Nanofluidics: a pedagogical introduction

Nanofluidics is the study of fluids confined in structures of nanometric dimensions (typically 1−100 nm). Fluids confined in these structures exhibit behaviours that are not observed in larger structures, due to a high surface to bulk ratio

Large permeabilities of hourglass nanopores: From hydrodynamics to single file transport

In fluid transport across nanopores, there is a fundamental dissipation that arises from the connection between the pore and the macroscopic reservoirs. This entrance effect can hinder the whole transport in certain situations, for short pores and/or highly slipping channels. In this paper, we explore the hydrodynamic permeability of hourglass shape nanopores using molecular dynamics (MD) simulations, with the central pore size ranging from several nanometers down to a few Angstr{\"o}ms. Surprisingly, we find a very good agreement between MD results and continuum hydrodynamic predictions, even for the smallest systems undergoing single file transport of water. An optimum of permeability is found for an opening angle around 5 degree, in agreement with continuum predictions, yielding a permeability five times larger than for a straight nanotube. Moreover, we find that the permeability of hourglass shape nanopores is even larger than single nanopores pierced in a molecular thin graphene sheet. This suggests that designing the geometry of nanopores may help considerably increasing the macroscopic permeability of membranes

Flow-Induced Shift of the Donnan Equilibrium for Ultra-Sensitive Mass Transport Measurement Through a Single Nanochannel

Despite mass flow is arguably the most elementary transport associated to nanofluidics, its measurement still constitutes a significant bottleneck for the development of this promising field. Here, we investigate how a liquid flow perturbs the ubiquitous enrichment-or depletion-of a solute inside a single nanochannel. Using Fluorescence Correlation Spectroscopy to access the local solute concentration, we demonstrate that the initial enrichment-the so-called Donnan equilibrium-is depleted under flow thus revealing the underlying mass transport. Combining theoretical and numerical calculations beyond the classical 1D treatments of nanochannels, we rationalize quantitatively our observations and demonstrate unprecedented flow rate sensitivity. Because the present mass transport investigations are based on generic effects, we believe they can develop into a versatile approach for nanofluidics

Adsorption kinetics in open nanopores as a source of low-frequency noise

Ionic current measurements through solid-state nanopores consistently show a power spectral density that scales as 1/f α at low frequency f, with an exponent α ∼ 0.5–1.5, but strikingly, the physical origin of this behavior remains elusive. Here, we perform simulations of particles reversibly adsorbing at the surface of a nanopore and show that the fluctuations in the number of adsorbed particles exhibit low-frequency pink noise. We furthermore propose theoretical modeling for the time-dependent adsorption of particles on the nanopore surface for various geometries, which predicts a frequency spectrum in very good agreement with the simulation results. Altogether, our results highlight that the low-frequency noise takes its origin in the reversible adsorption of ions at the pore surface combined with the long-lasting excursions of the ions in the reservoirs. The scaling regime of the power spectrum extends down to a cutoff frequency which is far smaller than simple diffusion estimates. Using realistic values for the pore dimensions and the adsorption–desorption kinetics, this predicts the observation of pink noise for frequencies down to the hertz for a typical solid-state nanopore, in good agreement with experiments

Determinants of hospital length of stay for people with serious mental illness in England and implications for payment systems: a regression analysis

BackgroundSerious mental illness (SMI), which encompasses a set of chronic conditions such as schizophrenia, bipolar disorder and other psychoses, accounts for 3.4 m (7 %) total bed days in the English NHS. The introduction of prospective payment to reimburse hospitals makes an understanding of the key drivers of length of stay (LOS) imperative. Existing evidence, based on mainly small scale and cross-sectional studies, is mixed. Our study is the first to use large-scale national routine data to track English hospitals’ LOS for patients with a main diagnosis of SMI over time to examine the patient and local area factors influencing LOS and quantify the provider level effects to draw out the implications for payment systems.MethodsWe analysed variation in LOS for all SMI admissions to English hospitals from 2006 to 2010 using Hospital Episodes Statistics (HES). We considered patients with a LOS of up to 180 days and estimated Poisson regression models with hospital fixed effects, separately for admissions with one of three main diagnoses: schizophrenia; psychotic and schizoaffective disorder; and bipolar affective disorder. We analysed the independent contribution of potential determinants of LOS including clinical and socioeconomic characteristics of the patient, access to and quality of primary care, and local area characteristics. We examined the degree of unexplained variation in provider LOS.ResultsMost risk factors did not have a differential effect on LOS for different diagnostic sub-groups, however we did find some heterogeneity in the effects. Shorter LOS in the pooled model was associated with co-morbid substance or alcohol misuse (4 days), and personality disorder (8 days). Longer LOS was associated with older age (up to 19 days), black ethnicity (4 days), and formal detention (16 days). Gender was not a significant predictor. Patients who self-discharged had shorter LOS (20 days). No association was found between higher primary care quality and LOS. We found large differences between providers in unexplained variation in LOS.ConclusionsBy identifying key determinants of LOS our results contribute to a better understanding of the implications of case-mix to ensure prospective payment systems reflect accurately the resource use within sub-groups of patients with SMI

