Significant Differences In Transport Research Articles

New paradigms of quantification of economic efficiency in the transport sector

Research background: In determining the prices in road transport, carriers usually use the calculations based on a so-called routes utilisation coefficient, which allows the carrier to also take the possibility of the return rides without load into account. Currently, it is usually used as a constant from the interval from zero to one.
 Purpose of the article: Considering a different offer of return transport from individual European Union (EU) countries, it can be assumed that the routes utilisation coefficient should have different values because there is a varying level of non-zero probability that the vehicle will return without a load. This study therefore proposes a new approach to determining the value of this coefficient based on transport direction. The study also aims to identify clusters of EU countries, for which the common value of the coefficient should be set.
 Methods: The Analysis of Variance (ANOVA) test was used to verify the assumption of the differences among the means of transport offers. Cluster analysis was used to identify the aforementioned groups of countries. This analysis is based on real data on transport offers to Slovakia from 18 different EU countries.
 Findings & value added: The results of the analysis can also be used in other EU countries because if significant differences in transport offers to Slovakia exist in individual countries, there is a reasonable assumption that this conclusion will also be valid in other countries. The analysis demonstrated that it is more appropriate to use the routes utilisation coefficient with various values, dependent on the transport direction. For the transport companies, implementation of the obtained results into practice is beneficial to increase their competitiveness through the more precise setting of transport prices, but also to the optimisation of the transport price itself with regard to the expected costs.

Compressive Properties and Hydraulic Permeability of Human Meniscus: Relationships With Tissue Structure and Composition

The meniscus is crucial in maintaining knee function and protecting the joint from secondary pathologies, including osteoarthritis. The meniscus has been shown to absorb up to 75% of the total load on the knee joint. Mechanical behavior of meniscal tissue in compression can be predicted by quantifying the mechanical parameters including; aggregate modulus (H) and Poisson modulus (ν), and the fluid transport parameter: hydraulic permeability (K). These parameters are crucial to develop a computational model of the tissue and for the design and development of tissue engineered scaffolds mimicking the native tissue. Hence, the objective of this study was to characterize the mechanical and fluid transport properties of human meniscus and relate them to the tissue composition. Specimens were prepared from the axial and the circumferential anatomical planes of the tissue. Stress relaxation tests yielded the H, while finite element modeling was used to curve fit for ν and K. Correlations of moduli with water and glycosaminoglycans (GAGs) content were investigated. On average H was found to be 0.11 ± 0.078 MPa, ν was 0.32 ± 0.057, and K was 2.9 ± 2.27 × 10−15 m4N−1s−1. The parameters H, ν, and K were not found to be statistically different across compression orientation or compression level. Water content of the tissue was 77 ± 3.3% while GAG content was 8.79 ± 1.1%. Interestingly, a weak negative correlation was found between H and water content (R2 ~ 34%) and a positive correlation between K and GAG content (R2 ~ 53%). In conclusion, while no significant differences in transport and compressive properties can be found across sample orientation and compression levels, data trends suggest potential relationships between magnitudes of H and K, and GAG content.

Video or Telephone? A Natural Experiment on the Added Value of Video Communication in Community Paramedic Responses

The objective of this study was to determine the effect of video versus telephonic communication between community paramedics and online medical control physicians on odds of patient transport to a hospital emergency department (ED). This was a retrospective analysis of data from a telemedicine-capable community paramedicine program operating within an advanced illness management program that provides home-based primary care to approximately 2,000 housebound patients per year who have advanced medical illness, multiple chronic conditions, activities of daily living dependencies, and past-year hospitalizations. Primary outcome was difference in odds of ED transport between community paramedicine responses with video communication versus those with telephonic communication. Secondary outcomes were physicians' perception of whether video enhanced clinical evaluation and whether perceived enhancement affected ED transport. Of 1,707 community paramedicine responses between 2015 and 2017, 899 (53%) successfully used video; 808 (47%) used telephonic communication. Overall, 290 patients (17%) were transported to a hospital ED. In the adjusted regression model, video availability was not associated with a significant difference in the odds of ED transport (odds ratio 0.80; 95% confidence interval 0.62 to 1.03). Online medical control physicians reported that video enhanced clinical evaluation 85% of the time, but this perception was not associated with odds of ED transport. We found support that video is considered an enhancement by physicians overseeing a community paramedicine response, but is not associated with a statistically significant difference in transport to the ED compared with telephonic communication in this nonrandom sample. These results have implications for new models of out-of-hospital care that allow patients to be evaluated and treated in the home.

