A modeling approach to understanding OLED performance improvements arising from spatial variations in guest:host blend ratio.

Phosphorescent organic light emitting diodes (OLEDs) suffer from efficiency roll off, where device efficiency rapidly decays at higher luminance. One strategy to minimize this loss of efficiency at higher luminance is the use of non-uniform or graded guest:host blend ratios within the emissive layer. This work applies a multi-scale modeling framework to elucidate the mechanisms by which a non-uniform blend ratio can change the performance of an OLED. Mobility and exciton data are extracted from a kinetic Monte-Carlo model, which is then coupled to a drift diffusion model for fast sampling of the parameter space. The model is applied to OLEDs with uniform, linear, and stepwise graduations in the blend ratio in the emissive layer. The distribution of the guests in the film was found to affect the mobility of the charge carriers, and it was determined that having a graduated guest profile broadened the recombination zone, leading to a reduction in second order annihilation rates. That is, there was a reduction in triplet-triplet and triplet-polaron annihilation. Reducing triplet-triplet and triplet-polaron annihilation would lead to an improvement in device efficiency.

Jewish cultural and religious factors and uptake of population-based BRCA testing across denominations: a cohort study.

OBJECTIVE: To evaluate the association of Jewish cultural and religious identity and denominational affiliation with interest in, intention to undertake and uptake of population-based BRCA (Breast Cancer Gene)-testing. DESIGN: Cohort-study set within recruitment to GCaPPS-trial (ISRCTN73338115). SETTING: London Ashkenazi-Jewish (AJ) population. POPULATION OR SAMPLE: AJ men and women, >18 years. METHODS: Participants were self-referred, and attended recruitment clinics (clusters) for pre-test counselling. Subsequently consenting individuals underwent BRCA testing. Participants self-identified to one Jewish denomination: Conservative/Liberal/Reform/Traditional/Orthodox/Unaffiliated. Validated scales measured Jewish Cultural-Identity (JI) and Jewish Religious-identity (JR). Four-item Likert-scales analysed initial 'interest' and 'intention to test' pre-counselling. Item-Response-Theory and graded-response models, modelled responses to JI and JR scales. Ordered/multinomial logistic regression modelling evaluated association of JI-scale, JR-scale and Jewish Denominational affiliation on interest, intention and uptake of BRCA testing. MAIN OUTCOME MEASURES: Interest, intention, uptake of BRCA testing. RESULTS: In all, 935 AJ women/men of mean age = 53.8 (S.D = 15.02) years, received pre-test education and counselling through 256 recruitment clinic clusters (median cluster size = 3). Denominational affiliations included Conservative/Masorti = 91 (10.2%); Liberal = 82 (9.2%), Reform = 135 (15.1%), Traditional = 212 (23.7%), Orthodox = 239 (26.7%); and Unaffiliated/Non-practising = 135 (15.1%). Overall BRCA testing uptake was 88%. Pre-counselling, 96% expressed interest and 60% intention to test. JI and JR scores were highest for Orthodox, followed by Conservative/Masorti, Traditional, Reform, Liberal and Unaffiliated Jewish denominations. Regression modelling showed no significant association between overall Jewish Cultural or Religious Identity with either interest, intention or uptake of BRCA testing. Interest, intention and uptake of BRCA testing was not significantly associated with denominational affiliation. CONCLUSIONS: Jewish religious/cultural identity and denominational affiliation do not appear to influence interest, intention or uptake of population-based BRCA testing. BRCA testing was robust across all Jewish denominations. TWEETABLE ABSTRACT: Jewish cultural/religious factors do not affect BRCA testing, with robust uptake seen across all denominational affiliations.

Randomised trial of population-based BRCA testing in Ashkenazi Jews: long-term outcomes.

