Frequency of fog events together with fog water chemical composition, pH, conductivity and liquid water content have systematically been measured from the end of the 1980's at the field station of ...San Pietro Capofiume, in the eastern Po Valley, Northern Italy. In agreement with what has been observed in other regions in Europe, fog frequency (visibility < 1 km) has decreased over the last three decades. Ionic strength and conductivity of fog samples also decreased over the period indicating a reduction of the ionic load of the droplets. Specifically, the three major inorganic ions (NH4+, SO42−, NO3−), accounting for 86% of the total fog water ionic strength, show a decreasing trend in concentration over the period, which can be linked to the decreasing trend of NH3, SO2 and NOx emissions registered in northern Italy over the same period. Sulphate exhibits the highest relative decrease (76%). Seasonal volume-weighted means of pH show an increasing trend over the observed period. The available data of total water-soluble organic matter concentrations indicate that organic compounds represent a considerable fraction (25% on average) of the total solute mass of fog water. Fog water samples often contain suspended insoluble particles, which were collected by filtering fog water through quartz fibre filters. EC-OC analysis performed on the filters collected over a four-year period, show that the sum of elemental carbon (EC) and water-insoluble organic mass accounts on average for 46%–56% of the total suspended material mass. Insoluble carbonaceous material is composed mainly of organic matter, with EC accounting on average only for 19% of the insoluble carbon.
•A 20 year long database of fog water chemical composition has been assembled.•Fog frequency at Bologna airport has decreased over the last three decades.•Ionic strength and conductivity trends indicate a reduction of ionic load in fog.•SO42− exhibits the highest decrease because of the high decrease of SO2 emissions.•A reduction of fog water acidity has been observed over the last two decades.
An experiment is performed to detect the onset of time-dependent flow regimes within a water-filled square-sectioned cavity containing a horizontal cylindrical heat source. Data are recorded on the ...cavity cross-section, where velocity fields and local temperature values are detected using a 2D PIV rig and thermocouples, respectively. Numerical predictions of the experimental runs are carried out, where the system is modeled as a 2D feature.
Results are provided for nine values of the leading parameter, the modified Rayleigh number Raq, ranging from 1.48×104 to 1.21×105. The system is witnessed to undergo a transition from steady-state, laminar flow to unsteady oscillatory flow at Raq≃5.88×104.
Experimental data and numerical predictions are compared and cross-validated. The evolution of the flow throughout the bifurcation is described by velocity and temperature profile plots, 2D field visualizations and Fourier analysis of experimental time series. The influence of the flow regime on the overall heat transfer rate of the system is finally discussed.
In this paper, infrared thermography is used to measure the transient contact temperature between impinging droplets and hot solid surfaces. Droplets are released onto the heated solid surface of a ...barium fluoride (BaF
2) disk, which has a high transmittance (about 90%) in the 8–12
μm range (typical of longwave infrared cameras). The interface temperature is measured from below, through the solid material, by infrared thermography. Since the solid is IR-transparent, a black coating layer is used to allow radiative heating of the surface and provide a method to measure the liquid–solid interface temperature. A numerical code is then presented, which simulates the evaporation of water droplets on hot solid surfaces. At the present stage of development, single-phase evaporation is addressed. The three-dimensional energy diffusion equation, discretized using the finite volume method, is employed to model the transient within both the droplets and the solid substrate. The numerical results are validated by comparison with the experimental data.
We present comprehensive results on continuous atmospheric cluster and particle measurements in the size range ~1-42 nm within the European Integrated project on Aerosol Cloud Climate and Air Quality ...interactions (EUCAARI) project. We focused on characterizing the spatial and temporal variation of new particle formation events and relevant particle formation parameters across Europe. Different types of air ion and cluster mobility spectrometers were deployed at 12 field sites across Europe from March 2008 to May 2009. The measurements were conducted in a wide variety of environments, including coastal and continental locations as well as sites at different altitudes (both in the boundary layer and the free troposphere). New particle formation events were detected at all of the 12 field sites during the year-long measurement period. From the data, nucleation and growth rates of newly formed particles were determined for each environment. In a case of parallel ion and neutral cluster measurements, we could also estimate the relative contribution of ion-induced and neutral nucleation to the total particle formation. The formation rates of charged particles at 2 nm accounted for 1-30% of the corresponding total particle formation rates. As a significant new result, we found out that the total particle formation rate varied much more between the different sites than the formation rate of charged particles. This work presents, so far, the most comprehensive effort to experimentally characterize nucleation and growth of atmospheric molecular clusters and nanoparticles at ground-based observation sites on a continental scale.
Filter-collected aerosol samples in the PM1 and PM10 fractions and particle number concentration were measured during experimental campaigns in a rural area near Bologna (Italy) in the periods 10–21 ...February 2014 and 19–30 May 2014. Ice nuclei particle (INP) concentrations measured off-line showed prevalently higher average values in the morning with respect to the afternoon, in the PM1 fraction with respect to PM1–10 (with the exception of the first campaign, at Sw=1.01), and at water saturation ratio Sw=1.01 with respect to Sw=0.96.
The aerosol in the coarse size range (1–10μm) contributed significantly to the total INP concentration. In the first campaign, the average INP concentration in the coarse fraction was 80% of the total in the morning and 74% in the afternoon, at Sw=1.01. In the second campaign, the contribution of the coarse size fraction to the INP number concentration was lower. On the whole, the results showed that the freezing activity of aerosol diameters larger than 1μm needs to be measured to obtain the entire INP population.
