Degree Of Stratification Research Articles

Patterns of legacy sediment deposits in a small South Carolina Piedmont catchment, USA

Anthropogeomorphic changes to channels and floodplains occurred in response to destructive agricultural practices following the arrival of European settlers into the Americas. The southeastern Piedmont physiographic region of the USA experienced severe erosion and sedimentation after settlement in the 1700s and farming up through the 1930s. In places, deep floodplain aggradation formed uninterrupted alluvial deposits that extend many kilometers. This research examines anthropogenic impacts of land-use change on valley bottom sedimentation in the Chicken Creek Watershed of South Carolina. Abrupt contacts between precolonial floodplain soils and a thick overburden of historical legacy sediment are common and well exposed throughout the two-km study reach and provide clear evidence of extensive postcolonial sedimentation. Soil stratigraphic and sedimentologic evidence are presented to identify and contrast pre- and postcolonial sediment characteristics and thicknesses. LiDAR-based spatial analysis is used to examine patterns of legacy sediment deposition and floodplain storage and—together with field observations of bank stratigraphy—examine the environments in which this occurred. Precolonial geomorphic stability is indicated by a buried soil epipedon (Ab horizon) and other features on precolonial floodplain surfaces.Legacy sediment 2 to 4 m thick rests on top of exposed precolonial soils throughout the stream corridor, with the pre−/postcolonial contact ~1.5 m above the channel bed on average. Linear regression analysis shows that legacy sediment thickness varies statistically with changes in valley width and proximity to tributary sediment sources. Thin precolonial alluvium over bedrock suggests modest erosion and sedimentation rates prior to the arrival of EuroAmerican settlers. Mean grain-sizes are similar between the pre- and postcolonial alluvium, but substantial contrasts in the degree of stratification and bulk density document differences between the respective depositional environments and post-depositional changes to the two units. Channel adjustments since the time of maximum aggradation include bed incision to at least as low as the precolonial longitudinal profile and widening that is ongoing.

Optimization of the coefficient of performance of a heat pump with an integrated storage tank – A computational fluid dynamics study

The performance of a heating system consisting of a heat pump with an integrated storage tank was evaluated by means of Computational Fluid Dynamics (CFD) calculations. The aim of the investigations was to elucidate how thermal stratification in the tank would influence the COP of the system. Differently designed storage tanks were investigated under typical operation conditions. CFD models of heat storage tanks were developed and validated by experiments on a test tank. Calculations with the validated models were carried out in order to find the optimal tank design and system settings for achieving the highest possible COP. The investigated parameters were volume flow rate, tank geometry, diffuser design and tank wall material. Two different system COPs were defined: one based only on charge operation and the other on both charge and discharge operations. It was found that there is a direct connection between the thermal stratification inside the tank and the COP of the heating system. Higher degree of stratification leads to higher COP. For the ideal case where there is no mixing, no vertical thermal conduction in the tank and no heat loss from the tank, the system COP after a charge-discharge cycle is 3.69. When the effect of mixing is taken into account, the obtained COP of the system is decreased by approximately 9%. If heat transfer to the tank wall and vertical thermal conduction are also taken into account, the obtained system COP is lowered by another 5%. Moreover, the COP of a heating system with high flow rates can be significantly increased by a diffuser plate installed in the tank with a small distance to the inlet/outlet. The best performing system studied consisted of an insulated tall and slim tank with a h/d ratio of 3.64 and a perforated plate diffuser, giving a COP of 3.23 which was 32% higher compared to a case without a diffuser. The performance of the suggested system was not affected by variations of flow rates in the range from 0.12 to 0.24 kg/s.

Computational study of full-scale VHTR lower plenum for turbulent mixing assessment