Anomalous thickness-dependent electrical conductivity in van der Waals layered transition metal halide, Nb3Cl8

Understanding the electronic transport properties of layered, van der Waals transition metal halides (TMHs) and chalcogenides is a highly active research topic today. Of particular interest is the evolution of those properties with changing thickness as the 2D limit is approached. Here, we present the electrical conductivity of exfoliated single crystals of the TMH, cluster magnet, Nb3Cl8, over a wide range of thicknesses both with and without hexagonal boron nitride (hBN) encapsulation. The conductivity is found to increase by more than three orders of magnitude when the thickness is decreased from 280 µm to 5 nm, at 300 K. At low temperatures and below ∼50 nm, the conductance becomes thickness independent, implying surface conduction is dominating. Temperature dependent conductivity measurements indicate Nb3Cl8 is an insulator, however, the effective activation energy decreases from a bulk value of 310 meV to 140 meV by 5 nm. X-ray photoelectron spectroscopy (XPS) shows mild surface oxidation in devices without hBN capping, however, no significant difference in transport is observed when compared to the capped devices, implying the thickness dependent transport behavior is intrinsic to the material. A conduction mechanism comprised of a higher conductivity surface channel in parallel with a lower conductivity interlayer channel is discussed.

After the Fall: Legacy Effects of Biogenic Structure on Wind-Generated Ecosystem Processes Following Mussel Bed Collapse

Blue mussels (Mytilus edulis) are ecosystem engineers with strong effects on species diversity and abundances. Mussel beds appear to be declining in the Gulf of Maine, apparently due to climate change and predation by the invasive green crab, Carcinus maenas. As mussels die, they create a legacy of large expanses of shell biogenic structure. In Maine, USA, we used bottom traps to examine effects of four bottom cover types (i.e., live mussels, whole shells, fragmented shells, bare sediment) and wind condition (i.e., days with high, intermediate, and low values) on flow-related ecosystem processes. Significant differences in transport of sediment, meiofauna, and macrofauna were found among cover types and days, with no significant interaction between the two factors. Wind condition had positive effects on transport. Shell hash, especially fragmented shells, had negative effects, possibly because it acted as bed armor to reduce wind-generated erosion and resuspension. Copepods had the greatest mobility and shortest turnover times (0.15 d), followed by nematodes (1.96 d) and the macrofauna dominant, Tubificoides benedeni (2.35 d). Shell legacy effects may play an important role in soft-bottom system responses to wind-generated ecosystem processes, particularly in collapsed mussel beds, with implications for recolonization, connectivity, and the creation and maintenance of spatial pattern.

Narrow Grass Hedge Effects on Microbial Transport Following Variable Applications of Beef Cattle Manure

