A simple and accurate method to determine fluid-crystal phase boundaries from direct coexistence simulations.

One method for computationally determining phase boundaries is to explicitly simulate a direct coexistence between the two phases of interest. Although this approach works very well for fluid-fluid coexistences, it is often considered to be less useful for fluid-crystal transitions, as additional care must be taken to prevent the simulation boundaries from imposing unwanted strains on the crystal phase. Here, we present a simple adaptation to the direct coexistence method that nonetheless allows us to obtain highly accurate predictions of fluid-crystal coexistence conditions, assuming that a fluid-crystal interface can be readily simulated. We test our approach on hard spheres, the screened Coulomb potential, and a 2D patchy-particle model. In all cases, we find excellent agreement between the direct coexistence approach and (much more cumbersome) free-energy calculation methods. Moreover, the method is sufficiently accurate to resolve the (tiny) free-energy difference between the face-centered cubic and hexagonally close-packed crystal of hard spheres in the thermodynamic limit. The simplicity of this method also ensures that it can be trivially implemented in essentially any simulation method or package. Hence, this approach provides an excellent alternative to free-energy based methods for the precise determination of phase boundaries.

Toward a Unified Description of the Electrostatic Assembly of Microgels and Nanoparticles.

The interplay of soft responsive particles, such as microgels, with nanoparticles (NPs) yields highly versatile complexes that show great potential for applications, ranging from plasmonic sensing to catalysis and drug delivery. However, the microgel-NP assembly process has not been investigated so far at the microscopic level, thus hindering the possibility of designing such hybrid systems a priori. In this work, we combine state-of-the-art numerical simulations with experiments to elucidate the fundamental mechanisms taking place when microgel-NP assembly is controlled by electrostatic interactions and the associated effects on the structure of the resulting complexes. We find a general behavior where, by increasing the number of interacting NPs, the microgel deswells up to a minimum size after which a plateau behavior occurs. This occurs either when NPs are mainly adsorbed to the microgel corona via the folding of the more external chains or when NPs penetrate inside the microgel, thereby inducing a collective reorganization of the polymer network. By varying microgel properties, such as fraction of cross-linkers or charge, as well as NP size and charge, we further show that the microgel deswelling curves can be rescaled onto a single master curve, for both experiments and simulations, demonstrating that the process is entirely controlled by the charge of the whole microgel-NP complex. Our results thus have a direct relevance in fundamental materials science and offer novel tools to tailor the nanofabrication of hybrid devices of technological interest.

Short- and long-term survival in patients over 90 years old undergoing pacemaker implantation.

AIMS: In Italy, 12-month survival in the general population between 90 and 94 years old is 26%. In very old patients, the benefit of pacemaker implantation in terms of quality and duration of life is unclear. The aim of our study was to analyse clinical characteristics, outcome and factors associated with survival in patients at least 90 years old at the time of the first pacemaker implant. METHODS: Clinical parameters, device characteristics, survival and predictors of outcome in patients at least 90 years old treated with a pacemaker in our centre in 2019-2020 were evaluated. RESULTS: Among the 554 patients undergoing pacemaker implantation in our centre during the study interval, 69 (12%) were at least 90 years old; a complete/advanced atrioventricular block was present in 65%. A cardiological comorbidity (excluding atrial fibrillation) was present in 22 patients (32%). Oncological, pulmonary and neurological comorbidities were present in 12 (17%), 19 (28%) and 32 (46%), respectively. Renal impairment was present in 25 patients (36%). After pacemaker implantation, a pneumothorax developed in two patients and lead dislodgment in one. During follow-up (median 17 months, interquartile range: 13-24), 32 patients died (46%), with a 12-month mortality probability of 24.6%. At multivariate analysis, the presence of oncological (hazard ratio (HR) 5.31; P < 0.001) and neurological (HR 6.44; P < 0.001) comorbidities was associated with mortality. Truncating the outcome at 6 months, renal impairment (HR 8.01; P = 0.003), anticoagulant therapy (HR 8.14; P = 0.003), oncological comorbidities (HR 14.1; P < 0.001) and left ventricular function (5% increase of left ventricular ejection fraction: HR 0.66; P < 0.001) were significantly associated with outcome. CONCLUSION: At our centre, patients at least 90 years old underwent pacemaker implantation mainly for advanced atrioventricular block. One-year survival was excellent, even better than expected in the general population.

Buckling and Interfacial Deformation of Fluorescent Poly(N-isopropylacrylamide) Microgel Capsules.

