Diffusion Coefficients of Variable-Size Amphiphilic Additives in a Glass-Forming Polyethylene Matrix.

Diffusion of additives in polymers is an important issue in the plastics industry since migratory-type molecules are widely used to tune the properties of polymeric composites. Predicting the diffusional behavior of new additives can minimize the need for repetitive experiments. This work presents molecular dynamics simulations at the microsecond time scale and uses the MARTINI force field to estimate self-diffusion coefficients, D, of six monounsaturated amides and their analogs carboxylic acids in polyethylene matrices (PE, MW = 5600 Da). The results are strongly influenced by the glass-forming properties of the PE matrix, which we characterize by three distinct temperatures. The metastability region (T < 325 K), the glass transition temperature (Tg = 256-260 K), and the end of the transition (T ≅ 200 K). Self-diffusion mechanisms are inferred from the results of the dependence of D on the molecular mass of the additive, observing a Rouse-like behavior at high temperatures and deviations from it within the metastability region of the matrix. Interestingly, D values are nonsensitive to the nature of the considered polar head for additives of similar size. The temperature-dependent behavior of D follows, at fixed additive size, a linear Arrhenius pattern at high temperatures and a super Arrhenius trend at lower temperatures, which is well represented with a power law equation as predicted by the Mode Coupling Theory (MCT). We offer a conceptual explanation for the observed super-Arrhenius behavior. This explanation draws on Truhlar and Kohen's interpretation of the available energies at both the initial and the transition states along the diffusion pathway. The matrix's mobility significantly affects solute self-diffusion, yielding equal activation enthalpies for the Arrhenius region or the same power law parameters for the super-Arrhenius regime. Finally, we establish a one-to-one time-equivalence of the self-diffusion processes between CG and all-atom systems for the largest additives and the PE matrix in the high-temperature regime.

S-layer proteins as immune players: Tales from pathogenic and non-pathogenic bacteria.

In bacteria, as in other microorganisms, surface compounds interact with different pattern recognition receptors expressed by host cells, which usually triggers a variety of cellular responses that result in immunomodulation. The S-layer is a two-dimensional macromolecular crystalline structure formed by (glyco)-protein subunits that covers the surface of many species of Bacteria and almost all Archaea. In Bacteria, the presence of S-layer has been described in both pathogenic and non-pathogenic strains. As surface components, special attention deserves the role that S-layer proteins (SLPs) play in the interaction of bacterial cells with humoral and cellular components of the immune system. In this sense, some differences can be predicted between pathogenic and non-pathogenic bacteria. In the first group, the S-layer constitutes an important virulence factor, which in turn makes it a potential therapeutic target. For the other group, the growing interest to understand the mechanisms of action of commensal microbiota and probiotic strains has prompted the studies of the role of the S-layer in the interaction between the host immune cells and bacteria bearing this surface structure. In this review, we aim to summarize the main latest reports and the perspectives of bacterial SLPs as immune players, focusing on those from pathogenic and commensal/probiotic most studied species.

Partition Constant of Binary Mixtures for the Equilibrium between a Bulk and a Confined Phase.

It is well-known that the thermodynamic, kinetic and structural properties of fluids, and in particular of water and its solutions, can be drastically affected in nanospaces. A possible consequence of nanoscale confinement of a solution is the partial segregation of its components. Thereby, confinement in nanoporous materials (NPM) has been proposed as a means for the separation of mixtures. In fact, separation science can take great advantage of NPM due to the tunability of their properties as a function of nanostructure, morphology, pore size, and surface chemistry. Alcohol-water mixtures are in this context among the most relevant systems. However, a quantitative thermodynamic description allowing for the prediction of the segregation capabilities as a function of the material-solution characteristics is missing. In the present study we attempt to fill this vacancy, by contributing a thermodynamic treatment for the calculation of the partition coefficient in confinement. Combining the multilayer adsorption model for binary mixtures with the Young equation, we conclude that the liquid-vapor surface tension and the contact angle of the pure substances can be used to predict the separation ability of a particular material for a given mixture to a semiquantitative extent. Moreover, we develop a Kelvin-type equation that relates the partition coefficient to the radius of the pore, the contact angle, and the liquid-vapor surface tensions of the constituents. To assess the validity of our thermodynamic formulation, coarse grained molecular dynamics simulations were performed on models of alcohol-water mixtures confined in cylindrical pores. To this end, a coarse-grained amphiphilic molecule was parametrized to be used in conjunction with the mW potential for water. This amphiphilic model reproduces some of the properties of methanol such as enthalpy of vaporization and liquid-vapor surface tension, and the minimum of the excess enthalpy for the aqueous solution. The partition coefficient turns out to be highly dependent on the molar fraction, on the interaction between the components and the confining matrix, and on the radius of the pore. A remarkable agreement between the theory and the simulations is found for pores of radius larger than 15 Å.