Abstract. The effectiveness of a 1.4 m wide grass hedge in reducing microbial transport following manure application was examined in this study. Beef cattle manure was applied to 0.75 m wide by 4.0 m long plots established on an Aksarben silty clay loam located in southeast Nebraska. Manure was added at rates required to meet none or the 1-, 2-, or 4-year nitrogen requirements for corn. The transport of phages, total coliforms, , and enterococci was measured for three 30 min simulated rainfall events, which were separated by approximately 24 h intervals. The narrow grass hedge reduced total counts of phages, , and enterococci from 10.8 to 9.01 log PFU ha-1, from 12.4 to 11.9 log CFU ha-1, and from 11.8 to 11.2 log CFU ha-1, respectively. For the plots that received manure, no significant differences in transport of phages or enterococci were found among the three manure application rates. Rainfall simulation run significantly affected measurements of phages, total coliforms, and enterococci, with measurements during the three runs varying from 8.91 to 10.5 log PFU ha-1, from 12.7 to 13.3 log CFU ha-1, and from 11.2 to 11.7 log CFU ha-1, respectively. Counts for phages, total coliforms, and enterococci were significantly less for the first than the second and third rainfall simulation runs. All four of the microbial constituents were significantly correlated to dissolved P, particulate P, total P, and total N. A narrow grass hedge placed on the contour significantly reduced microbial transport following variable applications of beef cattle manure. Keywords: Bacteria, Cattle manure, E. coli, Filter strips, Land application, Manure management, Manure runoff, Microbial, Microorganisms, Runoff.

High performance blue-emitting organic light-emitting diodes from thermally activated delayed fluorescence: A guest/host ratio study

Emitters displaying thermally activated delayed fluorescence (TADF) can lead to highly efficient organic light-emitting diodes (OLEDs). Such emitters are usually incorporated into the emissive layer (EML) at a relatively low concentration (<20 wt. %) with respect to a host material, a guest-host approach inherited from conventional fluorescent or phosphorescent OLEDs. Here, detailed studies on OLEDs, in which the concentration of oBFCzTrz (a blue-emitter displaying TADF) in a DPEPO host was varied from 8 to 100 wt. %, reveals that oBFCzTrz displays ambipolar transport and limited fluorescence-quenching due to aggregation. For instance, a neat film of oBFCzTrz maintains a photoluminescence quantum yield of 82%. We demonstrate that OLEDs with an EML having an oBFCzTrz concentration of 50 wt. % in DPEPO yield a maximum external quantum efficiency (EQE) of 25.5% with an EQE roll-off of 10% in the range from 10 to 1000 cd/m2 and Commission Internationale de l'Eclairage color coordinates of (0.20, 0.44). OLEDs with smaller or larger oBFCzTrz concentrations display smaller maximum EQE values. OLEDs with a neat oBFCzTrz EML display a maximum EQE of 14.0%. Time-resolved electroluminescent decay studies, and analysis using a simple model, reveal significant differences in transport, trapping, and recombination in these devices.

Studies in genetically modified mice implicate maternal HDL as a mediator of fetal growth.

Studies in humans have shown a direct association between maternal plasma cholesterol concentrations and infant birthweight. Similarly, previous studies in our laboratory have shown that chow-fed mice lacking apolipoprotein (apo) A-I, the major protein in HDL, have low HDL-cholesterol (HDL-C) concentrations and smaller fetuses in midgestation. In the current study, we measured fetal weights in mice with varying levels of apoA-I gene dose (knockout, wild-type, and transgenic) and examined metabolic pathways known to affect fetal growth. As expected, we found the differences in apoA-I expression led to changes in HDL particle size and protein cargo as well as plasma cholesterol concentrations. Fetal masses correlated directly with maternal plasma cholesterol and apoA-I concentrations, but placental masses and histology did not differ between groups of mice. There was no significant difference in glucose or amino acid transport to the fetus or in expression levels of the glucose (glucose transporter 1 and 2) or amino acid (sodium-coupled neutral amino acid transporter 1 and 2) transporters in whole placentas, although there was a trend for greater uptake of both nutrients in the whole fetal unit (fetus + placenta) of mice with greater apoA-I levels; significant differences in transport rates occurred when mice without apoA-I (knockout) vs. mice with apoA-I (wild-type and transgenic) were compared. Glucose tolerance tests were improved in the mice with the highest level of apoA-I, suggesting increased insulin-induced uptake of glucose by tissues of apoA-I transgenic mice. Thus, maternal HDL is associated with fetal growth, an effect that is likely mediated by plasma cholesterol or other HDL-cargo, including apolipoproteins or complement system proteins. A direct role of enhanced glucose and/or amino acid transport cannot be excluded.-Rebholz, S. L., Melchior, J. T., Davidson, W. S., Jones, H. N., Welge, J. A., Prentice, A. M., Moore, S. E., Woollett, L. A. Studies in genetically modified mice implicate maternal HDL as a mediator of fetal growth.

