A neural network potential based on pairwise resolved atomic forces and energies.

Molecular simulations have become a key tool in molecular and materials design. Machine learning (ML)-based potential energy functions offer the prospect of simulating complex molecular systems efficiently at quantum chemical accuracy. In previous work, we have introduced the ML-based PairF-Net approach to neural network potentials, that adopts a pairwise interatomic scheme to predicting forces within a molecular system. Here, we further develop the PairF-Net model to intrinsically incorporate energy conservation and couple the model to a molecular mechanical (MM) environment within the OpenMM package. The updated PairF-Net model yields energy and force predictions and dynamical distributions in good agreement with the rMD17 dataset of ten small organic molecules in the gas-phase. We further show that these in vacuo ML models of small molecules can be applied to force predictions in aqueous solution via hybrid ML/MM simulations. We present a new benchmark dataset for these ten molecules in solution, obtained from QM/MM simulations, which we denote as rMD17-aq (https://zenodo.org/records/10048644); and assess the ability of PairF-Net to reproduce the molecular energy, atomic forces and dynamical distributions of these solution conformations via ML/MM simulations.

General practitioners' role in improving health care in care homes: a realist review.

BACKGROUND: Despite recent focus on improving health care in care homes, it is unclear what role general practitioners (GPs) should play. To provide evidence for future practice we set out to explore how GPs have been involved in such improvements. METHODS: Realist review incorporated theory-driven literature searches and stakeholder interviews, supplemented by focussed searches on GP-led medication reviews and end-of-life care. Medline, Embase, CINAHL, PsycInfo, Web of Science, and the Cochrane library were searched. Grey literature was identified through internet searches and professional networks. Studies were included based upon relevance. Data were coded to develop and test contexts, mechanisms, and outcomes for improvements involving GPs. RESULTS: Evidence was synthesized from 30 articles. Programme theories described: (i) "negotiated working with GPs," where other professionals led improvement and GPs provided expertise; and (ii) "GP involvement in national/regional improvement programmes." The expertise of GPs was vital to many improvement programmes, with their medical expertise or role as coordinators of primary care proving pivotal. GPs had limited training in quality improvement (QI) and care home improvement work had to be negotiated in the context of wider primary care commitments. CONCLUSIONS: GPs are central to QI in health care in care homes. Their contributions relate to their specialist expertise and recognition as leaders of primary care but are challenged by available time and resources to develop this role.

'Weighing up risks': a model of care home staff decision-making about potential resident hospital transfers.

BACKGROUND: care home staff play a crucial role in managing residents' health and responding to deteriorations. When deciding whether to transfer a resident to hospital, a careful consideration of the potential benefits and risks is required. Previous studies have identified factors that influence staff decision-making, yet few have moved beyond description to produce a conceptual model of the decision-making process. OBJECTIVES: to develop a conceptual model to describe care home staff's decision-making when faced with a resident who potentially requires a transfer to the hospital. METHODS: data collection occurred in England between May 2018 and November 2019, consisting of 28 semi-structured interviews with 30 members of care home staff across six care home sites and 113 hours of ethnographic observations, documentary analysis and informal conversations (with staff, residents, visiting families, friends and healthcare professionals) at three of these sites. RESULTS: a conceptual model of care home staff's decision-making is presented. Except in situations that staff perceived to be urgent enough to require an immediate transfer, resident transfers tended to occur following a series of escalations. Care home staff made complex decisions in which they sought to balance a number of potential benefits and risks to: residents; staff (as decision-makers); social relationships; care home organisations and wider health and social care services. CONCLUSIONS: during transfer decisions, care home staff make complex decisions in which they weigh up several forms of risk. The model presented offers a theoretical basis for interventions to support deteriorating care home residents and the staff responsible for their care.

Selective Removal of Technetium from Water Using Graphene Oxide Membranes.