An Improved Immunization Record to Support Vaccination During the COVID-19 Pandemic at a University Hospital in Argentina.

WHO and UNICEF highlight vaccination as the most cost-effective method of prevention of infectious diseases. An effective public health strategy requires efficient tracking of vaccination to assess coverage, safety, and efficacy of these vaccines. Paper-based immunization records are still being used in most low and middle-income countries. Adequate Electronic Logistic Management Information Systems, Immunization Registries and Records are crucial for proper data collection and analysis, and for making better decisions at an individual and at a population level. In this paper we share our experience in the redesign of an interoperable immunization record to track vaccination, including the recently developed vaccines for the novel coronavirus SARS-CoV-2 (COVID-19).

A 31-Year-Old Man With Seizures, Brain Lesion, and Lung Nodules.

CASE PRESENTATION: A 31-year-old man was admitted to our hospital with a recent history of generalized seizures. Three months earlier, he started with intermittent hemoptysis. CT scan showed a cavitary lung lesion in the upper segment of the right inferior lobe (RIL). Because of his job as a social worker in a high-risk population, he started treatment for Mycobacterium TB; however, the BAL culture result was negative. At the time of his current admission, he has continued taking rifampicin, isoniazid, pyrazinamide, and levofloxacin. He denied the use of any illicit drugs or alcohol. He had no history of smoking. One year earlier, he visited Southeast Asia, Oceania, and South Africa for several months. He reported a weight loss of 7 kg since then. Except for a recurrent oral candidiasis, he did not have a relevant medical history. His family history was notable for mother with lupus, and brother with sarcoidosis.

Clinical characteristics and outcomes of hospitalized patients with SARS-CoV-2 infection in a Latin American country: Results from the ECCOVID multicenter prospective study.

BACKGROUND: Clinical features and outcomes of SARS-CoV-2 infections diverge in different countries. The aim of this study was to describe clinical characteristics and outcomes in a cohort of patients hospitalized with SARS-CoV-2 in Argentina. METHODS: Multicenter prospective cohort study of ≥18 years-old patients with confirmed SARS-CoV-2 infection consecutively admitted to 19 hospitals in Argentina. Multivariable logistic regression models were used to identify variables associated with 30-day mortality and admission to intensive care unit (ICU). RESULTS: A total of 809 patients were analyzed. Median age was 53 years, 56% were males and 71% had at least one comorbidity. The most common comorbidities were hypertension (32%), obesity (23%) and diabetes (17%). Disease severity at admission was classified as mild 25%, moderate 51%, severe 17%, and critical 7%. Almost half of patients (49%) required supplemental oxygen, 18% ICU, and 12% invasive ventilation. Overall, 30-day mortality was 11%. Factors independently associated with ICU admission were male gender (OR 1.81; 95%CI 1.16-2.81), hypertension (OR 3.21; 95%CI 2.08-4.95), obesity (OR 2.38; 95%CI 1.51-3.7), oxygen saturation ≤93% (OR 6.45; 95%CI 4.20-9.92) and lymphopenia (OR 3.21; 95%CI 2.08-4.95). Factors independently associated with 30-day mortality included age ≥60 years-old (OR 2.68; 95% CI 1.63-4.43), oxygen saturation ≤93% (OR 3.19; 95%CI 1.97-5.16) and lymphopenia (OR 2.65; 95%CI 1.64-4.27). CONCLUSIONS: This cohort validates crucial clinical data on patients hospitalized with SARS-CoV-2 in Argentina.

Linfomas extranodales de cabeza y cuello / Extranodal lymphomas of the head and neck

