Electrical Resistivity Measurements Research Articles

Synthesis and Physical Properties of the Misfit Layered Compound (EuS)1.13(NbSe2)2.

A new misfit layered compound with the stoichiometry (EuS)1+δ(NbSe2)2 (δ ≈ 0.13) has been successfully synthesized. High-resolution transmission electron microscopy and powder X-ray diffraction confirm the misfit structure with (EuS)-(EuS) spacing of 18.30(1) Å. Magnetization, electrical resistivity, heat capacity, and thermal transport measurements show that the material is a heavily doped semiconductor or poor metal with a low thermal conductivity of ∼1 W/m K and an antiferromagnetic ordering transition at TN = 4.7 K. In contrast to the parent materials, the misfit is neither ferromagnetic nor superconducting down to T = 0.4 K. We find evidence of a field-driven transition to a ferromagnetic state due to reorientation of ferromagnetic EuS layers at μoH = 0.5 T at T = 2 K.

In situ Electrical Resistance Measurement of Pure Titanium during Severe Plastic Deformation by High‐Pressure Sliding

This study presents in situ measurements of electrical resistance in pure Ti during severe plastic deformation (SPD) under high pressures. The process of high‐pressure sliding (HPS) is adopted for the SPD so that straining is feasible under various pressures covering α to ω allotropic phase transformation in pure Ti. Anvil surfaces are coated by a plasma‐sprayed alumina layer to maintain electrical insulation between the sample and the anvils during HPS operation. The electrical resistance increases continuously with straining by the HPS processing but the increase in the electrical resistance is more pronounced as the applied pressure increases, particularly when the ω phase formation occurs. The phase transformation is evidenced by X‐ray diffraction analysis as well as in situ static heating experiment. The continuous increase in the electrical resistance suggests that there is neither critical strain nor avalanche for the phase transformation to the ω phase.This article is protected by copyright. All rights reserved.

Electrical resistivity and magnetoresistance of Sr3Fe2+xMo1–xO9–3x/2 (x = 0.45, 0.60, and 1.00) prepared by the solid-state reaction

In this paper, we focus on understanding the behavior of the temperature dependence of electrical resistivity (ρ) and magnetoresistance (MR) in Sr3Fe2+xMo1–xO9–3x/2 perovskites with x = 0.45, 0.60, and 1.00. Three polycrystalline materials were synthesized using conventional solid-state reaction techniques. Rietveld analysis of room-temperature X-ray diffraction data reveals that all three compositions crystallize in tetragonal symmetry; where x = 0.45 and 0.60 undergo an I4/mcm space group, while x = 1.00 adopts a P4/mmm space group. Electrical resistivity measurements carried out at magnetic fields (0 and 1 T) reveal the presence of a transition from the ferromagnetic phase to the paramagnetic phase in the vicinity of the TMI. The metal-insulator transition temperature (TMI) decreases with increasing Fe content and rises slightly with changing magnetic field from 0 to 1 T. The magnetoresistance (MR) of the SrFeO3–δ sample (x = 1.00) has a large value of about 63.6%, indicating that it can be exploited for certain devices. A variety of theoretical models are used to study the behavior of electrical resistivity in various temperature ranges, showing excellent agreement with experimental results.

The barrier-protective effect of β-eudesmol against type 2-inflammatory cytokine-induced tight junction disassembly in airway epithelial cells.

