Monte Carlo Methods for Estimating Interfacial Free Energies and Line Tensions

Excess contributions to the free energy due to interfaces occur for many problems encountered in the statistical physics of condensed matter when coexistence between different phases is possible (e.g. wetting phenomena, nucleation, crystal growth, etc.). This article reviews two methods to estimate both interfacial free energies and line tensions by Monte Carlo simulations of simple models, (e.g. the Ising model, a symmetrical binary Lennard-Jones fluid exhibiting a miscibility gap, and a simple Lennard-Jones fluid). One method is based on thermodynamic integration. This method is useful to study flat and inclined interfaces for Ising lattices, allowing also the estimation of line tensions of three-phase contact lines, when the interfaces meet walls (where "surface fields" may act). A generalization to off-lattice systems is described as well. The second method is based on the sampling of the order parameter distribution of the system throughout the two-phase coexistence region of the model. Both the interface free energies of flat interfaces and of (spherical or cylindrical) droplets (or bubbles) can be estimated, including also systems with walls, where sphere-cap shaped wall-attached droplets occur. The curvature-dependence of the interfacial free energy is discussed, and estimates for the line tensions are compared to results from the thermodynamic integration method. Basic limitations of all these methods are critically discussed, and an outlook on other approaches is given

Single diffraction dissociation at the CERN SPS collider

The reaction pp \u2192 pX was studied at a centre-of-mass energy s = 540 GeV by measuring the momentum spectrum of the antiproton. Data are presented in the four-momentum transfer range 05 < 12t < 1.2GeV2. The shape of the mass distribution of the system X shows a diffractive component as already observed at lower energies. The differential cross section scales approximately with energy when compared to the ISR data

Pseudorapidity distribution of charged particles in diffraction dissociation events at the CERN SPS collider

The reaction pp \u2192 pX was studied as a function of the mass M of the system X at the centre-of-mass energy s = 546 GeV in the kinematical region where diffraction dissociation dominates. The pseudorapidity distribution of charged tracks, produced in the fragmentation of the system X, is well described within the limits of cylindrical phase space. The fragments of the X-system behave very similarly to the products of non-diffractive inelastic collisions at s = M

Extracorporeal life support in COVID-19-related acute respiratory distress syndrome: A EuroELSO international survey

Extracorporeal life support (ECLS) is a means to support patients with acute respiratory failure. Initially, recommendations to treat severe cases of pandemic coronavirus disease 2019 (COVID-19) with ECLS have been restrained. In the meantime, ECLS has been shown to produce similar outcomes in patients with severe COVID-19 compared to existing data on ARDS mortality. We performed an international email survey to assess how ECLS providers worldwide have previously used ECLS during the treatment of critically ill patients with COVID-19. A questionnaire with 45 questions (covering, e.g., indication, technical aspects, benefit, and reasons for treatment discontinuation), mostly multiple choice, was distributed by email to ECLS centers. The survey was approved by the European branch of the Extracorporeal Life Support Organization (ELSO); 276 ECMO professionals from 98 centers in 30 different countries on four continents reported that they employed ECMO for very severe COVID-19 cases, mostly in veno-venous configuration (87%). The most common reason to establish ECLS was isolated hypoxemic respiratory failure (50%), followed by a combination of hypoxemia and hypercapnia (39%). Only a small fraction of patients required veno-arterial cannulation due to heart failure (3%). Time on ECLS varied between less than 2 and more than 4 weeks. The main reason to discontinue ECLS treatment prior to patient's recovery was lack of clinical improvement (53%), followed by major bleeding, mostly intracranially (13%). Only 4% of respondents reported that triage situations, lack of staff or lack of oxygenators, were responsible for discontinuation of ECLS support. Most ECLS physicians (51%, IQR 30%) agreed that patients with COVID-19-induced ARDS (CARDS) benefitted from ECLS. Overall mortality of COVID-19 patients on ECLS was estimated to be about 55%. ECLS has been utilized successfully during the COVID-19 pandemic to stabilize CARDS patients in hypoxemic or hypercapnic lung failure. Age and multimorbidity limited the use of ECLS. Triage situations were rarely a concern. ECLS providers stated that patients with severe COVID-19 benefitted from ECLS