RESUMEN Antecedentes: los linfomas extranodales de cabeza y cuello (LECC) son neoplasias infrecuentes. El papel diagnóstico de la cirugía justifica considerar estas entidades entre los diagnósticos diferenciales de la patología quirúrgica de la región. Objetivo: describir las características clínico-patológicas, la localización y la asociación con enfermeda des sistémicas de una serie de pacientes operados con LECC. Material y métodos: se realizó una revisión retrospectiva de las historias clínicas de 5489 pacientes operados entre junio de 2009 y junio de 2019. Diecinueve de ellos (0,35%) presentaron LECC. Resultados: el promedio de edad fue de 56 años (rango 17- 84, DS 19,3), 16 fueron mujeres (84%). La localización de los LECC fue: glándula parótida en 12 casos (63%), glándula submaxilar en 3 casos (16%), glándula salival menor en 2 casos (11%), glándula lagrimal en 1 caso (5%), glándula tiroides en 1 caso (5%). Todos fueron linfomas no Hodgkin. Los tipos citológicos fueron: linfoma de tejido linfoideo asociado a mucosas (MALT) 9 (48%), linfoma folicular 4 (21%), linfoma de células B grandes 3 (16%), linfoma de células pequeñas 1 (5%), linfoma del manto 1 (5%), linfoma anaplásico 1 (5%). Cuatro pa cientes (21%) presentaron síndrome de Sjögren en el momento del diagnóstico, tres linfomas MALT y uno linfoma folicular. Diferentes procedimientos quirúrgicos permitieron llegar al diagnóstico. Conclusión: los LECC constituyen una forma singular de presentación de neoplasias oncohematológica. En la presente serie se manifestaron en un amplio rango de edad, con mayor frecuencia de mujeres y en la glándula parótida. Su diagnóstico pudo alcanzarse con la biopsia o resección de la zona afectada.

ABSTRACT Background: Extranodal lymphomas of the head and neck (ELHN) are rare neoplasms. The role of surgery for the diagnosis justifies thinking of these neoplasms among the differential diagnoses of the surgical disorders of the region. Objective: The aim of this study was to describe the clinical and pathological characteristics of ELHN, their location and association with systemic diseases in a series of patients undergoing surgery. Material and methods: The clinical records of 5489 patients undergoing surgery between June 2009 and June 2019 were retrospectively reviewed. Nineteen patients (0.35%) presented ELHN. Results: Mean age was 56 years (range: 17-84; SD 19.3) and 84% (n = 16) were women. The location of ELHN were the parotid gland (n =12, 63%), submaxillary gland (n = 3, 16%), salivary gland (n = 1, 5%), lacrimal gland (n = 1, 5%) and thyroid gland (n =1, 5%). All the tumors were non-Hodgkin lymphomas with the following subtypes: mucosa associated lymphoid tissue (MALT) lymphoma (n = 9, 48%), follicular lymphoma (n = 4, 21%), large B-cell lymphoma (n = 3, 16%), small B-cell lymphoma (n = 1, 5%), mantle cell lymphoma (n = 1, 5%), and anaplastic lymphoma (n =1, 5%). Four patients (21%) presented Sjögren syndrome at the moment of the diagnosis; three were MALT lymphomas and one patient had follicular lymphoma. The diagnosis was made with different surgical procedures. Conclusion: ELHN constitute a singular presentation of onco-hematology neoplasms. In our series, these tumors occurred within a wide age range and were more common in women. The parotid gland was more commonly affected. The diagnosis was made by surgical biopsy or resection of the area affected.

Effects of prolonged elevated temperature on leaf gas exchange and other leaf traits in young olive trees.

Despite the economic importance of long-lived crop species in the Mediterranean Basin and their expansion to new warmer regions, their potential responses to prolonged temperature increases have not been adequately addressed. The objectives of this study were to: (i) assess leaf gas exchange responses to prolonged elevated temperature in young olive trees; (ii) evaluate some additional leaf traits such as stomatal density and size under these same conditions; and (iii) determine whether photosynthetic acclimation to temperature was apparent. A field experiment with two temperature levels was conducted using well-irrigated, potted olive trees (cvs. Arbequina, Coratina) grown in open-top chambers during the summer and early fall in two growing seasons. The temperature levels were a near-ambient control (T0) and a heated (T+) treatment (+4 °C). Maximum photosynthetic rate (Amax), stomatal conductance (gs), transpiration (E) and chlorophyll fluorescence were measured. Stomatal size and density and trichome density were also determined. The Amax, gs and chlorophyll fluorescence were little affected by heating. However, leaf E was higher at T+ than T0 in the summer in both seasons due in large part to the moderate increase in vapor pressure deficit that accompanied heating, and consequently water-use efficiency was reduced in heated leaves. When reciprocal temperature measurements were conducted in mid-summer of the second season, Amax values of T0 and T+ leaves were higher under the temperature level at which they grew than when measured at the other temperature level, which suggests some thermal acclimation. Stomatal size and density were greater in T+ than in T0 grown leaves in some cases, which was consistent with a greater E in T+ leaves when measured at both temperature levels. These results suggest that acclimation to long-term changes in temperature must be carefully considered to help determine how olive trees will be influenced by global warming.

Last Interglacial Iberian Neandertals as fisher-hunter-gatherers.