Magnetic and Transport Properties of Transition Metal Doped Polycrystalline In$_2$O$_3$

Synthesis and characterization of transition metal (TM)-doped In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> oxide is reported. Most of the samples were found to be paramagnetic, and only Fe and Cr co-doped sample showed as light trace of ferromagnetism at 300 K with saturation magnetization M <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> = 0.35 emug/g. Measured transport properties revealed significant differences in transport among the samples. The absolute value of electrical resistivity for the In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1.8</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.1</sub> Mn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.1</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> sample at 300 K was rho=9.4times10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> Omega middot cm, while In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1.8</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.1</sub> Cr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.1</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> had rho=62 Omega middot cm at the same temperature. Furthermore, magnetoresistance (MR) studies of In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1.8</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.1</sub> Cr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.1</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> showed that the sign of MR changes from negative (200 K), with MR <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">(200K) </sub> =-0.2%, to positive T< 50 K reaching maximum absolute value at 10 K, i.e., MR <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">(10K)</sub> =5.2%

Comparison of Escherichia coli and Campylobacter jejuni Transport in Saturated Porous Media

Due to the difficulties in testing for specific pathogens, water samples are tested for the presence of nonpathogenic indicator organisms to determine whether a water supply has been contaminated by fecal material. An implicit assumption in this approach is that where pathogenic microorganisms are present fecal indicator organisms are present as well; yet surprisingly few studies have been conducted that directly compare the transport of indicator organisms with pathogenic organisms in ground water environments. In this study we compared the cell properties and transport of Escherichia coli, a commonly used indicator organism, and Campylobacter jejuni, an important enteropathogen commonly found in agricultural wastes, through saturated porous media. Differences in cell properties were determined by measuring cell geometry, hydrophobicity, and electrophoretic mobility. Transport differences were determined by conducting miscible displacement experiments in laboratory columns. Under the experimental conditions tested, C. jejuni was much more negatively charged and more hydrophobic than E. coli. In addition, C. jejuni cells were slightly longer, narrower, and less spherical than E. coli. The variations in cell properties, primarily surface charge, resulted in significant differences in transport between these two microorganisms, with the transport of C. jejuni exceeding that of E. coli when conditions favored low attachment rates, thus calling into question the usefulness of using E. coli as an indicator organism for this important pathogen.

Multidrug resistance-associated protein 2 (MRP2) affects hepatobiliary elimination but not the intestinal disposition of tenofovir disoproxil fumarate and its metabolites

The role of multidrug resistance-associated protein 2 (MRP2) on the intestinal disposition and hepatobiliary elimination of tenofovir disoproxil fumarate (DF) and its metabolites [tenofovir (mono)ester and tenofovir] was studied in the Caco-2 system, Ussing chambers and rat in-situ efflux experiments. In the Caco-2 model and Ussing chambers, no statistically significant differences in transport could be observed when the MRP inhibitor probenecid was included. In Ussing chambers, transport was also similar when using intestinal tissue from MRP2-deficient rats. After intravenous administration of tenofovir DF, the excretion of tenofovir [(mono)ester] in bile was significantly decreased in MRP2-deficient rats and in rats treated with probenecid. The area under the blood concentration–time curve was increased in MRP2-deficient rats [1.0 ± 0.1 and 0.36 ± 0.03 µM.min−1 for tenofovir and tenofovir (mono)ester, respectively] and rats treated with probenecid (1.42 ± 0.04 and 0.36 ± 0.02 µM.min−1) compared with control rats (0.64 ± 0.05 and 0.15 ± 0.06 µM.min−1). The appearance of tenofovir [(mono)ester] in intestinal perfusate was similar in control rats upon co-administering probenecid or when using MRP2-deficient rats. In conclusion, MRP2 appeared to have no modulatory effect on the intestinal disposition of tenofovir and tenofovir (mono)ester. However, inhibition (probenecid) or the total absence of MRP2 (MRP2-deficient rats) significantly reduced hepatobiliary elimination, which was accompanied by increased systemic exposure.