Next-generation nuclear reactors are poised to efficiently provide reliable power at enhanced safety levels for many years to come. Among the fundamental designs for these reactors is the very-high-temperature reactor (VHTR), which employs helium as the primary coolant and has the potential of reaching elevated temperatures such that chemical processing (e.g., electrolysis for hydrogen production) is viable alongside traditional electricity generation. This and other next-generation reactors also represent a strategic bridge for ultimately transitioning from fossil fuel-dominated energy portfolios to one where renewable options abound. For the VHTR, the ultimate goal of constructing a new plant will be preceded by additional fundamental research aimed at generating trusted models for behavior prediction under normal and accident scenarios. This paper presents a detailed computational fluid dynamics simulation of the lower plenum, where hot coolant from the core mixes together in a turbulent fashion before traveling to power conversion equipment. Because the flow is expected to enter the lower plenum across a wide range of temperatures and velocities, concerns exist when the mixing is incomplete. The potential hot spots on cylindrical support pedestals and the uniformity of the main outlet are the primary metrics of interest in this study, along with flow velocities and temperatures at different locations within the lower plenum. Three locations are probed in detail and suggest a large range exists for approach velocities and temperatures. A large degree of stratification is also seen on the surfaces of the support pedestals, suggesting a facility should accommodate testing for such behavior. The characterizations presented provide the valuable data needed in order to design appropriate experimental testbeds, where scaled modeling can be carried out in a manner meaningful in predicting the full-scale behavior.

Stratification of drying particle suspensions: Comparison of implicit and explicit solvent simulations.

Large scale molecular dynamics simulations are used to study drying suspensions of a binary mixture of large and small particles in explicit and implicit solvents. The solvent is first modeled explicitly and then mapped to a uniform viscous medium by matching the diffusion coefficients and the pair correlation functions of the particles. "Small-on-top" stratification of the particles, with an enrichment of the smaller ones at the receding liquid-vapor interface during drying, is observed in both models under the same drying conditions. With the implicit solvent model, we are able to model much thicker films and study the effect of the initial film thickness on the final distribution of particles in the dry film. Our results show that the degree of stratification is controlled by the Péclet number defined using the initial film thickness as the characteristic length scale. When the Péclet numbers of large and small particles are much larger than 1, the degree of "small-on-top" stratification is first enhanced and then weakens as the Péclet numbers are increased.

A new approach to design self stratifying coatings containing nano and micro pigments

A self-stratifying coating contains at least two resins of different natures which spontaneously stratify after application onto a substrate. Various self-stratifying systems are reported in the literature, but the incorporation of nano pigments in such coatings and impact of the pigment size on stratification phenomenon are rarely discussed. In this paper, a self-stratifying coating based on epoxy and chlorinated rubber resins was formulated, and two pigments, i.e. nano titanium dioxide and micro red iron oxide were incorporated in the formulation, separately or together. The formulations were then applied on glass substrates. Various formulas of different viscosities and with different ratios of epoxy and chlorinated rubber were made to find the best formulas with acceptable stratification and pigment migration. SEM–EDX cross section analyses and mappings were carried out to characterize stratification and pigment location. It was found that, in clear coat, a very neat stratification is observed, with the chlorinated rubber resin above the epoxy layer. When iron oxide is added in the epoxy resin, it migrates during curing to the chlorinated rubber, without affecting the self-stratification. When both pigments are incorporated, stratification is not observed anymore. However, by changing the viscosity of the formulation (by modifying the epoxy ratio), an acceptable degree of stratification was obtained, and both pigments were obtained in the desired location. These pigments being used for anticorrosive and antibacterial applications, so this formulation could lead to the design of multifunctional coatings.

Influence of light stratification on the growth of Scenedesmus quadricauda

Light availability and light stratification within any photobioreactor and their impact on the growth of microalgae are important issues in the analysis, modeling and design of a photobioreactor. In this work, the microalga Scenedesmus quadricauda was grown in a laboratory scale photobioreactor irradiated with different arrangements of white LEDs giving rise to different degrees of light stratification within the culture medium. To ensure that the observed effects were solely caused by the inhomogeneity of the radiation field properties, the different arrangements of LEDs were required that they emit the same total number of photons per unit time and per unit volume of culture. Assessment of light availability in the culture medium was made using the volumetric average rate of photon absorption and the distribution function of volumetric photons absorption rates. The results obtained highlight the importance of systematically quantifying the degree of stratification of light in the culture medium for the purpose of optimization and scaling up of photobioreactors.