Marine food-reliant subsistence systems such as those in the African Middle Stone Age (MSA) were not thought to exist in Europe until the much later Mesolithic. Whether this apparent lag reflects taphonomic biases or behavioral distinctions between archaic and modern humans remains much debated. Figueira Brava cave, in the Arrábida range (Portugal), provides an exceptionally well preserved record of Neandertal coastal resource exploitation on a comparable scale to the MSA and dated to ~86 to 106 thousand years ago. The breadth of the subsistence base-pine nuts, marine invertebrates, fish, marine birds and mammals, tortoises, waterfowl, and hoofed game-exceeds that of regional early Holocene sites. Fisher-hunter-gatherer economies are not the preserve of anatomically modern people; by the Last Interglacial, they were in place across the Old World in the appropriate settings.

Papel de la proteína C reactiva y la velocidad de sedimentación globular en la predicción de colecistectomía laparoscópica dificultosa: su aplicación en un programa de residencia universitario / Role of C-reactive protein and erythrocyte sedimentation rate to predict difficult laproscopic cholecystectomy in a university residency program

Antecedentes: la colecistectomía laparoscópica es uno de los procedimientos quirúrgicos más frecuentemente realizados. Las diferencias en la anatomía y en el grado de inflamación vesicular suelen causar dificultades técnicas intraoperatorias. Objetivo: determinar el valor de la proteína C reactiva (PCR) y la velocidad de sedimentación globular (VSG) como predictores de colecistectomía dificultosa y evaluar su aplicación en la planificación prequirúrgica de un programa de residencia universitario. Material y métodos: se confeccionó un estudio retrospectivo, analítico, en un hospital universitario de tercer nivel. Se incluyeron 104 pacientes adultos operados de colecistectomía laparoscópica por litiasis vesicular sintomática entre enero y julio de 2019. Se categorizó a los pacientes en un grupo de colecistectomías dificultosas y otro de colecistectomías no dificultosas. Resultados: se obtuvieron diferencias estadísticamente significativas al comparar los valores de VSG y PCR de ambos grupos (p < 0,001). La sensibilidad de la VSG fue del 100%, la especificidad del 45%, el VPP del 40% y el VPN de 100%. La sensibilidad de la PCR fue del 87,5%, la especificidad del 86,3%, el VPP del 70% y el VPN de 95%. Ambos parámetros se vieron elevados en 14 de 16 colecistectomías dificultosas y en 2 de 44 colecistectomías no dificultosas. La sensibilidad para ambos parámetros elevados fue del 87,5%, la especificidad del 95%, el VPP del 87,5% y el VPN de 95%. Conclusión: la VSG y la PCR han demostrado ser un método fiable en la predicción de colecistectomías dificultosas por litiasis vesicular sintomática. Esto podría ser aplicado en la programación de cirugías dentro de un programa de residencia universitario.

Background: laparoscopic cholecystectomy is one of the most common procedures performed in general surgery. The anatomical differences of the gallbladder and the presence of factors related to inflammation can cause technical issues during surgery. Objective: the aim of the present study was to determine the value of C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) as predictors of difficult cholecystectomy and to evaluate their application during presurgical planning within a university residency program. Material and methods: we conducted a retrospective and analytical study in a tertiary university hospital. A total of 104 adult patients undergoing laparoscopic cholecystectomy due to symptomatic cholelithiasis between January and July 2019 were included. The patients were categorized into two groups: difficult cholecystectomy and non-difficult cholecystectomy. Results: there were statistically significant differences in ESR and CRP values between both groups (p < 0.001). Sensitivity of ESR was 100%, specificity was 45%, with a PPV of 40% and NPV of 100%. Sensitivity of CRP was 87.5%, specificity was 86.3%, with a PPV of 70% and NPV of 95%. Both parameters were elevated in 14 of 16 difficult cholecystectomies and in 2 of 44 non-difficult cholecystectomies. Sensitivity of CRP was 87.5%, specificity was 86.3%, with a PPV of 70% and NPV of 95%. Conclusion: measuring ESR and CRP has proved to be a reliable method to predict difficult cholecystectomies due to symptomatic cholelithiasis. This could be applied for surgical planning within a university residency program.

Can clathrates heterogeneously nucleate ice?

