Three-phase equilibria of hydrates from computer simulation. I. Finite-size effects in the methane hydrate

Clathrate hydrates are vital in energy research and environmental applications. Understanding their stability is crucial for harnessing their potential. In this work, we employ direct coexistence simulations to study finite-size effects in the determination of the three-phase equilibrium temperature (T3) for methane hydrates. Two popular water models, TIP4P/Ice and TIP4P/2005, are employed, exploring various system sizes by varying the number of molecules in the hydrate, liquid, and gas phases. The results reveal that finite-size effects play a crucial role in determining T3. The study includes nine configurations with varying system sizes, demonstrating that smaller systems, particularly those leading to stoichiometric conditions and bubble formation, may yield inaccurate T3 values. The emergence of methane bubbles within the liquid phase, observed in smaller configurations, significantly influences the behavior of the system and can lead to erroneous temperature estimations. Our findings reveal finite-size effects on the calculation of T3 by direct coexistence simulations and clarify the system size convergence for both models, shedding light on discrepancies found in the literature. The results contribute to a deeper understanding of the phase equilibrium of gas hydrates and offer valuable information for future research in this field.

Strategies to improve the implementation and effectiveness of community-based psychosocial support interventions for displaced, migrant and host community women in Latin America

As evidence supporting the effectiveness of mental health and psychosocial interventions grows, more research is needed to understand optimal strategies for improving their implementation in diverse contexts. We conducted a qualitative process evaluation of a multicomponent psychosocial intervention intended to promote well-being among refugee, migrant and host community women in three diverse contexts in Ecuador and Panamá. The objective of this study is to describe the relationships among implementation determinants, strategies and outcomes of this community-based psychosocial intervention. The five implementation strategies used in this study included stakeholder engagement, promoting intervention adaptability, group and community-based delivery format, task sharing and providing incentives. We identified 10 adaptations to the intervention and its implementation, most of which were made during pre-implementation. Participants (n = 77) and facilitators (n = 30) who completed qualitative interviews reported that these strategies largely improved the implementation of the intervention across key outcomes and aligned with the study's intervention and implementation theory of change models. Participants and facilitators also proposed additional strategies for improving reach, implementation and maintenance of this community-based psychosocial intervention.

Madrid-2019 force field: An extension to divalent cations Sr2+ and Ba2

In this work, we present a parameterization of Sr2+ and Ba2+ cations, which expands the alkali earth set of cations of the Madrid-2019 force field. We have tested the model against the experimental densities of eight different salts, namely, SrCl2, SrBr2, SrI2, Sr(NO3)2, BaCl2, BaBr2, BaI2, and Ba(NO3)2. The force field is able to reproduce the experimental densities of all these salts up to their solubility limit. Furthermore, we have computed the viscosities for two selected salts, finding that the experimental values are overestimated, but the predictions are still reasonable. Finally, the structural properties for all the salts have been calculated with this model and align remarkably well with experimental observations.

Growth rate of CO2 and CH4 hydrates by means of molecular dynamics simulations

CO2 and CH4 hydrates are of great importance both from an energetic and from an environmental point of view. It is therefore highly relevant to quantify and understand the rate with which they grow. We use molecular dynamics simulations to shed light on the growth rate of these hydrates. We put the solid hydrate phase in contact with a guest aqueous solution in equilibrium with the pure guest phase and study the growth of both hydrates at 400 bars with temperature. We compare our results with previous calculations of the ice growth rate. We find a growth rate maximum as a function of the supercooling in all cases. The incorporation of guest molecules into the solid structure strongly decelerates hydrate growth. Consistently, ice grows faster than either hydrate and the CO2 hydrate grows faster than the CH4 one because of the higher solubility of CO2. We also quantify the molecular motion required to build the solids under study and find that the distance traveled by liquid molecules exceeds by orders of magnitude that advanced by any solid. Less molecular motion is needed in order for ice to grow as compared to the hydrates. Moreover, when temperature increases, more motion is needed for solid growth. Finally, we find a good agreement between our growth rate calculations and experiments of hydrate growth along the guest-solution interface. However, more work is needed to reconcile experiments of hydrate growth toward the solution among each other and with simulations.

A chimeric protein-based vaccine elicits a strong IgG antibody response and confers partial protection against Shiga toxin-producing Escherichia coli in mice

Background

Shiga toxin-producing Escherichia coli (STEC) is a foodborne pathogen that causes gastrointestinal infections, ranging from acute diarrhea and dysentery to life-threatening diseases such as Hemolytic Uremic Syndrome. Currently, a vaccine to prevent STEC infection is an unmet medical need.

Results

We developed a chimeric protein-based vaccine targeting seven virulence factors of STEC, including the Stx2B subunit, Tir, Intimin, EspA, Cah, OmpT, and AggA proteins. Immunization of mice with this vaccine candidate elicited significant humoral and cellular immune responses against STEC. High levels of specific IgG antibodies were found in the serum and feces of immunized mice. However, specific IgA antibodies were not detected in either serum or feces. Furthermore, a significantly higher percentage of antigen-specific CD4+ T cells producing IFN-γ, IL-4, and IL-17 was observed in the spleens of immunized mice. Notably, the immunized mice showed decreased shedding of STEC O157:H7 and STEC O91:H21 strains and were protected against weight loss during experimental infection. Additionally, infection with the STEC O91:H21 strain resulted in kidney damage in control unimmunized mice; however, the extent of damage was slightly lower in immunized mice. Our findings suggest that IgG antibodies induced by this vaccine candidate may have a role in inhibiting bacterial adhesion and complement-mediated killing.

Conclusion

This study provides evidence that IgG responses are involved in the host defense against STEC. However, our results do not rule out that other classes of antibodies also participate in the protection against this pathogen. Additional work is needed to improve the protection conferred by our vaccine candidate and to elucidate the relevant immune responses that lead to complete protection against this pathogen.

