Rise In Electrical Resistivity Research Articles

Investigating structural, optical, and electron-transport properties of lithium intercalated few-layer MoS2 films: Unraveling the influence of disorder

Molybdenum disulfide is a promising candidate for various applications in electronics, optoelectronics, or alkali-ion batteries. The natural presence of the van der Waals gap allows intercalating alkali ions, such as lithium, into MoS2 films. Intercalation can modify the electronic structure as well as the electrical and optical properties. Here, we present a structural, optical, and electrical characterization of Li-intercalated few-layer MoS2 films. The intercalation was carried out by annealing MoS2 film in the presence of Li2S powder, serving as a lithium source. The initial MoS2 layers were prepared by pulsed laser deposition (PLD) and by sulfurization of 1 nm thick Mo film (TAC). The presence of lithium was confirmed by synchrotron-based x-ray Photoelectron Spectroscopy. The Raman spectroscopy, x-ray diffraction, and optical absorption measurements confirmed semiconducting behavior for all samples. All samples exhibited the thermally activated dependence of the electrical resistance, R, typical for the Efros–Shklovskii variable range hopping in a disordered semiconductor, ln R(T) ∝ (TES/T)1/2, where kBTES is the hopping activation energy. The PLD-grown MoS2 samples exhibited a relatively mild initial disorder primarily caused by grain boundaries. Lithium intercalation led to an increase in disorder, evident in the increase in kBTES and a substantial rise in electrical resistance. The TAC-grown undoped MoS2 sample already exhibited significant resistance, and the impact of Li intercalation on resistance was minimal. This observation was attributed to the fact that the TAC-grown MoS2 samples exhibit a perturbed stoichiometry (the S:Mo ratio ∼ 2.20), causing strong disorder even before Li intercalation. The electron doping caused by lithium, if any, was completely obscured by the effect of disorder.

Electrical resistance of brain tissue during terminal ischemia

Terminal ischemia is characterized by several electrophysiological processes, including hyperpolarization, spreading depolarization (tSD), and negative ultraslow potentials (NUP) [1]. tSD is knowin to induce depolarization of neuron membranes to roughly 0 mV, accompanied by the influx of positive ions into cells, which results in the displacement of extracellular fluids into neurons, leading to cell swelling. In addition to the movement of extracellular fluid, cerebrospinal fluid flows into the perivascular region of the penetrating vessels. These processes result in a reduction of extracellular space and brain edema [2], which can elevate the likelihood of patient mortality up to 80% [3]. The decrease in extracellular space may lead to an upsurge in the electrical resistance of the tissue, enabling it to function as an important indicator of the anatomical and functional state of the brain during traumatic injuries and hemorrhages [4]. Our goal was to assess the resistance of the extracellular space in the rat’s barrel cortex by measuring voltage step amplitudes caused by current injection between the V1 cortex and the tail vein of an animal. We used 16-channel probes with iridium electrode sites and glass microelectrodes containing Ag/AgCl conductors filled with NaCl solution. We used a metal Ag/AgCl electrode as a reference, implanted in the cerebellum. The experimental animals were euthanized via inhalation of isoflurane at a lethal concentration. Isoflurane-induced respiratory arrest led to the subsequent development of a sequence of electrophysiological processes that included hyperpolarization, terminal spreading depression, and negative ultraslow potential. The NUP persisted throughout the entirety of the recording period (30–90 minutes), with a significant increase in extracellular space resistance occurring during this time. The rise in resistance began concurrently with the end of respiration. The resistance increased by 40 [23–57]% (median [25th–75th percentile], p=0.002, n=11) after 30 minutes of breath cessation, and by 46 [(–15)–64]% (p=0.109, n=8) after 60 minutes. The resistance demonstrated equivalent changes in all cerebral cortex depths. Additionally, the NUP amplitude following respiratory arrest had a correlation with the increase of voltage step amplitudes at 30 minutes (R=–0.713, p=0.014). The resistances measured using signals from both Ag/AgCl- and Ir electrodes did not vary in any of the experiments conducted (p=1, n=5). Thus, the rise in electrical resistance in brain tissue was shown to initiate at the point of respiratory arrest in the animal and progresses alongside the terminal processes in the cerebral cortex. This correlation is specifically linked to the fluctuations in the negative ultraslow potential. In tDS and NUP, a significant increase in tissue edema occurs due to the movement of water from the extracellular spaces into the cells, which leads to a decrease in extracellular space volume and an increase in resistance. The process can last for several minutes and is characterized by a continuous increase in voltage step amplitudes. These results suggest that tissue resistance increases during focal ischemia, as SD and NUP are also present during the formation of the ischemic focus [5].