Influence of El Niño Southern Oscillation on stratosphere/troposphere exchange and the global tropospheric ozone budget

We use a combined climate/chemistry model to assess the interannual variability of tropospheric ozone associated with the El Niño Southern Oscillation (ENSO). Simulations cover the years 1990 to 2001 with prescribed SSTs. El Niño and La Niña events are reproduced by the model. Previous studies have emphasized the impact of ENSO on tropospheric composition through changing emissions or convection. Here we show that there is a close relationship between ENSO and stratosphere‐troposphere exchange (STE); different patterns of circulation and meteorology in El Niño and La Niña years result in significant differences in transport of ozone‐rich air from the stratosphere to the troposphere. We calculate an anomalously large increase of STE following a typical El Niño year, most evident after the 1997–1998 El Niño event. La Niña events result in a decrease of STE. STE is one factor affecting tropospheric ozone; we find highest ozone after the 1997–1998 El Niño.

Improving emergency medical services for children with special health care needs: Does training make a difference?

This study evaluated the impact of a paramedic training program on emergency medical services (EMS) responses for children with special health care needs. EMS responses for children with a congenital or acquired condition or a chronic physical or mental illness, were reviewed. Responses, related to the child's special health care need, involving paramedics who had completed our training program were compared with responses with paramedics not participating in the training. There was significantly more advanced life support treatment for responses with paramedics completing the training program compared with other responses. However, there was no significant difference in transport to a hospital or in-hospital admission between these 2 groups. This finding suggests that existing EMS protocols may play a more important role in emergency treatment and transport of children with special health care needs than specialized training of already certified paramedics.

The permeability of the nuclear envelope in dividing and nondividing cell cultures.

The objective of this study was to determine whether the permeability characteristics of the nuclear envelope vary during different phases of cellular activity. Both passive diffusion and signal-mediated transport across the envelope were analyzed during the HeLa cell cycle, and also in dividing, confluent (growth-arrested), and differentiated 3T3-L1 cultures. Colloidal gold stabilized with BSA was used to study diffusion, whereas transport was investigated using gold particles coated with nucleoplasmin, a karyophilic Xenopus oocyte protein. The gold tracers were microinjected into the cytoplasm, and subsequently localized within the cells by electron microscopy. The rates of diffusion in HeLa cells were greatest during the first and fifth hours after the onset of anaphase. These results correlate directly with the known rates of pore formation, suggesting that pores are more permeable during or just after reformation. Signal-mediated transport in HeLa cells occurs through channels that are located within the pore complexes and have functional diameters up to 230-250 A. Unlike diffusion, no significant differences in transport were observed during different phases of the cell cycle. A comparison of dividing and confluent 3T3-L1 cultures revealed highly significant differences in the transport of nucleoplasmin-gold across the envelope. The nuclei of dividing cells not only incorporated larger particles (230 A versus 190 A in diameter, including the protein coat), but the relative uptake of the tracer was about seven times greater than that in growth-arrested cells. Differentiation of confluent cells to adipocytes was accompanied by an increase in the maximum diameter of the transport channel to approximately 230 A.

