Positronium Decay : Gauge Invariance and Analyticity

The construction of positronium decay amplitudes is handled through the use of dispersion relations. In this way, emphasis is put on basic QED principles: gauge invariance and soft-photon limits (analyticity). A firm grounding is given to the factorization approaches, and some ambiguities in the spin and energy structures of the positronium wavefunction are removed. Non-factorizable amplitudes are naturally introduced. Their dynamics is described, especially regarding the enforcement of gauge invariance and analyticity through delicate interferences. The important question of the completeness of the present theoretical predictions for the decay rates is then addressed. Indeed, some of those non-factorizable contributions are unaccounted for by NRQED analyses. However, it is shown that such new contributions are highly suppressed, being of order alpha^3. Finally, a particular effective form factor formalism is constructed for parapositronium, allowing a thorough analysis of binding energy effects and analyticity implementation.Comment: 34 pages, 13 figure

Reclaimed wastewater reuse impacts: from literature data gaps to integrated risk modelling

The complexity and the inherent interconnection of the reclaimed wastewater reuse (RWW) system requires the proper quantification of its advantages and drawbacks. In this context, water utilities and decision makers would benefit from a comprehensive risk-based framework of models aimed at the assessment of its associated impacts. In this work, a critical literature review on the models available for the assessment of RWW reuse impacts is performed to highlight which gaps need to be filled and indicate the future research directions. A simplified approach for evaluating and integrating different type of risks was proposed to address the prioritization of critical endpoints and contaminants within regulations

Sound velocity and absorption measurements under high pressure using picosecond ultrasonics in diamond anvil cell. Application to the stability study of AlPdMn

We report an innovative high pressure method combining the diamond anvil cell device with the technique of picosecond ultrasonics. Such an approach allows to accurately measure sound velocity and attenuation of solids and liquids under pressure of tens of GPa, overcoming all the drawbacks of traditional techniques. The power of this new experimental technique is demonstrated in studies of lattice dynamics, stability domain and relaxation process in a metallic sample, a perfect single-grain AlPdMn quasicrystal, and rare gas, neon and argon. Application to the study of defect-induced lattice stability in AlPdMn up to 30 GPa is proposed. The present work has potential for application in areas ranging from fundamental problems in physics of solid and liquid state, which in turn could be beneficial for various other scientific fields as Earth and planetary science or material research

Robust inference for geographic regression discontinuity designs: assessing the impact of police precincts

We study variation in policing outcomes attributable to differential policing practices in New York City (NYC) using geographic regression discontinuity designs (GeoRDDs). By focusing on small geographic windows near police precinct boundaries we can estimate local average treatment effects of precincts on arrest rates. The standard GeoRDD relies on continuity assumptions of the potential outcome surface or a local randomization assumption within a window around the boundary. These assumptions, however, can easily be violated in realistic applications. We develop a novel and robust approach to testing whether there are differences in policing outcomes that are caused by differences in police precincts across NYC. In particular, our test is robust to violations of the assumptions traditionally made in GeoRDDs and is valid under much weaker assumptions. We use a unique form of resampling to identify new geographic boundaries that are known to have no treatment effect, which provides a valid estimate of our test statistic's null distribution even under violations of standard assumptions. This procedure gives substantially different results in the analysis of NYC arrest rates than those that rely on standard assumptions, thereby providing more robust tests of the effect of police precincts on arrest rates in NYC

Does ozonation enhance activated carbon adsorption of PFAS in textile wastewater?

Per- and polyfluoroalkyl substances (PFAS) are used in numerous industrial applications, such as in textile manufacturing, because of their special chemical properties. To avoid PFAS spread in the environment, removal strategies need to be implemented at the wastewater treatment plants (WWTP) to reduce their environmental risk on receiving water bodies. The fate of 14 PFAS in a full-scale WWTP treating textile and civil wastewater (WW) was investigated. The addition of an adsorption step before or after the ozonation process was studied through adsorption isotherms tested on the WW collected before and after the full-scale ozonation step. Ozonation is not aimed at PFAS removing, but it lowers organic matter competition towards long-chain PFAS in the following adsorption step. The removal of UVA254 seems to be a good proxy variable for PFAS adsorption, with relationships not dependent on the presence of ozonation step