Detection of Ice Formation With the Polymeric Mixed Ionic‐Electronic Conductor PEDOT: PSS for Aeronautics

AbstractIce formation detection is important in telecommunications and aeronautics, e.g., ice on the wings of an aircraft affects its aerodynamic performance and leads to fatal accidents. While many types of sensors exist, resistive sensors for ice detection have been poorly explored. They are however attractive because of their simplicity and the possibility to install an array of sensors on large areas to map the ice formation on wings. Hygroscopic ionic conductors have been demonstrated for resistive ice sensing but their high resistance prevents the readout of sensor arrays. In this work, mixed ionic‐electronic polymer conductors (MIEC) are considered for the first time for ice detection. The polymer blend poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) is solution deposited on a pair of electrodes. The sensor displays an abrupt rise in electrical resistance during the transition phase between water liquid to solid. It is proposed that the morphology and electronic transport in PEDOT are affected by the freezing event because the absorbed water in the PSS‐rich phase undergoes dilatation upon forming ice crystals. For the aeronautics application, successful tests of integration of sensing layer in pre‐preg layers of aeronautical grade and freezing detection are carried out to validate the ice detection principle.

Substitution driven ground states of Fe1-xCrxSi: A resistivity study

We report the electrical resistivity of Fe1-xCrxSi with nominal compositions of × = 0.0, 0.005, 0.025, 0.075, 0.1, 0.125, 0.15, 0.2, 0.5, 0.75 and 1. Composition-temperature (x-T) phase diagram is constructed based on the variation of electrical properties with substitution and temperature. The compositions below the critical concentration of metal-to-insulator transition (i.e., xc ∼ 0.02) are noticed to exhibit Kondo behaviour at low temperatures and semiconducting behaviour (due to activated charge carriers) at high temperature. Above xc, a gradual reduction of low temperature insulating phase is compensated by the enhancement of metallic phase. Additionally, the high temperature semiconducting phase is noticed to reduce with increasing x. For the compositions xc ≤ x < 0.5, the low temperature rise of electrical resistivity with the reduction of temperature is attributed to the magnetic correlations aided by localization effects. The two-band (metallic and semiconducting parallel conductive channels) analysis reveals the formation of impurity states and reduction of energy gap. Nevertheless, the compositions × ≥ 0.5 exhibit pseudo-gap behavior. The energy band gap of CrSi is found to be 0.320 ± 0.019 meV with a residual resistivity of 4.773 μΩ-cm.

3D analysis of the MT data for resistivity structure beneath the Ashute geothermal site, Central Main Ethiopian Rift (CMER)

The Ashute geothermal field (around Butajira) is located near the western rift escarpment of the Central Main Ethiopian Rift (CMER), about 5–10 km west of the axial part of the Silti Debre Zeit fault zone (SDFZ). Several active volcanoes and caldera edifices are hosted in the CMER. Most of the geothermal occurrences in the region are often associated with these active volcanoes. The magnetotelluric (MT) method has become the most widely used geophysical technique for the characterization of geothermal systems. It enables the determination of the subsurface electrical resistivity distribution at depth. The high resistivity under the conductive clay products of hydrothermal alteration related to the geothermal reservoir is the main target in the geothermal system. The subsurface electrical structure of the Ashute geothermal site was analyzed using the 3D inversion model of MT data, and the results are endorsed in this work. The ModEM inversion code was used to recover the 3D model of subsurface electrical resistivity distribution. According to the 3D inversion resistivity model, the subsurface directly beneath the Ashute geothermal site can be represented by three major geoelectric horizons. On top, a relatively thin resistive layer (>100 Ωm) represents the unaltered volcanic rocks at shallow depths. This is underlain by a conductive body (< 10 Ωm), possibly associated with the presence of clay horizon (smectite and illite/chlorite zones), resulting from the alteration of volcanic rocks within the shallow subsurface. In the third bottom geoelectric layer, the subsurface electrical resistivity gradually increases to an intermediate range (10–46 Ωm). This could be related to the formation of high-temperature alteration minerals such as chlorite and epidote at depth, suggesting the presence of a heat source. As in a typical geothermal system, the rise in electrical resistivity under the conductive clay bed (products of hydrothermal alteration) may indicate the presence of a geothermal reservoir. Otherwise, no exceptional low resistivity (high conductivity) anomaly is detected at depth.