Hollow microgels are fascinating model systems at the crossover between polymer vesicles, emulsions, and colloids as they deform, interpenetrate, and eventually shrink at higher volume fraction or when subjected to an external stress. Here, we introduce a system consisting of microgels with a micrometer-sized cavity enabling a straightforward characterization in situ using fluorescence microscopy techniques. Similarly to elastic capsules, these systems are found to reversibly buckle above a critical osmotic pressure, conversely to smaller hollow microgels, which were previously reported to deswell at high volume fraction. Simulations performed on monomer-resolved in silico hollow microgels confirm the buckling transition and show that the presented microgels can be described with a thin shell model theory. When brought to an interface, these microgels, that we define as microgel capsules, strongly deform and we thus propose to utilize them to locally probe interfacial properties within a theoretical framework adapted from the Johnson-Kendall-Roberts (JKR) theory. Besides their capability to sense their environment and to address fundamental questions on the elasticity and permeability of microgel systems, microgel capsules can be further envisioned as model systems mimicking anisotropic responsive biological systems such as red blood and epithelial cells thanks to the possibility offered by microgels to be synthesized with custom-designed properties.

Hand-Sewn Versus Stapled Small Bowel Anastomoses in Patients With Secondary Mesenteric Ischemia.

INTRODUCTION: Although stapled anastomoses have been widely evaluated in the context of the elective surgery, few reports compared manual with stapled anastomoses in patients undergoing emergency surgery. The aim of this study is to compare the outcome of hand-sewn end-to-end anastomoses with stapled side-to-side and stapled end-to-side anastomoses in patients undergoing small bowel resection for acute mesenteric ischemia secondary to intestinal obstruction. METHODS: From January 2015 to June 2021 all the hemodynamically stable patients undergoing emergency surgery with small bowel resection for intestinal obstruction were enrolled in this study. According to surgical technique in performing anastomosis, the patients were divided into three groups: group 1: hand-sewn end-to-end anastomosis, group 2: stapled end-to-side anastomosis, and group 3: stapled side-to-side anastomosis. RESULTS: Although the anastomosis failure rate was higher in group 3, it was not significantly different between the three groups (P = 0.78: chi-square test). Likewise, no significant differences in the median hospital stay were found between the patients' groups (P = 0.87: Kruskal-Wallis test). The median operating time was similar in patients undergoing stapled anastomoses and was significantly higher in patients undergoing hand-sewn anastomoses (P = 0.0009: Kruskal-Wallis test). CONCLUSIONS: In patients undergoing emergency small bowel resection for complicated intestinal obstruction, a similar outcome in terms of dehiscence rate and hospital stay can be achieved performing stapled or hand-sewn anastomoses, even if restoring the intestinal continuity with stapled technique is associated with lower operating time.

Two-step deswelling in the Volume Phase Transition of thermoresponsive microgels.

Thermoresponsive microgels are one of the most investigated types of soft colloids, thanks to their ability to undergo a Volume Phase Transition (VPT) close to ambient temperature. However, this fundamental phenomenon still lacks a detailed microscopic understanding, particularly regarding the presence and the role of charges in the deswelling process. This is particularly important for the widely used poly(N-isopropylacrylamide)-based microgels, where the constituent monomers are neutral but charged groups arise due to the initiator molecules used in the synthesis. Here, we address this point combining experiments with state-of-the-art simulations to show that the microgel collapse does not happen in a homogeneous fashion, but through a two-step mechanism, entirely attributable to electrostatic effects. The signature of this phenomenon is the emergence of a minimum in the ratio between gyration and hydrodynamic radii at the VPT. Thanks to simulations of microgels with different cross-linker concentrations, charge contents, and charge distributions, we provide evidence that peripheral charges arising from the synthesis are responsible for this behavior and we further build a universal master curve able to predict the two-step deswelling. Our results have direct relevance on fundamental soft condensed matter science and on applications where microgels are involved, ranging from materials to biomedical technologies.

Dynamical properties of different models of elastic polymer rings: Confirming the link between deformation and fragility.

We report extensive numerical simulations of different models of 2D polymer rings with internal elasticity. We monitor the dynamical behavior of the rings as a function of the packing fraction to address the effects of particle deformation on the collective response of the system. In particular, we compare three different models: (i) a recently investigated model [N. Gnan and E. Zaccarelli, Nat. Phys. 15, 683 (2019)] where an inner Hertzian field providing the internal elasticity acts on the monomers of the ring, (ii) the same model where the effect of such a field on the center of mass is balanced by opposite forces, and (iii) a semi-flexible model where an angular potential between adjacent monomers induces strong particle deformations. By analyzing the dynamics of the three models, we find that in all cases, there exists a direct link between the system fragility and particle asphericity. Among the three, only the first model displays anomalous dynamics in the form of a super-diffusive behavior of the mean-squared displacement and of a compressed exponential relaxation of the density auto-correlation function. We show that this is due to the combination of internal elasticity and the out-of-equilibrium force self-generated by each ring, both of which are necessary ingredients to induce such a peculiar behavior often observed in experiments of colloidal gels. These findings reinforce the role of particle deformation, connected to internal elasticity, in driving the dynamical response of dense soft particles.