Mixed-methods evaluation of a group psychosocial intervention for refugee, migrant and host community women in Ecuador and Panamá: Results from the Entre Nosotras cluster randomized feasibility trial

Community-based psychosocial interventions are key elements of mental health and psychosocial support; yet evidence regarding their effectiveness and implementation in humanitarian settings is limited. This study aimed to assess the appropriateness, acceptability, feasibility and safety of conducting a cluster randomized trial evaluating two versions of a group psychosocial intervention. Nine community clusters in Ecuador and Panamá were randomized to receive the standard version of the Entre Nosotras intervention, a community-based group psychosocial intervention co-designed with community members, or an enhanced version of Entre Nosotras that integrated a stress management component. In a sample of 225 refugees, migrants and host community women, we found that both versions were safe, acceptable and appropriate. Training lay facilitators to deliver the intervention was feasible. Challenges included slow recruitment related to delays caused by the COVID-19 pandemic, high attrition due to population mobility and other competing priorities, and mixed psychometric performance of psychosocial outcome measures. Although the intervention appeared promising, a definitive cluster randomized comparative effectiveness trial requires further adaptations to the research protocol. Within this pilot study we identified strategies to overcome these challenges that may inform adaptations. This comparative effectiveness design may be a model for identifying effective components of psychosocial interventions.

Minimum in the pressure dependence of the interfacial free energy between ice Ih and water

Despite the importance of ice nucleation, this process has been barely explored at negative pressures. Here, we study homogeneous ice nucleation in stretched water by means of molecular dynamics seeding simulations using the TIP4P/Ice model. We observe that the critical nucleus size, interfacial free energy, free energy barrier, and nucleation rate barely change between isobars from -2600 to 500 bars when they are represented as a function of supercooling. This allows us to identify universal empirical expressions for homogeneous ice nucleation in the pressure range from -2600 to 500 bars. We show that this universal behavior arises from the pressure dependence of the interfacial free energy, which we compute by means of the mold integration technique, finding a shallow minimum around -2000 bars. Likewise, we show that the change in the interfacial free energy with pressure is proportional to the excess entropy and the slope of the melting line, exhibiting in the latter a reentrant behavior also at the same negative pressure. Finally, we estimate the excess internal energy and the excess entropy of the ice Ih-water interface.

Homogeneous nucleation rate of methane hydrate formation under experimental conditions from seeding simulations

In this work, we shall estimate via computer simulations the homogeneous nucleation rate for the methane hydrate at 400 bars for a supercooling of about 35 K. The TIP4P/ICE model and a Lennard-Jones center were used for water and methane, respectively. To estimate the nucleation rate, the seeding technique was employed. Clusters of the methane hydrate of different sizes were inserted into the aqueous phase of a two-phase gas-liquid equilibrium system at 260 K and 400 bars. Using these systems, we determined the size at which the cluster of the hydrate is critical (i.e., it has 50% probability of either growing or melting). Since nucleation rates estimated from the seeding technique are sensitive to the choice of the order parameter used to determine the size of the cluster of the solid, we considered several possibilities. We performed brute force simulations of an aqueous solution of methane in water in which the concentration of methane was several times higher than the equilibrium concentration (i.e., the solution was supersaturated). From brute force runs, we infer the value of the nucleation rate for this system rigorously. Subsequently, seeding runs were carried out for this system, and it was found that only two of the considered order parameters were able to reproduce the value of the nucleation rate obtained from brute force simulations. By using these two order parameters, we estimated the nucleation rate under experimental conditions (400 bars and 260 K) to be of the order of log₁₀ (J/(m³ s)) = -7(5).

Scaled charges for ions: An improvement but not the final word for modeling electrolytes in water

In this work, we discuss the use of scaled charges when developing force fields for NaCl in water. We shall develop force fields for Na⁺ and Cl^- using the following values for the scaled charge (in electron units): ±0.75, ±0.80, ±0.85, and ±0.92 along with the TIP4P/2005 model of water (for which previous force fields were proposed for q = ±0.85 and q = ±1). The properties considered in this work are densities, structural properties, transport properties, surface tension, freezing point depression, and maximum in density. All the developed models were able to describe quite well the experimental values of the densities. Structural properties were well described by models with charges equal to or larger than ±0.85, surface tension by the charge ±0.92, maximum in density by the charge ±0.85, and transport properties by the charge ±0.75. The use of a scaled charge of ±0.75 is able to reproduce with high accuracy the viscosities and diffusion coefficients of NaCl solutions for the first time. We have also considered the case of KCl in water, and the results obtained were fully consistent with those of NaCl. There is no value of the scaled charge able to reproduce all the properties considered in this work. Although certainly scaled charges are not the final word in the development of force fields for electrolytes in water, its use may have some practical advantages. Certain values of the scaled charge could be the best option when the interest is to describe certain experimental properties.

A Longitudinal Evaluation of a Multimodal POCUS Curriculum in Pediatric Residents

Introduction: Pediatric residency programs often do not include a point of care ultrasound (POCUS) curriculum. We analyzed a novel POCUS curriculum for pediatric residents that incorporated an online question bank (QB), in addition to a traditional teaching model of didactic instruction and hands-on learning experience. Methods: Four high-yield POCUS topics were chosen: Focused Assessment by Sonography for Trauma (FAST), soft tissue, lung, and cardiac. Residents completed online multiple-choice quizzes before and after each of four in-person learning sessions, taught by ultrasound faculty and fellows. At the end of the academic year participants completed a knowledge retention quiz. Confidence surveys were administered to participants throughout the course of the study. Differences in means were compared by Student's t-test. Results: Learners demonstrated post-intervention score improvement for each of the four modules. Retention testing demonstrated retained improvement for the soft tissue and cardiac modules, but not for the FAST module. Self-reported confidence increased across all four topics. Conclusion: A multimodal POCUS curriculum utilizing a combination of an online QB and in-person teaching demonstrated lasting knowledge for pediatric trainees.

