A new insight into the temperature induced molecular aggregations in tris(8-hydroxyquinoline) metals

Abstract Annealing of tris(8-hydroxyquinoline) gallium (Gaq3) film at various temperatures in dry N2 atmosphere has shown the existences of four different phases of molecular aggregations before the burning out of the film at about 310 °C. The first three phases, up to 235 °C, are amorphous molecular aggregations, while the fourth one at 255 °C is a crystalline structure, very likely α-polymorph. The photoluminescence (PL) intensity was increased to about five times greater than that of the pristine film at 235 °C, while the PL peak was blue shifted consistently. Although a small contribution of Rayleigh scattering cannot be excluded at high temperatures when crystallites appear, the PL blueshift was mainly attributed to the nanostructured molecular aggregations followed by enhanced PL intensity. These new findings can be a common characteristic of organometallic complexes at varied annealing temperatures. The presented results open a new route of fabricating highly emissive thin films of amorphous nanostructure, which are specifically important for organic light emitting diode (OLED) based displays

An ultra-spatially resolved method to quali-quantitative monitor particulate matter in urban environment

Monitoring the amount and composition of airborne particulate matter (PM) in the urban environment is a crucial aspect to guarantee citizen health. To focus the action of stakeholders in limiting air pollution, fast and highly spatially resolved methods for monitoring PM are required. Recently, the trees’ capability in capturing PM inspired the development of several methods intended to use trees as biomonitors; this results in the potential of having an ultra-spatially resolved network of low-cost PM monitoring stations throughout cities, without the needing of on-site stations. Within this context, we propose a fast and reliable method to qualitatively and quantitatively characterize the PM present in urban air based on the analysis of tree leaves by scanning electron microscopy combined with X-ray spectroscopy (SEM/EDX). We have tested our method in the Real Bosco di Capodimonte urban park (Naples, Italy), by collecting leaves from Quercus ilex trees along transects parallel to the main wind directions. The coarse (PM10–2.5) and fine (PM2.5) amounts obtained per unit leaf area have been validated by weighting the PM washed from leaves belonging to the same sample sets. PM size distribution and elemental composition match appropriately with the known pollution sources in the sample sites (i.e., traffic and marine aerosol). The proposed methodology will then allow the use of the urban forest as an ultra-spatially resolved PM monitoring network, also supporting the work of urban green planners and stakeholders.5s

Magnetically Stabilized Luminescent Excitations in Hexagonal Boron Nitride

Magnetically stabilized luminescence is observed in hexagonal boron nitride. The luminescence is induced by absorption of cold neutrons and is in the visible region. In the absence of a magnetic field, the photon emission level is observed to decay over several hundred seconds. A fraction of this luminescence can be suppressed if the temperature is T <~ 0.6 K and the magnetic field is B >~ 1.0 T. Subsequent to irradiation and suppression, luminescence can be induced by an increase in T or lowering of B. Possible explanations include stabilization of triplet states or the localization and stabilization of excitons.Comment: 11 pages, 7 figures, to appear in the Journal of Luminescenc

Comparing the modeled deposition of PM2.5 with the Eddy Covariance flux and SEM analysis of an urban forest in Naples

Trees can remove particles from the air through the physical deposition on the leaf surface. This process depends on pollution concentration and weather conditions as wind speed and precipitation, in addition to leaf characteristics. Wind speed increases at the same time the deposition velocity and the resuspension of PM deposited, instead, the rain washes off into the soil the particles accumulated on the leaf. The PM flux removed by trees has been modeled in the i-Tree Eco model considering the effect of wind speed on deposition velocity and resuspension and fixing a threshold of leaf washing (0.2 mm x LAI). However, the results of the model have not been validated with measured data and especially the washing threshold and resuspension classes based on wind speed still remain uncertain. In this study, we compared the modeled deposition of PM2.5 with the Eddy Covariance flux measured in an urban forest in Naples. The results of the model have been further validated by comparing the expected PM2.5 accumulations on the leaf (net flux integral) with the average PM load experimentally determined in the same site where the model input data (i.e., PM concentration, wind speed and rain) have been collected. The model and Eddy Covariance presented a good agreement in assessing the deposition flux on leaves but we show that also precipitation events higher than the threshold are not able to wash all particles accumulated on leaves as confirmed by the higher accumulation of PM2.5 measured with the SEM analysis. Furthermore, a wind speed above 20 m s-1 strongly affects the deposition because of the high resuspension back to the atmosphere. Finally, we highlight the importance of including a species-specific parametrization in the model to take into account the influence of leaf characteristics on the deposition velocity, resuspension, and leaf washing

Association between mothers' screening uptake and daughters' HPV vaccination: A quasi-experimental study on the effect of an active invitation campaign

Objectives In Emilia-Romagna, the Human Papillomavirus (HPV) vaccination campaign started in 2008 offering free vaccines for 1996 and 1997 cohorts. Systematic active invitation was implemented for the 1997 cohort. Our study aimed at measuring the impact of the active invitation campaign on HPV vaccine coverage and on coverage inequalities in 11-year-old girls. Second, we evaluated the effect of the HPV vaccination campaign on participation in cervical cancer screening by mothers of target girls. Methods We collected information on vaccination status for girls residing in Reggio Emilia in 2008 and mothers' screening history, before and after the 2008 vaccination campaign. Log-binomial regression models were performed to estimate Relative Risk (RR) and 95% confidence intervals (CIs) of being vaccinated as regarded citizenship, siblings, mothers' education, marital status and screening history, stratified by birth cohort. We also calculated RR of receiving a Pap test after the vaccination campaign as regarded education, daughter's cohort and mothers' decision to have their daughter vaccinated. Interaction between education and cohort in mothers overdue for Pap testing was calculated. Results Vaccination coverage was 46.3% for the uninvited cohort (1046/2260) and 77.9% for the invited cohort (1798/2307). In the uninvited cohort, daughters' vaccination showed association with mothers' education (8 to 11 years of education vs. graduated mothers, RR 1.61 95% CI 1.14-2.28), citizenship (foreigners vs. Italians, RR 0.45 95% CI 0.37-0.56) and screening history (regular vs. non-participant; RR 1.72 95% CI 1.26-2.36). In the invited cohort, only a slight association with screening history persisted (regular vs. non-participant; RR 1.20 95% CI 1.04-1.40). Highly educated under-screened mothers of the invited cohort showed a higher probability of receiving a Pap test after the vaccination campaign period (RR 1.27 95% CI 1.04-1.56) compared with those not invited, Conclusion Active invitation could increase overall HPV immunisation coverage and reduce socio-demographic inequalities and the association with mothers' screening participation

Spallative ablation of dielectrics by X-ray laser

Short laser pulse in wide range of wavelengths, from infrared to X-ray, disturbs electron-ion equilibrium and rises pressure in a heated layer. The case where pulse duration $\tau_L$ is shorter than acoustic relaxation time $t_s$ is considered in the paper. It is shown that this short pulse may cause thermomechanical phenomena such as spallative ablation regardless to wavelength. While the physics of electron-ion relaxation on wavelength and various electron spectra of substances: there are spectra with an energy gap in semiconductors and dielectrics opposed to gapless continuous spectra in metals. The paper describes entire sequence of thermomechanical processes from expansion, nucleation, foaming, and nanostructuring to spallation with particular attention to spallation by X-ray pulse