Methane hydrates can be preserved at ambient pressure, beyond their region of thermodynamic stability, by storing them at temperatures from 240 to 270 K. The origin of this anomalous self-preservation is the formation of an ice coating that covers the clathrate particles and prevents further loss of gas. While there have been several studies on self-preservation, the question of what is the mechanism by which ice nucleates on the decomposing clathrate hydrates has not yet been fully explained. Here, we use molecular simulations, thermodynamic analysis, and nucleation theory to investigate possible scenarios for the nucleation of ice: heterogeneous nucleation at the clathrate/vapor or clathrate/liquid interfaces and homogeneous nucleation from supercooled water. Our results indicate that clathrates cannot heterogeneously nucleate ice and that ice nucleation is due to the cooling of water at the decomposing clathrate/liquid interface, which suffices to trigger homogeneous ice nucleation. We find that the (111) face of the sII structure clathrate can bind to the (111) plane of cubic ice or the basal plane of hexagonal ice through domain matching, resulting in a weak binding that-while insufficient to promote heterogeneous ice nucleation-suffices to produce epitaxy and alignment between these crystals. We use thermodynamic relations, theory, and the contact angles of ice at the (111) sII clathrate/liquid interface to determine-for the first time-the interfacial free energy of this most favorable ice-clathrate interface, 59 ± 5 mJ/m2. We discuss the implications of our results for the feasibility of heterogeneous nucleation of gas clathrates at ice/vapor interfaces.

Resultados del tratamiento quirúrgico de sarcomas de partes blandas en adultos / Outcomes of surgical treatment of soft-tissue sarcomas in adults

Antecedentes: los sarcomas de partes blandas son raros tumores mesenquimáticos con varios tipos histológicos y diferentes comportamientos clínicos. Objetivo: describir las características clínicas y patológicas, así como los resultados del tratamiento quirúrgico de una serie de pacientes operados por sarcomas de partes blandas. Material y métodos: se realizó una revisión retrospectiva de las historias clínicas de 2403 pacientes operados entre octubre de 2014 y abril de 2018. Veintidós de ellos (0,91%) presentaron sarcomas de partes blandas. Resultados: el promedio de edad fue 52 años (rango 19-92), 13 (59%) eran mujeres. La localización de los tumores fue: miembro inferior en 12 casos, cabeza y cuello en 5, tronco en 3 y miembro superior en 2. Catorce casos (63,6%) fueron tumores de alto grado. Los tipos patológicos fueron: sarcoma pleomórfico 7 (32%), sarcoma sinovial 4 (18%), liposarcoma 3 (14%), otros 4 (36 %). Todos fueron extirpados en forma completa y en 5 casos (35,7%) requirieron amputación: 4 de miembro inferior y uno superior. Según el tamaño y la ubicación del tumor se emplearon diferentes procedimientos reconstructivos, incluyendo 3 colgajos libres. Aquellos pacientes con lesiones de alto grado o con márgenes histológicamente positivos recibieron radioterapia posoperatoria. Durante el seguimiento (promedio 16 meses), seis pacientes presentaron recidivas locales, cuatro con metástasis pulmonares sincrónicas, todos ellos con tumores de alto grado. La sobrevida global fue del 86,4%. Conclusión: los sarcomas de partes blandas son neoplasias infrecuentes e invasivas, ampliamente distribuidas, que requieren procedimientos quirúrgicos agresivos. Es necesario tratamiento adyuvante en casos seleccionados y seguimiento periódico debido a la alta tasa de recidiva y metástasis a distancia.

Background: Soft-tissue sarcomas (STS) are rare mesenchymal tumors with several histologic subtypes and different clinical patterns. Objective: The aim of this study was to describe the clinical and pathological characteristics and surgical outcomes of a series of patients with STS. Material and methods: The clinical records of 2403 undergoing surgery between October 2014 and April 2018 were retrospectively reviewed. Twenty-two patients (0.91%) presented STS. Results: Mean age was 52 years (range: 19-92) and 13 (59%) were women. The tumors were located in the lower extremities in 12 cases, head and neck in five, trunk in three and upper extremities in two. Fourteen cases (63.6%) were high-grade tumors. Pleomorphic sarcoma was the most common histologic type (32%) followed by synovial sarcoma (18%), liposarcoma (14%), and other types (36%). All the tumors were completely resected and five patients (35.7%) required amputation, four in the lower extremity and on in the upper extremity. Different reconstructive procedures were performed according to tumor size and location, including three free flaps. Those patients with high-grade sarcomas or with positive margins received postoperative radiotherapy. After a mean follow-up of 16 months, six patients presented local recurrences and four patients had synchronous metastatic disease in the lungs; all these patients had high-grade tumors. Overall survival was 86.4%. Conclusion: STS are rare and invasive neoplasms, widely distributed, requiring aggressive and occasionally complex surgical procedures. It is necessary to consider adjuvant treatments in selected cases and to maintain regular follow-up due to the high rate of recurrences and distant metastases.