P-177 Non-invasive aneuploidy testing versus conventional morphological embryo selection in good prognosis patients

Study question

Can non-invasive preimplantation genetic testing of aneuploidies (niPGT-A) improve the clinical outcome in good prognosis patients compared to morphological embryo selection without aneuploidy testing?

Summary answer

Embryonic cell-free DNA (cfDNA) in the blastocyst culture medium offers more objective information for blastocyst selection, resulting in higher ongoing pregnancy rate in good-prognosis patients.

What is known already

One of the biggest challenges in IVF is accurately selecting viable embryos that are most likely to produce a healthy child at home after embryo transfer. Trophectoderm biopsy and PGT-A have improved implantation and clinical pregnancy rates per transfer; however, two recent studies have shown that PGTA does not improve clinical pregnancy rates below 35 years. A non-invasive alternative is to analyze (the cfDNA) in blastocyst culture medium. Several studies have shown that cfDNA testing on blastocyst culture medium at day 6 of development allows detection of aneuploidies with high concordance rates compared to TE biopsy and inner cell mass

Study design, size, duration

This observational study reports data from September 2020 to December 2021. During this period, niPGT-A was performed on 25 patients under 35 years of age whit average age of 32, where cfDNA analysis was applied to the culture medium of 92 blastocysts. A total of 20 single embryo transfers (SETs) have been performed so far, comparing the results with 31 transfers performed in the same period based only on morphological criteria.

Participants/materials, setting, methods

In the niPGT-A group, embryos were cultured in a Geri incubator up to day-4, and then individually cultured in 10 µl drops of CCSS (Fujifilm) until day 6 in an ESCO –system whit low oxygen concentration. At day-6, blastocysts were vitrified, and media collected in sterile PCR tubes after at least 40 hours in culture. After collection, media were immediately frozen and analyzed by Next Generation Sequencing analysis. Deferred transfer was performed according to media results.

Main results and the role of chance

In the niPGT-A group euploidy rate was 57% whit 8% non- informative results. Pregnancy rate was 80% with 75% ongoing pregnancy and 5% miscarriage rates, having 8 live births up to now. For the morphology group, pregnancy rate was 58% with 55% ongoing pregnancy and 3% miscarriage rates.

We did a secondary analysis identifiying which blastocyst we would be transfered, if only morphology would be considered. We observed that in 65% of the cases we would choose the same embryo as with niPGT-A, however in 35% of the cases we would have transferred a blastocyst with an aneuploid medium. Regarding blastocyst quality for throphoectoderm classified as A,B or C the euploidy rate were 62%,58% and 33% respectively, and pregnancy rates were 100%, 78% and 33%. For inne cell mass, similar euploidy rates werw observed for blastocyst classified as A,B or C (59%,52% and 57% respectively) and pregnancy rates were 100%, 73% and 100%. Evaluating the expansion grade in blastocoel no differences were observed in euploidy rates for cathegories 4, 5 and 6 (52%, 54% and 50% respectively) and pregnancy rates were 82%, 100% and 100%. We observed the lower pregnancy rate for blastocysts whit throphoectoderm C previously suggested by other authors.

Limitations, reasons for caution

Our results are encouraging since this group of good prognosis could improve their ongoing pregnancy rate even having a good reproductive prognosis whit morphology selection. Larger randomized controlled trials are needed to verify and extend our findings in this age range

Wider implications of the findings

These results support the clinical application of niPGT-A in the laboratory routine as a proritization tool, without the need of embryo manipulation, reducing subjectivity for blastocyst selection compared to morphology and increasing the ongoing pregnancy rate in good prognosis patients

Trial registration number

Sa-16552/19-EC:428

Evaluating the feasibility of a group psychosocial intervention for migrant and host community women in Ecuador and Panamá: protocol for a multi-site feasibility cluster trial

BACKGROUND

Community- and strengths-based psychosocial interventions are central to mental health and psychosocial support guidelines, but rigorous evidence regarding the effectiveness of these interventions is limited. The complexity and variability that is inherent to many community-based psychosocial interventions requires innovative strategies in order to facilitate the comparability and synthesis across research studies without compromising the fit and appropriateness of interventions to specific study populations and context. Entre Nosotras is a community-based psychosocial intervention developed for migrant and host community women that is designed to be flexible enough to enable integration of external intervention components and adaptable to diverse study contexts and populations. This protocol describes a study that aims to evaluate the appropriateness, acceptability, and feasibility of integrating a standardized stress management intervention into Entre Nosotras.

METHODS

This study will evaluate the appropriateness, acceptability, feasibility, and safety of intervention and research procedures for a cluster randomized comparative effectiveness trial conducted in Ecuador and Panamá with migrant and host community women. In this feasibility trial, we will allocate communities nested within the three study sites to the integrated Entre Nosotras + stress management intervention versus Entre Nosotras alone through stratified randomization. Migrant and host community women residing in these study communities who report low to moderate levels of distress will be allocated to the intervention condition that their community is assigned (n = 220 total). We will collect quantitative measures of psychosocial wellbeing, psychological distress, coping, social support, and functioning from study participants. We will collect quantitative measures of fidelity and facilitator competencies through observation and facilitator self-assessment. Data on appropriateness, acceptability, feasibility, and safety will be gathered from participants and facilitators through quantitative assessments at 0, 5, and 10 weeks post-enrollment and qualitative interviews conducted with all facilitators and a subset of 70 study participants during the post-intervention follow-up period.