Enhancement of breakdown strength and electromigration reliability for cobalt lines lightly doped with boron

Conventional copper interconnect is facing a considerable rise in electrical resistivity for applications in nanoscale devices due mainly to its significant-high electron mean free path. Cobalt, a metal with a shorter electron mean free path, has been suggested as the most promising interconnecting material for the next-generation device. Thus, this work studies alloying cobalt film with a small amount of boron as an electromigration retarder without sacrificing its electrical conductivity through evaluating its electrical properties, electromigration resistance, bonding structure, and thermal stability. Examining composition of the boron lightly-doped cobalt films shows that it can be intentionally controlled by the deposition power, yielding the incorporating boron not significantly increasing its electrical resistivity. Additionally, boron incorporation strongly intensifies the breakdown strength and electromigration reliability of the cobalt film. However, boron addition leads to a higher surface energy, and thus causes a degradation of the thermal stability. Nevertheless, the studied boron lightly-doped cobalt film is still thermally stable up to 600 °C, making it a promising interconnecting material for application in nanoscale devices.

Dye-Sensitized Solar Cells Based on a New Type of Non-Volatile Co(II)/Co(III) Electrolyte Delivering Higher Power Conversion Efficiency for Indoor Applications

Background: Electrolyte is an essential constituent of a dye-sensitized solar cell (DSSC) as it mediates charge transport and regenerates the oxidized dye. Iodide/triiodide (I-/I3-) based electrolytes are the ones widely being used in DSSCs. These types of electrolytes are usually made by dissolving high concentrations of triiodide and polyiodide species in solvents, such as acetonitrile and methoxypropionitrile. These solvents face evaporation issues and lead to stability problems, which reduces the life span of the DSSC. For solving these issues, various types of electrolytes, such as ionic liquids and gelated liquid electrolytes, have been used to replace conventional volatile electrolytes. Objective: To solve the solvent evaporation issue and the electrical resistance rise, we aim to synthesis a non-volatile electrolyte with excellent open-circuit voltage and stability. Method: A new genre of nonvolatile Co(II)/Co(III) redox electrolyte was synthesized by the reaction of tris(2-(1H-pyrazol-1-yl)pyridine)cobalt(II) and tris(2-(1H-pyrazol-1-yl)pyridine) cobalt(III) with 2,4,6-tris(dodecyloxy)benzaldehyde. As a proof-of-principle experiment, a DSSC was fabricated using the as-synthesized electrolyte, N-719 dye as the light harvester, and TiO2 as the photoanode, and their performances were analyzed in room light conditions. Results: The DSSCs deliver a remarkable power conversion efficiency of 22.1%, an open circuit voltage of 1 V, and a power output of 88.5 μW cm–2 at 1000 lux, under illumination from a Deltron LED light. Conclusion: Cobalt-based non-volatile electrolytes are efficient candidates that can replace the conventional volatile electrolytes in DSSCs. Further research into this new type of electrolyte could pave ways to deliver high open-circuit voltage as well as good current density with high stability.

Highly efficient bismuth telluride–based thermoelectric microconverters

The flash evaporation method was used to fabricate high-performance p- and n-type Bi2Te3-based thermoelectric (TE) thin films. Optimized technological conditions of film preparation, as well as subsequent annealing, give the possibility to achieve a significant improvement in the TE properties of the designed TE films, which are state-of-the-art compared with bulk materials. Furthermore, a brand-new sandwich-layered design of the flexible film thermoelectric microconverter (FTEM) is offered here through the use of perforation cuts between p- and n-legs and a flexible polyimide substrate. Such a unique design makes it possible to avoid a rise in electrical resistance due to an increase in the number of elements in the microconverter. The dimensionless effective figure of merit ZT ≈0.6 (including losses due to parasite heat flux along with the substrate, radiation, and conversion) and TE efficiency ηmax ≈3.4% were achieved for the FTEM prototype at the temperature difference ΔT of 100 K (Tc = 300 K). Therefore, the use of flash evaporation technology offers the possibility to produce large-scale film TE devices with high efficiency. Moreover, the applicability of the developed FTEM is demonstrated for a thermal detector with a high output voltage, which is used to determine a weak heat flux up to ~10−7 W.

