Direct simulation Monte Carlo applications to liquid-vapor flows

The paper aims at presenting Direct Simulation Monte Carlo (DSMC) extensions and applications to dense fluids. A succinct review of past and current research topics is presented, followed by a more detailed description of DSMC simulations for the numerical solution of the Enskog-Vlasov equation, applied to the study of liquid-vapor flows. Results about simulations of evaporation of a simple liquid in contact with a dense vapor are presented as an example

Simulations of condensation flows induced by reflection of weak shocks from liquid surfaces

The condensation of a vapor onto a planar liquid surface, caused by the reflection of a weak shock wave, is studied by three different simulation method. The first one is based on molecular dynamics (MD) simulations of the Lennard-Jones fluid which are supposed to provide reference solutions. The second method is based on a Diffuse Interface Model (DIM), consistent with the thermodynamic properties of the Lennard-Jones fluid as well as with its transport properties. The third method is based on a hybrid model (HM) in which the liquid is described by a purely hydrodynamic approach, whereas the vapor is described by the Boltzmann equation. The two phases are connected by kinetic boundary conditions. The results show that DIM fails to accurately predict the condensation rate when the vapor is dilute but becomes more accurate when the vapor phase gets denser. HM reproduces MD simulations of nearly ideal vapor condensations with good accuracy, assuming unit condensation coefficient

Extraordinary blowing snow transport events in East Antarctica

In the convergence slope/coastal areas of Antarctica, a large fraction of snow is continuously eroded and exported by wind to the atmosphere and into the ocean. Snow transport observations from instruments and satellite images were acquired at the wind convergence zone of Terra Nova Bay (East Antarctica) throughout 2006 and 2007. Snow transport features are well-distinguished in satellite images and can extend vertically up to 200 m as first-order quantitatively estimated by driftometer sensor FlowCapt™. Maximum snow transportation occurs in the fall and winter seasons. Snow transportation (drift/blowing) was recorded for ~80% of the time, and 20% of time recorded, the flux is >10-2 kg m-2 s-1 with particle density increasing with height. Cumulative snow transportation is ~4 orders of magnitude higher than snow precipitation at the site. An increase in wind speed and transportation (~30%) was observed in 2007, which is in agreement with a reduction in observed snow accumulation. Extensive presence of ablation surface (blue ice and wind crust) upwind and downwind of the measurement site suggest that the combine processes of blowing snow sublimation and snow transport remove up to 50% of the precipitation in the coastal and slope convergence area. These phenomena represent a major negative effect on the snow accumulation, and they are not sufficiently taken into account in studies of surface mass balance. The observed wind-driven ablation explains the inconsistency between atmospheric model precipitation and measured snow accumulation value. © 2009 The Author(s)

Characterization of snowfall estimated by in situ and ground-based remote-sensing observations at Terra Nova Bay, Victoria Land, Antarctica

AbstractKnowledge of the precipitation contribution to the Antarctic surface mass balance is essential for defining the ice-sheet contribution to sea-level rise. Observations of precipitation are sparse over Antarctica, due to harsh environmental conditions. Precipitation during the summer months (November–December–January) on four expeditions, 2015–16, 2016–17, 2017–18 and 2018–19, in the Terra Nova Bay area, were monitored using a vertically pointing radar, disdrometer, snow gauge, radiosounding and an automatic weather station installed at the Italian Mario Zucchelli Station. The relationship between radar reflectivity and precipitation rate at the site can be estimated using these instruments jointly. The error in calculated precipitation is up to 40%, mostly dependent on reflectivity variability and disdrometer inability to define the real particle fall velocity. Mean derived summer precipitation is ~55 mm water equivalent but with a large variability. During collocated measurements in 2018–19, corrected snow gauge amounts agree with those derived from the relationship, within the estimated errors. European Centre for the Medium-Range Weather Forecasts (ECMWF) and the Antarctic Mesoscale Prediction System (AMPS) analysis and operational outputs are able to forecast the precipitation timing but do not adequately reproduce quantities during the most intense events, with overestimation for ECMWF and underestimation for AMPS

Health-related quality of life in patients with primary open-angle glaucoma. An Italian multicentre observational study