Allergic inflammation, which is the pathogenesis of allergic rhinitis and asthma, is associated with disruption of the airway epithelial barrier due to the effects of type 2 inflammatory cytokines, i.e. interleukin-4 and interleukin-13 (IL-4/13). The anti-allergic inflammatory effect of β-eudesmol (BE) on the tight junction (TJ) of the airway epithelium has not previously been reported. Herein, the barrier protective effect of BE was determined by measurement of transepithelial electrical resistance and by paracellular permeability assay in an IL-4/13-treated 16HBE14o- monolayer. Pre-treatment of BE concentration- and time- dependently inhibited IL-4/13-induced TJ barrier disruption, with the most significant effect observed at 20 μM. Cytotoxicity analyses showed that BE, either alone or in combination with IL-4/13, had no effect on cell viability. Western blot and immunofluorescence analyses showed that BE inhibited IL-4/13-induced mislocalization of TJ components, including occludin and zonula occludens-1 (ZO-1), without affecting the expression of these two proteins. In addition, the mechanism of the TJ-protective effect of BE was mediated by inhibition of IL-4/13-induced STAT6 phosphorylation, in which BE might serve as an antagonist of cytokine receptors. In silico molecular docking analysis demonstrated that BE potentially interacted with the site I pocket of the type 2 IL-4 receptor, likely at Asn-126 and Tyr-127 amino acid residues. It can therefore be concluded that BE is able to prevent IL-4/13-induced TJ disassembly by interfering with cytokine-receptor interaction, leading to suppression of STAT6-induced mislocalization of occludin and ZO-1. BE is a promising candidate for a therapeutic intervention for inflammatory airway epithelial disorders driven by IL-4/13.

How do Porosity, Size and Interconnectivity of Pores Influence The Values of the Archie Equation Exponents in Carbonate and Sandy Rocks?

Objective: The aim of this study is to investigate the exponents of the Archie equation in order to support the evaluation of hydrocarbon or groundwater reserves through electrical resistivity measurements of subsurface rocks.   Theoretical Framework: The Archie equation describes the relationship between the electrical resistivity of a rock and its water saturation and depends on the cementation (m) and saturation (n) exponents. Several authors state that electrical resistivity and the exponents m and n depend on the size, geometry, and connectivity of the pores.   Method: This article applies the finite element method to simulate the propagation of the electric field in digital rock models and thus evaluate the Archie exponents.   Results and Discussion: Our results indicate that the relationship between these exponents and pore attributes is different for values below or above a threshold. The variables with the greatest influence on m are the porosity of macropores and their interconnectivity, as well as the volumetric fraction of the microporous phase. As for the saturation exponent, the variables with the greatest influence are the porosity of macropores and the interconnectivity of both potentially conductive domains.   Research Implications: The practical and theoretical implications of this research are discussed, providing insights into how the results can be applied or influence practices in the field of underground natural resource assessment. These implications may cover the sectors of hydrocarbon production, groundwater, geo-environmental investigations, and geotechnical studies.   Originality/Value: This study contributes to the literature by presenting an innovative method for determining the exponents of the Archie equation. The relevance and value of this research are evidenced by its high economic impact on the aforementioned sectors and by its applicability anywhere.

A three-probe method for accurate nanoscale thermal transport measurements

Measurements of transport phenomena are constantly plagued by contact resistance, prohibiting the sample's intrinsic electrical or thermal conductivity from being accurately determined. This predicament is particularly severe in thermal transport measurements due to the inability to meet similar impedance requirements for a four-probe method used in electrical resistance measurements. Here, we invent a three-probe measurement method that makes an accurate determination of thermal conductivity possible for nanomaterials. Incorporating electron beam heating provided by a scanning electron microscope (SEM) on a diffusive thermal conductor not only quantifies the thermal contact resistance, which may introduce an error of more than 270% to a sample's thermal conductivity, but also eliminates several device uncertainties that may contribute an additional 17% error in a measurement. The method also enables local temperature measurements, revealing nanoscale structural variations unfound by SEM. The high accuracy of the technique would make standardization of nanoscale thermal transport measurement possible.

From Insulator to Superconductor: A Series of Pressure-Driven Transitions in Quasi-One-Dimensional TiS3 Nanoribbons.

Transition metal trichalcogenides (TMTCs) offer remarkable opportunities for tuning electronic states through modifications in chemical composition, temperature, and pressure. Despite considerable interest in TMTCs, there remain significant knowledge gaps concerning the evolution of their electronic properties under compression. In this study, we employ experimental and theoretical approaches to comprehensively explore the high-pressure behavior of the electronic properties of TiS3, a quasi-one-dimensional (Q1D) semiconductor, across various temperature ranges. Through high-pressure electrical resistance and magnetic measurements at elevated pressures, we uncover a distinctive sequence of phase transitions within TiS3, encompassing a transformation from an insulating state at ambient pressure to the emergence of an incipient superconducting state above 70 GPa. Our findings provide compelling evidence that superconductivity at low temperatures of ∼2.9 K is a fundamental characteristic of TiS3, shedding new light on the intriguing high-pressure electronic properties of TiS3 and underscoring the broader implications of our discoveries for TMTCs in general.