The effective removal of radioactive technetium ((99)Tc) from contaminated water is of enormous importance from an environmental and public health perspective, yet many current methodologies are highly ineffective. In this work, however, we demonstrate that graphene oxide membranes may remove (99)Tc, present in the form of pertechnetate (TcO4(-)), from water with a high degree of selectivity, suggesting they provide a cost-effective and efficient means of achieving (99)Tc decontamination. The results were obtained by quantifying and comparing the free energy changes associated with the entry of the ions into the membrane capillaries (ΔFperm), using molecular dynamics simulations. Initially, three capillary widths were investigated (0.35, 0.68, and 1.02 nm). In each case, the entry of TcO4(-) from aqueous solution into the capillary is associated with a decrease in free energy, unlike the other anions (SO4(2-), I(-), and Cl(-)) investigated. For example, in the model with a capillary width of 0.68 nm, ΔFperm(TcO4(-)) = -6.3 kJ mol(-1), compared to ΔFperm(SO4(2-)) = +22.4 kJ mol(-1). We suggest an optimum capillary width (0.48 nm) and show that a capillary with this width results in a difference between ΔFperm(TcO4(-)) and ΔFperm(SO4(2-)) of 89 kJ mol(-1). The observed preference for TcO4(-) is due to its weakly hydrating nature, reflected in its low experimental hydration free energy.

A classical force field for tetrahedral oxyanions developed using hydration properties: The examples of pertechnetate (TcO4(-)) and sulfate (SO4(2-)).

Radioactive pertechnetate, (99)TcO4(-), is one of the most problematic ionic species in the context of the clean up and storage of nuclear waste. Molecular simulations can be used to understand the behavior of TcO4(-) in dilute aqueous solutions, providing reliable potentials are available. This work outlines the development of a new potential model for TcO4(-) and competing SO4(2-), optimized using their hydration properties, such as the Gibbs hydration free energy (calculated using Bennett's acceptance ratio method). The findings show that the TcO4(-) oxyanion has a very low hydration free energy (-202 kJ mol(-1)) compared to other anions (Cl(-), I(-), SO4(2-)) leading to fast water exchange dynamics and explaining its observed high mobility in the aqueous environment. Its hydrated structure, investigated using ion-water radial distribution functions, shows that it is unique amongst the other anions in that it does not possess well-defined hydration shells. Since contaminants and ubiquitous species in the aqueous environment are often present as tetrahedral oxyanions, it is proposed that the approach could easily be extended to a whole host of other species.

AMH in women with diminished ovarian reserve: potential differences by FMR1 CGG repeat level.

PURPOSE: We explored whether AMH, as a surrogate for oocyte supply, varies by FMR1 genotype in women diagnosed with diminished ovarian reserve (DOR), a subset of the Primary Ovarian Insufficiency phenotype. Research is inconsistent on the relationship between AMH and FMR1 repeat length, controlling for age. METHOD: Seventy-nine cycling women diagnosed with DOR, and without a family history of fragile X syndrome, provided blood for FMR1 and AMH testing. DOR was defined as elevated FSH and/or low AMH and/or low antral follicle count, with regular menses. FMR1 CGG repeats were stratified by the larger allele <35 repeats (n = 70) v. ≥35 repeats (n = 9). Quadratic and linear models were fit to predict log (AMH) controlling for age. The AMH sample used as the outcome variable was drawn at a later date than the diagnostic AMH. RESULTS: Serum AMH concentration median was 0.30 ng/mL; Ages ranged from 26-43 years. A quadratic model (including age(2)) did not show a relationship with FMR1 CGG level (p-value = 0.25). A linear model of log (AMH), corresponding to an exponential decline of AMH with increasing age, was significantly different, and had a steeper slope, for women with ≥ 35 CGG repeats than women with < 35 repeats (p = 0.035). CONCLUSION: Findings suggest a greater rate of follicular loss that starts at later ages in women with DOR and ≥ 35 CGG repeats.