Numerical investigation of the baffle plates effect on the solar water storage tank efficiency

ABSTRACTThis paper presents a numerical research of the influence of baffle plates integration inside a horizontal storage tank on the solar water storage tank efficiency. In this work, the baffle plates are integrated inside the tank with different locations and different distances between them to study their effects and also to determine the optimum position in order to enhance the thermal storage system (TSS) performance. The CFD comparison between all proposed designs was carried out and different methods of evaluating mixing and stratification such as temperature evolution, outlet temperature, Richardson number, and full efficiency were calculated to quantify the degree of stratification. Results show that the TSS performance depends on the baffle locations and distance between them. Therefore, a superior thermal performance was achieved for baffles with superior distance between them which are maintained in top of the water storage tank (WST).

Ситуация на рынке продовольствия: новые сигналы и старые проблемы

Современная ситуация на агропродовольственном рынке характеризуется, с одной стороны, дифференциацией его сегментов по степени насыщения, а с другой–снижением спроса. Падение реальных доходов населения обусловило снижение потребительского спроса и увеличение доли расходов на питание в домашних хозяйствах, о чем свидетельствует анализ региональной статистики. В последние годы растет расслоение как по производству, так и по потреблению продовольствия на душу населения. Опережающий рост цен на продовольствие ставит под сомнение верность выбора мер и инструментов политики протекционизма. Правильный протекционизм, по мнению автора, не может осуществляться за счет снижения уровня жизни населения, а должен сочетать рыночные механизмы с точечной временной поддержкой тех отраслей экономики, для которых характерны растущая доходность и высокая отдача на инвестиции. Автор считает необходимым использование инструментов «зеленой корзины» (в частности программу продовольственных карточек), отмену эмбарго на импорт продовольствия и дифференциацию экспортных и импортных таможенных пошлин в зависимости от степени насыщения и сформированности внутренних отраслевых рынков.

Understanding the Relationship between Water Infrastructure and Socio-Political Configurations: A Case Study from Sri Lanka

Academic scholarship in the social sciences has, in recent years, documented how water management infrastructure connects and disconnects people and flows, portraying and defining inequalities. The present work contributes to advancing this perspective by undertaking a case study to comparatively examine two irrigation-based water infrastructure systems in Sri Lanka: the tank cascade system and the surface irrigation system. The analysis demonstrates that differences in the layout of the water infrastructure directly contribute to the ways in which downstream communities are socially, economically and politically configured. Specifically, the arrangement of water infrastructure influences the degree of water users’ dependence on each other, the degree of social stratification between head-end and tail-end farmers, and the degree to which water is regarded as an ‘economic’ object. It can be concluded that the technical system of water infrastructure is inextricably bound to society and should, therefore, be considered a socio-material assemblage. Thus, it is important that policy decisions on water infrastructure management treat the structuring of infrastructure as experimental and potentially reversible.

Combustion and emissions of controlled auto-ignition engine under stratified mixture conditions

Controlled auto-ignition (CAI) is an advanced combustion technology offering high thermal efficiency and low NOX emissions. One promising approach to achieve CAI combustion is application of negative valve overlap resulting in internal exhaust gas re-circulation. However, combustion control is still an issue which should be resolved before wide application of CAI combustion. Introduction of some degree of fuel stratification via direct fuel injection is interesting approach to control combustion process.In this study a gasoline-fuelled single-cylinder research engine was used to investigate the effects of stratification on combustion and emissions of CAI engine. The stratification was achieved using split direct fuel injection technique, where the second fuel injection controlled the degree of stratification. The results shown that variability of the second injection timing and mass of fuel injected is a viable method to control combustion on-set as well as its duration. However, the trends in both combustion and emissions were found to be non-monotonic, revealing complex relationships between mixture formation and combustion process. It has been found that small degree of mixture stratification delays combustion on-set, whereas large stratification advances combustion. The obtained results confirmed superior combustion controllability via mixture stratification, however with some limitations resulting from reduced efficiency at high degree of stratification.

Las trampas de las publicaciones académicas

Las revistas cientificas se han transformado profundamente a partir de su constitucion como los elementos centrales de la evaluacion de academicos y cientificos en las universidades y otras instituciones de investigacion. La construccion de indicadores de impacto y de desempeno a partir del numero de publicaciones y las citas recibidas ha producido una distorsion en la seleccion de temas, la identificacion de audiencias, y las caracteristicas del trabajo academico. Los indicadores de impacto y otras metricas reproducen sesgos —tematicos, disciplinarios y de idioma— que profundizan la estratificacion entre los academicos y las instituciones. Es importante reconocer las trampas en que se encuentran las publicaciones academicas y las distorsiones que producen, para disenar alternativas editoriales que fortalezcan tanto a las revistas como a la produccion academica que las sostiene.