Electrical Resistivity and Phase Evolution of Fe–N Binary System at High Pressure and High Temperature

Partitioning experiments and the chemistry of iron meteorites indicate that the light element nitrogen could be sequestered into the metallic core of rocky planets during core–mantle differentiation. The thermal conductivity and the mineralogy of the Fe–N system under core conditions could therefore influence the planetary cooling, core crystallization, and evolution of the intrinsic magnetic field of rocky planets. Limited experiments have been conducted to study the thermal properties and phase relations of Fe–N components under planetary core conditions, such as those found in the Moon, Mercury, and Ganymede. In this study, we report results from high-pressure experiments involving electrical resistivity measurements of Fe–N phases at a pressure of 5 GPa and temperatures up to 1400 K. Four Fe–N compositions, including Fe–10%N, Fe–6.4%N, Fe–2%N, and Fe–1%N (by weight percent), were prepared and subjected to recovery experiments at 5 GPa and 1273 K. These experiments show that Fe–10%N and Fe–6.4%N form a single hexagonal close-packed phase (ɛ-nitrides), while Fe–2%N and Fe–1%N exhibit a face-centered cubic structure (γ-Fe). In separate experiments, the resistivity data were collected during the cooling after compressing the starting materials to 5 GPa and heating to ~1400 K. The resistivity of all compositions, similar to the pure γ-Fe, exhibits weak temperature dependence. We found that N has a strong effect on the resistivity of metallic Fe under rocky planetary core conditions compared to other potential light elements such as Si. The temperature-dependence of the resistivity also revealed high-pressure phase transition points in the Fe–N system. A congruent reaction, ε ⇌ γ’, occurs at ~673 K in Fe–6.4%N, which is ~280 K lower than that at ambient pressure. Furthermore, the resistivity data provided constraints on the high-pressure phase boundary of the polymorphic transition, γ ⇌ α, and an eutectoid equilibrium of γ’ ⇌ α + ε. The data, along with the recently reported phase equilibrium experiments at high pressures, enable construction of a phase diagram of the Fe–N binary system at 5 GPa.

Cryopreservation and Rapid Recovery of Differentiated Intestinal Epithelial Barrier Cells at Complex Transwell Interfaces Is Enabled by Chemically Induced Ice Nucleation.

Cell-based models, such as organ-on-chips, can replace and inform in vivo (animal) studies for drug discovery, toxicology, and biomedical science, but most cannot be banked "ready to use" as they do not survive conventional cryopreservation with DMSO alone. Here, we demonstrate how macromolecular ice nucleators enable the successful cryopreservation of epithelial intestinal models supported upon the interface of transwells, allowing recovery of function in just 7 days post-thaw directly from the freezer, compared to 21 days from conventional suspension cryopreservation. Caco-2 cells and Caco-2/HT29-MTX cocultures are cryopreserved on transwell inserts, with chemically induced ice nucleation at warmer temperatures resulting in increased cell viability but crucially retaining the complex cellular adhesion on the transwell insert interfaces, which other cryoprotectants do not. Trans-epithelial electrical resistance measurements, confocal microscopy, histology, and whole-cell proteomics demonstrated the rapid recovery of differentiated cell function, including the formation of tight junctions. Lucifer yellow permeability assays confirmed that the barrier functions of the cells were intact. This work will help solve the long-standing problem of transwell tissue barrier model storage, facilitating access to advanced predictive cellular models. This is underpinned by precise control of the nucleation temperature, addressing a crucial biophysical mode of damage.