Large-t elastic scattering at the Cern SPS collider at s\sqrt s = 630 GeV

none28Proton-antiproton elastic scattering was measured at the centre-of-mass energy s = 630 GeV in the four-momentum transfer range 0.7 ⩽ − t ⩽ 2.2 GeV2. The new data confirm our previous results at s = 546 GeV on the presence of a break in the t-distribution at −t ≃ 0.9 GeV2 which is followed by a shoulder, and extend the momentum transfer range to larger values. The t-dependence of the differential cross section beyond the break is discussed.D. Bernard;M. Bozzo;P. Braccini;F. Carbonara;R. Castaldi;F. Cervelli;G. Chiefari;E. Drago;M. Haguenauer;V. Innocente;P. Kluit;B. Koene;S. Lanzano;G. Matthiae;L. Merola;M. Napolitano;V. Palladino;G. Sanguinetti;P. Scampoli;S. Scapellato;G. Sciacca;G. Sette;R. v. Swol;J. Timmermans;C. Vannini;J. Velasco;P. Verdini;F. ViscoD., Bernard; Bozzo, Marco; P., Braccini; F., Carbonara; R., Castaldi; F., Cervelli; G., Chiefari; E., Drago; M., Haguenauer; V., Innocente; P., Kluit; B., Koene; S., Lanzano; G., Matthiae; L., Merola; M., Napolitano; V., Palladino; G., Sanguinetti; P., Scampoli; S., Scapellato; G., Sciacca; Sette, Giuseppe; R. v., Swol; J., Timmermans; C., Vannini; J., Velasco; P., Verdini; F., Visc

Extracorporeal life support in COVID-19-related acute respiratory distress syndrome: A EuroELSO international survey

Extracorporeal life support (ECLS) is a means to support patients with acute respiratory failure. Initially, recommendations to treat severe cases of pandemic coronavirus disease 2019 (COVID-19) with ECLS have been restrained. In the meantime, ECLS has been shown to produce similar outcomes in patients with severe COVID-19 compared to existing data on ARDS mortality. We performed an international email survey to assess how ECLS providers worldwide have previously used ECLS during the treatment of critically ill patients with COVID-19. A questionnaire with 45 questions (covering, e.g., indication, technical aspects, benefit, and reasons for treatment discontinuation), mostly multiple choice, was distributed by email to ECLS centers. The survey was approved by the European branch of the Extracorporeal Life Support Organization (ELSO); 276 ECMO professionals from 98 centers in 30 different countries on four continents reported that they employed ECMO for very severe COVID-19 cases, mostly in veno-venous configuration (87%). The most common reason to establish ECLS was isolated hypoxemic respiratory failure (50%), followed by a combination of hypoxemia and hypercapnia (39%). Only a small fraction of patients required veno-arterial cannulation due to heart failure (3%). Time on ECLS varied between less than 2 and more than 4 weeks. The main reason to discontinue ECLS treatment prior to patient's recovery was lack of clinical improvement (53%), followed by major bleeding, mostly intracranially (13%). Only 4% of respondents reported that triage situations, lack of staff or lack of oxygenators, were responsible for discontinuation of ECLS support. Most ECLS physicians (51%, IQR 30%) agreed that patients with COVID-19-induced ARDS (CARDS) benefitted from ECLS. Overall mortality of COVID-19 patients on ECLS was estimated to be about 55%. ECLS has been utilized successfully during the COVID-19 pandemic to stabilize CARDS patients in hypoxemic or hypercapnic lung failure. Age and multimorbidity limited the use of ECLS. Triage situations were rarely a concern. ECLS providers stated that patients with severe COVID-19 benefitted from ECLS

The \u201cRoman pot\u201d spectrometer and the vertex detector of experiment UA4 at the CERN SPS collider

We describe the apparatus used in experiment UA4 to study proton-antiproton elastic and inelastic interactions at the CERN SPS Collider. Elastically scattered particles, travelling at very small angles, are observed by detectors placed inside movable sections (\u201cRoman pots\u201d) of the SPS vacuum chamber. The deflection in the field of the machine quadrupoles allow the measurement of the particle momentum. Inelastic interactions are observed by a left-right symmetric system of trigger counter hodoscopes and drift-chamber telescopes. The apparatus reconstructs the interaction vertex and measures the pseudorapidity \u3b7 of charged particles in the range 2.5 < \u2016\u3b7\u2016 < 5.6