Association of coffee and caffeine consumption with fatty liver disease, nonalcoholic steatohepatitis, and degree of hepatic fibrosis.

UNLABELLED: Coffee caffeine consumption (CC) is associated with reduced hepatic fibrosis in patients with chronic liver diseases, such as hepatitis C. The association of CC with nonalcoholic fatty liver disease (NAFLD) has not been established. The aim of this study was to correlate CC with the prevalence and severity of NAFLD. Patients involved in a previously published NAFLD prevalence study, as well as additional NASH patients identified in the Brooke Army Medical Center Hepatology clinic, were queried about their caffeine intake. A validated questionnaire for CC was utilized to assess for a relationship between caffeine and four groups: ultrasound negative (controls), bland steatosis/not-NASH, NASH stage 0-1, and NASH stage 2-4. A total of 306 patients responded to the CC questionnaire. Average milligrams of total caffeine/coffee CC per day in controls, bland steatosis/not-NASH, NASH stage 0-1, and NASH stage 2-4 were 307/228, 229/160, 351/255, and 252/152, respectively. When comparing patients with bland steatosis/not-NASH to those with NASH stage 0-1, there was a significant difference in CC between the two groups (P = 0.005). Additionally, when comparing patients with NASH stage 0-1 to those with NASH stage 2-4, there was a significant difference in coffee CC (P = 0.016). Spearman's rank correlation analysis further supported a negative relationship between coffee CC and hepatic fibrosis (r = -0.215; P = 0.035). CONCLUSION: Coffee CC is associated with a significant reduction in risk of fibrosis among NASH patients.

Preparing for the bundled-payment initiative: the cost and clinical outcomes of total shoulder arthroplasty for the surgical treatment of glenohumeral arthritis at an average 4-year follow-up.

BACKGROUND: The purpose of this study is to report on cost, outcomes, reliability, and safety of total shoulder arthroplasty (TSA) in patients with symptomatic glenohumeral joint arthritis. MATERIALS AND METHODS: Eighty-three primary TSA patients operated on at a single institution by a single surgeon were prospectively studied for a mean of 48 months (range, 32-69 months). For each patient, validated subjective and independently evaluated objective outcome measures were collected to determine clinical reliability of TSA. In addition, safety-defined as the lack of major complications-and direct costs specific to each patient were collected and analyzed. RESULTS: There were significant improvements (P < .01) in all clinical measures with the exception of the general health component of the Short Form 36 version 2. In addition, the majority of the patients met the criteria set forth for clinical reliability (76 of 83 [92%]) and safety (80 of 83 [96%]). The mean 4-year cost was $17,587, with the hospitalization accounting for 88% of this cost. Fiscal year was found to be responsible for the greatest fluctuation in total cost (P < .001). In addition, greater improvements in American Shoulder and Elbow Surgeons function scores (P = .022), higher preoperative social functioning scores on the Short Form 36 version 2 (P < .001), and female gender (P = .001) were correlated with lower cost. CONCLUSION: Before operative treatment, patients had moderate to severe shoulder pain and were limited in performing their activities. The mean 4-year cost of $17,587 allowed the purchase of treatment with TSA, leading to a greater than 5-fold reduction in pain and a nearly double improvement in shoulder function with a small risk of harm.

Preparing for the bundled-payment initiative: the cost and clinical outcomes of reverse shoulder arthroplasty for the surgical treatment of advanced rotator cuff deficiency at an average 4-year follow-up.