A probabilistic interpretation of corrosion state through half-cell potential and electrical resistivity measures: The Flaminio Bridge in Rome

During the last decades, non-destructive investigation approaches have played an essential role in preserving structural integrity, capacity, and finding early defects in reinforced concrete (RC) heritage affected by time-dependent degradation. One of the most widespread structural RC damages belongs to corrosion phenomena. Electro-chemical approaches stand out among the non-destructive techniques presently available for identifying corrosive problems in-situ. The latter gives some knowledge in terms of physical quantities aiming to evaluate structural conditions by collecting indirect measures. Nevertheless, results are correlated to strong interpretative scale codes, which may not always provide appropriate interpretation of the defect's identity. In the paper a probabilistic degradation model, based on a statistical interpretation of the in situ electro-chemical measurements, has been proposed with the aim to give a contribution for structural diagnosis. Finally, results are validated through structural visual inspection.

A 3D bioprinted hydrogel gut-on-chip with integrated electrodes for transepithelial electrical resistance (TEER) measurements

Conventional gut-on-chip (GOC) models typically represent the epithelial layer of the gut tissue, neglecting other important components such as the stromal compartment and the extracellular matrix (ECM) that play crucial roles in maintaining intestinal barrier integrity and function. These models often employ hard, flat porous membranes for cell culture, thus failing to recapitulate the soft environment and complex 3D architecture of the intestinal mucosa. Alternatively, hydrogels have been recently introduced in GOCs as ECM analogs to support the co-culture of intestinal cells in in vivo-like configurations, and thus opening new opportunities in the organ-on-chip field. In this work, we present an innovative GOC device that includes a 3D bioprinted hydrogel channel replicating the intestinal villi architecture containing both the epithelial and stromal compartments of the gut mucosa. The bioprinted hydrogels successfully support both the encapsulation of fibroblasts and their co-culture with intestinal epithelial cells under physiological flow conditions. Moreover, we successfully integrated electrodes into the microfluidic system to monitor the barrier formation in real time via transepithelial electrical resistance measurements.

Improved humidity sensing performances of boron doped ZnO nanostructured thin films depending on boron concentration

Abstract This study details the production and analysis of undoped zinc oxide (uZnO) and boron (B) doped zinc oxide nanostructured thin films, with a specific focus on assessing the influence of varying B doping concentrations on humidity sensing performance. The synthesis of undoped ZnO and B doped ZnO nanoparticles was carried out using sol–gel method. B doping concentrations within the ZnO lattice were adjusted to 1, 3, 4, 5, and 10 mol%. Subsequently, nanostructured thin films were obtained through the spin coating technique on glass substrates. X-ray diffraction analysis revealed a hexagonal wurtzite structure for all nanostructured thin films. Notably, a change in preferential orientation from the (002) plane to the (100) plane occurred when B doping concentration exceeded 5 mol%. Scanning electron microscopy showcased nano-sized grains and capillary nanopores on the surface of each thin film. Energy dispersive X-ray spectra confirmed the presence of zinc, oxygen, and boron elements in the nanostructured thin films. Humidity sensing performance was assessed through electrical resistance measurements in the range of 45%–90% relative humidity at room temperature. All fabricated sensors exhibited sensitivity to humidity. Remarkably, the sensor with a 5 mol% B doping concentration demonstrated the highest humidity sensitivity (438.44 times) and the fastest response (2.0 s) and recovery times (14.2 s). The study concluded that the optimal B doping concentration for designing a highly efficient humidity sensor was determined to be 5 mol%. Overall, the study underscores the potential of B doped ZnO nanostructures for humidity sensor applications, given their exceptional sensor performance.

Resistivity and chloride diffusion coefficient of cement-based materials characterized by non-contact electrical resistivity method and resistivity model

The present study involves the application of the non-contact electrical resistivity measurement (NC-ERM) as a non-destructive method to continuously and in-situ measure the resistivity changes of cement-based materials. The NC-ERM was enhanced and utilized to evaluate the resistivity of the materials, and the steady-state chloride diffusion coefficients of various types of cement-based materials were experimentally determined. The results revealed that the highest resistivity was observed in mortar with a sand-to-cement ratio of 1.0 and concrete with an aggregate-to-cement ratio of 0.6, and the steady-state chloride diffusion coefficient increased with the concentration of the pore solution. Furthermore, a novel multi-level series-parallel model was developed to predict the resistivity and steady-state chloride diffusion coefficient of cement-based materials, with calculated values differing by 5% or less. The calculated chloride diffusion coefficient closely matched the value obtained from NC-ERM, indicating the satisfactory accuracy of the non-destructive experiment and theoretical calculation model.