Movement and distribution of 14C‐indole‐3‐acetic acid in branches and rooted cuttings of Douglas‐fir

The transport of 14C‐indole‐3‐acetic acid in branch terminals and stems of rooted cuttings of Pseudotsuga menziesii (Mirb.) Franco was studied to determine if the plagiotropic growth of cuttings might result from an accumulation of basipetally transported auxin in the morphologically upper side of cuttings stems. Twenty‐four h after application of 10 μl of 14C‐IAA solution to the cut surface of decapitated, rooted cuttings, nearly twice as much activity was detected in extracts of tissue from the morphologically upper than from the lower halves of the stems. A similar distribution of activity was observed in horizontal branch terminals and in branch terminals which had been tied vertically for 2 weeks. The magnitude of the difference in activity between the 2 sides of the stem was greater in the horizontal than in the vertical branches.There was no significant difference in transport through the upper and lower sides of excised stem segments from cuttings or branch terminals. In segments from rooted cutting stems, however, significantly more radioactivity from 14C‐IAA donor blocks was detected in the lower than in the upper halves of segments.

The transient response of the North Atlantic: Some model studies

Four numerical experiments have been designed to clarify the role of stratification and topography on the transient response of the ocean to a change in wind forcing. The geometry and topography appropriate to the North Atlantic between the equator and 50°N are used to make the study more appropriate to a real ocean. In all four experiments, zonally symmetric wind stresses are ‘switched on’ at the upper surface of a resting model ocean. Two short experiments, 1 and 2, with a duration of 100 days, are first discussed. These are for a homogeneous ocean with and without topography. The response in the flat‐bottomed case can be described either in terms of planetary waves or basin modes, but when topography is present, no obvious wave propagation was identified. Higher‐frequency basin modes are detectable, but their amplitude is much lower than that in the flat‐bottomed case. They are damped out on a time scale of ∼50 days. Two longer experiments, 3 and 4, are then analyzed. These are the analogs of 1 and 2, but stratification was included. The introduction of stratification for the ocean with topography leads to a new, longer time scale, not just for the baroclinic modes, but also for the barotropic. Despite the presence of topography, modal analysis was found useful in analyzing the results. Propagation effects are analyzed, both on the moderately fast time scale of internal Kelvin waves and on the slow time scale of internal planetary waves. Kelvin waves are apparent along the equator, the northern boundary, and on the eastern coast in the Gulf of Guinea from the equator to 20°N. They are not clearly visible anywhere on the west coast. Planetary waves can be detected in the interior both in the presence and absence of topography. When topography is present without stratification, the transport of the Gulf Stream is reduced from 30 to 14 million tons per second. This is a well‐known result. With stratification there is no significant difference in transport between the case with or without topography.

ELECTRON MICROSCOPY OF ABSORPTION OF TRACER MATERIALS BY TOAD URINARY BLADDER EPITHELIUM.

The absorption of Thorotrast and saccharated iron oxide by the epithelium of the toad urinary bladder was studied by electron microscopy. Whether the toads were hydrated, dehydrated, or given Pitressin, no significant differences in transport of colloidal particles by epithelial cells were observed. This implies that these physiological factors had little effect on the transport of the tracer particles. Tracer particles were encountered in three types of epithelial cells which line the bladder lumen, but most frequently in the mitochondria-rich cells. Tracer materials were incorporated into the cytoplasm of epithelial cells after being adsorbed to the coating layer covering the luminal surface of the cells. In the intermediate stage (1 to 3 hours after introducing tracer) particles were present in small vesicles, tubules, and multivesicular bodies. In the later stages (up to 65 hours), the particles were more commonly seen to be densely packed within large membrane-bounded bodies which were often found near the Golgi region. These large bodies probably were formed by the fusion of small vesicles. Irrespective of the stages of absorption, no particles were found in the intercellular spaces or in the submucosa. Particles apparently did not penetrate the intercellular spaces of the epithelium beyond the level of the tight junction.