Structural and electrical behavior of Ag nanolayer grown on graphene-doped ZrO2 sheet

This work presents a novel tape‐casting method for producing flexible, graphene‐enhanced diatomite ceramic sheets. These sheets target dielectric substrates for applications in the critical yet under‐explored, high‐frequency range. Structural and morphological analyses confirmed the incorporation of graphene nanoplatelets into the ceramics matrix, validating the efficiency of the tape‐casting process. The results show the crucial role of the composite's crystalline structure in its dielectric response, where oxygenated functional groups within the graphene nanoplatelets act as intrinsic barriers to restrict leakage current, resulting in low dielectric loss. Doping of flexible ceramic plates with graphene nanoplatelets led to significant dielectric variations of approximately 100% over a wide frequency range. The capacitance increased by 215.35 with the addition of 10 wt. graphene compared to pure diatomite. Our results demonstrate the ability to adapt the framework's structural, morphological, and dielectric properties through doping with graphene in diatomite, offering promising prospects for applying flexible ceramic sheets at high frequency.

Laminated carbon fiber reinforced polymer (CFRP) composites have been used in many aircraft components. Because it is quite difficult to detect delamination cracking visually, many cracking monitoring methods have been proposed. One of these methods is the self-sensing method, where electrical resistance change is used to detect the damage to the laminated CFRP. For a thick CFRP plate, however, a delamination crack is usually accompanied by a dent. The dent causes a decrease in the electrical resistance of the CFRP plate. Although dent monitoring using this decrease in electrical resistance has been proposed, it is also important to clarify the mechanism of the decrease in electrical resistance. In this study, therefore, experimental investigations were undertaken to understand the mechanism of the decrease in electrical resistance induced by the dent. An elastic-plastic finite element analysis was also performed to confirm the material deformation under the dent. We found that a decrease in the fiber spacing in the thickness direction caused by plastic deformation causes contact between the fibers, and this causes the decrease in the electric resistance in the thickness direction.

The effect of polymerization kinetics and resin viscosity on the electrical response of a single carbon nanotube yarn (CNTY) embedded in a vinyl ester resin (VER) during polymerization was investigated. To analyze the effect of the polymerization kinetics, the concentration of initiator (methyl ethyl ketone peroxide) was varied at three levels, 0.6, 0.9, and 1.2 wt.%. Styrene monomer was added to VER, to reduce the polymer viscosity and to determine its effect on the electrical response of the CNTY upon resin wetting and infiltration. Upon wetting and wicking of the CNTY by VER, a transient decrease in the CNTY electrical resistance (ca. −8%) was observed for all initiator concentrations. For longer times, this initial decrease in electrical resistance may become a monotonic decrease (up to ca. −17%) or change its trend, depending on the initiator concentration. A higher concentration of initiator showed faster and more negative electrical resistance changes, which correlate with faster gel times and higher build-up of residual stresses. An increase in styrene monomer concentration (reduced viscosity) resulted in an upward shift of the electrical resistance to less negative values. Several mechanisms, including wetting, wicking, infiltration, electronic transfer, and shrinkage, are attributed to the complex electrical response of the CNTY upon resin wetting and infiltration.

Cockroach extract antigen increases bronchial airway epithelial permeability.

N,N′-bis(dichloroacetyl)-1,12-diaminododecane is a potent inhibitor of microsomal drug metabolism and also uncouples succinate-linked mitochondrial oxidative phosphorylation, apparently by promoting a transient permeability to anions. When added in very small concentrations to synthetic phospholipid bilayers made from a 1∶4∶4 mixture of purified cardiolipin, phosphatidylcholine, and phosphatidylethanolamine, the drug causes a rapid, transient decrease in electrical resistance with a return to an end-resistance somewhat lower than the initial one. The magnitude of the decrease was related to drug concentration. However, the drug produced a nontransitory, i.e. permanent decrease in resistance of bilayers made from pure phosphatidylcholine or cardiolipin. The 1∶4∶4 mixture of lipids, which closely resembles the lipid composition of the inner mitochondrial membrane yielded drug effects most closely resembling those observed in intact mitochondria. Transference number measurements on the 1∶4∶4 bilayer with an impressed KCl gradient revealed that the drug-induced decrease in electrical resistance was caused by an increase in the fraction of current carried by the anions in the system. The 1∶4∶4 phospholipid bilayer thus mimics the mitochondrial inner membrane in its response to this drug and indicates that the lipid composition of the lipid bilayer is a major determinant of at least some of its physical characteristics. The effect of varying the structure of the drug was also examined.