Two Gallium data sets, spin flavour precession and KamLAND

We reexamine the possibility of a time modulation of the low energy solar neutrino flux which is suggested by the average decrease of the Ga data in line with our previous arguments. We perform two separate fits to the solar neutrino data, one corresponding to 'high' and the other to 'low' Ga data, associated with low and high solar activity respectively. We therefore consider an alternative to the conventional solar+KamLAND fitting, which allows one to explore the much wider range of the $\theta_{12}$ angle permitted by the KamLAND fitting alone. We find a solution with parameters $\Delta m^2_{21}=8.2\times 10^{-5} eV^2, tan^{2}\theta=0.31$ in which the 'high' and the 'low' Ga rates lie far apart and are close to their central values and is of comparable quality to the global best fit, where these rates lie much closer to each other. This is an indication that the best fit in which all solar and KamLAND data are used is not a good measure of the separation of the two Ga data sets, as the information from the low energy neutrino modulation is dissimulated in the wealth of data. Furthermore for the parameter set proposed one obtains an equally good fit to the KamLAND energy spectrum and an even better fit than the 'conventional' LMA one for the reactor antineutrino survival probability as measured by KamLAND.Comment: V2: 15 pages, 3 eps figures, fit improved, final version to appear in Journal of Physics

Lattice diffusion and surface segregation of B during growth of SiGe heterostructures by molecular beam epitaxy: effect of Ge concentration and biaxial stress

Si1-xGex/Si1-yGey/Si(100) heterostructures grown by Molecular Beam Epitaxy (MBE) were used in order to study B surface segregation during growth and B lattice diffusion. Ge concentration and stress effects were separated. Analysis of B segregation during growth shows that: i) for layers in epitaxy on (100)Si), B segregation decreases with increasing Ge concentration, i.e. with increased compressive stress, ii) for unstressed layers, B segregation increases with Ge concentration, iii) at constant Ge concentration, B segregation increases for layers in tension and decreases for layers in compression. The contrasting behaviors observed as a function of Ge concentration in compressively stressed and unstressed layers can be explained by an increase of the equilibrium segregation driving force induced by Ge additions and an increase of near-surface diffusion in compressively stressed layers. Analysis of lattice diffusion shows that: i) in unstressed layers, B lattice diffusion coefficient decreases with increasing Ge concentration, ii) at constant Ge concentration, the diffusion coefficient of B decreases with compressive biaxial stress and increases with tensile biaxial stress, iii) the volume of activation of B diffusion () is positive for biaxial stress while it is negative in the case of hydrostatic pressure. This confirms that under a biaxial stress the activation volume is reduced to the relaxation volume

Drinking water recontamination in distribution networks: the case of bisphenol A release from epoxy resins

Monitoring and management of drinking water distribution networks (DWDNs), including possible release from materials in contact with drinking water (DW), have been stressed as crucial to avoid DW re-contamination leading to a potential increase of human health risk. Recent scientific studies and regulations clearly highlighted the release of bisphenol A (BPA) from plastic materials used to renovate DWDNs pipelines as one the major hazardous events. Lab tests on three epoxy resins were designed with the Design of Experiments (DoE) method to calibrate a migration model. In order to predict water quality variation in DWDNs, the migration model was combined with a hydraulic model, through EPANET-MSX, and validated in relevant environmental conditions, in collaboration with an Italian water utility. The model allowed to simulate BPA propagation in the DWDN identifying the most vulnerable areas and permitting to customize a site-specific monitoring and intervention plan to minimize the risk

Emerging contaminants in drinking water treatment plants: how ozonation affects activated carbon adsorption

Contaminants of Emerging Concern (CECs) in drinking water are a growing concern for potential negative effects on human health. This study combines full-scale monitoring campaigns in a drinking water treatment plant (DWTP) and lab-scale experiments using real water matrices without CECs spike. Monitoring campaigns were performed over one year and over 116 monitored CECs, a maximum of 22 compounds have been detected at the DWTP inlet. The analyses show that ozonation and adsorption on activated carbon (AC) have the main impact in reducing a wide variety of CECs, with performances influenced by their characteristics. At lab-scale adsorption isotherms were performed on 4 different water matrices, before and after ozonation, the evaluate the effect of ozonation on the adsorption process. Ozonation is less effective than AC adsorption in CECs removal, but the combination of the two processes allows to reduce the variability of the removal efficiencies, providing a highest performance for the removal of all the investigated CECs