DISCUSSION

Results from this feasibility trial will determine whether a multi-site cluster randomized comparative effectiveness trial of an adaptable community-based psychosocial intervention for migrant and host community women is relevant, acceptable, and feasible.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT05130944 . Registered November 23, 2021-retrospectively registered.

Melting points of water models: Current situation

By using the direct coexistence method, we have calculated the melting points of ice I h at normal pressure for three recently proposed water models, namely, TIP3P-FB, TIP4P-FB, and TIP4P-D. We obtained T m = 216 K for TIP3P-FB, T m = 242 K for TIP4P-FB, and T m = 247 K for TIP4P-D. We revisited the melting point of TIP4P/2005 and TIP5P obtaining T m = 250 and 274 K, respectively. We summarize the current situation of the melting point of ice I h for a number of water models and conclude that no model is yet able to simultaneously reproduce the melting temperature of ice I h and the temperature of the maximum in density at room pressure. This probably points toward our both still incomplete knowledge of the potential energy surface of water and the necessity of incorporating nuclear quantum effects to describe both properties simultaneously.

Maximum in density of electrolyte solutions: Learning about ion-water interactions and testing the Madrid-2019 force field

In this work, we studied the effect of Li⁺, Na⁺, K⁺, Mg²⁺, and Ca²⁺ chlorides and sulfates on the temperature of maximum density (TMD) of aqueous solutions at room pressure. Experiments at 1 molal salt concentration were carried out to determine the TMD of these solutions. We also performed molecular dynamics simulations to estimate the TMD at 1 and 2 m with the Madrid-2019 force field, which uses the TIP4P/2005 water model and scaled charges for the ions, finding an excellent agreement between experiment and simulation. All the salts studied in this work shift the TMD of the solution to lower temperatures and flatten the density vs temperature curves (when compared to pure water) with increasing salt concentration. The shift in the TMD depends strongly on the nature of the electrolyte. In order to explore this dependence, we have evaluated the contribution of each ion to the shift in the TMD concluding that Na⁺, Ca²⁺, and SO₄ ^2- seem to induce the largest changes among the studied ions. The volume of the system has been analyzed for salts with the same anion and different cations. These curves provide insight into the effect of different ions upon the structure of water. We claim that the TMD of electrolyte solutions entails interesting physics regarding ion-water and water-water interactions and should, therefore, be considered as a test property when developing force fields for electrolytes. This matter has been rather unnoticed for almost a century now and we believe it is time to revisit it.

Toys and Toy Accessories Strike Back: Pediatric Injuries From Plush Toys, Toy Figurines, and Doll and Toy Accessories

OBJECTIVE

The aim of the study was to examine age-associated injury trends and severe injury proportions for plush toys, toy figurines, and doll and toy accessories. We hypothesized that the proportion of severe injuries would be highest in the younger than 3-year and 3- to 5-year age groups.

METHODS

We analyzed injury patterns from plush toys, toy figurines, and doll and toy accessories for ages of 0 to 18 years from 2010 to 2018 using the Consumer Product Safety Commission National Electronic Injury Surveillance System. Exclusion criteria included unspecified toy categories, adult or pet involvement, or unspecified disposition. National estimates were calculated with National Electronic Injury Surveillance System sample weights. Outcome of interest was severe injury proportions per age and toy category. Severe injury was defined as life- or limb-threatening injuries or injuries requiring admission. χ2 test was used to analyze the distribution of categorical variables.

RESULTS

We analyzed 1360 injuries. The majority occurred in female (n = 771, 56.7%) and ages of 3 to 5 years (n = 580, 42.7%). Annual injury frequency remained stable. One fifth of injuries were severe (n = 321, 23.6%), with a national estimate of 9304.7. The majority of both total (n = 778, 57.2%) and severe injuries (n = 182, 56.7%) resulted from toy figurines. Life-threatening injury secondary to foreign body aspiration or ingestion with a risk for asphyxiation was the most common severe injury. Severe injuries were significantly more common in the younger than 3-year group (odds ratio, 3.59; 95% confidence interval, 2.40-5.36) and 3- to 5-year age group (odds ratio, 2.97; 95% confidence interval, 2.01-4.39) than the older than 5-year age group.

CONCLUSIONS

Injury frequency remained stable. The greatest proportion of injuries were in ages up to 5 years, with most injuries occurring in the 3- to 5-year age category, and a significant proportion of injuries were severe.

On the thermodynamics of curved interfaces and the nucleation of hard spheres in a finite system

We determine, for hard spheres, the Helmholtz free energy of a liquid that contains a solid cluster as a function of the size of the solid cluster by means of the formalism of the thermodynamics of curved interfaces. This is done at the constant total number of particles, volume, and temperature. We show that under certain conditions, one may have several local minima in the free energy profile, one for the homogeneous liquid and others for the spherical, cylindrical, and planar solid clusters surrounded by liquid. The variation of the interfacial free energy with the radius of the solid cluster and the distance between equimolar and tension surfaces are inputs from simulation results of nucleation studies. This is possible because stable solid clusters in the canonical ensemble become critical in the isothermal-isobaric ensemble. At each local minimum, we find no difference in chemical potential between the phases. At local maxima, we also find equal chemical potential, albeit in this case the nucleus is unstable. Moreover, the theory allows us to describe the stable solid clusters found in simulations. Therefore, we can use it for any combination of the total number of particles, volume, and global density as long as a minimum in the Helmholtz free energy occurs. We also study under which conditions the absolute minimum in the free energy corresponds to a homogeneous liquid or to a heterogeneous system having either spherical, cylindrical, or planar geometry. This work shows that the thermodynamics of curved interfaces at equilibrium can be used to describe nucleation.