Self-sensing multifunctional composite has sensing function using electrical resistance changes. Carbon Fiber Reinforced Polymer (CFRP) composite is one of the self-sensing multifunctional composites. For the reliability of the self-sensing, electrical contact between the lead wire and the carbon fibers is the most important issue. The present study focuses on the effect of the cyclic loading of lower applied strain range than the fatigue damage level. As a result, the electrical contact resistance at the copper electrode increased with the increase of cycles. That means that the electrical change at the electrodes must be considered for the long-term self-sensing monitoring system. When a four-probe method is used to measure the electrical resistance, the contact resistance effect is minimized. Moreover, angle-ply laminates have plastic deformation caused by shear loading, and that causes electrical resistance decrease during the cyclic loading. Cross-ply laminates of CFRP composites have no electrical resistance increase without damage. Quasi-isotropic laminates of CFRP composites, however, have electrical resistance decrease with the increase of the number of cycles because of the plastic deformation of the angle-ply laminates.

The adhesive force generated by the interaction of integrin receptors with extracellular matrix (ECM) at the focal adhesion complex may regulate endothelial cell shape, and thereby the endothelial barrier function. We studied the role of focal adhesion kinase (FAK) activated by integrin signalling in regulating cell shape using cultured human pulmonary artery endothelial cells. We used FAK antisense oligonucleotide (targeted to the 3'-untranslated region of FAK mRNA (5'-CTCTGGTTGATGGGATTG-3') to determine the role of FAK in the mechanism of thrombin-induced increase in endothelial permeability. Reduction in FAK expression by the antisense augmented the thrombin-induced decrease in transendothelial electrical resistance (decrease in mock transfected cells of -43 +/- 1 % and in sense-transfected cells of -40 +/- 4 %, compared to the decrease in antisense-transfected cells of -60 +/- 3 %). Reduction in FAK expression also prolonged the drop in electrical resistance and prevented the recovery seen in control endothelial cells. Thus, the thrombin-induced increase in permeability is both greater and attenuated in the absence of FAK expression. Inhibition of actin polymerization with latrunculin-A prevented the translocation of FAK to focal adhesion sites and tyrosine phosphorylation of FAK and paxillin, and concomitantly reduced the thrombin-induced decrease in electrical resistance by approximately 50 %. Thus, the modulatory role of FAK on endothelial barrier function is dependent on actin polymerization. FAK translocation to focal adhesion complex in endothelial cells guided by actin cables and the consequent activation of FAK-associated proteins serve to reverse the decrease in endothelial barrier function caused by inflammatory mediators such as thrombin.

The effects of applied voltage and the duration of application upon human epidermal membrane (HEM) alterations and recovery were investigated. All experiments were conducted using a two-chamber diffusion cell with constant DC voltage (250-4000 mV) applied over a predetermined period, and HEM changes were monitored by measuring the electrical resistance before and after voltage termination. The key findings were that the rate of decrease in resistance was strongly dependent upon the applied voltage, the reversible recovery times were dependent upon both the magnitude and the duration of the applied field (frequently were several orders of magnitude greater than times for attaining significant resistance reduction), and reversible recovery times were much longer when lower voltages were applied for longer times to attain the same decrease in electrical resistance than for higher voltages at short times. These findings closely parallel those obtained on electrical breakdown/recovery of bilayer membranes (electroporation). The second part of this work examined the hypothesis that decreases in HEM electrical resistance induced by the applied voltage are accompanied by proportional increases in HEM permeability. A study was designed to test this hypothesis involving a four-stage protocol with HEM: passive transport, 250-mV iontophoresis, 2000-mV iontophoresis for 10 min, then back to 250-mV iontophoresis. The data obtained strongly support the view that the HEM alterations induced by the electric field result in pore formation and in the expected changes in HEM permeability.