The effect of Sn-doping on optical, electrical and morphological properties of spray-pyrolysed ZnO films

The present work has investigated the effects of tin doping on morphological and optical-electrical properties of zinc oxide films produced by spray-pyrolysis technique. The films exhibited droplet impact marks along the surface. Top-view micrographs disclosed black clusters of non-decomposed salts after tin doing. These morphological aspects have not compromised optical performance although they may have contributed to the rise in electrical resistivity due to charge scattering on the surface. Electrical conductivity was lowered as tin-doping concentration increased. Tin ions occupied interstitial sites in the host matrix and acted as conventional defects. The film transmittance at 550 nm was not significantly affected by tin doping, yet a slight loss in transparency was observed after 1 at. % Sn doping. Optical bandgap was reduced from 3.25 to 3.16 eV due to deep states when doping with 1 at. % Sn. The optical bandgap widened to 3.23 eV with incorporation of 2 at. % Sn. This behaviour is attributed to the Burstein-Moss effect.

Failure analysis on over-temperature combustion of transformers in 4 MW offshore wind turbines

Abstract Wind power is one of the prevailing types of renewable energy, but the reliability of its components is always challenged by the severe service environment, especially on the offshore. Hence, case studies on failed components deserve to be publicly reported for experience sharing and failure prevention. In this event, severe degradations like combustion and abnormal electrical resistance rise were frequently detected on a large number of windings and lead bars within the transformers in 4 MW offshore wind turbines. To solve this problem, a series of characterization methods were utilized to investigate the assembly structure, matrix materials and macro/microscopic morphologies of the failed transformers. Temperature simulation experiment was also carried out to evaluate the normal operating conditions. The analysis results showed that risky factors induced from inappropriate installation, unreasonable design, unqualified fabrication and improper maintenance were the root causes for the failure. Finally, relevant mechanisms were discussed in detail and specific countermeasures were put forward.

Effect of Zr on magnetic properties and electrical resistivity of Sm(CobalFe0.09Cu0.09Zrx)7.68 magnets

In this work, the effect of Zr content on magnetic properties and electrical resistivity of Sm(CobalFe0.09Cu0.09Zrx)7.68 (x = 0.020, 0.025, 0.030, 0.035) high temperature magnets has been investigated. More Zr content results in the decrease of average cell size and the increase of the density of lamellar structure. In addition, a large number of phase boundaries between lamellar phase and cellular structure have also been formed. The intrinsic coercivity of 550 °C enhances from 3.21 kOe to 6.05 kOe with the increase of Zr content. Furthermore, electrical resistivity shows obviously different variation in different directions with increasing Zr content. At room temperature and 127 °C, the electrical resistivity improves from 68.2 μΩ cm to 91.7 μΩ cm and from 87.1 μΩ cm to 103.3 μΩ cm with increasing x from 0.020 to 0.035 in the direction parallel to c-axis, respectively. However, there is only a slight increase in the electrical resistivity in the direction perpendicular to c-axis. The rise of electrical resistivity in different directions has been discussed. Research results indicate that increasing the density of the lamellar phase is an effective way to increase electrical resistivity in the 2:17-type Sm-Co magnets.

Magnetotransport and magnetothermal properties of the ternary intermetallic compound TbFe2Al10

We have studied the temperature and field dependences of electrical resistivity and heat capacity of TbFe2Al10, and have also complimented the above studies with low field magnetization measurements. In zero magnetic field, TbFe2Al10 exhibits paramagnetic (PM) to ferrimagnetic (Ferri-I) and Ferri-I to antiferromagnetic (AFM) phase transitions below 17.6 and 10 K respectively. We have found that the electrical resistivity of TbFe2Al10 exhibits a sharp rise across the PM to Ferri-I phase transition in this compound. Our analysis indicates that this sharp rise of electrical resistivity is related to the formation of new zone boundaries (across the PM to Ferri-I phase transition) that reduce the area of the Fermi surface. We have found that TbFe2Al10 exhibits large magnetoresistance (MR) below 100 K. Overall, the MR behaviour of TbFe2Al10 below 17.6 K in different magnetic fields reveals strong competition between AFM and ferromagnetic (FM) correlations, which seems to be quite intrinsic to the magnetic structure of the compound. Our analysis indicates that the large MR and magnetocaloric effect persisting deep inside the PM regime of TbFe2Al10 is mainly related to the presence of FM spin fluctuations and the formation of a Griffiths like (GL) phase consisting of FM clusters within the PM regime. The formation of the GL phase may be mediated by the static crystal defects in the midst of the competing inter and intra layer magnetic interactions.