Homogeneous nucleation of NaCl in supersaturated solutions

The seeding method is an approximate approach to investigate nucleation that combines molecular dynamics simulations with classical nucleation theory. Recently, this technique has been successfully implemented in a broad range of nucleation studies. However, its accuracy is subject to the arbitrary choice of the order parameter threshold used to distinguish liquid-like from solid-like molecules. We revisit here the crystallization of NaCl from a supersaturated brine solution and show that consistency between seeding and rigorous methods, like Forward Flux Sampling (from previous work) or spontaneous crystallization (from this work), is achieved by following a mislabelling criterion to select such threshold (i.e. equaling the fraction of the mislabelled particles in the bulk parent and nucleating phases). This work supports the use of seeding to obtain fast and reasonably accurate nucleation rate estimates and the mislabelling criterion as one giving the relevant cluster size for classical nucleation theory in crystallization studies.

Critical COVID-19 rarely associated with left ventricular systolic impairment

Introduction

For some individuals infection with SARS-CoV-2 leading to COVID-19 can result in a life-threatening multi-system disease. Multiple potential pathophysiological mechanisms for the development of cardiovascular complications have been postulated [1]. Early reports suggested that more than a third of hospitalised patients undergoing TTE had evidence of LV impairment [2].

Purpose

To ascertain the incidence of ventricular impairment among critically ill adults with COVID-19 admitted to the intensive care unit (ICU).

Methods

Retrospective analysis of transthoracic echocardiograms (TTE) performed on patients admitted to ICU with COVID-19 between 10th March and 10th May 2020. Archived studies were reviewed by accredited professionals. Studies were performed according to a modified British Society of Echocardiography (BSE) Level 1 protocol [3], with the addition of right ventricle (RV) focused apical 4 chamber, as well as apical 2 and 3 chamber views, and without ECG synchronisation as per infection control protocols. In the majority of patients the left ventricular ejection fraction (LVEF) was estimated from biplane Simpson's method. The RV function was assessed using the TAPSE in most patients. In the remaining patients the LV or RV function was visually assessed.

Results

Of 179 patients admitted to ICU, 85 (47.5%) had at least one TTE of diagnostic quality. Studies were performed a median of 7 days after ICU admission (IQR 3–17 days). Baseline and clinical characteristics and key echocardiographic measurements are summarised in table 1. The majority of patients were undergoing mechanical ventilation at the time of the scan (94.1%). One hundred and fifty-nine patients (89%) had elevated Troponin T (≥14ng/L) on the day of the study. LV systolic impairment (LVSD) was present in 5 patients (6.0%). This was known to be chronic in 3 patients (1 with coronary artery disease, 1 with chemotherapy induced cardiomyopathy and 1 with dilated cardiomyopathy of unknown aetiology), whilst pre-morbid cardiac function was unknown in the other 2 patients. No patient had severe LVSD (LVEF ≤35%). RV systolic dysfunction (RVSD) was found in 25 patients (31.3%). Amongst patients receiving mechanical ventilation there was no significant difference in Positive End Expiratory Pressure (PEEP) between patients with and without RVSD (9.4cmH2O vs. 9.8cmH2O, p=0.64), however there was a non-significant trend towards lower PaO2/FiO2 (P/F ratio) amongst patients with RVSD (18.9kPa vs 25.7kPa, p=0.07).

Conclusions

In contrast to other studies which have reported high frequency of LV impairment amongst hospitalised patients with COVID-19 [3], de novo LVSD was rarely found in this study, occurring in just 2 patients (2.4%), and being severe in neither. RV dilatation and systolic impairment were commonly found. A trend towards lower P/F ratios in patients with RVSD suggests severity of lung injury may be a factor in developing RV impairment.

Funding Acknowledgement

Type of funding sources: None.

Hypothermia: A Sign of Sepsis in Young Infants in the Emergency Department?

OBJECTIVES

Diagnosis of sepsis in young infants can be challenging due to the nonspecific signs, which can include hypothermia. Whether the presence of hypothermia in young infants should prompt evaluation for serious infection is unclear. The objectives were to measure the prevalence of serious infection among infants ≤60 days of age with hypothermia in the emergency department (ED) and determine other clinical features of hypothermic infants who have serious infection.

METHODS

This is a retrospective analysis of all infants ≤60 days seen in a children's hospital ED from April 2014 to February 2017. Primary outcome was presence of serious infection, defined as urinary tract infection, bacteremia, meningitis, pneumonia, or herpes virus infection. Hypothermia was defined as a rectal temperature of 36.0°C or less.

RESULTS

Of 4797 infants ≤60 days of age seen in the ED, 116 had hypothermia. The prevalence of serious infection was 2.6% (3/116) in hypothermic infants compared with 15.2% (61/401) in febrile infants (P < 0.01). Hypothermic infants with serious infections were more likely to have a history of prematurity, apnea, poor feeding, lethargy, ill-appearance, and respiratory signs than hypothermic infants without serious infection. All 3 hypothermic infants with serious infection had other concerning features.

CONCLUSIONS

The prevalence of serious infection in hypothermic young infants in the ED is low. Serious infection is unlikely in infants with isolated hypothermia.

Acute Hemorrhagic Edema of Infancy With Associated Hemorrhagic Lacrimation

ABSTRACT

Acute hemorrhagic edema of infancy is a rare leukocytoclastic vasculitis that affects infants and children aged 4 to 24 months. We report a case of a 5-month-old girl with purpuric lesions with associated hemorrhagic lacrimation and epistaxis.