Surface treatment of TaN for sub-2 nm, smooth, and conducting atomic layer deposition Ru films

Atomic layer deposition (ALD) of ruthenium (Ru) is being investigated for next generation interconnects and conducting liners for copper metallization. However, integration of ALD Ru with diffusion barrier refractory metal nitrides, such as tantalum nitride (TaN), continues to be a challenge due to its slow nucleation rates. Here, we demonstrate that an ultraviolet-ozone (UV-O3) pretreatment of TaN leads to an oxidized surface that favorably alters the deposition characteristics of ALD Ru from islandlike to layer-by-layer growth. The film morphology and properties are evaluated via spectroscopic ellipsometry, atomic force microscopy, electrical sheet resistance measurements, and thermoreflectance. We report a 1.83 nm continuous Ru film with a roughness of 0.19 nm and a sheet resistance of 10.8 KΩ/□. The interface chemistry between TaN and Ru is studied by x-ray photoelectron spectroscopy. It is shown that UV-O3 pretreatment, while oxidizing TaN, enhances Ru film nucleation and limits further oxidation of the underlying TaN during ALD. An oxygen “gettering” mechanism by TaN is proposed to explain reduced oxygen content in the Ru film and higher electrical conductivity compared to Ru deposited on native-TaN. This work provides a simple and effective approach using UV-O3 pretreatment for obtaining sub-2 nm, smooth, and conducting Ru films on TaN surfaces.

Epitaxial growth and characterization of (110)-oriented YBCO/PBCGO bilayer and YBCO/PBCGO/YBCO trilayer heterostructures

We have grown and characterized (110)-oriented YBa2Cu3O7−x (YBCO)/PrBa2(Cu0.8Ga0.2)3O7−x (PBCGO) bilayer and YBCO/PBCGO/YBCO trilayer heterostructures, which were deposited by pulsed laser deposition technique for the nanofabrication of (110)-oriented YBCO-based superconductor (S)/insulator (I)/superconductor (S) tunneling vertical geometry Josephson junction and other superconductor electronic devices. The structural properties of these heterostructures, investigated through various x-ray diffraction techniques (profile, x-ray reflectivity, pole figure, and reciprocal mapping), showed (110)-oriented epitaxial growth with a preferred c-axis-in-plane direction for all layers of the heterostructures. The atomic force microscopy measurement on the top surface of the heterostructures showed crack-free and pinhole-free, compact surface morphology with about a few nanometer root mean square roughness over the 5 × 5 μm2 region. The electrical resistivity measurements on the (110)-direction of the heterostructures showed superconducting critical temperature (Tc) values above 77 K and a very small proximity effect due to the interfacial contact of the superconducting YBCO layers with the PBCGO insulating layer. Raman spectroscopy measurements on the heterostructures showed the softening of the Ag-type Raman modes associated with the apical oxygen O(4) and O(2)-O(3)-in-phase vibrations compared to the stand-alone (110)-oriented PBCGO due to the residual stress and additional two Raman modes at ∼600 and ∼285 cm−1 frequencies due to the disorder at the Cu–O chain site of the PBCGO. The growth process and structural, electrical transport, and Raman spectroscopy characterization of (110)-oriented YBCO/PBCGO bilayer and YBCO/PBCGO/YBCO trilayer heterostructures are discussed in detail.

Impact of Micro- and Nano-Plastics on Human Intestinal Organoid-Derived Epithelium.

