also stratified and analyzed by sex, and the same finding was observed. Therefore, the results suggest a negative association between sleep duration and overweight/obesity in these children. Although more studies are necessary, this finding highlights the need of a global approach which includes sleep assessment and counselling when promoting an appropriate nutritional status

Micromegas operation in high pressure xenon: charge and scintillation readout

The operational characteristics of a Micromegas operating in pure xenon at the pressure range of 1 to 10 bar are investigated. The maximum charge gain achieved in each pressure is approximately constant, around 4x10^2, for xenon pressures up to 5 bar and decreasing slowly above this pressure down to values somewhat above 10^2 at 10 bar. The MM presents the highest gains for xenon pressures above 4 bar, when compared to other micropattern gaseous multipliers. The lowest energy resolution obtained for X-rays of 22.1 keV exhibits a steady increase with pressure, from 12% at 1bar to about 32% at 10 bar. The effective scintillation yield, defined as the number of photons exiting through the MM mesh holes per primary electron produced in the conversion region was calculated. This yield is about 2x10^2 photons per primary electron at 1 bar, increasing to about 6x10^2 at 5 bar and, then, decreasing again to 2x10^2 at 10 bar. The readout of this scintillation by a suitable photosensor will result in higher gains but with increased statistical fluctuations.Comment: 22 pages, 11 figure

Impact of atmospherical stability and intra-hour variation of meteorological data in the variability of building air change rates

In contrast with structural engineering, where the focus for design is on extreme values, for the proper assessment and modelling of air change rates in natural ventilation and infiltration, one must use the full range of input variables. Most of the modelling in infiltration research relies on hourly datasets for air infiltration balance. This consideration overlooks the intra-hour variability on meteorological variables. Additionally, it is customary to assume unchanging neutral atmospheric conditions when modelling, which affects the calculated airflows. This work intends to detail and quantify these effects in a case study representative of an average single-family dwelling in a Southern European climate setup. By comparing four setups with an increasing degree of complexity, a median of 0.04 h(-1) of the hourly standard deviations in air change rates (ACH) is attributed to the time step effect. Approximately 43% of the occurrences experienced non-neutral atmospheric stability, skewing for stable conditions. This effect contributed to differences in the ACHs ranging from-0.202 to 0.131 h(-1) at the 5% and 95% quantiles. Overall, by using hourly uniform distributions and smart sampling of meteorological variables, one ensures that the values in between and others potentially occurring around the boundaries are being considered for air change rates calculation, and therefore providing a more detailed picture of actual conditions.This work was financially supported by: Base Funding -UIDB/04708/2020 and Programmatic Funding - UIDP/04708/2020 of the CONSTRUCT -Instituto de I&D em Estruturas e Construcoes - funded by national funds through the FCT/MCTES (PIDDAC). The author would like to acknowledge the support of FCT - Fundacao para a Ciencia e a Tecnologia, the funding of the Doctoral Grant PD/BD/135162/2017, through the Doctoral Programme EcoCoRe.The authors also acknowledge Dr. Ricardo Deus and the Portuguese Institute for Sea and Atmosphere, I. P. (IPMA, IP) for providing the meteorological dataset for this work