BACKGROUND: The purpose of this study is to report on cost, outcomes, reliability, and safety of reverse shoulder arthroplasty (RSA) in patients with symptomatic advanced rotator cuff deficiency. METHODS: Fifty-five primary RSA patients operated on at a single institution by a single surgeon were prospectively studied for a mean of 48 months (range, 31-71 months). For each patient, validated subjective and independently evaluated objective outcome data were collected to determine clinical reliability. In addition, safety, defined as major complications, as well as direct costs specific to each patient, were collected and analyzed. RESULTS: There were significant improvements (P < .05) in all clinical measures with the exception of the general health and vitality components as well as the mental component summary scores of the Short Form 36 version 2 (SF-36v2). In addition, the majority of the patients met the criteria set forth for clinical reliability (53 of 55 [96%]) and safety (49 of 55 [89%]). The mean total 4-year cost was $24,661, with the hospitalization accounting for 92% of this cost. Fiscal year was found to be responsible for the greatest fluctuation in total cost (P < .001). In addition, a lower comorbidity burden (P < .001), a higher preoperative extremity impairment rating (P < .001), higher postoperative role-emotional component scores on the SF-36v2 (P = .001), and lower postoperative social functioning component scores on the SF-36v2 (P = .005) were correlated with less cost. CONCLUSION: The mean 4-year total cost of $24,661 allowed the purchase of treatment with RSA, leading to a greater than 5-fold reduction in pain and a 70% improvement in shoulder function with a small risk of harm.

Key aspects of the biology of snail-killing Sciomyzidae flies.

The biology of snail-killing flies (Diptera: Sciomyzidae) has been studied intensively over the past half-century, especially over the past decade. Today, sciomyzids are biologically the best-known group of higher Diptera. The overarching research objectives are evaluation of sciomyzids as biocontrols of disease-carrying or agriculturally important snails and slugs and as a paradigm group for the study of the evolution of diverse feeding and associated behaviors in flies. We present reviews and analyses of some key features of particular scientific and societal interest, including behavioral and phenological groups; laboratory experimental studies on behavior and development; population biology, bioindicators, ecosystem service provision, and conservation; phylogenetics, molecular studies, and evolutionary biology; and biocontrol.

The genome sequence of the common buff snailkiller, Tetanocera ferruginea (Fallén, 1820).

We present a genome assembly from an individual male Tetanocera ferruginea (the common buff snailkiller; Arthropoda; Insecta; Diptera; Sciomyzidae). The genome sequence is 790.4 megabases in span. Most of the assembly is scaffolded into 7 chromosomal pseudomolecules, including the X and Y sex chromosomes. The mitochondrial genome has also been assembled and is 17.07 kilobases in length.

Decoding the Interplay between Topology and Surface Charge in Graphene Oxide Membranes During Humidity Induced Swelling.

Graphene oxide (GO) membranes are known to have a complex morphology that depends on the degree of oxidation of the graphene flake and the membrane preparation technique. In this study, using Grand Canonical Monte Carlo simulations, we investigate the mechanism of swelling of GO membranes exposed to different relative humidity (RH) values and show how this is intimately related to the graphene surface chemistry. We show that the structure of the GO membrane changes while the membrane adsorbs water from the environment and that graphene oxide flakes become charged as the membrane is loaded with water and swells. A detailed comparison between simulation and experimental adsorption data reveals that the flake surface charge drives the water adsorption mechanism at low RH when the membrane topology is still disordered and the internal pores are small and asymmetric. As the membrane is exposed to higher RH (80%), the flake acquires more surface charge as more oxide groups deprotonate, and the pores grow in size, yet maintain their disordered geometry. Only for very high relative humidity (98%) does the membrane undergo structural changes. At this level of humidity, the pores in the membrane become slit-like but the flake surface charge remains constant. Our results unveil a very complex mechanism of swelling and show that a single molecular model cannot fully capture the ever-changing chemistry and morphology of the membrane as it swells. Our computational procedure provides the first atomically resolved insight into the GO membrane structure of experimental samples.

Hierarchical Aggregation in a Complex Fluid─The Role of Isomeric Interconversion.