Detection of mixture stratification in controlled auto-ignition engine using spontaneous optical emission signal

In this study an optical-fiber sensor was utilized to observe spontaneous emissions of controlled auto-ignition (CAI) engine under stratified mixture combustion. Mixture stratification, achieved with the use of late direct fuel injection, is an effective approach to improve combustion controllability of the engine operated in the CAI mode. However, observed effects of injection timing on combustion show high combustion sensitivity even for early fuel injection. This study pertains identification of the reasons for such a high sensitivity to injection timing. To identify possible mixture stratification and resulting gradual combustion, optical-fiber sensor was used to observe spontaneous combustion emissions. Optical measurements enabled identification of stratified combustion, which was manifested by double optical signal peaks. The observed peaks of different amplitudes resulted from stepwise combustion in local zones with different mixture composition and flame temperature. The performed measurements enabled better understanding non-linear combustion timing behavior with variable degree of mixture stratification.

Thermal stratification and its relationship with water quality in the typical tributary bay of the Three Gorges Reservoir

AbstractThe effect of thermal stratification and its relationship with water quality was researched by field observation in this study. Through assessing the degree of thermal stratification by calculating the dimensionless parameter of thermal resistance to mixing (RTRM) indices from 2008 to 2010, it indicated that the water body of Xiangxi River was stratified strongly in the summer months. The analysis of the degree of thermal stratification with both the meteorological and hydrodynamic factors showed thermal stratification intensity was more sensitive to meteorological factors in Xiangxi River. Through the analysis of the relationship between thermal stratification and water quality, the results indicated that the concentration of Chlorophyll a was higher in the epilimnion affected by the thermal stratification, which could cause algal bloom. The results may further help to evaluate the thermal stratification role in eutrophication process and algal bloom formation in Xiangxi River.

Dynamics of sediment transport and stratification in Changjiang River Estuary, China

Suspended sediment transport and stratification in the entire Changjiang River Estuary were examined using the field data of sea-surface level, currents, salinity, and suspended sediment concentration (SSC). The data were simultaneously observed at one-hour intervals and at six vertical layers at 23 stations covering two spring tidal cycles in May, 2004. The results showed that ebbing tides had a longer tidal duration and stronger tidal currents than flooding tides, due to a fresh water discharge. The tidal range reached about 4 m and the peak tidal current of about 2.9 m/s occurred in the north passage in the observed period. A stratification caused by salinity and suspended sediment appeared and varied with tides indicated by the overall Richardson number. The potential energy anomaly was larger when SSC was factored in to the water density. A stratification ratio (Sr), which is the ratio of potential energy required to induce complete mixing to the overall potential energy, was proposed to measure the degree of sediment stratification. Sr values indicated that mixing the stratified turbid water took as much as 0.25% of the overall potential energy at a particular field station. A turbidity maximum zone (TMZ) was observed in the north passage, where the salt-fresh-water interface and stratification appeared, due to the advective and tidal transport component. The main components controlling the vertical-averaged net sediment transport were the Eulerian velocity, Stokes drift and tidal pumping. Salinity intrusion creates the stratification in the north passage, which depresses the turbulence and re-suspension of sediment. The stratification is further enhanced by the vertical distribution of suspended sediment, which results in a TMZ and induces sediment deposition/trapping in the channel. Hence, the SSC was essential to be considered in the study of estuarine stratification, particularly in the highly turbid estuaries.

Biogeochemical controls on black shale deposition during the Frasnian-Famennian biotic crisis in the Illinois and Appalachian Basins, USA, inferred from stable isotopes of nitrogen and carbon