Influence of individual or group housing of newborn calves on rotavirus and coronavirus infection during the first 2 months of life

Bovine rotavirus A (RVA) and bovine coronavirus (CoV) are the two main viral enteropathogens associated with neonatal calf diarrhea. The aim of the present work was to study the impact of group and individual housing systems in the epidemiology of RVA and CoV infection. Eleven calves reared in individual housing (FA) and nine calves in group housing (FB) were monitored during the first 7 weeks of life. Stool and serum samples were screened for RVA and CoV antigens by ELISA. IgG1 antibodies (Ab) to both antigens were also measured. From the 160 fecal samples collected, the proportion of positive samples to RVA and CoV was significantly higher in FB (23.6%) than in FA (9%) (p = 0.03). The geometric mean of colostral IgG1 Ab titers to CoV and RVA in FA (IgG1 anti-CoV 1024 and anti-RVA 1782.9) was lower than in FB (IgG1 anti-CoV 10,321.2 and anti-RVA 4096) at birth. Calves less than 2 weeks of life from FB had a higher risk of being infected by RVA (OR = 4.9; p = 0.01) and CoV (OR = 17.15; p = 0.01) than calves from FA. The obtained results showed that there was higher RVA and CoV shedding in group-housed calves than in individual-housed animals.

Equivalence between condensation and boiling in a Lennard-Jones fluid

Condensation and boiling are phase transitions highly relevant to industry, geology, and atmospheric science. These phase transitions are initiated by the nucleation of a drop in a supersaturated vapor and of a bubble in an overstretched liquid, respectively. The surface tension between both phases, liquid and vapor, is a key parameter in the development of such nucleation stage. Whereas the surface tension can be readily measured for a flat interface, there are technical and conceptual limitations to obtain it for the curved interface of the nucleus. On the technical side, it is quite difficult to observe a critical nucleus in experiments. From a conceptual point of view, the interfacial free energy depends on the choice of the dividing surface, being the surface of tension the one relevant for nucleation. We bypass the technical limitation by performing simulations of a Lennard-Jones fluid where we equilibrate critical nuclei (both drops and bubbles). Regarding the conceptual hurdle, we find the relevant cluster size by searching the radius that correctly predicts nucleation rates and nucleation free energy barriers when combined with Classical Nucleation Theory. With such definition of the cluster size we find the same value of the surface tension for drops and bubbles of a given radius. Thus, condensation and boiling can be viewed as two sides of the same coin. Finally, we combine the data coming from drops and bubbles to obtain, via two different routes, estimates of the Tolman length, a parameter that allows describing the curvature dependence of the surface tension in a theoretical framework.

First report of group A rotavirus and bovine coronavirus associated with neonatal calf diarrhea in the northwest of Argentina

Group A rotavirus (RVA) and bovine coronavirus (BCoV) are the two main viral enteropathogens associated with neonatal calf diarrhea. The aim of the present survey was to investigate the epidemiology and the role of RVA and BCoV in the presentation of dairy and beef calf diarrhea in Lerma Valley of Salta province, within the Northwest region of Argentina. Stool samples of calves with or without diarrhea younger than 2 months of age were collected from 19 dairy farms and 20 beef farms between the years 2014 and 2016. Stool samples were screened for RVA and BCoV detection by ELISA. Heminested multiplex RT-PCR was used for RVA typing and RT-PCR to confirm BCoV. Positive samples were submitted to sequencing analysis. Bovine RVA and BCoV were circulating in 63% (12/19) and 10.52% (2/19) of the dairy farms, respectively, where 9.5% (46/484) of the calves were positives to RVA and 0.4% (2/484) to BCoV. In beef herds, RVA was detected in 40% (8/20) of the farms and in 6.75% (21/311) of the calves, without positives cases of BCoV. Molecular analysis showed that in dairy farms, G6P[11] and G10P[11] were the prevalent RVA strains, while in beef farms, G10P[11] was the prevalent. The main finding was the detection for the first time of a G15P[11] causing diarrhea in beef calves of Argentina that represents a new alert to be consider for future vaccine updates. Analysis of detected BCoV showed that it is related to the other circulating strains of Argentina.

Seeding approach to nucleation in the NVT ensemble: The case of bubble cavitation in overstretched Lennard Jones fluids

Simulations are widely used to study nucleation in first order phase transitions due to the fact that they have access to the relevant length and time scales. However, simulations face the problem that nucleation is an activated process. Therefore, rare event simulation techniques are needed to promote the formation of the critical nucleus. The Seeding method, where the simulations are started with the nucleus already formed, has proven quite useful in efficiently providing estimates of the nucleation rate for a wide range of orders of magnitude. So far, Seeding has been employed in the NPT ensemble, where the nucleus either grows or redissolves. Thus, several trajectories have to be run in order to find the thermodynamic conditions that make the seeded nucleus critical. Moreover, the nucleus lifetime is short and the statistics for obtaining its properties is consequently poor. To deal with these shortcomings we extend the Seeding method to the NVT ensemble. We focus on the problem of bubble nucleation in a metastable Lennard Jones fluid. We show that, in the NVT ensemble, it is possible to equilibrate and stabilise critical bubbles for a long time. The nucleation rate inferred from NVT-Seeding is fully consistent with that coming from NPT-Seeding. The former is quite suitable to obtain the nucleation rate along isotherms, whereas the latter is preferable if the dependence of the rate with temperature at constant pressure is required. Care should be taken with finite size effects when using NVT-Seeding. Further work is required to extend NVT seeding to other sorts of phase transitions.