Fatigue life study of ITO/PET specimens in cyclic bending tests

A commercial micro-compression tester and a self-designed bending tester in reciprocating motion are adopted to study the fatigue resistance and thus fatigue life of indium tin oxide (ITO) films deposited on a poly(ethylene terephthalate) substrate with various prestrain levels. The fatigue life obtained from tests reflects the size-dependent fatigue behavior. Two points symmetric with respect to the specimen central line are marked on the specimens of these two testers in order to measure the film’s electrical resistance variation with the number of cycles in the bending tests. The fatigue life is obtained as the number of cycles in the bending test based on the number of cycles corresponding to a 63 % failure strain of the specimen. The electrical resistance change in a test with a sufficiently large number of cycles increases nonlinearly with the compression force. The mean value of the total lengths of microcracks formed at fixed locations in the ITO film is identified as a major factor in the electrical resistance rise (ΔR). The (622) peak intensity of the X-ray diffraction patterns slightly affects ΔR. The combined effect of the microcrack length and (622) peak intensity can explain the ΔR trend for the specimens with different substrate prestrain. The fatigue lives predicted using a 10 % rise in the initial electrical resistance and a 63 % Weibull strain percentile are compared and discussed.

Geometrical spin frustration in Pr5Ni2Si3 composed of triangular crystal lattices

We have studied the transport, magnetic and thermal properties of Pr5Ni2Si3 with complex triangular lattices under various magnetic fields. The ferromagnetic transitions in the basal plane were observed at TC1 = 52 K and TC2 = 65 K. A decrease in magnetization below 30 K and the reduced paramagnetic Curie temperature θP are indicative of the development of antiferromagnetic correlation. These features are well understood by the frustration effect of the magnetic moments of Pr ions which constitute the triangular structural unit. The frustration caused the rapid rise of electrical resistivity below 30 K and an enormous entropy in low-temperature regions. The antiferromagnetic correlation acting between the frustrated Pr ions never causes any long-range order down to 0.6 K.

Contamination Thresholds of Pt- and ${\rm RuO}_{2}$-Coated Ohmic Switches

Micro- and nano-mechanical switches are being considered as complements to solid state transistors. While several different device designs may satisfy performance requirements, contact reliability due to hydrocarbon contamination remains a critical concern in each. This issue can be addressed by identifying contact materials and environments that optimize immunity to contaminants. Here we demonstrate that RuO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , a conducting oxide, does not exhibit contaminant-induced degradation at up to 130 parts per million (PPM) benzene in a nitrogen/oxygen background, and experiences minimal electrical resistance rise at 1,300 PPM. In comparison, Pt-coated switches degrade significantly at only 0.02 PPM benzene contaminant level in nitrogen background. This paper establishes that a proper selection of materials and environment is a promising path toward achieving reliable micro- and nanoswitches.

Low-Resistivity Ru-Ta-C Barriers for Cu Interconnects

Ru-Ta-C films deposited on silicon substrates were evaluated as barriers for copper metalization. The films were prepared by magnetron cosputtering using a Ru target and a Ta-C target. Compositions and structure of resultant films were optimally tuned by the respective deposition power of each target. The fabricated Ru-Ta-C films were characterized via four-point probe measurement, x-ray diffractometry, field-emission electron probe microanalysis, and transmission electron microscopy. Failure temperature was evaluated by the sudden rise in electrical resistivity after annealing the Cu/Ru-Ta-C/Si sandwich films, and a reference bilayer Cu/(5 nm Ru)/(5 nm Ta-C)/Si scheme. The optimal compositions were 10 nm Ru77Ta15C7 and (5 nm Ru)/(5 nm Ta-C), both of which showed failure temperature of 650°C for 30 min and electrical resistivity less than 150 μΩ cm. Because of their high thermal stability and low electrical resistivity, both Ru-Ta-C and Ru/Ta-C films are promising barriers for Cu metalization.

Thermoelectric properties of rare earth–ruthenium–germanium compounds

We report our studies of the thermoelectric properties of a class of compounds of composition R3Ru4Ge13 (R=Y, Dy, Ho, and Lu). Magnetization measurements show that the R ion is in the trivalent state in each of these compounds. Each of these compounds displays a semiconductorlike rise in electrical resistivity with decreasing temperature. The magnitude of the resistivity is much larger than typical metals and is similar to that of a heavily doped semiconductor or semimetal. The Seebeck coefficient is positive throughout the temperature range of 2–800K with room temperature values of approximately 40μVK−1. The lattice thermal conductivity is remarkably low and exhibits a very flat temperature dependence. This is consistent with the observed internal disorder associated with the cagelike structure of these compounds. Cobalt substitution for ruthenium enhances the semiconductor character but does not improve the thermoelectric properties.

