Wide band observations of the X-ray burster GS 1826-238

GS 1826-238 is a well-studied X-ray bursting neutron star in a low mass binary system. Thermal Comptonisation by a hot electron cloud is a widely accepted mechanism accounting for its high energy emission, while the nature of most of its soft X-ray output is not completely understood. A further low energy component is typically needed to model the observed spectra: pure blackbody and Comptonisation-modified blackbody radiation by a lower temperature (a few keV) electron plasma were suggested to explain the low energy data. We studied the steady emission of GS 1826-238 by means of broad band (X to soft Gamma-rays) measurements obtained by the INTEGRAL observatory in 2003 and 2006. The newly developed, up-to-date Comptonisation model CompTB is applied for the first time to study effectively the low-hard state variability of a low-luminosity neutron star in a low-mass X-ray binary system. We confirm that the 3-200 keV emission of \GS is characterised by Comptonisation of soft seed photons by a hot electron plasma. A single spectral component is sufficient to model the observed spectra. At lower energies, no direct blackbody emission is observed and there is no need to postulate a low temperature Compton region. Compared to the 2003 measurements, the plasma temperature decreased from 20 to 14 keV in 2006, together with the seed photons temperature. The source intensity was also found to be 30% lower in 2006, whilst the average recurrence frequency of the X-ray bursts significantly increased. Possible explanations for this apparent deviation from the typical limit-cycle behaviour of this burster are discussed.Comment: 6 pages, 2 figures. Accepted for publication in A&

Learning state-variable relationships for improving POMCP performance

We address the problem of learning state-variable relationships across different episodes in Partially Observable Markov Decision Processes (POMDPs) to improve planning performance. Specifically, we focus on Partially Observable Monte Carlo Planning (POMCP) and we represent the acquired knowledge with Markov Random Fields (MRFs). We propose three different methods to compute MRF parameters while the agent acts in the environment. Our tech- niques acquire information from agent action outcomes, and from the belief of the agent, which summarizes the knowledge acquired from observations. We also propose a stopping criterion to deter- mine when the MRF is accurate enough and the learning process can be stopped. Results show that the proposed approach allows to effectively learn state-variable probabilistic constraints and to outperform standard POMCP with no computational overhead

The X-ray spectrum of the bursting atoll source 4U~1728-34 observed with INTEGRAL

We present for the first time a study of the 3-200 keV broad band spectra of the bursting atoll source 4U 1728-34 (GX 354-0) along its hardness intensity diagram. The analysis was done using the INTEGRAL public and Galactic Center deep exposure data ranging from February 2003 to October 2004. The spectra are well described by a thermal Comptonization model with an electron temperature from 35 keV to 3 keV and Thomson optical depth, tau_T, from 0.5 to 5 in a slab geometry. The source undergoes a transition from an intermediate/hard to a soft state where the source luminosity increases from 2 to 12% of Eddington. We have also detected 36 type I X-ray bursts two of which show photospheric radius expansion. The energetic bursts with photospheric radius expansion occurred at an inferred low mass accretion rate per unit area of \dot m ~ 1.7x10E3 g/cm2/s, while the others at a higher one between 2.4x10E3 - 9.4x10E3 g/cm2/s. For 4U1728-34 the bursts' total fluence, and the bursts' peak flux are anti-correlated with the mass accretion rate. The type I X-ray bursts involve pure helium burning either during the hard state, or during the soft state of the source.Comment: 11 pages, 7 figures, and 2 tables. Accepted for publication in A&

Formation of Halogenated Byproducts upon Water Treatment with Peracetic Acid

Peracetic acid has quickly gained ground in water treatment over the last decade. Specifically, its disinfection efficacy toward a wide spectrum of microorganisms in wastewater is accompanied by the simplicity of its handling and use. Moreover, peracetic acid represents a promising option to achieve disinfection while reducing the concentration of typical chlorination byproducts in the final effluent. However, its chemical behavior is still amply debated. In this study, the reactivity of peracetic acid in the presence of halides, namely, chloride and bromide, was investigated in both synthetic waters and in a real contaminated water. While previous studies focused on the ability of this disinfectant to form halogenated byproducts in the presence of dissolved organic matter and halides, this work indicates that peracetic acid also contributes itself as a primary source in the formation of these potentially carcinogenic compounds. Specifically, this study suggests that 1.5 mM peracetic acid may form around 1-10 μg/L of bromoform when bromide is present. Bromoform formation reaches a maximum at near neutral pH, which is highly relevant for wastewater management