Sahara dust events (SDEs) took place during both campaigns, in the periods 17–20 February and 21–23 May 2014. Results show that the averaged particle number concentration was higher during SDE than during no-Saharan dust events. A low correlation between INP and total aerosol number concentration was generally measured, except for SDEs observed in February, in which the correlation coefficient between aerosol concentration in the coarse fraction and INP in the same range, at water supersaturation, was about 0.8.
Precipitation events influenced the aerosol concentration. In the February campaign, lower values of INP and particle concentrations were measured in case of heavy rain events. During the May campaign, an average number concentration of the aerosol in the range 0.5–10μm was slightly higher than on days when no precipitation was measured, the rainfall intensity being low. Only in a few cases did we note a sharp drop in INP in the PM10 fraction at Sw=1.01 (26 May, 8a.m. and 1p.m.; 27 May, 1p.m.).
•Aerosol in the coarse range contributed significantly to the INP concentration.•Particle number concentration was higher during SDE.•Precipitation events influenced the aerosol concentration.•There was mainly a low correlation between INP and total aerosol concentration.
Natural circulation of distilled water and FC43 has been experimentally investigated in a rectangular loop characterized by internal diameter of 30
mm and total length of 4.1
m. The aim of the ...present study is to analyse the influence of thermal boundary conditions on the flow regimes inside the pipes and on the stability of the system. The new aspect of the present research is the possibility of tuning the heat sink temperature in a range between −20
°C and +30
°C by means of a cryostat. This kind of analysis could be useful for the design of systems characterized by a wide range of environment temperatures, as for example for aerospatial applications. The other parameters investigated were the heat flux transferred to the fluid, which varied between 0.1
kW and 2.5
kW, and the thermo-physical properties of the working fluid. The system showed both stable and unstable behaviour. In particular, in the case of FC43 the loop was more unstable and it was characterized by higher velocities and frequencies compared to the case of distilled water.
It was found that the stability threshold could be crossed by varying only the heat sink temperature, demonstrating the importance of this boundary condition on the dynamics of the system. Different flow regimes and fluid velocities were observed. In the case of steady-state flow, Vijayan’s correlation (Vijayan et al., 2000) was tested and found to give good agreement with experimental data. Linear stability analysis was made following the Vijayan’s model. In particular, the effect of heat sink temperature was considered in the dimensionless Stanton number based on the overall heat transfer coefficient at the heat sink. Finally, Ultrasound Pulsed Doppler Velocimeter (UPDV) was used on a natural circulation loop for the first time, and gave a preliminary validation of the traditional fluid velocity measurement method based on the frequency analysis.
Objective: Background: at present, few data are available on the prognosis of hypertensive emergencies and urgencies admitted to Emergency Departments (ED). The aim of our study was to evaluate the ...incidence of total and cardiovascular events during follow-up in hypertensive patients admitted in 2 ED in Italy and Greece with hypertensive emergencies or urgencies. Design and method: Methods: medical records of patients aged > 18 yrs, admitted to the ED with blood pressure values > = 180 mmHg (SBP) and/or > = 120 mmHg (DBP) were collected and analysed (24% of patients were classified as “hypertensive emergency” and 76 % as “hypertensive urgency”). Data in 1218 patients (556 men and 662 women, mean age 70 + 13 years) were analysed; the mean duration of follow-up after admission to the ED was 19.5 + 7 months years. Results: Results: During the follow-up cardiovascular events occurred in 148 patients (69 cardiac events, 43 cerebrovascular events). In 272 pts (22 %) a new episode of acute BP rise was recorded. A total of 87 deaths was recorded during follow-up (in 28 patients for cardiovascular causes). All cause and CV mortality were greater in patients with a previous hypertensive emergency (14.7 vs 4.7 %, chisquare p = 0.0001 and 5.8 vs 1.2% chisquare p < 0.0001 for all-cause and for CV mortality, respectively). The incidence of non fatal cardiovascular events was 10,11 and 2,11 per 100 patient-years in patients with hypertensive emergency and urgency, respectively and similar results were obtained when we considered separately the occurrence of cerebrovascular events. Conclusions: Conclusions: admission to the ED for hypertensive emergencies identifies hypertensive patients at increased risk for fatal and non fatal cardiovascular events. Our results underline the need for an accurate follow-up in patients with hypertensive emergencies and urgencies.
Most ancient or traditional buildings in Italy show steep-slope roofs covered by red clay tiles. As the rooms immediately below the roof are often inhabited in historical or densely urbanized ...centres, the combination of low solar reflectance of tile coverings and low thermal inertia of either wooden roof structures or sub-tile insulation panels makes summer overheating a major problem. The problem can be mitigated by using tiles coated with cool colours, that is colours with the same spectral response of clay tiles in the visible, but highly reflecting in the near infrared range, which includes more than half of solar radiation. Cool colours can yield the same visible aspect of common building surfaces, but higher solar reflectance.
Studies aimed at developing cool colour tile coverings for traditional Italian buildings have been started. A few coating solutions with the typical red terracotta colour have been produced and tested in the laboratory, using easily available materials. The spectral response and the solar reflectance have been measured and compared with that of standard tiles.
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