S-Layer Glycoprotein From Lactobacillus kefiri Exerts Its Immunostimulatory Activity Through Glycan Recognition by Mincle.

The development of new subunit vaccines has promoted the rational design of adjuvants able to induce a strong T-cell activation by targeting specific immune receptors. The S-layer is a (glyco)-proteinaceous envelope constituted by subunits that self-assemble to form a two-dimensional lattice that covers the surface of different species of Bacteria and Archaea. Due to their ability to self-assemble in solution, they are attractive tools to be used as antigen/hapten carriers or adjuvants. Recently, we have demonstrated that S-layer glycoprotein from Lactobacillus kefiri CIDCA 8348 (SLP-8348) enhanced the LPS-induced response on macrophages in a Ca2+-dependent manner, but the receptors involved in these immunomodulatory properties remain unknown. Therefore, we aim to determine the C-type lectin receptors (CLRs) recognizing this bacterial surface glycoprotein as well as to investigate the role of glycans in both the immunogenicity and adjuvant capacity of SLP-8348. Here, using a mild periodate oxidation protocol, we showed that loss of SLP-8348 glycan integrity impairs the cell-mediated immune response against the protein. Moreover, our data indicate that the adjuvant capacity of SLP-8348 is also dependent of the biological activity of the SLP-8348 glycans. In order to evaluate the CLRs involved in the interaction with SLP-8348 an ELISA-based method using CLR-hFc fusion proteins showed that SLP-8348 interacts with different CLRs such as Mincle, SingR3, and hDC-SIGN. Using BMDCs derived from CLR-deficient mice, we show that SLP-8348 uptake is dependent of Mincle. Furthermore, we demonstrate that the SLP-8348-induced activation of BMDCs as well as its adjuvant capacity relies on the presence of Mincle and its signaling adaptor CARD9 on BMDCs, since SLP-8348-activated BMDCs from Mincle-/- or CARD9-/- mice were not capable to enhance OVA-specific response in CD4+ T cells purified from OT-II mice. These findings significantly contribute to the understanding of the role of glycans in the immunomodulation elicited by bacterial SLPs and generate a great opportunity in the search for new adjuvants derived from non-pathogenic microorganisms.

Grand Canonical Investigation of the Quasi Liquid Layer of Ice: Is It Liquid?

In this study, the solid-vapor equilibrium and the quasi liquid layer (QLL) of ice Ih exposing the basal and primary prismatic faces were explored by means of grand canonical molecular dynamics simulations with the monatomic mW potential. For this model, the solid-vapor equilibrium was found to follow the Clausius-Clapeyron relation in the range examined, from 250 to 270 K, with a Δ Hsub of 50 kJ/mol in excellent agreement with the experimental value. The phase diagram of the mW model was constructed for the low pressure region around the triple point. The analysis of the crystallization dynamics during condensation and evaporation revealed that, for the basal face, both processes are highly activated, and in particular cubic ice is formed during condensation, producing stacking-disordered ice. The basal and primary prismatic surfaces of ice Ih were investigated at different temperatures and at their corresponding equilibrium vapor pressures. Our results show that the region known as QLL can be interpreted as the outermost layers of the solid where a partial melting takes place. Solid islands in the nanometer length scale are surrounded by interconnected liquid areas, generating a bidimensional nanophase segregation that spans throughout the entire width of the outermost layer even at 250 K. Two approaches were adopted to quantify the QLL and discussed in light of their ability to reflect this nanophase segregation phenomena. Our results in the µVT ensemble were compared with NPT and NVT simulations for two system sizes. No significant differences were found between the results as a consequence of model system size or of the working ensemble. Nevertheless, certain advantages of performing µVT simulations in order to reproduce the experimental situation are highlighted. On the one hand, the QLL thickness measured out of equilibrium might be affected because of crystallization being slower than condensation. On the other, preliminary simulations of AFM indentation experiments show that the tip can induce capillary condensation over the ice surface, enlarging the apparent QLL.

Stability and Vapor Pressure of Aqueous Aggregates and Aerosols Containing a Monovalent Ion.

The incidence of charged particles on the nucleation and the stability of aqueous aggregates and aerosols was reported more than a century ago. Many studies have been conducted ever since to characterize the stability, structure, and nucleation barrier of ion-water droplets. Most of these studies have focused on the free-energy surface as a function of cluster size, with an emphasis on the role of ionic charge and radius. This knowledge is fundamental to go beyond the rudimentary ion-induced classical nucleation theory. In the present article, we address this problem from a different perspective, by computing the vapor pressures of (H2O)nLi+ and (H2O)nCl- aggregates using molecular simulations. Our calculations shed light on the structure, the critical size, the range of stability, and the role of ion-water interactions in aqueous clusters. Moreover, they allow one to assess the accuracy of the classical thermodynamic model, highlighting its strengths and weaknesses.