OBJECTIVE: Unselected population-based BRCA testing provides the opportunity to apply genomics on a population-scale to maximise primary prevention for breast-and-ovarian cancer. We compare long-term outcomes of population-based and family-history (FH)/clinical-criteria-based BRCA testing on psychological health and quality of life. DESIGN: Randomised controlled trial (RCT) (ISRCTN73338115) GCaPPS, with two-arms: (i) population-screening (PS); (ii) FH/clinical-criteria-based testing. SETTING: North London Ashkenazi-Jewish (AJ) population. POPULATION/SAMPLE: AJ women/men. METHODS: Population-based RCT (1:1). Participants were recruited through self-referral, following pre-test genetic counselling from the North London AJ population. INCLUSION CRITERIA: AJ women/men >18 years old; exclusion-criteria: prior BRCA testing or first-degree relatives of BRCA-carriers. INTERVENTIONS: Genetic testing for three Jewish BRCA founder-mutations: 185delAG (c.68_69delAG), 5382insC (c.5266dupC) and 6174delT (c.5946delT), for (i) all participants in PS arm; (ii) those fulfilling FH/clinical criteria in FH arm. Linear mixed models and appropriate contrast tests were used to analyse the impact of BRCA testing on psychological and quality-of-life outcomes over 3 years. MAIN OUTCOME MEASURES: Validated questionnaires (HADS/MICRA/HAI/SF12) used to analyse psychological wellbeing/quality-of-life outcomes at baseline/1-year/2-year/3-year follow up. RESULTS: In all, 1034 individuals (691 women, 343 men) were randomised to PS (n = 530) or FH (n = 504) arms. There was a statistically significant decrease in anxiety (P = 0.046) and total anxiety-&-depression scores (P = 0.0.012) in the PS arm compared with the FH arm over 3 years. No significant difference was observed between the FH and PS arms for depression, health-anxiety, distress, uncertainty, quality-of-life or experience scores associated with BRCA testing. Contrast tests showed a decrease in anxiety (P = 0.018), health-anxiety (P < 0.0005) and quality-of-life (P = 0.004) scores in both PS and FH groups over time. Eighteen of 30 (60%) BRCA carriers identified did not fulfil clinical criteria for BRCA testing. Total BRCA prevalence was 2.9% (95% CI 1.97-4.12%), BRCA1 prevalence was 1.55% (95% CI 0.89-2.5%) and BRCA2 prevalence was 1.35% (95% CI 0.74-2.26%). CONCLUSION: Population-based AJ BRCA testing does not adversely affect long-term psychological wellbeing or quality-of-life, decreases anxiety and could identify up to 150% additional BRCA carriers. TWEETABLE ABSTRACT: Population BRCA testing in Ashkenazi Jews reduces anxiety and does not adversely affect psychological health or quality of life.

Attitude towards and factors affecting uptake of population-based BRCA testing in the Ashkenazi Jewish population: a cohort study.

OBJECTIVE: To evaluate factors affecting unselected population-based BRCA testing in Ashkenazi Jews (AJ). DESIGN: Cohort-study set within recruitment to the GCaPPS trial (ISRCTN73338115). SETTING: North London AJ population. POPULATION OR SAMPLE: Ashkenazi Jews women/men >18 years, recruited through self-referral. METHODS: Ashkenazi Jews women/men underwent pre-test counselling for BRCA testing through recruitment clinics (clusters). Consenting individuals provided blood samples for BRCA testing. Data were collected on socio-demographic/family history/knowledge/psychological well-being along with benefits/risks/cultural influences (18-item questionnaire measuring 'attitude'). Four-item Likert-scales analysed initial 'interest' and 'intention-to-test' pre-counselling. Uni- and multivariable logistic regression models evaluated factors affecting uptake/interest/intention to undergo BRCA testing. Statistical inference was based on cluster robust standard errors and joint Wald tests for significance. Item-Response Theory and graded-response models modelled responses to 18-item questionnaire. MAIN OUTCOME MEASURES: Interest, intention, uptake, attitude towards BRCA testing. RESULTS: A total of 935 individuals (women = 67%/men = 33%; mean age = 53.8 (SD = 15.02) years) underwent pre-test genetic-counselling. During the pre-counselling, 96% expressed interest in and 60% indicated a clear intention to undergo BRCA testing. Subsequently, 88% opted for BRCA testing. BRCA-related knowledge (P = 0.013) and degree-level education (P = 0.01) were positively and negatively (respectively) associated with intention-to-test. Being married/cohabiting had four-fold higher odds for BRCA testing uptake (P = 0.009). Perceived benefits were associated with higher pre-counselling odds for interest in and intention to undergo BRCA testing. Reduced uncertainty/reassurance were the most important factors contributing to decision-making. Increased importance/concern towards risks/limitations (confidentiality/insurance/emotional impact/inability to prevent cancer/marriage ability/ethnic focus/stigmatisation) were significantly associated with lower odds of uptake of BRCA testing, and discriminated between acceptors and decliners. Male gender/degree-level education (P = 0.001) had weaker correlations, whereas having children showed stronger (P = 0.005) associations with attitudes towards BRCA testing. CONCLUSIONS: BRCA testing in the AJ population has high acceptability. Pre-test counselling increases awareness of disadvantages/limitations of BRCA testing, influencing final cost-benefit perception and decision-making on undergoing testing. TWEETABLE ABSTRACT: BRCA testing in Ashkenazi Jews has high acceptability and uptake. Pre-test counselling facilitates informed decision-making.