Charge affinity and solvent effects in numerical simulations of ionic microgels.

Ionic microgel particles are intriguing systems in which the properties of thermo-responsive polymeric colloids are enriched by the presence of charged groups. In order to rationalize their properties and predict the behaviour of microgel suspensions, it is necessary to develop a coarse-graining strategy that starts from the accurate modelling of single particles. Here, we provide a numerical advancement of a recently-introduced model for charged co-polymerized microgels by improving the treatment of ionic groups in the polymer network. We investigate the thermoresponsive properties of the particles, in particular their swelling behaviour and structure, finding that, when charged groups are considered to be hydrophilic at all temperatures, highly charged microgels do not achieve a fully collapsed state, in favorable comparison to experiments. In addition, we explicitly include the solvent in the description and put forward a mapping between the solvophobic potential in the absence of the solvent and the monomer-solvent interactions in its presence, which is found to work very accurately for any charge fraction of the microgel. Our work paves the way for comparing single-particle properties and swelling behaviour of ionic microgels to experiments and to tackle the study of these charged soft particles at a liquid-liquid interface.

Treatment of acute diverticulitis with open abdomen technique.

AIM: The aim of this study is to highlight our experience about the use of open Abdomen's technique as strategy for the management of complicated colon diverticulitis with a delayed anastomosis or colostomy. MATERIALS AND METHODS: Thirty patients, with III and IV Hinchey stage, have been undertaken to a surgical procedure with Open Abdomen technique and application of Ab-thera device. A second surgical look was made after 48-72 hours in order to evaluate the possibility to do an anastomosis or colostomy. RESULTS: No deaths in patients with anastomosis were reported, but one case of leakage at the 8th day and one case of micro pulmonary embolism had been displayed. Elderly patients were discharged between the 15TH /18th day. One patient affected by lymphoma was sent in haematology department for other treatment. DISCUSSION: Today trend is to treat the diverticular disease with colic and paracolic abscess by a medical therapy and percutaneous drainage under CT scan or ultrasound view. With III and IV of Hinchey scale we perform the resection with anastomosis or colostomy. The open abdomen technique allows the surgeons to make the decision of colostomy or anastomosis in the second surgical look at 48-72 hours after the first treatment with irrigation and aspiration during AB-Thera. CONCLUSION: The Open Abdomen technique is a valid therapeutic alternative approach for patients with acute diverticulitis disease in III and IV Hinchey grade. This therapeutic approach gives important advantages in patients with delayed colostomy. KEY WORDS: Diverticulitis, Damage Control Surgery, Open Abdomen.

Numerical insights on ionic microgels: structure and swelling behaviour.

Recent progress has been made in the numerical modelling of neutral microgel particles with a realistic, disordered structure. In this work we extend this approach to the case of co-polymerised microgels where a thermoresponsive polymer is mixed with acidic groups. We compare the cases where counterions directly interact with microgel charges or are modelled implicitly through a Debye-Hückel description. We do so by performing extensive numerical simulations of single microgels across the volume phase transition (VPT) varying the temperature and the fraction of charged monomers. We find that the presence of charges considerably alters the microgel structure, quantified by the monomer density profiles and by the form factors of the microgels, particularly close to the VPT. We observe significant deviations between the implicit and explicit models, with the latter comparing more favourably to available experiments. In particular, we observe a shift of the VPT temperature to larger values as the amount of charged monomers increases. We also find that below the VPT the microgel-counterion complex is almost neutral, while it develops a net charge above the VPT. Interestingly, under these conditions the collapsed microgel still retains a large amount of counterions inside its structure. Since these interesting features cannot be captured by the implicit model, our results show that it is crucial to explicitly include the counterions in order to realistically model ionic thermoresponsive microgels.

Advantages of Damage Control Strategy With Abdominal Negative Pressure and Instillation in Patients With Diffuse Peritonitis From Perforated Diverticular Disease.