The Frasnian-Famennian biotic crisis is marked by two distinct intervals known as the Lower and Upper Kellwasser Events (KWEs) that in many locations are associated with deposition of organic-rich shales. Sedimentary nitrogen and carbon isotopes offer insight into the biogeochemical processing of nutrients, production of organic matter, and palaeoceanographic conditions during the KWEs. Here we present new bulk nitrogen (δ15Nbulk) and organic carbon (δ13Corg) isotope data from the Late Devonian Appalachian and Illinois Basins (AB and IB), with a focus on intervals encompassing the KWEs. Black shales from the IB and AB, including the KWEs, are 15N-depleted (−1.0–+2.0‰) and have significantly lower δ15Nbulk than interbedded grey shales (+0.5–+4.0‰), a trend consistent with many instances of black shale deposition in the Phanerozoic. Organic carbon isotopes exhibit the broad, positive excursions (~+3.5‰ from background) that are typical of the KWEs globally. Superimposed over these positive excursions in δ13Corg are sharp decreases of up to ~3.0‰ within the black shale beds, to as low as −30.5‰. The pattern of δ15Nbulk and δ13Corg values suggests that the depth of the chemocline and the degree of water-column stratification exert a primary control on both δ15Nbulk and δ13Corg during black shale deposition. In the context of the Frasnian-Famennian biotic crisis, the oscillating redox state and changing temperatures would have likely placed extreme stress on organisms within the marine environment of the AB and IB and may potentially have been a contributing factor to diversity loss over this time period.

A minimal spatial cell lineage model of epithelium: tissue stratification and multi-stability

A minimal model which includes spatial and cell lineage dynamics for stratified epithelia is presented. The dependence of tissue steady state on cell differentiation models, cell proliferation rate, cell differentiation rate, and other parameters are studied numerically and analytically. Our minimal model shows some important features. First, we find that morphogen or mechanical stress mediated interaction is necessary to maintain a healthy stratified epithelium. Furthermore, comparing with tissues in which cell differentiation can take place only during cell division, tissues in which cell division and cell differentiation are decoupled can achieve relatively higher degree of stratification. Finally, our model also shows that in the presence of short-range interactions, it is possible for a tissue to have multiple steady states. The relation between our results and tissue morphogenesis or lesion is discussed.

A layered model for inclined pipe flow of settling slurry

The paper deals with mathematical and physical modelling of flow of partially-stratified settling slurry in inclined pipes. Experimental results are presented of flows of aqueous slurries of four fractions of sand and gravel in two laboratory loops of different pipe diameters. They show a considerable variation in pressure drop and distribution of solids with the pipe slope. The degree of flow stratification and frictional pressure drop decrease with the increasing angle of inclination in the ascending pipe while the opposite applies in the descending pipe. A predictive mathematical model is presented which is based on a description of a layered structure of partially stratified slurry flow and takes flow inclination into account. The experimentally observed effects of pipe inclination are well reproduced by model predictions. Predicted pressure drops and solids distributions are in a very reasonable agreement with the experimental results and indicate suitability of the model for engineering practise.

MP39-04 GENE EXPRESSION PROFILES IN URINARY BLADDER MUSCOSA ARE HIGHLY CORRELATED WITH ANESTHETIZED BLADDER CAPACITY IN IC/BPS PATIENTS