There is an ever-increasing body of evidence that metallic complexes involving amphiliphic ligands do not form normal solutions in organic solvents. Instead, they form complex fluids with intricate structures. For example, the metallic complexes may aggregate into clusters, and these clusters themselves may aggregate into superclusters. To gain a deeper insight into the mechanisms at play, we have used an improved force field to conduct extensive molecular dynamics simulations of a system composed of zirconium nitrate, water, nitric acid, tri-n-butyl phosphate, and n-octane. The important new finding is that a dynamic equilibrium between the cis and trans isomers of the metal complex is likely to play a key role in the aggregation behavior. The isolated cis and trans isomers have similar energies, but simulation indicates that the clusters consist predominantly of cis isomers. With increasing metal concentration, we hypothesize that more clustering occurs and the chemical equilibrium shifts toward the cis isomer. It is possible that such isomeric effects play a role in the liquid-liquid extraction of other species and the inclusion of such effects in flow sheet modeling may lead to a better description of the process.

Features, diagnosis, and treatment of nonalcoholic fatty liver disease.

As the global incidence of obesity has increased, nonalcoholic fatty liver disease (NAFLD) has become a worldwide health concern. NAFLD occurs in children and adults of all ethnicities and includes isolated fatty liver and nonalcoholic steatohepatitis (NASH). Patients with NASH are at risk for developing cirrhosis, hepatic decompensation, and hepatocellular carcinoma and have increased all-cause mortality. NAFLD is associated with a variety of clinical conditions and is an independent risk factor for hepatocellular carcinoma. The pathogenesis of NAFLD and the specific steps that lead to NASH and advanced fibrosis are not fully understood, although researchers have found that a combination of environmental, genetic, and metabolic factors lead to advanced disease. There have been improvements in noninvasive radiographic methods to diagnose NAFLD, especially for advanced disease. However, liver biopsy is still the standard method of diagnosis for NASH. There are many challenges to treating patients with NASH, and no therapies have been approved by the U.S. Food and Drug Administration; multimodal approaches are being developed and becoming the standard of care. We review pathogenesis and treatment approaches for the West's largest liver-related public health concern.

Prevalence of nonalcoholic fatty liver disease and nonalcoholic steatohepatitis among a largely middle-aged population utilizing ultrasound and liver biopsy: a prospective study.

BACKGROUND & AIMS: Prevalence of nonalcoholic fatty liver disease (NAFLD) has not been well established. The purpose of this study was to prospectively define the prevalence of both NAFLD and nonalcoholic steatohepatitis (NASH). METHODS: Outpatients 18 to 70 years old were recruited from Brooke Army Medical Center. All patients completed a baseline questionnaire and ultrasound. If fatty liver was identified, then laboratory data and a liver biopsy were obtained. RESULTS: Four hundred patients were enrolled. Three hundred and twenty-eight patients completed the questionnaire and ultrasound. Mean age (range, 28-70 years) was 54.6 years (7.35); 62.5% Caucasian, 22% Hispanic, and 11.3% African American; 50.9% female; mean body mass index (BMI) (calculated as kg/m(2)) was 29.8 (5.64); and diabetes and hypertension prevalence 16.5% and 49.7%, respectively. Prevalence of NAFLD was 46%. NASH was confirmed in 40 patients (12.2% of total cohort, 29.9% of ultrasound positive patients). Hispanics had the highest prevalence of NAFLD (58.3%), then Caucasians (44.4%) and African Americans (35.1%). NAFLD patients were more likely to be male (58.9%), older (P = .004), hypertensive (P < .00005), and diabetic (P < .00005). They had a higher BMI (P < .0005), ate fast food more often (P = .049), and exercised less (P = 0.02) than their non-NAFLD counterparts. Hispanics had a higher prevalence of NASH compared with Caucasians (19.4% vs 9.8%; P = .03). Alanine aminotransferase, aspartate aminotransferase, BMI, insulin, Quantitative Insulin-Sensitivity Check Index, and cytokeratin-18 correlated with NASH. Among the 54 diabetic patients, NAFLD was found in 74% and NASH in 22.2%. CONCLUSION: Prevalence of NAFLD and NASH is higher than estimated previously. Hispanics and patients with diabetes are at greatest risk for both NAFLD and NASH.