Cambios estructurales y funcionales del ventrículo derecho en deportistas de alto rendimiento evaluados por ecocardiografía con strain por speckle tracking / Structural and functional changes of right ventricle in highly trained athletes evaluated by echocardiography by speckle tracking strain / Alterações estruturais e funcionais do ventrículo direito em atletas altamente treinados avaliados por ecocardiografia com strain por speckle tracking

Introducción. El entrenamiento físico intenso se asocia a cambios cardíacos estructurales tanto del ventrículo izquierdo como del ventrículo derecho (VD). Sin embargo, no hay estudios en atletas argentinos que valoren con técnicas ecocardiográficas actuales dichos cambios, con el fin de reconocer precozmente aquellos que presentan dilataciones o hipertrofias patológicas que puedan asociarse a aumento del riesgo de muerte súbita. Objetivo. Evaluar la anatomía, función y comportamiento del VD en deportistas que realizan actividades isométricas o estáticas (GE), isotónicas o dinámicas (GD) y compararlo con pacientes controles no deportistas (GC). Materiales y métodos. Se realizó un ecocardiograma transtorácico, evaluando principalmente el VD a través del TAPSE, los diámetros diastólicos y sistólicos, el Doppler tisular (DTI), y el strain y strain rate por speckle tracking. Resultados. Incluimos 117 pacientes, 11 en GE, 56 en GD, y 50 controles. En los deportistas el acortamiento longitudinal con strain rate a nivel apical y basal, el diámetro diastólico apical y basal, el diámetro sistólico basal, las ondas S, E y A a nivel basal de la pared libre del VD por DTI, y las ondas S y E a nivel medio de la pared libre del VD por DTI mostraron diferencias significativas, con valores mayores en el grupo de deportistas tanto estáticos como dinámicos. Conclusión. Nuestro estudio demostró que los diámetros mayores del VD en los deportistas sanos se asocian a aumento de la deformación miocárdica medida por DTI y a través del acortamiento longitudinal del strain.

Introduction. The intense physical training is associated with cardiac structural changes in both the left ventricle and the right ventricle (RV). However, no studies in Argentine athletes who value with current echocardiographic techniques such changes, in order to recognize early those with dilations or pathological hypertrophy that may be associated with increased risk of sudden death. Objective. Evaluate the anatomy, function and behavior of RV in athletes who perform isometric or static (SG), isotonic or dynamic activities (DG) and compared with control patients non-athletes (CG). Materials and methods. Each patient underwent transthoracic echocardiography, evaluating primarily the RV through TAPSE, the diastolic and systolic diameters, Doppler tissue imaging (DTI), and the strain and strain rate by speckle tracking. Results. We included 117 patients, 11 in SG, 56 in DG, and 50 controls. In athletes the longitudinal shortening with strain rate at apical and basal level, the diastolic diameter apical and basal systolic diameter baseline, the S, E and A waves at baseline of the RV free wall by DTI, and waves S and E at the middle level of the RV free wall by DTI showed significant differences, with higher values in the group of both static and dynamic athletes. Conclusion. Our study showed that the largest diameters of RV in healthy athletes are associated with increased myocardial deformation measured by DTI and through the longitudinal shortening strain.

Introdução. O treinamento físico intenso está associado a alterações estruturais cardíacas, tanto no ventrículo esquerdo e do ventrículo direito (VD). No entanto, não existem estudos em atletas argentinos que valorizam com técnicas de ecocardiografia atuais tais mudanças, a fim de reconhecer cedo aqueles com dilatações ou hipertrofia patológica que pode estar associado ao aumento do risco de morte súbita. Objetivo. Avaliar a anatomia, função e comportamento do VD em atletas que realizam atividades isométricas ou estáticas (GE), isotônicas ou dinâmicas (GD) e em comparação com pacientes de controle não-atletas (GC). Materiais e métodos. Cada paciente foi submetido a uma ecocardiografia transtorácica, avaliando principalmente o RV através do TAPSE, os diâmetros diastólicos e sistólicos, o Doppler tecidual (DTI), e o strain e strain rate por speckle tracking. Resultados. Foram incluídos 117 pacientes, 11 no GE, 56 no GD, e 50 controles. Em os atletas o encurtamento longitudinal com strain rate a nível apical e basal, o diâmetro diastólico apical e basal, o diâmetro sistólico basal, as ondas S, E e A na níveis basal da parede livre do VD pelo DTI, e ondas S e E no nível médio da parede livre do VD por DTI apresentou diferenças significativas, com valores mais elevados no grupo de ambos os atletas estáticas e dinâmicas. Conclusão. Nosso estudo mostrou que os maiores diâmetros de VD em atletas saudáveis são associados com aumento da deformação miocárdica medida pelo DTI e através do encurtamento longitudinal do strain.