Integration of swimming kinematics and ram suspension feeding in a model American paddlefish, Polyodon spathula.

Ram suspension-feeding fishes swim with an open mouth to force water through the oral cavity and extract prey items that are too small to be pursued individually. Recent research has indicated that, rather than using a dead-end mechanical sieve, American paddlefish (Polyodon spathula) employ vortical cross-step filtration. In this filtration mechanism, vortical flow that is generated posterior to the branchial arches organizes crossflow filtration processes into a spatial structure across the gill rakers. Despite the known impact of locomotor kinematics on fluid flow around the bodies of swimming fish, the effects of locomotor kinematics on filtration mechanisms in ram suspension feeders are unknown. Potential temporal organization of filtration mechanisms in ram suspension-feeding fish has not been studied previously. We investigated the effects of locomotor kinematics associated with undulatory swimming on intra-oral flow patterns and food particle transport. A mechanized model of the oral cavity was used to simulate the swimming kinematics of suspension-feeding paddlefish. We recorded fluctuations of flow speed and pressure within the model, which occurred at a frequency that corresponded with the frequency of the model's strides. Using the mechanized model in a flow tank seeded with Artemia cysts, we also showed that swimming kinematics aided the transport of this simulated food to the posterior margins of the gill slots, although the time scale of this transport is expected to vary with prey parameters such as size and concentration. Dye stream experiments revealed that, although stable vortical flow formed because of flow separation downstream of backward-facing steps in control trials, vortical flow structures in mechanized trials repeatedly formed and shed. These findings suggest strong integration between locomotor and feeding systems in ram suspension-feeding fishes.

Quantification of CD4(+) T Cell Alloreactivity and Its Control by Regulatory T Cells Using Time-Lapse Microscopy and Immune Synapse Detection.

Assays designed to select transplant recipients for immunosuppression withdrawal have met with limited success, perhaps because they measure events downstream of T cell-alloantigen interactions. Using in vitro time-lapse microscopy in a mouse transplant model, we investigated whether transplant outcome would result in changes in the proportion of CD4(+) T cells forming prolonged interactions with donor dendritic cells. By blocking CD4-MHC class II and CD28-B7 interactions, we defined immunologically relevant interactions as those ≥500 s. Using this threshold, T cell-dendritic cell (T-DC) interactions were examined in rejection, tolerance and T cell control mediated by regulatory T cells. The frequency of T-DC contacts ≥500 s increased with T cells from mice during acute rejection and decreased with T cells from mice rendered unresponsive to alloantigen. Regulatory T cells reduced prolonged T-DC contacts. Importantly, this effect was replicated with human polyclonally expanded naturally occurring regulatory T cells, which we have previously shown can control rejection of human tissues in humanized mouse models. Finally, in a proof-of-concept translational context, we were able to visualize differential allogeneic immune synapse formation in polyclonal CD4(+) T cells using high-throughput imaging flow cytometry.

Mucous contribution to gut nutrient content in American gizzard shad Dorosoma cepedianum.

This study developed and applied an approach to calculate the proportion of fish gut content composed of mucus secreted by the oropharyngeal cavity and gut. The amount of nitrogen in the contents of the foregut (oesophagus and gizzard) and the epibranchial organs of suspension-feeding American gizzard shad Dorosoma cepedianum was significantly higher than the nitrogen in the homogeneous food source. Using data collected from suspension-feeding experiments and the nitrogen content of D. cepedianum mucus, a series of equations illustrated that mucus constituted c. 10% of D. cepedianum foregut content and 12% of epibranchial organ content by dry mass. Future quantification of fish feeding selectivity and absorption efficiency can use this approach to take into account the contribution of fish mucus to the nutrients in the gut contents. This study supports the conclusion that suspension-feeding D. cepedianum in a heterogeneous environment selectively ingest nutrient-rich particles, even when gut nutrient content is adjusted to take into account the contribution of mucus.

Hydrodynamic analysis of bioinspired vortical cross-step filtration by computational modelling.