Purpose. To evaluate the results of Damage Control Strategy (DCS) in the treatment of generalized peritonitis from perforated diverticular disease in patients with preoperative severe systemic diseases. Methods. All the patients with diffuse peritonitis (Hinchey 3 and 4) and the American Society of Anesthesiologists (ASA) score ≥3 were included and underwent DCS consisting of a 2-step procedure. The first was peritoneal lavage, perforated colon-stapled resection, and temporary abdominal closure with negative pressure wound therapy combined with instillation. The second step, 48 hours later, included the possibility of restoring intestinal continuity basing on local and general patients' conditions. Results. Thirty patients (18 [60%] women and 12 [40%] men, median age 68.5 [range = 35-84] years) were included (18 [60%] ASA III, 11 [36.7%] ASA IV, and 1 [0.03%] ASA V). Seven patients (23.3%) showed sepsis and 1 (3.33%) septic shock. At second surgery, 24 patients (80%) received a colorectal anastomosis and 6 patients (20%) underwent a Hartmann's procedure. Median hospital stay was 18 days (range = 12-62). Postoperative morbidity rate was 23.3% (7/30) and included 1 anastomotic leak treated with Hartmann's procedure. Consequently, at discharge from hospital, 23 patients (76.6%) were free of stoma. Primary fascial closure was possible in all patients. Conclusions. DCS with temporary abdominal closure by negative pressure wound therapy combined with instillation in patients with diffuse peritonitis from complicated diverticulitis could represent a feasible surgical option both in hemodynamically stable and no stable patients, showing encouraging results including a low stoma rate and an acceptable morbidity rate.

IPHEN--a real-time network for phenological monitoring and modelling in Italy.

This paper aims to describe the Italian PHEnology Network (IPHEN), a cooperative project started in 2006 with the aim of producing nationwide maps of analysis and forecast of plants phenological stages mainly used to satisfy the needs of agriculture, health and environmental care. Iphen is a data processing system composed of the following main segments (a) collection of atmospheric and phenological data, (b) processing of data with suitable phenological and geo-statistical models and (c) phenological maps of analysis and forecast. In more detail, IPHEN maps of analysis (featuring phenological stages reached at the date of processing) are produced with models based on a Normal Heat Hours approach which weighs hourly air temperature effectiveness for plant phenological progression applied to national grids of hourly temperature derived from the operational agro-meteorological network of CRA-CMA. A correction scheme based on phenological surveys provided by volunteer observers is applied to the first guess maps of analysis to obtain final maps. Forecast maps (prediction of the days of occurrence of relevant phenological stages) are produced on the basis of GFS model medium range forecasts and climatic data. Freeware IPHEN maps for grapevine, common and Arizona cypress, black elder, olive and locust trees are broadcasted weekly on the CRA-CMA website. The positive operational results of IPHEN are testified by 150 maps broadcasted during the 2011 season for the above-mentioned species. The system performances and reliability have been analysed focusing on the analysis of phenological simulation errors and on the sensitivity of phenological maps to anomalous atmospheric circulation patterns. The error analysis shows that phenological models are characterized by advances/delays that justify the adoption of an observation based correction scheme. The sensitivity analysis highlights that the system is responsive to the effects of circulation blocking systems leading to phenological advances and delays.

[Our experience in the management of patients with Mirizzi syndrome]. / Orlentamenti attuali nel trattamento della sindrome di Mirizzi. Nostra esperienza.

The authors report their experience in the management of patients with Mirizzi Syndrome (MS) admitted, over a period of 15 years, at the General Surgery of Emergency Department of Cardarelli Hospital, Naples, Italy. All patients were admitted and surgically treated in emergency save for one. Out of 12 patients, cholecystectomy was performed in 7 cases. In others 5 patients, with cholecystocholedochal fistula, cholecystectomy with positionig of T-Tube was performed in 4 cases (MS-II); finally, 1 patient with MS type III undewrwent choledochojejunostomy. According to literature, the diagnostic protocol included abdominal ultrasonography and CT scan of the abdomen for all patients; in one case, a cholangio-MRI was performed to clarify the diagnosis. The preoperative diagnosis is essential to reduce risk of iatrogenic injuries. The cholangio-MRI, used to this extent, clarifies the site of obstruction, shows the anatomy of the biliary tree and allows to make all the possible differential diagnoses in order to exclude the presence of biliary tumors before surgery. The intraoperative cholangiography remains mandatory to clarify the anatomy of the biliary tree. In the cases we have treated, ERCP was never performed. We believe that ERCP has limited indications and unsatisfactory outcomes for both diagnosis and treatment of MS. Pathological examination of the fresh-frozen surgical specimens was always performed intraoperatively to exclude the presence of concomitant cancer of the gallbladder. The traditional treatment of patients with MS is surgery, as confirmed by our experience. We perform cholecystectomy for MS type I and cholecystectomy with direct repair of the biliary fistula over aT tube for MS type II. Patients with MS type III usually undergo a tailored operation based on the intraoperative findings, while choledochojejunostomy is mandatory for patients with MS type IV. Laparoscopic surgery is indicated only for MS type I and II. It seems to carry a higher risk for the patient and we do not use this approach in the emergency settings.