The development of patient-derived intestinal organoids represents an invaluable model for simulating the native human intestinal epithelium. These stem cell-rich cultures outperform commonly used cell lines like Caco-2 and HT29-MTX in reflecting the cellular diversity of the native intestinal epithelium after differentiation. In our recent study examining the effects of polystyrene (PS), microplastics (MPs), and nanoplastics (NPs), widespread pollutants in our environment and food chain, on the human intestinal epithelium, these organoids have been instrumental in elucidating the absorption mechanisms and potential biological impacts of plastic particles. Building on previously established protocols in human intestinal organoid culture, we herein detail a streamlined protocol for the cultivation, differentiation, and generation of organoid-derived monolayers. This protocol is tailored to generate monolayers incorporating microfold cells (M cells), key for intestinal particle uptake but often absent in current in vitro models. We provide validated protocols for the characterization of MPs/NPs via scanning electron microscopy (SEM) for detailed imaging and their introduction to intestinal epithelial monolayer cells via confocal immunostaining. Additionally, protocols to test the impacts of MP/NP exposure on the functions of the intestinal barrier using transendothelial electrical resistance (TEER) measurements and assessing inflammatory responses using cytokine profiling are detailed. Overall, our protocols enable the generation of human intestinal organoid monolayers, complete with the option of including or excluding M cells, offering crucial techniques for observing particle uptake and identifying inflammatory responses in intestinal epithelial cells to advance our knowledge of the potential effects of plastic pollution on human gut health. These approaches are also amendable to the study of other gut-related chemical and biological exposures and physiological responses due to the robust nature of the systems. © 2024 Wiley Periodicals LLC. Basic Protocol 1: Human intestinal organoid culture and generation of monolayers with and without M cells Support Protocol 1: Culture of L-WRN and production of WRN-conditioned medium Support Protocol 2: Neuronal cell culture and integration into intestinal epithelium Support Protocol 3: Immune cell culture and integration into intestinal epithelium Basic Protocol 2: Scanning electron microscopy: sample preparation and imaging Basic Protocol 3: Immunostaining and confocal imaging of MP/NP uptake in organoid-derived monolayers Basic Protocol 4: Assessment of intestinal barrier function via TEER measurements Basic Protocol 5: Cytokine profiling using ELISA post-MP/NP exposure.

Structural and superconducting properties of non-stoichiometric Nb1+xSe2

The composition-dependent crystal and defect structures, and superconducting properties of Nb1+xSe2 (0 ≤ x ≤ 0.09) polycrystalline samples were revealed by x-ray diffraction, electrical resistivity, magnetization and specific-heat measurements. Stacking-disordered structures were characterized by gradually broadened and weakened (h0l) reflections: disordered 2Ha structure for x ≤ 0.04 and 2Hb + 3R mixed-layer structure for x ≥ 0.05. Superconducting transition temperature (Tc) is 7.3K in pristine NbSe2, which decreases with increasing the content of interstitial-Nb (Nbint), down to below 2K in x = 0.09. The lowered Tc originates from the decreased electron-phonon coupling and density of states at the Fermi level EF. Upper critical field μ0Hc2 of all samples evidently exceed the Pauli limit except for pristine NbSe2. μ0Hc2, irreversible field μ0Hirr and critical current density Jc are all raised in slight-Nbint samples compared with NbSe2. The enhancements are due to the increase in charge carrier scattering and vortex pinning by Nbint impurity and stacking disorders. These results indicate that minor nonmagnetic impurity doping could improve the current-carrying capacity under the premise of small impact on Tc, which thus is a promising strategy to develop high-field superconducting magnets.

A geophysical assessment for engineering performance of subgrade soils: a case study of the Ago-Iwoye/Ilishan road, South-Western Nigeria

Geophysical application of electrical resistivity method has been employed to differentiate subsurface target of interest from the encompassing strata along the Ago-Iwoye/Ilishan road in South-western Nigeria. However, a geological model which links variation in lithological characteristics of subgrade soils to the engineering performance of the road is yet to be a research subject. This research is a special geotechnical application of geophysics for revealing the subsurface disposition and predicting the stability state of subgrade materials. Field assessment of rock types, and their relationship was followed by electrical resistivity measurement along the road. Schlumberger and dipole – dipole arrays were adopted for fifty-eight (58) Vertical Electrical Sounding (VES) and 2-D resistivity imaging involving Dipole-Dipole profiling technique was adopted in the sedimentary segment. Field data were inverted to 2-D resistivity structures inferentially delineated contour colorations using ‘DIPRO for Windows’ software. Geo-electric layers revealed Sedimentary Basin (SB) between Ilishan and Irolu, between Irolu and Ijesha-Ijebu, Transitional Zone (TR) with abrupt contrast along the plane of an unconformity and crystalline Basement Complex (BC) towards Ago-Iwoye. The 2-D resistivity structures across the different geological terrains revealed with 50Ωm - 3289Ωm at SB,233Ωm - 8028Ωm at TZ and 8Ωm - 3009Ωm at BC. From geotechnical view, subgrade materials underlying the SB and TZ segments can be adjudged competent to sand and clayey sand units with minor occurrences of incompetent clay and sandy clay lenses. The occurrence of subsurface discontinuities at the BC end of TZof the road would adversely affect the pavement stability.