Research on the suspension-feeding apparatus of fishes has led recently to the identification of novel filtration mechanisms involving vortices. Structures inside fish mouths form a series of 'backward-facing steps' by protruding medially into the mouth cavity. In paddlefish and basking shark mouths, porous gill rakers lie inside 'slots' between the protruding branchial arches. Vortical flows inside the slots of physical models have been shown to be important for the filtration process, but the complex flow patterns have not been visualised fully. Here we resolve the three-dimensional hydrodynamics by computational fluid dynamics simulation of a simplified mouth cavity including realistic flow dynamics at the porous layer. We developed and validated a modelling protocol in ANSYS Fluent software that combines a porous media model and permeability direction vector mapping. We found that vortex shape and confinement to the medial side of the gill rakers result from flow resistance by the porous gill raker surfaces. Anteriorly directed vortical flow shears the porous layer in the centre of slots. Flow patterns also indicate that slot entrances should remain unblocked, except for the posterior-most slot. This new modelling approach will enable future design exploration of fish-inspired filters.

Biomimetic models of fish gill rakers as lateral displacement arrays for particle separation.

Ram suspension-feeding fish, such as herring, use gill rakers to separate small food particles from large water volumes while swimming forward with an open mouth. The fish gill raker function was tested using 3D-printed conical models and computational fluid dynamics simulations over a range of slot aspect ratios. Our hypothesis predicting the exit of particles based on mass flow rates, dividing streamlines (i.e. stagnation streamlines) at the slots between gill rakers, and particle size was supported by the results of experiments with physical models in a recirculating flume. Particle movement in suspension-feeding fish gill raker models was consistent with the physical principles of lateral displacement arrays ('bump arrays') for microfluidic and mesofluidic separation of particles by size. Although the particles were smaller than the slots between the rakers, the particles skipped over the vortical region that was generated downstream from each raker. The particles 'bumped' on anterior raker surfaces during posterior transport. Experiments in a recirculating flume demonstrate that the shortest distance between the dividing streamline and the raker surface preceding the slot predicts the maximum radius of a particle that will exit the model by passing through the slot. This theoretical maximum radius is analogous to the critical separation radius identified with reference to the stagnation streamlines in microfluidic and mesofluidic devices that use deterministic lateral displacement and sieve-based lateral displacement. These conclusions provide new perspectives and metrics for analyzing cross-flow and cross-step filtration in fish with applications to filtration engineering.

Prevalence, course and impact of HLA donor-specific antibodies in liver transplantation in the first year.

The presence of preformed donor-specific HLA antibodies (DSA) in liver transplant recipients is increasingly recognized; however, the prevalence of DSA and their impact on early allograft function remains unknown. We prospectively followed serum DSA levels of 90 consecutive liver transplant recipients from baseline to 4 months. Twenty recipients (22.2%) had preformed DSA. No antibody-targeting treatments were undertaken. Seven days after transplantation, DSA levels decreased markedly in all but three patients. Day 7 protocol biopsies showed diffuse C4d deposition along the portal stroma, central vein, subendothelial and stromal space in the patients with persistent high DSA levels. The rate of acute cellular rejection was not significantly different in patients with DSA. The transaminase and bilirubin levels remained comparable during the first year despite the presence of DSA. The three patients with persistently high DSA levels continue to have normal allograft function. We conclude that in most cases, DSA disappear after liver transplant, however in rare instances where they persist, there is evidence of complement activation in the liver allograft, without significant clinical impact in the first year.

Computational fluid dynamics of fish gill rakers during crossflow filtration.

We study crossflow filtration mechanisms in suspension-feeding fishes using computational fluid dynamics to model fluid flow and food particle movement in the vicinity of the gill rakers. During industrial and biological crossflow filtration, particles are retained when they remain suspended in the mainstream flow traveling across the filter surface rather than traveling perpendicularly to the filter. Here we identify physical parameters and hydrodynamic processes that determine food particle movement and retention inside the fish oral cavity. We demonstrate how five variables affect flow patterns and particle trajectories: (1) flow speed inside the fish oral cavity, (2) incident angle of the flow approaching the filter, (3) dimensions of filter structures, (4) particle size, and (5) particle density. Our study indicates that empirical experiments are needed to quantify flow parameters inside the oral cavity, and morphological research is needed to quantify dimensions of the filter apparatus such as gill rakers, the gaps between rakers, and downstream barriers. Ecological studies on suspension-feeding fishes are also needed to quantify food particle size and density, as these variables can affect particle retention due to hydrodynamic processes during crossflow filtration.