Purpose: As a progressive condition, glaucoma may impair health-related quality of life (HRQoL), due to vision loss and other factors. This study evaluated HRQoL in a cohort of patients treated for primary open-angle glaucoma (POAG) and assessed its association with clinical features. Methods: This was an Italian, multicentre, cross-sectional, observational study with the subgroup of newly diagnosed patients with POAG prospectively followed up for one year. Patients with previous or new diagnosis (or strong clinical suspicion) of POAG aged >18 years were considered eligible. Information was collected on demographic characteristics, medical history, clinical presentation and POAG treatments. HRQoL was measured using the 25-item National Eye Institute Visual Function Questionnaire (NEI-VFQ-25) and Glaucoma Symptom Scale (GSS). Subscale and total scores were obtained and a Pearson correlation coefficient between instruments’ scores calculated. Results: A total of 3227 patients were enrolled from 2012 to 2013 and 3169 were analysed. Mean age was 66.9 years. A total of 93.8% had a previous diagnosis (median duration: 8.0 years). Median values for mean deviation and pattern standard deviation were 3.9 and 3.6 dB, respectively. Mean scores on most subscales of the NEI-VFQ-25 exceeded 75.0 and mean GSS subscale scores ranged between 70.8 and 79.7 (with a total mean score of 74.8). HRQoL scores on both scales were significantly inversely associated with POAG severity. Conclusion: In this large sample of Italians treated for POAG, disease severity was limited and HRQoL scores were high. QoL decreased with advancing disease severity. These findings confirm the role of vision loss in impairing QoL in POAG, underlying the importance of timely detection and appropriate treatment

Blindness and glaucoma: A multicenter data review from 7 academic eye clinics

Purpose To evaluate frequency, conversion rate, and risk factors for blindness in glaucoma patients treated in European Universities. Methods This multicenter retrospective study included 2402 consecutive patients with glaucoma in at least one eye. Medical charts were inspected and patients were divided into those blind and the remainder (''controls''). Blindness was defined as visual acuity-0.05 and/or visual field loss to less than 10°. Results Unilateral and bilateral blindness were respectively 11.0% and 1.6%at the beginning, and 15.5%and 3.6% at the end of the observation period (7.5±5.5 years, range:1-25 years)//conversion to blindness (at least unilateral) was 1.1%/year. 134 eyes (97 patients) developed blindness by POAG during the study. At the first access to study centre, they had mean deviation (MD) of -17.1±8.3 dB and treated intraocular pressure (IOP) of 17.1±6.6 mmHg. During follow-up the IOP decreased by 14%in these eyes but MD deteriorated by 1.1±3.5 dB/year, which was 5-fold higher than controls (0.2±1.6 dB/year). In a multivariate model, the best predictors for blindness by glaucoma were initial MD (p<0.001), initial IOP (p<0.001), older age at the beginning of follow-up (p<0.001), whereas final IOP was found to be protective (p<0.05). Conclusions In this series of patients, blindness occurred in about 20%. Blindness by glaucoma had 2 characteristics: late diagnosis and/or late referral, and progression of the disease despite in most cases IOP was within the range of normality and target IOP was achieved//it could be predicted by high initial MD, high initial IOP, and old age

Pseudoscalar decay constants fK/fπf_K/f_\pi, fDf_D and fDsf_{D_s} with Nf=2+1+1N_f = 2 + 1 + 1 ETMC congurations

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Age of the Mt. Ortles ice cores, the Tyrolean Iceman and glaciation of the highest summit of South Tyrol since the Northern Hemisphere Climatic Optimum

In 2011 four ice cores were extracted from the summit of Alto dell'Ortles (3859 m), the highest glacier of South Tyrol in the Italian Alps. This drilling site is located only 37 km southwest from where the Tyrolean Iceman, similar to 5.3 kyrs old, was discovered emerging from the ablating ice field of Tisenjoch (3210 m, near the Italian-Austrian border) in 1991. The excellent preservation of this mummy suggested that the Tyrolean Iceman was continuously embedded in prehistoric ice and that additional ancient ice was likely preserved elsewhere in South Tyrol. Dating of the ice cores from Alto dell'Ortles based on Pb-210, tritium, beta activity and C-14 determinations, combined with an empirical model (COPRA), provides evidence for a chronologically ordered ice stratigraphy from the modern glacier surface down to the bottom ice layers with an age of similar to 7 kyrs, which confirms the hypothesis. Our results indicate that the drilling site has continuously been glaciated on frozen bedrock since similar to 7 kyrs BP. Absence of older ice on the highest glacier of South Tyrol is consistent with the removal of basal ice from bedrock during the Northern Hemisphere Climatic Optimum (6-9 kyrs BP), the warmest interval in the European Alps during the Holocene. Borehole inclinometric measurements of the current glacier flow combined with surface ground penetration radar (GPR) measurements indicate that, due to the sustained atmospheric warming since the 1980s, an acceleration of the glacier Alto dell'Ortles flow has just recently begun. Given the stratigraphic-chronological continuity of the Mt. Ortles cores over millennia, it can be argued that this behaviour has been unprecedented at this location since the Northern Hemisphere Climatic Optimum