The association between primary care quality and healthcare utilisation, costs and outcomes for people with serious mental illness: retrospective observational study

Background Serious mental illness (SMI), including schizophrenia, bipolar disorder and other psychoses, is linked with high disease burden, poor outcomes, high treatment costs and lower life expectancy. In the UK, most people with SMI are treated in primary care by general practitioners (GPs), who are financially incentivised to meet quality targets for patients with chronic conditions, including SMI, under the Quality and Outcomes Framework (QOF). The QOF, however, omits important aspects of quality. Objective(s) We examined whether better quality of primary care for people with SMI improved a range of outcomes. Design and setting We used administrative data from English primary care practices that contribute to the Clinical Practice Research Datalink GOLD database, linked to Hospital Episode Statistics, Accident & Emergency (A&E) attendances, Office for National Statistics mortality data, and community mental health records in the Mental Health Minimum Dataset. We used survival analysis to estimate whether selected quality indicators affect the time until patients experience an outcome. Participants Four cohorts of people with SMI depending on the outcomes examined and inclusion criteria. Interventions Quality of care was measured with: i) QOF indicators: care plans and annual physical reviews ;and ii) non-QOF indicators identified through a systematic review (antipsychotic polypharmacy and continuity of care provided by GPs). Main outcome measures Several outcomes were examined: emergency admissions for i) SMI and ii) ambulatory care sensitive conditions (ACSCs); iii) all unplanned admissions; iv) A&E attendances; v) mortality; vi) re-entry into specialist mental health services; vii) costs attributed to primary, secondary and community mental healthcare. Results Care plans were associated with lower risk of A&E attendance (Hazard ratio (HR) 0.74, 95%CI 0.69-0.80), SMI admission (HR 0.67, 95%CI 0.59-0.75), ACSC admission (HR 0.73, 95%CI 0.64-0.83), and lower overall healthcare (£53), primary care (£9), hospital (£26), and mental healthcare costs (£12). Annual reviews were associated with reduced risk of A&E attendance (HR 0.80, 95%CI 0.76-0.85), SMI admission (HR 0.75, 95%CI 0.67-0.84), ACSC admission (HR 0.76, 95%CI 0.67-0.87), and lower overall healthcare (£34), primary care (£9), and mental healthcare costs (£30). Higher GP continuity was associated with lower risk of A&E presentation (HR 0.89, 95%CI 0.83-0.97), ACSC admission (HR 0.77, 95%CI 0.65-0.92), but not SMI admission. High continuity was associated with lower primary care costs (£3). Antipsychotic polypharmacy was not statistically significantly associated with the risk of unplanned admission, death or A&E presentation. None of the quality measures were statistically significantly associated with risk of re-entry into specialist mental healthcare. Limitations There is risk of bias from unobserved factors. To mitigate this, we controlled for observed patient characteristics at baseline and adjusted for the influence of time-invariant unobserved patient differences. Conclusions Better performance on QOF measures and continuity of care are associated with better outcomes and lower resource utilisation and could generate moderate cost savings. Future work Future research should examine the impact of primary care quality on measures that capture broader aspects of health and functioning

Impact of family practice continuity of care on unplanned hospital use for people with serious mental illness

Objective: To investigate whether continuity of care in family practice reduces unplanned hospital use for people with serious mental illness (SMI). Data Sources Linked administrative data on family practice and hospital utilization by people with SMI in England, 2007-2014. Study Design: This observational cohort study used discrete-time survival analysis to investigate the relationship between continuity of care in family practice and unplanned hospital use: emergency department (ED) presentations, and unplanned admissions for SMI and ambulatory care-sensitive conditions (ACSC). The analysis distinguishes between relational continuity and management/ informational continuity (as captured by care plans) and accounts for unobserved confounding by examining deviation from long-term averages. Data Collection/Extraction Methods: Individual-level family practice administrative data linked to hospital administrative data. Principal Findings: Higher relational continuity was associated with 8-11 percent lower risk of ED presentation and 23-27 percent lower risk of ACSC admissions. Care plans were associated with 29 percent lower risk of ED presentation, 39 percent lower risk of SMI admissions, and 32 percent lower risk of ACSC admissions. Conclusions: Family practice continuity of care can reduce unplanned hospital use for physical and mental health of people with SMI

Towards comprehensive observing and modeling systems for monitoring and predicting regional to coastal sea level