Rosiglitazone versus rosiglitazone and metformin versus rosiglitazone and losartan in the treatment of nonalcoholic steatohepatitis in humans: a 12-month randomized, prospective, open- label trial.

UNLABELLED: Medication combinations that improve the efficacy of thiazolidinediones or ameliorate weight-gain side effects of therapy represent an attractive potential treatment for (NASH). The aim of this randomized, open-label trial was to assess the efficacy of rosiglitazone and metformin in combination versus rosiglitazone and losartan, compared to rosiglitazone alone, after 48 weeks of therapy. A total of 137 subjects with biopsy-proven NASH were enrolled and randomly assigned to receive either 4 mg twice-daily of rosiglitazone, 4 mg of rosiglitazone and 500 mg of metformin twice-daily, or 4 mg of rosiglitazone twice-daily and 50 mg of losartan once-daily for 48 weeks. Patients were screened for other etiologies of chronic liver disease, including daily alcohol intake in excess of 20 g. Repeat liver biopsy was performed after 48 weeks of therapy and reviewed in a blinded fashion by a single expert hepatopathologist. The primary aim of the study was to assess for differences between treatment groups in the improvement of steatosis, hepatocellular inflammation, and fibrosis. In total, 108 subjects completed the trial. Primary outcome revealed no significant difference between treatment groups in all histologic parameters (steatosis, P = 0.137; hepatocellular inflammation, P = 0.320; fibrosis, P = 0.229). Overall improvement in steatosis, hepatocellular inflammation, ballooning degeneration, and fibrosis was observed (P ≤ 0.001). Serum aminotransferases were reduced in all three groups (P < 0.001 within treatment, P > 0.05 between groups). Metformin did not significantly mitigate weight gain (P = 0.051). CONCLUSIONS: Forty-eight weeks of combination therapy with rosiglitazone and metformin or rosiglitazone and losartan confers no greater benefit than rosiglitazone alone with respect to histopathology.

Sexual function in women with polycystic ovary syndrome.

INTRODUCTION: Polycystic ovary syndrome (PCOS) is a common endocrinologic disorder. Little is known about the effects of PCOS on overall sexual functioning, phases of the sexual response cycle, and sexual satisfaction. AIM: To compare the differences in sexual function between women with PCOS and controls, and to assess the relationship of serum testosterone, body mass index (BMI), hirsutism, and acne with sexual function scores in women with PCOS. METHODS: A cross-sectional analysis in which women who met the National Institute of Child Health and Human Development criteria for PCOS were compared with a group of healthy volunteers. MAIN OUTCOME MEASURES: Results from the validated Changes in Sexual Functioning Questionnaire (CSFQ) were used to assess sexual function. In women with PCOS, serum testosterone levels, BMI, self-reported hirsutism, and acne were assessed as independent variables. RESULTS: Ninety-two women with PCOS and 82 controls were studied. Based on total CSFQ scores, sexual dysfunction was present in 27.2% of cases vs. 24.4% of controls (not signifcant). Women with PCOS had a significantly lower orgasm/completion score compared with women in the control group (P < 0.001). Women with PCOS whose testosterone levels were >1 standard deviation above the mean had significantly better sexual functioning vs. those within 1 SD (P = 0.015) and those >1 SD below the mean (P = 0.033). In women with PCOS, increasing BMI was associated with a significant reduction in the orgasm/completion subdomain, but no significant associations were found in regard to acne or hirsutism. CONCLUSIONS: Women with PCOS have similar sexual functioning scores compared with controls except in regard to orgasm/completion. The subpopulation of women with PCOS whose serum testosterone levels are in the normal reproductive range are at increased risk for sexual dysfunction.