Learning environment properties in Partially Observable Monte Carlo Planning

We tackle the problem of learning state-variable relationships in Partially Observable Markov Decision Processes to improve planning performance on mobile robots. The proposed approach extends Partially Observable Monte Carlo Planning (POMCP) and represents state-variable relationships with Markov Random Fields. A ROS-based implementation of the approach is proposed and evaluated in rocksample, a standard benchmark for probabilistic planning under uncertainty. Experiments have been performed in simulation with Gazebo. Results show that the proposed approach allows to effectively learn state- variable probabilistic constraints on ROS-based robotic platforms and to use them in subsequent episodes to outperform standard POMC

The Weight of Time: Time influences on overweight and obesity in women

We know that adults’ weight increases with age, at least until around the age of 55 years or older. Recent National Australian surveys show that men and women of all age groups were heavier in 2000 than in 1995 or 1990. These studies also found that a greater proportion of people of all ages were overweight or obese in 2000 than in the previous surveys. These studies also suggested that different generations, also known as ‘birth cohorts’, had different patterns of weight gain. These birth cohort influences mean that the year a person is born and the unique set of experiences people born at that time experience, have an effect on weight gain patterns. People born at other times experience different conditions and have different weight gain patterns. Some birth cohorts or ‘generations’ are well-known, such as the ‘baby boomer’ generation, or pre-war generation. For example, Australians born in the first three decades of the twentieth century experienced World War I and II and the Great Depression during their childhood and early adult life. During these times food was scarce and everyday life required high levels of physical activity. This group overall had lower body weights than more recent generations, meaning they were less at risk of becoming obese. Australians born after 1980 were born into an advanced technological society with greater availability of food, a vastly increased range of food products and increasing serving sizes. At the same time, levels of physical activity in everyday life have been decreasing. Together these factors produce an obesogenic environment. The three National Health surveys, conducted by the Australian Bureau of Statistics for the Australian Institute of Health and Welfare in 1990, 1995 and 2000, produced data which the NSW Centre for Overweight and Obesity has analyzed to find out what effects three time factors -- ageing, the time of the surveys and birth cohort, have on body mass index (BMI) and the prevalence of overweight and obesity. [Note – BMI used as the indicator of weight status, where BMI = weight (kg)/height2 (M2)] This report provides an overview of key findings of the analyses of the effects of these three time factors on female weight patterns. The complete findings have been published in a comprehensive technical report. The results from the analysis of the effect of birth cohorts have been used to predict the mean body mass index of women in NSW in 2010. The graphs in this report show the results for women, and the results for men are available in a separate document. The overall patterns and implications for men are generally similar to those for women. NS

The Weight of Time: Time influences on overweight and obesity in men

We know that adults’ weight increases with age, at least until around the age of 55 years or older. Recent National Australian surveys show that men and women of all age groups were heavier in 2000 than in 1995 or 1990. These studies also found that a greater proportion of people of all ages were overweight or obese in 2000 than in the previous surveys. These studies also suggested that different generations, also known as ‘birth cohorts’, had different patterns of weight gain. These birth cohort influences mean that the year a person is born and the unique set of experiences people born at that time experience, have an effect on weight gain patterns. People born at other times experience different conditions and have different weight gain patterns. Some birth cohorts or ‘generations’ are well-known, such as the ‘baby boomer’ generation, or pre-war generation. For example, Australians born in the first three decades of the twentieth century experienced World War I and II and the Great Depression during their childhood and early adult life. During these times food was scarce and everyday life required high levels of physical activity. This group overall had lower body weights than more recent generations, meaning they were less at risk of becoming obese. Australians born after 1980 were born into an advanced technological society with greater availability of food, a vastly increased range of food products and increasing serving sizes. At the same time, levels of physical activity in everyday life have been decreasing. Together these factors produce an obesogenic environment. The three National Health surveys, conducted by the Australian Bureau of Statistics for the Australian Institute of Health and Welfare in 1990, 1995 and 2000, produced data which the NSW Centre for Overweight and Obesity has analyzed to find out what effects three time factors -- ageing, the time of the surveys and birth cohort -- have on body mass index (BMI) and the prevalence of overweight and obesity. [Note – BMI used as the indicator of weight status, where BMI = weight (kg)/height2 (M2)] This report provides an overview of key findings of the analyses of the effects of these three time factors on male weight patterns. The complete findings have been published in a comprehensive technical report. The results from the analysis of the effect of birth cohorts have been used to predict the mean body mass index of men in NSW in 2010. The graphs in this report show the results for men but the results for women are available. The overall patterns and implications for women are generally similar to those for men