A major challenge for managing impacts and implementing effective mitigation measures and adaptation strategies for coastal zones affected by future sea level (SL) rise is our limited capacity to predict SL change at the coast on relevant spatial and temporal scales. Predicting coastal SL requires the ability to monitor and simulate a multitude of physical processes affecting SL, from local effects of wind waves and river runoff to remote influences of the large-scale ocean circulation on the coast. Here we assess our current understanding of the causes of coastal SL variability on monthly to multi-decadal timescales, including geodetic, oceanographic and atmospheric aspects of the problem, and review available observing systems informing on coastal SL. We also review the ability of existing models and data assimilation systems to estimate coastal SL variations and of atmosphere-ocean global coupled models and related regional downscaling efforts to project future SL changes. We discuss (1) observational gaps and uncertainties, and priorities for the development of an optimal and integrated coastal SL observing system, (2) strategies for advancing model capabilities in forecasting short-term processes and projecting long-term changes affecting coastal SL, and (3) possible future developments of sea level services enabling better connection of scientists and user communities and facilitating assessment and decision making for adaptation to future coastal SL change.RP was funded by NASA grant NNH16CT00C. CD was supported by the Australian Research Council (FT130101532 and DP 160103130), the Scientific Committee on Oceanic Research (SCOR) Working Group 148, funded by national SCOR committees and a grant to SCOR from the U.S. National Science Foundation (Grant OCE-1546580), and the Intergovernmental Oceanographic Commission of UNESCO/International Oceanographic Data and Information Exchange (IOC/IODE) IQuOD Steering Group. SJ was supported by the Natural Environmental Research Council under Grant Agreement No. NE/P01517/1 and by the EPSRC NEWTON Fund Sustainable Deltas Programme, Grant Number EP/R024537/1. RvdW received funding from NWO, Grant 866.13.001. WH was supported by NASA (NNX17AI63G and NNX17AH25G). CL was supported by NASA Grant NNH16CT01C. This work is a contribution to the PIRATE project funded by CNES (to TP). PT was supported by the NOAA Research Global Ocean Monitoring and Observing Program through its sponsorship of UHSLC (NA16NMF4320058). JS was supported by EU contract 730030 (call H2020-EO-2016, “CEASELESS”). JW was supported by EU Horizon 2020 Grant 633211, Atlantos

Incentives in the Public Sector : Evidence from a Government Agency

We study the impact of team-based performance pay in a major UK government agency, the public employment service. The scheme covered quantity and quality targets, measured with varying degrees of precision. We use unique data from the agency’s performance management system and personnel records, linked to local labour market data. We show that on average the scheme had no significant effect but had a substantial positive effect in small teams, fitting an explanation combining free riding and peer monitoring. We also show that the impact was greater on better-measured quantity outcomes than quality outcomes. The scheme was very cost effective in small offices

Systematic review: Effects, design choices, and context of pay-for-performance in health care

<p>Abstract</p> <p>Background</p> <p>Pay-for-performance (P4P) is one of the primary tools used to support healthcare delivery reform. Substantial heterogeneity exists in the development and implementation of P4P in health care and its effects. This paper summarizes evidence, obtained from studies published between January 1990 and July 2009, concerning P4P effects, as well as evidence on the impact of design choices and contextual mediators on these effects. Effect domains include clinical effectiveness, access and equity, coordination and continuity, patient-centeredness, and cost-effectiveness.</p> <p>Methods</p> <p>The systematic review made use of electronic database searching, reference screening, forward citation tracking and expert consultation. The following databases were searched: Cochrane Library, EconLit, Embase, Medline, PsychINFO, and Web of Science. Studies that evaluate P4P effects in primary care or acute hospital care medicine were included. Papers concerning other target groups or settings, having no empirical evaluation design or not complying with the P4P definition were excluded. According to study design nine validated quality appraisal tools and reporting statements were applied. Data were extracted and summarized into evidence tables independently by two reviewers.</p> <p>Results</p> <p>One hundred twenty-eight evaluation studies provide a large body of evidence -to be interpreted with caution- concerning the effects of P4P on clinical effectiveness and equity of care. However, less evidence on the impact on coordination, continuity, patient-centeredness and cost-effectiveness was found. P4P effects can be judged to be encouraging or disappointing, depending on the primary mission of the P4P program: supporting minimal quality standards and/or boosting quality improvement. Moreover, the effects of P4P interventions varied according to design choices and characteristics of the context in which it was introduced.</p> <p>Future P4P programs should (1) select and define P4P targets on the basis of baseline room for improvement, (2) make use of process and (intermediary) outcome indicators as target measures, (3) involve stakeholders and communicate information about the programs thoroughly and directly, (4) implement a uniform P4P design across payers, (5) focus on both quality improvement and achievement, and (6) distribute incentives to the individual and/or team level.</p> <p>Conclusions</p> <p>P4P programs result in the full spectrum of possible effects for specific targets, from absent or negligible to strongly beneficial. Based on the evidence the review has provided further indications on how effect findings are likely to relate to P4P design choices and context. The provided best practice hypotheses should be tested in future research.</p