Seeding approach to bubble nucleation in superheated Lennard-Jones fluids

We investigate vapor homogeneous nucleation in a superheated Lennard-Jones liquid with computer simulations. Special simulation techniques are required to address this study since the nucleation of a critical vapor bubble-one that has an equal chance to grow or shrink-in a moderately superheated liquid is a rare event. We use the Seeding method, which combines Classical Nucleation Theory with computer simulations of a liquid containing a vapor bubble to provide bubble nucleation rates in a wide temperature range. Seeding has been successfully applied to investigate the nucleation of crystals in supercooled fluids, and here we apply it to the liquid-to-vapor transition. We find that the Seeding method provides nucleation rates that are consistent with independent calculations not based on the assumptions of Classical Nucleation Theory. Different criteria to determine the radius of the critical bubble give different rate values. The accuracy of each criterion depends of the degree of superheating. Moreover, seeding simulations show that the surface tension depends on pressure for a given temperature. Therefore, using Classical Nucleation Theory with the coexistence surface tension does not provide good estimates of the nucleation rate.

A force field of Li+, Na+, K+, Mg2+, Ca2+, Cl-, and SO4 2- in aqueous solution based on the TIP4P/2005 water model and scaled charges for the ions

In this work, a force field for several ions in water is proposed. In particular, we consider the cations Li⁺, Na⁺, K⁺, Mg²⁺, and Ca²⁺ and the anions Cl^- and SO₄ ^2-. These ions were selected as they appear in the composition of seawater, and they are also found in biological systems. The force field proposed (denoted as Madrid-2019) is nonpolarizable, and both water molecules and sulfate anions are rigid. For water, we use the TIP4P/2005 model. The main idea behind this work is to further explore the possibility of using scaled charges for describing ionic solutions. Monovalent and divalent ions are modeled using charges of 0.85 and 1.7, respectively (in electron units). The model allows a very accurate description of the densities of the solutions up to high concentrations. It also gives good predictions of viscosities up to 3 m concentrations. Calculated structural properties are also in reasonable agreement with the experiment. We have checked that no crystallization occurred in the simulations at concentrations similar to the solubility limit. A test for ternary mixtures shows that the force field provides excellent performance at an affordable computer cost. In summary, the use of scaled charges, which could be regarded as an effective and simple way of accounting for polarization (at least to a certain extend), improves the overall description of ionic systems in water. However, for purely ionic systems, scaled charges will not adequately describe neither the solid nor the melt.

Masseter muscle atrophy impairs bone quality of the mandibular condyle but not the alveolar process early after induction

BACKGROUND

Masseter muscle function influences mandibular bone homeostasis. As previously reported, bone resorption markers increased in the mouse mandibular condyle two days after masseter paralysis induced with botulinum toxin type A (BoNTA), followed by local bone loss.

OBJECTIVE

This study aimed to evaluate the bone quality of both the mandibular condyle and alveolar process in the mandible of adult mice during the early stage of a BoNTA-induced masseter muscle atrophy, using a combined 3D histomorphometrics and shape analysis approach.

METHODS

Adult BALB/c mice were divided into an untreated control group and an experimental group; the latter received one single BoNTA injection in the right masseter (BoNTA-right) and saline in the left masseter (Saline-left). 3D bone microstructural changes in the mandibular condyle and alveolar process were determined with high-resolution microtomography. Additionally, landmark-based geometric morphometrics was implemented to assess external shape changes.

RESULTS

After 2 weeks, masseter mass was significantly reduced (P-value <0.001). When compared to Saline-left and untreated condyles, BoNTA-right condyles showed significant bone loss (P-value <0.001) and shape changes. No significant bone loss was observed in the alveolar processes of any of the groups (P-value >0.05).

CONCLUSION

Condyle bone quality deteriorates at an early stage of BoNTA-induced masseter muscle atrophy, and before the alveolar process is affected. Since the observed bone microstructural changes resemble those in human temporomandibular joint degenerative disorders, the clinical safety of BoNTA intervention in the masticatory apparatus remains to be clarified.

On the time required to freeze water

By using the seeding technique the nucleation rate for the formation of ice at room pressure will be estimated for the TIP4P/ICE model using longer runs and a smaller grid of temperatures than in the previous work. The growth rate of ice will be determined for TIP4P/ICE and for the mW model of water. Although TIP4P/ICE and mW have a similar melting point and melting enthalpy, they differ significantly in the dynamics of freezing. The nucleation rate of mW is lower than that of TIP4P/ICE due to its higher interfacial free energy. Experimental results for the nucleation rate of ice are between the predictions of these two models when obtained from the seeding technique, although closer to the predictions of TIP4P/ICE. The growth rate of ice for the mW model is four orders of magnitude larger than for TIP4P/ICE. Avrami's expression is used to estimate the crystallization time from the values of the nucleation and growth rates. For mW the minimum in the crystallization time is found at approximately 85 K below the melting point and its value is of about a few ns, in agreement with the results obtained from brute force simulations by Moore and Molinero. For the TIP4P/ICE the minimum is found at about 55 K below the melting point, but its value is about ten microseconds. This value is compatible with the minimum cooling rate required to avoid the formation of ice and obtaining a glass phase. The crossover from the nucleation controlled crystallization to the growth controlled crystallization will be discussed for systems of finite size. This crossover could explain the apparent discrepancy between the values of J obtained by different experimental groups for temperatures below 230 K and should be considered as an alternative hypothesis to the two previously suggested: internal pressure and/or surface freezing effects. A maximum in the compressibility was found for the TIP4P/ICE model in supercooled water. The relaxation time is much smaller than the crystallization time at the temperature at which this maximum occurs, so this maximum is a real thermodynamic feature of the model. At the temperature of minimum crystallization time, the crystallization time is larger than the relaxation time by just two orders of magnitude.

Early molecular response and microanatomical changes in the masseter muscle and mandibular head after botulinum toxin intervention in adult mice

BACKGROUND

Masseter muscle paralysis induced by botulinum toxin type A (BoNTA) evokes subchondral bone loss in mandibular heads of adult rats and growing mice after 4 weeks. However, the primary cellular and molecular events leading to altered bone remodeling remain unexplored. Thus, the aim of the current work has been to assess the molecular response that precedes the early microanatomical changes in the masseter muscle and subchondral bone of the mandibular head in adult mice after BoNTA intervention.