You have accessJournal of UrologyInfections/Inflammation/Cystic Disease of the Genitourinary Tract: Interstitial Cystitis1 Apr 2018MP39-04 GENE EXPRESSION PROFILES IN URINARY BLADDER MUSCOSA ARE HIGHLY CORRELATED WITH ANESTHETIZED BLADDER CAPACITY IN IC/BPS PATIENTS Stephen Walker, Gopal Badlani, Catherine Matthews, Joao Zambon, and Robert Evans Stephen WalkerStephen Walker More articles by this author , Gopal BadlaniGopal Badlani More articles by this author , Catherine MatthewsCatherine Matthews More articles by this author , Joao ZambonJoao Zambon More articles by this author , and Robert EvansRobert Evans More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2018.02.1251AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES The goal of this study is to further explore our working hypothesis that the low capacity (= 400 ml) bladder mucosal gene expression profile represents a bladder-centric IC/BPS sub-phenotype. This hypothesis is based on data from our earlier pilot study showing that a subset of IC/BPS patients (those with a severely diminished bladder capacity {BC; = 400 ml}) displayed a unique gene expression profile. METHODS IC/BPS patient biopsy samples for gene expression profiling were selected from our tissue bank (IRB00018552) on the basis of anesthetic bladder capacity between 200-900ml (at least two individuals at each of 12 representative BCs; 33 samples total). All patients had undergone therapeutic bladder hydrodistention per the AUA guideline algorithm. Total RNA was isolated from mucosal biopsies (per standard protocols) and assayed on whole genome microarrays (Illumina HT v4 BeadArray). RESULTS Bladder capacity accounted for approximately 54% of the variation in mucosal gene expression profiles between samples (PCA plot; Figure 1, left panel). Hierarchical clustering revealed three subgroups: (1) BC 200-300ml, (2) BC 350-500ml, and (3) BC > 500 ml (heatmap; Figure 1, right panel). Subgroup #1 consisted almost exclusively of samples from individuals with low capacity and Hunners lesions (HL). This likely accounted for the large number of upregulated cytokines and chemokines (e.g. CXCL9, CCL18, CCL19, CCL21 and IL10RA) seen in this cluster. Subgroup #2 consisted of samples from patients with low capacity and mostly without HL, and Subgroup #3 were all patients with higher BC and without HL. CONCLUSIONS Gene expression in mucosal biopsy tissue from IC/BPS patients provides a degree of stratification when correlated with anesthetic bladder capacity. These pilot data reveal three distinct IC/BPS subgroups and information mined from differentially-expressed genes within each subgroup may provide further insight into the heterogeneity seen in IC/BPS. © 2018FiguresReferencesRelatedDetails Volume 199Issue 4SApril 2018Page: e510-e511 Advertisement Copyright & Permissions© 2018MetricsAuthor Information Stephen Walker More articles by this author Gopal Badlani More articles by this author Catherine Matthews More articles by this author Joao Zambon More articles by this author Robert Evans More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Numerical investigation of potential stratification caused by a cryogenic helium spill inside a tunnel

The sudden release of cryogenic fluid into an accelerator tunnel can pose a significant health and safety risk. For this reason, it is important to evaluate the consequences of such a spill. Previous publications concentrated on either Oxygen Deficiency Hazard or the evaluation of mathematical models using experimental data. No studies to date have focussed on the influence of cryogen inlet conditions on flow development. In this paper, the stratification behaviour of low-temperature helium released into an air-filled accelerator tunnel is investigated for varying helium inlet diameters. A numerical model was constructed using the OpenFOAM Toolbox of a generalised 3D geometry, with similar hydraulic characteristics to the CERN and SLAC tunnels. This model has been validated against published experimental and numerical data. A dimensionless parameter, based on Bakke number, was then determined for the onset of stratification, taking into account the helium inlet diameter; a dimensionless parameter for the degree of stratification was also employed. The simulated flow behaviour is described in terms of these dimensionless parameters, as well as the temperature and oxygen concentration at various heights throughout the tunnel.

Melting performance enhancement of phase change material by a limited amount of metal foam: Configurational optimization and economic assessment

In the paper, melting performance of a latent heat thermal energy storage (LHTES) unit with phase change materials (PCMs) locally enhanced by porous media was numerically investigated. The filling ratio of the porous inserts was fixed to a low degree to reduce the material cost. The optimal configuration of the porous inserts was obtained after the discussion about the effects of porous geometry and porosity on the velocity and temperature distribution of melting process. To reveal the superiority of the optimized result, different cases were compared with the help of a new comprehensive criterion about the input-output performance. Then a generalization expression was fitted out with some dimensionless parameters for the rapid calculation of melting fraction of the optimized result in practical application. The results indicated that in the horizontal LHTES unit, the limited porous inserts should be concentrated in the bottom part without interval between the neighboring porous inserts, providing an effective enhancement in the lower part and a low degree of thermal stratification. If the mass of porous inserts is fixed, high porosity is preferred to make the thermal-conduction-dominated area sufficiently covered by the porous inserts. Compared with the non-enhancement case, the selected result in this study can remarkably save more than 80% of the melting time and enhance the melting rate by 5.1 times. More significantly, the selected result has the highest melting rate per cost of the material when the price ratio of the addition to the PCM is larger than 5 based on the results of economic assessment. Therefore, it offers an economical solution to the thermal enhancement problem of the LHTES unit in the practical application. The normalized equation of melting fraction is obtained for the parameter range of 0.187 < Ste < 0.374, 1.325 × 106 < Ra < 2.649 × 106: f=0.596X+0.0438X2-0.0825X3+0.0130X4, where X = SteFoRa1/8 < 2.796.