ObjectivesThis study aims to propose a novel method to detect articular penetration of screws by relying on their electrical conductivity properties and control the validity of this method.Materials and methodsIn this ex vivo study, conducted between June 2017 and August 2017, we used five fresh sheep shoulder joints. First, the shoulder joint space was filled with saline solution. An insulated cannula was placed in the joint capsule, and a conductive wire was introduced into the joint via this cannula. A single titanium screw was inserted from the tuberculum majus into the posteroinferior quadrant of the humeral head under fluoroscopic observation. Conductivity was continuously measured using a digital multimeter. When a sudden decrease in conduction resistance was detected, fluoroscopic images were obtained in the anteroposterior (AP) and lateral directions. These images were assessed for penetration by a blinded surgeon. Penetration was confirmed by dissection of the joint.ResultsThere was a significant decrease in electrical resistance when screw penetration occurred (p<0.001). All penetration events were confirmed using our novel method. For all five of the specimens, either AP or lateral images could not be used to confirm penetration. For two of these specimens, penetration was undetectable in both AP and lateral fluoroscopic images, but a decrease in resistance was recorded.ConclusionThe described method exhibits greater sensitivity and accuracy for metal penetration to joint, and it is effective in detecting screws in the joints. The novel method described in this paper was applied in a prototype setting, and we believe that this concept can continue to be developed.

Short-circuit current (SCC) techniques were used to monitor the effects of various diuretic agents on Na+ transport in isolated frog skin, a model for the late distal tubule and the collecting duct of the mammalian kidney. Acetazolamide, hydrochlorothiazide, torasemide, and ethacrynic acid did not affect sodium transport (as indicated by the SCC) or transepithelial electrical resistance when added either to the apical (outer) or to the inner (basolateral, corial) bathing solution of the tissue. However, Na+ transport was sensitive to amiloride, the triamterene derivate dimethylamino-hydroxypropoxytriamterene (RPH 2823), and to furosemide. Whereas apical amiloride, and RPH 2823 induced a dose-dependent decrease in SCC and increase in transepithelial electrical resistance, apical furosemide resulted in a dose-dependent increase in SCC and a decrease in electrical resistance. None of the three diuretic agents caused a significant change in SCC when applied to the inner bathing Ringer's solution. The small furosemide-induced decrease in resistance compared with the huge increase in SCC suggests that furosemide affects Cl- permeability as well as Na+ permeability. Evidence for this notion was achieved by the following findings: The decrease in resistance after furosemide was more pronounced in tissues bathed in Cl(-)-free solutions compared with Cl(-)-containing solutions. n contrast, SCC stimulation by apical furosemide is Cl(-)-ion independent, but strongly Na+-ion dependent. SCC stimulation by furosemide is amiloride-sensitive. With respect to the onset, locus, and reversibility of action, it seems reasonable to assume that amiloride, RPH 2823, and furosemide all influence transepithelial Na+ transport by interacting with the Na+ channel or a regulator site of it within the apical membrane. The stoichiometry of the amiloride (RPH 2823)-receptor site interaction revealed Hill-coefficient(s) of less than 1, indicating a negative cooperativity among the receptor sites. The interaction between Na+ ions and amiloride or RPH 2823 displayed mixed competitive-noncompetitive inhibition. Taken together, these results support the hypothesis that amiloride and Na+ as well as RPH 2823 and Na+ may act at different loci on the apical entry mechanism in Rana esculenta skin.

We report on the influence of heat treatments on the electrical properties of ZnO films grown by molecular-beam epitaxy. We note that the electrical resistance of the ZnO films is significantly changed by the heat treatments: the electrical resistance increases with the increase of ambient temperature, but above a critical temperature the resistance decreases with the increase of temperature, irrespective of ambient gases. On the other hand, it is found that the large amount of photocurrent is generated in the ZnO films, exposed to white sources: the photocurrent decreases with the increase of the obtained resistance, and the current increases with the decrease of the resistance. Also, it is shown that the x-ray diffraction linewidth of the ZnO films is significantly decreased by the heat treatments. These indicate that the increase/decrease of the electrical resistance is ascribed to the annihilation/formation of the residual donor-type defects in the ZnO films by the heat treatments. It is suggested that the increase of the electrical resistance is due to the annihilation of Zni-complex defects, while the decrease of the electrical resistance is due to the formation of VO-complex defects.