METHODS

A pre-clinical in vivo study was performed by a single intramuscular injection of 0.2 U BoNTA in the right masseter (experimental) of adult BALB/c mice. The contralateral masseter was injected with vehicle (control). Changes in mRNA levels of molecular markers of bone loss or muscle atrophy/regeneration were addressed by qPCR at day 2 or 7, respectively. mRNA levels of receptor activator of nuclear factor-κB ligand (RANKL) was assessed in mandibular heads, whilst mRNA levels of Atrogin-1/MAFbx, MuRF-1 and Myogenin were addressed in masseter muscles. In order to identify the early microanatomical changes at day 14, fiber diameters in transversal sections of masseter muscles were quantified, and histomorphometric analysis was used to determine the bone per tissue area and the trabecular thickness of subchondral bone of the mandibular heads.

RESULTS

An increase of up to 4-fold in RANKL mRNA levels were detected in mandibular heads of the BoNTA-injected sides as early as 2 days after intervention. Moreover, a 4-6 fold increase in Atrogin-1/MAFbx and MuRF-1 and an up to 25 fold increase in Myogenin mRNA level were detected in masseter muscles 7 days after BoNTA injections. Masseter muscle mass, as well as individual muscle fiber diameter, were significantly reduced in BoNTA-injected side after 14 days post-intervention. At the same time, in the mandibular heads from the treated side, the subchondral bone loss was evinced by a significant reduction in bone per tissue area (-40%) and trabecular thickness (-55%).

CONCLUSIONS

Our results show that masseter muscle paralysis induced by BoNTA leads to significant microanatomical changes by day 14, preceded by molecular changes as early as 2 days in bone, and 7 days in muscle. Therefore, masseter muscle atrophy and subchondral bone loss detected at 14 days are preceded by molecular responses that occur during the first week after BoNTA intervention.

A new intermolecular potential for simulations of methanol: The OPLS/2016 model

In this work, a new rigid-nonpolarizable model of methanol is proposed. The model has three sites, located at the same positions as those used in the OPLS model previously proposed by Jorgensen [J. Phys. Chem. 90, 1276 (1986)]. However, partial charges and the values of the Lennard-Jones parameters were modified by fitting to an adequately selected set of target properties including solid-fluid experimental data. The new model was denoted as OPLS/2016. The overall performance of this model was evaluated and compared to that obtained with other popular models of methanol using a similar test to that recently proposed for water models. In the test, a certain numerical score is given to each model. It was found that the OPLS/2016 obtained the highest score (7.4 of a maximum of 10) followed by L1 (6.6), L2 (6.4), OPLS (5.8), and H1 (3.5) models. The improvement of OPLS/2016 with respect to L1 and L2 is mainly due to an improvement in the description of fluid-solid equilibria (the melting point is only 14 K higher than the experimental value). In addition, it was found that no methanol model was able to reproduce the static dielectric constant and the isobaric heat capacity, whereas the better global performance was found for models that reproduce the vaporization enthalpy once the so-called polarization term is included. Similar conclusions were suggested previously in the analysis of water models and are confirmed here for methanol.

Consensus on the solubility of NaCl in water from computer simulations using the chemical potential route

The solubility of NaCl in water is evaluated by using three force field models: Joung-Cheatham for NaCl dissolved in two different water models (SPC/E and TIP4P/2005) and Smith Dang NaCl model in SPC/E water. The methodology based on free-energy calculations [E. Sanz and C. Vega, J. Chem. Phys. 126, 014507 (2007)] and [J. L. Aragones et al., J. Chem. Phys. 136, 244508 (2012)] has been used, except, that all calculations for the NaCl in solution were obtained by using molecular dynamics simulations with the GROMACS package instead of homemade MC programs. We have explored new lower molalities and made longer runs to improve the accuracy of the calculations. Exploring the low molality region allowed us to obtain an analytical expression for the chemical potential of the ions in solution as a function of molality valid for a wider range of molalities, including the infinite dilute case. These new results are in better agreement with recent estimations of the solubility obtained with other methodologies. Besides, two empirical simple rules have been obtained to have a rough estimate of the solubility of a certain model, by analyzing the ionic pairs formation as a function of molality and/or by calculating the difference between the NaCl solid chemical potential and the standard chemical potential of the salt in solution.

Ionization Suppression and Recovery in Direct Biofluid Analysis Using Paper Spray Mass Spectrometry

Paper spray mass spectrometry is a method for the direct analysis of biofluid samples in which extraction of analytes from dried biofluid spots and electrospray ionization occur from the paper on which the dried sample is stored. We examined matrix effects in the analysis of small molecule drugs from urine, plasma, and whole blood. The general method was to spike stable isotope labeled analogs of each analyte into the spray solvent, while the analyte itself was in the dried biofluid. Intensity of the labeled analog is proportional to ionization efficiency, whereas the ratio of the analyte intensity to the labeled analog in the spray solvent is proportional to recovery. Ion suppression and recovery were found to be compound- and matrix-dependent. Highest levels of ion suppression were obtained for poor ionizers (e.g., analytes lacking basic aliphatic amine groups) in urine and approached -90%. Ion suppression was much lower or even absent for good ionizers (analytes with aliphatic amines) in dried blood spots. Recovery was generally highest in urine and lowest in blood. We also examined the effect of two experimental parameters on ion suppression and recovery: the spray solvent and the sample position (how far away from the paper tip the dried sample was spotted). Finally, the change in ion suppression and analyte elution as a function of time was examined by carrying out a paper spray analysis of dried plasma spots for 5 min by continually replenishing the spray solvent. Graphical Abstract ᅟ.