Vapor Pressure of Aqueous Solutions of Electrolytes Reproduced with Coarse-Grained Models without Electrostatics.

The vapor pressure of water is a key property in a large class of applications from the design of membranes for fuel cells and separations to the prediction of the mixing state of atmospheric aerosols. Molecular simulations have been used to compute vapor pressures, and a few studies on liquid mixtures and solutions have been reported on the basis of the Gibbs Ensemble Monte Carlo method in combination with atomistic force fields. These simulations are costly, making them impractical for the prediction of the vapor pressure of complex materials. The goal of the present work is twofold: (1) to demonstrate the use of the grand canonical screening approach ( Factorovich , M. H. J. Chem. Phys. 2014 , 140 , 064111 ) to compute the vapor pressure of solutions and to extend the methodology for the treatment of systems without a liquid-vapor interface and (2) to investigate the ability of computationally efficient high-resolution coarse-grained models based on the mW monatomic water potential and ions described exclusively with short-range interactions to reproduce the relative vapor pressure of aqueous solutions. We find that coarse-grained models of LiCl and NaCl solutions faithfully reproduce the experimental relative pressures up to high salt concentrations, despite the inability of these models to predict cohesive energies of the solutions or the salts. A thermodynamic analysis reveals that the coarse-grained models achieve the experimental activity coefficients of water in solution through a compensation of severely underestimated hydration and vaporization free energies of the salts. Our results suggest that coarse-grained models developed to replicate the hydration structure and the effective ion-ion attraction in solution may lead to this compensation. Moreover, they suggest an avenue for the design of coarse-grained models that accurately reproduce the activity coefficients of solutions.

Hydrogen-Bond Heterogeneity Boosts Hydrophobicity of Solid Interfaces.

Experimental and theoretical studies suggest that the hydrophobicity of chemically heterogeneous surfaces may present important nonlinearities as a function of composition. In this article, this issue is systematically explored using molecular simulations. The hydrophobicity is characterized by computing the contact angle of water on flat interfaces and the desorption pressure of water from cylindrical nanopores. The studied interfaces are binary mixtures of hydrophilic and hydrophobic sites, with and without the ability to form hydrogen bonds with water, intercalated at different scales. Water is described with the mW coarse-grained potential, where hydrogen-bonds are modeled in the absence of explicit hydrogen atoms, via a three-body term that favors tetrahedral coordination. We found that the combination of particles exhibiting the same kind of coordination with water gives rise to a linear dependence of contact angle with respect to composition, in agreement with the Cassie model. However, when only the hydrophilic component can form hydrogen bonds, unprecedented deviations from linearity are observed, increasing the contact angle and the vapor pressure above their values in the purely hydrophobic interface. In particular, the maximum enhancement is seen when a 35% of hydrogen bonding molecules is randomly scattered on a hydrophobic background. This effect is very sensitive to the heterogeneity length-scale, being significantly attenuated when the hydrophilic domains reach a size of 2 nm. The observed behavior may be qualitatively rationalized via a simple modification of the Cassie model, by assuming a different microrugosity for hydrogen bonding and non-hydrogen bonding interfaces.

Vapor pressure of water nanodroplets.

Classical thermodynamics is assumed to be valid up to a certain length-scale, below which the discontinuous nature of matter becomes manifest. In particular, this must be the case for the description of the vapor pressure based on the Kelvin equation. However, the legitimacy of this equation in the nanoscopic regime can not be simply established, because the determination of the vapor pressure of very small droplets poses a challenge both for experiments and simulations. In this article we make use of a grand canonical screening approach recently proposed to compute the vapor pressures of finite systems from molecular dynamics simulations. This scheme is applied to water droplets, to show that the applicability of the Kelvin equation extends to unexpectedly small lengths, of only 1 nm, where the inhomogeneities in the density of matter occur within spatial lengths of the same order of magnitude as the size of the object. While in principle this appears to violate the main assumptions underlying thermodynamics, the density profiles reveal, however, that structures of this size are still homogeneous in the nanosecond time-scale. Only when the inhomogeneity in the density persists through the temporal average, as it is the case for clusters of 40 particles or less, do the macroscopic thermodynamics and the molecular descriptions depart from each other.