Identification of a CD4+ T cell-stimulating antigen of pathogenic bacteria by expression cloning.

Identifying the immunogenic proteins that elicit pathogen-specific T cell responses is key to rational vaccine design. While several approaches have succeeded in identifying major histocompatibility complex (MHC) class I bound peptides that stimulate CD8+ T cells, these approaches have been difficult to extend to peptides presented by MHC class II molecules that stimulate CD4+ T cells. We describe here a novel strategy for identifying CD4+ T cell-stimulating antigen genes. Using Listeria monocytogenes-specific, lacZ-inducible T cells as single-cell probes, we screened a Listeria monocytogenes genomic library as recombinant Escherichia coli that were fed to macrophages. The antigen gene was isolated from the E. coli clone that, when ingested by the macrophages, allowed generation of the appropriate peptide/MHC class II complex and T cell activation. We show that the antigenic peptide is derived from a previously unknown listeria gene product with characteristics of a membrane-bound protein.

Oropharyngeal morphology related to filtration mechanisms in suspension-feeding American shad (Clupeidae).

To assess potential filtration mechanisms, scanning electron microscopy was used in a comprehensive quantification and analysis of the morphology and surface ultrastructure for all five branchial arches in the ram suspension-feeding fish, American shad (Alosa sapidissima, Clupeidae). The orientation of the branchial arches and the location of mucus cells on the gill rakers were more consistent with mechanisms of crossflow filtration and cross-step filtration rather than conventional dead-end sieving. The long, thin gill rakers could lead to a large area for the exit of water from the oropharyngeal cavity during suspension feeding (high fluid exit ratio). The substantial elongation of gill rakers along the dorsal-ventral axis formed d-type ribs with a groove aspect ratio of 0.5 and a Reynolds number of approximately 500, consistent with the potential operation of cross-step filtration. Mucus cell abundance differed significantly along the length of the raker and the height of the raker. The mucus cell abundance data and the observed sloughing of denticles along the gill raker margins closest to the interior of the oropharyngeal cavity suggest that gill raker growth may occur primarily at the raker tips, the denticle bases, and the internal raker margins along the length of the raker. These findings will be applied in ongoing experiments with 3D-printed physical models of fish oral cavities in flow tanks, and in future ecological studies on the diet and nutrition of suspension-feeding fishes.

The FTO gene and measured food intake in children.

OBJECTIVE: Polymorphisms in the obesity-associated gene, FTO, have been linked with sensitivity to satiety in children, indicating FTO may be influencing one of the regulatory drivers underlying food intake. In this study, we tested the hypothesis that food intake in a standard eating behaviour paradigm in which palatable food is offered under conditions of satiety would be associated with FTO genotype status, after controlling for differences in body mass index (BMI). METHODS: Participants were 131 children aged 4-5 years, taking part in a behavioural study of food intake for whom DNA was available for genotyping. The phenotypic indicator of intake was the child's consumption of palatable food presented after having eaten a meal. We also assessed physical activity using parental reports of the child's enjoyment of active games, their level of activity relative to other children and a standard measure of fidgetiness. Associations between polymorphisms of the intronic FTO single nucleotide polymorphism (rs9939609) and behaviour (food intake and activity) were assessed by analysis of variance controlling for sex, age and BMI s.d. scores. RESULTS: The distribution of AA (homogenous for A allele), AT (heterogeneous T and A alleles) and TT (homogenous for T allele) genotypes was 18, 50 and 32%, respectively. As predicted, TT homozygotes ate significantly less than heterozygotes (P=0.03) or AA homozygotes (P=0.02). The effect was not diminished by controlling for BMI s.d. scores. There were no significant associations between FTO genotype and any marker of physical activity. CONCLUSIONS: We showed that children with two copies of the lower-risk FTO alleles ate less than those with one or two higher-risk alleles. We conclude that the T allele is protective against overeating by promoting responsiveness to internal signals of satiety.

Fluid dynamics in suspension-feeding blackfish.

Measurements of flow patterns and water velocities inside the oral cavity of blackfish (Orthodon microlepidotus), made with a fiberoptic endoscope and thermistor flow probe, revealed that gill-arch structures act in blackfish as barriers that direct particle-laden water to the mucus-covered roof of the oral cavity, where particles are retained. Gill-arch structures have previously been assumed to be the site of particle retention in suspension-feeding fishes. Water does not pass between these structures in blackfish, and they do not serve as filters that separate particles from the water. These results emphasize the importance of directly assessing flow velocity and direction inside the oral cavity of vertebrate suspension feeders, particularly at the level of the filtering elements.