Normal-state dielectric and transport properties of In-doped Bi–Pb–Sr–Ca–Cu–O

The effect of indium doping on the normal-state transport and dielectric properties of the Bi 1.84Pb 0.34Sr 1.91Ca 2.03Cu 3.06In x O y (0≤ x≤0.15) has been investigated. The dielectric constant, loss tangent, carrier concentration and electrical resistivity were measured at room temperature as a function of indium concentration. The dielectric constant is found to increase with increasing dopant concentration possibly due to increase in polarization. Impurities in any crystalline lattice generally cause deformation of the surrounding volume and modification in the local fields. The loss tangent of the indium doped-system decreased with increasing dopant concentration. Decrease in the loss tangent with increase in the dopant concentration indicates the decrease in the dielectric losses in the sample during doping. The carrier concentration is found to decrease with increasing indium concentration. This could be due to charge imbalance, which leads to a decrease in the number of holes in the system. Consequently, the electrical resistivity at 50 °C increased with the dopant concentration. Also, above x=0.05 dopant concentration there was a rapid rise in electrical resistivity, possibly due to disorder in the Cu–O 2 planes. The temperature dependence of the electrical resistivity above room temperature is consistent with metallic behavior.

Pseudogap and transport properties inFe3−xVxAly(x=0.5–1.05;y=0.95,1.05)

We have measured the Hall resistivity for the intermetallic compound ${\mathrm{Fe}}_{3\ensuremath{-}x}{\mathrm{V}}_{x}{\mathrm{Al}}_{y}$ $(x=0.5--1.05;$ $y=0.95,1.05)$ at room temperature. The Hall coefficient changed its sign from positive to negative around the Heusler composition (i.e., $x=y=1)$ with increasing x value or decreasing y value. We have measured the temperature dependence of the Hall coefficient and the electrical resistivity for ${\mathrm{Fe}}_{1.98}{\mathrm{V}}_{1.02}\mathrm{Al}$ and quenched ${\mathrm{Fe}}_{1.95}{\mathrm{V}}_{1.05}\mathrm{Al}$ in the temperature range of 5--300 K. These two compounds showed very different behavior in the electrical resistivity but the behavior of the Hall coefficient was quite similar. At higher temperatures, the Hall coefficient showed a strong temperature dependence but it approached a constant value at low temperatures suggesting that these compounds are semimetals with a pseudogap. The charge carrier density was found to be less than a few tenths per unit cell. The rise of electrical resistivity at low temperatures is not owing to an energy gap but due to magnetic scattering while the negative temperature coefficient at high temperatures is attributable to pseudogap.

Platelet-conditioned medium increases endothelial electrical resistance independently of cAMP/PKA and cGMP/PKG.

Platelets release a soluble factor into blood and conditioned medium (PCM) that decreases vascular endothelial permeability. The objective of this study was to determine the signal-transduction pathway that elicits this decrease in permeability. Permeability-decreasing activity of PCM was assessed by the real-time measurement of electrical resistance across cell monolayers derived from bovine pulmonary arteries and microvessels. Using a desensitization protocol with cAMP/protein kinase A (PKA)-enhancing agents and pharmacological inhibitors, we determined that the activity of PCM is independent of PKA and PKG. Genistein, an inhibitor of tyrosine kinases, prevented the increase in endothelial electrical resistance. Because lysophosphatidic acid (LPA) has been proposed to be responsible for this activity of PCM and is known to activate the G(i) protein, inhibitors of the G protein pertussis toxin and of the associated phosphatidylinositol 3-kinase (PI3K) wortmannin were used. Pertussis toxin and wortmannin caused a 10- to 15-min delay in the characteristic rise in electrical resistance induced by PCM. Inhibition of phosphorylation of extracellular signal-regulated kinase with the mitogen-activated kinase kinase inhibitors PD-98059 and U-0126 did not prevent the activity of PCM. Similar findings with regard to the cAMP protocols and inhibition of G(i) and PI3K were obtained for 1-oleoyl-LPA. These results demonstrate that PCM increases endothelial electrical resistance in vitro via a novel, signal transduction pathway independent of cAMP/PKA and cGMP/PKG. Furthermore, PCM rapidly activates a signaling pathway involving tyrosine phosphorylation, the G(i) protein, and PI3K.