Longitudinal anti-müllerian hormone in women with polycystic ovary syndrome: an acupuncture randomized clinical trial.

Others have studied acupuncture treatment for polycystic ovary syndrome (PCOS). Anti-müllerian hormone (AMH) is positively correlated with the ovarian follicle pool, thus making it a useful ovarian reserve measure. AMH is elevated in women with PCOS and has been suggested as a diagnostic tool. This study examined the impact of electroacupuncture on AMH concentration in women with PCOS. Seventy-one women with PCOS participated in a randomized, double-blind, sham-controlled clinical trial of acupuncture. Three longitudinal AMH samples over the 5-month protocol were compared with objective ovulation parameters primarily using nonparametric statistics. Results indicated that AMH levels in PCOS were higher than published norms in women without PCOS. There was no difference between the true and sham acupuncture arms in the change in AMH longitudinally. Baseline AMH, but not the change in AMH over time, was inversely correlated with ovulation and menstrual cycle frequencies in both arms combined (P < 0.001). In conclusion, AMH correlated with an increased likelihood of monthly ovulation, as expected from the literature on women without PCOS. The lack of difference by intervention in AMH was consistent with the underlying clinical trial. AMH may be clinically useful to predict which PCOS women are more likely to respond to an intervention.

A molecular simulation study into the stability of hydrated graphene nanochannels used in nanofluidics devices.

Graphene-based nanochannels are a popular choice in emerging nanofluidics applications because of their tunable and nanometer-scale channels. In this work, molecular dynamics (MD) simulations were employed both to (i) assess the stability of dry and hydrated graphene nanochannels and (ii) elucidate the properties of water confined in these channels, using replica-scale models with 0.66-2.38 nm channel heights. The use of flexible nanochannel walls allows the nanochannel height to relax in response to the solvation forces arising from the confined fluid and the forces between the confining surfaces, without the need for application of arbitrarily high external pressures. Dry nanochannels were found to completely collapse if the initial nanochannel height was less than 2 nm, due to attractive van der Waals interactions between the confining graphene surfaces. However, the presence of water was found to prevent total nanochannel collapse, due to repulsive hydration forces opposing the attractive van der Waals force. For nanochannel heights less than ∼1.7 nm, the confining surfaces must be relaxed to obtain accurate hydration pressures and water diffusion coefficients, by ensuring commensurability between the number of confined water layers and the channel height. For very small (∼0.7 nm), hydrated channels a pressure of 231 MPa due to the van der Waals forces was obtained. In the same system, the confined water forms a mobile, liquid monolayer with a diffusion coefficient of 4.0 × 10-5 cm2 s-1, much higher than bulk liquid water. Although this finding conflicts with most classical MD simulations, which predict in-plane order and arrested dynamics, it is supported by experiments and recently published first-principles MD simulations. Classical simulations can therefore be used to predict the properties of water confined in sub-nanometre graphene channels, providing sufficiently realistic molecular models and accurate intermolecular potentials are employed.

High-throughput molecular simulations reveal the origin of ion free energy barriers in graphene oxide membranes.

Graphene oxide (GO) membranes are highly touted as materials for contemporary separation challenges including desalination, yet understanding of the interplay between their structure and salt rejection is limited. K+ ion permeation through hydrated GO membranes was investigated by combining structurally realistic molecular models and high-throughput molecular dynamics simulations. We show that it is essential to consider the complex GO microstructure to quantitatively reproduce experimentally-derived free energy barriers to K+ permeation for membranes with various interlayer distances less than 1.3 nm. This finding confirms the non-uniformity of GO nanopores and the necessity of the high-throughput approach for this class of material. The large barriers arise due to significant dehydration of K+ inside the membrane, which can have as few as 3 coordinated water molecules, compared to 7 in bulk solution. Thus, even if the membranes have an average pore size larger than the ion's hydrated diameter, the significant presence of pores whose size is smaller than the hydrated diameter creates bottlenecks for the permeation process.