Development of helical, fish-inspired cross-step filter for collecting harmful algae.

A new filter was developed to collect harmful algae colonies by adapting the cross-step filtration structures and mechanisms discovered recently in filter-feeding fish. Extending beyond previously published models that closely emulated the basic morphology of the fish, the new cross-step filter's major innovations are helical slots, radial symmetry, and rotation as an active anti-clogging mechanism. These innovations enable the transport of concentrated particles to the downstream end of the filter. This advance was made possible by recognizing that biologically imposed constraints such as bilateral symmetry do not apply to human-made filters. The use of helical slots was developed in a series of iterative tests that used water-tracing dye and algae-sized microspheres. The major products of the iterative tests were refinements in the helical design and an understanding of how varying the major structural parameters qualitatively influenced fluid flow and filter performance. Following the iterative tests, the clogging behavior of select filters was quantified at high particle concentrations. Vortices in the helical filter were effective at reducing clogging in the center of the slots. By considering the design space that is free of the biological constraints on the system and exploring the effects of variations in major structural parameters, our work has identified promising new directions for cross-step filtration and provided key insights into the biological system.

Intra-oral flow patterns and speeds in a suspension-feeding fish with gill rakers removed versus intact.

Oreochromis aureus, a species of tilapia, is a suspension-feeding fish that employs a pumping action to bring water into its mouth for filtering.To address questions about water flow inside the mouth, we used a microthermistor flow probe to determine the speed of intra-oral flow during suspension feeding in this species before and after surgical removal of gill rakers. Synchronization with high-speed external videotapes of the fish and high-speed video endoscopy inside the oropharyngeal cavity allowed the first correlation of oral actions with intra-oral flow patterns and speeds during feeding. This analysis established the occurrence of a brief reversal of flow ( approximately 80-ms duration) from posterior to anterior in the oropharyngeal cavity prior to every feeding pump (250-500-ms duration). In industrial crossflow filtration, oscillating or pulsatile flow increases filtration performance by enhancing the back-migration of particles from the region near the filter surface to the bulk flow region, thus reducing particle accumulation that can clog the filter. In endoscopic videotapes, these pre-pump reversals, as well as post-pump reversals ( approximately 500-ms duration), were observed to lift mucus and particles from the branchial arches for subsequent transport toward the esophagus. Intra-oral flow speeds were reduced markedly after removal of the gill rakers. We hypothesize that the decrease in crossflow speed during feeding pumps following the removal of gill rakers and mucus could be due to increased loss of water between the anterior branchial arches.

Physical modeling of vortical cross-step flow in the American paddlefish, Polyodon spathula.

Vortical cross-step filtration in suspension-feeding fish has been reported recently as a novel mechanism, distinct from other biological and industrial filtration processes. Although crossflow passing over backward-facing steps generates vortices that can suspend, concentrate, and transport particles, the morphological factors affecting this vortical flow have not been identified previously. In our 3D-printed models of the oral cavity for ram suspension-feeding fish, the angle of the backward-facing step with respect to the model's dorsal midline affected vortex parameters significantly, including rotational, tangential, and axial speed. These vortices were comparable to those quantified downstream of the backward-facing steps that were formed by the branchial arches of preserved American paddlefish in a recirculating flow tank. Our data indicate that vortices in cross-step filtration have the characteristics of forced vortices, as the flow of water inside the oral cavity provides the external torque required to sustain forced vortices. Additionally, we quantified a new variable for ram suspension feeding termed the fluid exit ratio. This is defined as the ratio of the total open pore area for water leaving the oral cavity via spaces between branchial arches that are not blocked by gill rakers, divided by the total area for water entering through the gape during ram suspension feeding. Our experiments demonstrated that the fluid exit ratio in preserved paddlefish was a significant predictor of the flow speeds that were quantified anterior of the rostrum, at the gape, directly dorsal of the first ceratobranchial, and in the forced vortex generated by the first ceratobranchial. Physical modeling of vortical cross-step filtration offers future opportunities to explore the complex interactions between structural features of the oral cavity, vortex parameters, motile particle behavior, and particle morphology that determine the suspension, concentration, and transport of particles within the oral cavity of ram suspension-feeding fish.