A thermally conductive Martian core and implications for its dynamo cessation.

Mars experienced a dynamo process that generated a global magnetic field ~4.3 (or earlier) to 3.6 billion years ago (Ga). The cessation of this dynamo strongly affected Mars' history and is expected to be linked to thermochemical evolution of Mars' iron-rich liquid core, which is strongly influenced by its thermal conductivity. Here, we directly measured thermal conductivities of solid iron-sulfur alloys to pressures relevant to the Martian core and temperatures to 1023 Kelvin. Our results show that a Martian core with 16 weight % sulfur has a thermal conductivity of ~19 to 32 Watt meter-1 Kelvin-1 from its top to the center, much higher than previously inferred from electrical resistivity measurements. Our modeled thermal conductivity profile throughout the Martian deep-mantle and core indicates a ~4- to 6-fold discontinuity across the core-mantle boundary. The core's efficient cooling resulting from the depth-dependent, high conductivity diminishes thermal convection and forms thermal stratification, substantially contributing to cessation of Martian dynamo.

Abstract 2125: The use of intestinal organoids as a preclinical screen to assess gastrointestinal (GI) toxicity and barrier integrity

Abstract Gastrointestinal (GI) toxicity is a common and often severe limiting factor in the development of antineoplastic drugs. Symptoms include diarrhoea, dehydration and ulceration which increase susceptibility to infection, partly due to damage of crypt and/or villus structures in the small intestine, impairing the barrier function. As novel targeted therapies are emerging, assessment of their potential GI toxicity remains crucial. Small intestinal (SI) organoids are 3D in vitro models of the epithelium which recapitulate the structure and function of the small intestine. We have further developed and validated the organoid model as a screening tool to predict GI toxicity and subsequent mucosal regeneration in four species: mouse, rat, dog and human. The culture conditions have been designed to mimic the stem cell niche and allow cell differentiation and proliferation to occur. All intestinal lineages were present in the organoids derived from each species and the epithelial hierarchy closely resembled that observed in vivo. The toxic effects of antineoplastic drugs on the organoids were assessed by quantification of the total cell viability upon treatment, coupled to morphometric analysis of the organoids (size, area, perimeter, and branching efficiency). Immunofluorescence and RNAseq can be used to identify the targeted cells and the toxicity mechanisms of the drugs. To further assess the effect of drugs on barrier integrity, we have developed transwell-grown cell monolayers derived from normal human small intestinal organoids. This model allows direct access to both apical and basal surfaces, which is not possible when using organoids where their geometry prevents access to the apical surface. The monolayer formation was followed by live imaging and Trans-Epithelial Electrical Resistance (TEER) measurements and treatments with toxic drugs were applied after TEER reached a plateau. The direct effect on barrier integrity was evaluated by TEER reduction, increased FITC-Dextran permeability and analysis of TJ proteins by immunofluorescence. Furthermore, effects on cell death were assessed by measuring the levels of Lactate Dehydrogenase (LDH) released into the medium by dying cells. In conclusion, our models provide an innovative in vitro solution to further study the toxic effects of drugs on the normal small intestine and to analyse direct effects on barrier integrity. The monolayer assay may also be useful for developing models of transient TJ impairment to improve the bioavailability of orally administered antineoplastic drugs. The model can be considered more representative of the normal intestine than transformed cell lines such as CaCo2. Citation Format: Valentina Ubertini, Sarah Hall, Frida Ponthan, James Wilson. The use of intestinal organoids as a preclinical screen to assess gastrointestinal (GI) toxicity and barrier integrity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2125.