Due to their electroconductive properties, flexible open-cell polyurethane foam/silver nanowire (PUF/AgNW) structures can provide an alternative for the construction of cheap pressure transducers with limited lifetimes or used as filter media for air conditioning units, presenting bactericidal and antifungal properties. In this paper, highly electroconductive metal-polymer hybrid foams (MPHFs) based on AgNWs were manufactured and characterized. The electrical resistance of MPHFs with various degrees of AgNW coating was measured during repeated compression. For low degrees of AgNW coating, the decrease in electrical resistance during compression occurs in steps and is not reproducible with repeated compression cycles due to the reduced number of electroconductive zones involved in obtaining electrical conductivity. For high AgNW coating degrees, the decrease in resistance is quasi-linear and reproducible after the first compression cycle. However, after compression, cracks appear in the foam cell structure, which increases the electrical resistance and decreases the mechanical strength. It can be considered that PUFs coated with AgNWs have a compression memory effect and can be used as cheap solutions in industrial processes in which high precision is not required, such as exceeding a maximum admissible load or as ohmic seals for product security.

An electrical resistance method was developed to measure volume changes in substratum-attached monolayer cultures. Astrocytes in primary monolayer cultures prepared from neonatal rat cerebral cortex were placed in a confined channel containing a balanced salt solution, and the electrical resistance of the channel was measured using an applied alternating current. If the volume of the cells increases, then the volume of the solution within the channel available for current flow decreases by the same amount, resulting in an increase in the measured resistance through the channel. If the volume of the cells decreases, a decrease in resistance would be recorded. This method allows continuous measurements of volume changes in real time. When primary astrocyte monolayers were exposed to hyposmotic solutions (93-193 mosmol/kgH2O), they showed a rapid initial swelling and, in the continued presence of hyposmotic media, a characteristic regulatory volume decrease (RVD) in which there was a return to normal cell volume within approximately 20 min. Astrocytes exposed to hyperosmotic media (343-493 mosmol/kgH2O) gave a decrease in electrical resistance, indicating shrinkage. Putative endogenous effectors of astrocytic swelling, such as high extracellular K+ and glutamate, resulted in a much slower onset of swelling and no sign of RVD. This system can reliably measure the average change in cell monolayer volume to 1-2% and thus provides a sensitive means of continuous measurements of changes in cell volume in monolayer cultures.

Graphene‐skinned fiber fabric is prepared by chemical vapor deposition (CVD) of continuous graphene on fabric, which enables conformal graphene coverage on fibers and inherits high electrical and thermal conductivity of graphene. However, in the fabric‐shaped configuration, high electrical and thermal contact resistances between fibers, and the lack of conductive and thermal pathways along radial direction of fibers limit the improvement of electrical and thermal conductivity. Herein, carbon nanotubes (CNTs), due to the 1D structure with excellent electrical and thermal conductivity, are introduced to build rich “bridges” to connect the isolated fibers to build new electron and phonon transport channels. Thus, the conceptual design of CNT/graphene‐skinned glass fiber fabric (CNT/GGFF) is creatively proposed and realized by a carefully designed CVD. Constructing the 3D electrically and thermally conductive network in CNT/GGFF leads to &gt;90% decrease of sheet resistance, 4.5 times increase of tensile strength, and &gt;70% decrease of thermal resistance compared with GGFF, making it promising for applications in composite materials, heat dissipation, and de‐icing. Moreover, the thermal resistance of CNT/GGFF exhibits temperature‐independent, extending applications to aviation and space because changes in thermal conductivity of traditional materials with environmental temperatures can adversely affect the thermal stability, reliability, and lifetime of aircrafts.

The effect of temporary longitudinal traction on the electrical resistance of cobalt was determined by a method similar to that already described in a former portion of this memoir, and it was found that, like nickel, this metal has its resistance decreased by moderate temporary stress, in spite of the changes of dimensions which ensue. Whether the decrease of resistance would be changed to increase, as it is with nickel, by a greater amount of stress, has not yet been ascertained, but should this be the case, the magnitude of the stress per unit area which would suffice for the purpose must be much greater with cobalt than with nickel. As with nickel, permanent extension and rolling diminish the effect of temporary longitudinal traction, so that there is a larger decrease of resistance caused by a given stress with annealed than with unannealed cobalt. Cobalt is remarkable for the extreme persistence with which the same load, when applied again, and again, continues to produce per­ manent increase of resistance, and probably increase of length, but for a moderate amount of permanent extension the increase of resistance is more than accounted for by the permanent increase of length and diminution of section which take place; so that, as with iron and nickel, the specific resistance is decreased by moderate permanent extension. The permanent decrease of specific resistance per unit for unit permanent increase of length is, for iron, cobalt, and nickel, 0.02, 1.44, and 2.37 respectively; thus the permanent decrease of specific resistance, as well as the temporary decrease of resistance, is greater with nickel than with cobalt.