Junction resistance

Figure 11. Experimental and predicted differential conductance plots of the double-island device of Figure 10(b). (a) Differential conductance measured at 4.2 K four peaks are found per gate period. Above the threshold for the Coulomb blockade, the current can be described as linear with small oscillations superposed, which give the peaks in dljdVj s- The linear component corresponds to a resistance of 20 GQ. (b) Electrical modeling of the device. The silicon substrate acts as a common gate electrode for both islands, (c) Monte Carlo simulation of a stability plot for the double-island device at 4.2 K with capacitance values obtained from finite-element modeling Cq = 0.84aF (island-gate capacitance). Cm = 3.7aF (inter-island capacitance). Cl = 4.9 aF (lead-island capacitance) the left, middle and right tunnel junction resistances were, respectively, set to 0.1, 10 and 10 GQ to reproduce the experimental data. (Reprinted with permission from Ref [28], 2006, American Institute of Physics.)...

Fig. 21 The variation of the balancing tunneling current of the four branches four electrodes monomolecular Wheatstone bridge connected as presented in (a). In (b), the dashed line is for the current intensity 7W (in absolute value) measured by the ammeter A and deduced from the standard Kirchoff laws calculating each molecular wire tunneling junction resistance of the bridge one after the other from the EHMO-ESQC technique. In (b), Hie full line is the same tunnel current intensity but obtained with the new intramolecular circuit rules discussed in Sect. 2. (c) The resistance of the branch used to balance the bridge as a function of its rotation angle. The minimum accessible resistance by rotation is 78 MQ for the short tolane molecular wire used here...

Fry. In agreement with that would be the observation that acidosis increases the rate and alkalinity does the opposite. Acidosis would increase gap junction resistance, so if it was going to have to be through cell-cell coupling then you would expect the opposite result from what you got. To a certain extent that fits in with your supposition. What was the magnitude of the pH changes ... 

Gorodeski GI, Eckert RL, Pal D, Utian WH, and Rorke EA [1997] Retinoids regulate tight junctional resistance of cultured human cervical cells. Am J Physiol 273 C1707-C1713... 

Zeng R, Li X, and Gorodeski GI [2004] Estrogen abrogates transcervical tight junctional resistance by acceleration of Occludin modulation. J Clin Endocrinol Metab 89 5145-5155... 

Zhu L, Li X, Zeng R, and Gorodeski GI [2006] Changes in tight junctional resistance of the cervical epithelium are associated with modulation of content and phosphorylation of occludin 65 kDa and 50 kDa forms. Endocrinology... 

Jovov B, Lewis SA, Crowe WE, Berg JR, and Wills NK [1994] Role of intracellular Ca2+ in modulation of tight junction resistance in A6 cells. Am J Physiol 266 F775-F784... 

Gorodeski GI [2006] A new model of occludin regulation of tight-junctional resistance in low resistance epithelia. Medical Hypotheses and Research 3 769-784... 

Fig. 7 IjV characteristics for an 8-nm Co/0.6-nm Al203/1.6-nm Alqs/lO-nm NigoFe2o junction. The fit to the IjV curve is shown as the line through the data points. The inset shows the exponential dependence of the junction resistance (Sj) vs Alq3 thickness, for a total of 72 junctions made in a single deposition. Taken from [48] with permission...

Fig. 8 TMR for 8 nm Co/0.6nm Al203/1.6nm Alq3/10nmNlgoFe2o junction. In (a) the TMR was measured at a 10-mV bias. The inset shows the temperature dependence of the junction resistance and the chemical structure of the Alq3 molecule. In (b) the bias dependence of the TMR is shown. The inset in (b) is a cross-sectional high-resolution TEM image of the junction showing the continuous barrier. Taken from [48] with permission...

In Fig. 11 the change in the junction resistance (at 2 mV) is plotted as an external magnetic field which goes from 1,500 to —1,500 Oe (circles) and is then reversed from —1,500 to 1,500 Oe (triangles) with the sample held at 80 K. When the magnetic field is between 20 and 200 Oe, the magnetization direction of the LSMO layer becomes antiparaUel to the Co layer. Using the conventional definition of MR, defined as AR/R p = (Rap p)/ ap> where Rap is the junction resistance in... 

Fig. 12 (a) Temperature dependence of the magnetoresistance for the junction shown in Fig. 10. The inset shows the corresponding junction resistance vs temperature with no applied magnetic field, (b) Magnetoresistance as a function of applied DC bias at 11 K for the same device in (a). Taken from [50] with permission...

Fig. 16 (a) Schematic band diagram of Alq3 in between two ferromagnetic electrodes, (b) Valence band spectra for an increasing Alqa layer on AI2O3, where the characteristic occupied molecular orbitals are seen in the 3-nm film. Calculation of (c) junction resistance and TMR for two-step tunneling as a function of dj. (d) 1// as a function of d. Taken from [59] with permission... 

In crayfish septate axon, a more complex action of lowering pH has been described [Peracchia, 1991a] superfusion with Na-acetate led to a rapid increase in junctional resistance (Rj) with a concomitant fall in pi (, but the recovery curve for pi f was slower than that for Rj. A concomitant increase in intracellular [Ca2+] was observed so that it was concluded that the pHj effect on cellular uncoupling in crayfish septate axon is mediated by calcium. Thus, generalizations of the various mechanisms should be avoided and the specific experimental model has to be taken into account. 

In addition to ions, other small molecules have been described to play an important physiological and pathophysiological role in the regulation of gap junctional resistance. Thus, ATP acts as an important regulator. In 1979 Wojtcak described that hypoxia in glucose free solution resulted in a rise in Rj in cow ventricular trabeculae indicating that the intracellular ATP content... 

Acetylcholine is involved in many aspects of the regulation of the cardiovascular system. Thus, it may also play a role in the control of intercellular communication. Very early in gap junction research the effect of acetylcholine as an important transmitter on gap junction conductance has been investigated. First, Petersen and Ueda [1976] demonstrated an increase in junctional resistance in pancreatic acinar cells following the application of acetylcholine. Concomitantly, the release of amylase was stimulated. A minimum concentration of 1 pmol/l acetycholine was required to evoke uncoupling. The next question was, how is the acetylcholine effect mediated Calcium has been considered to contribute to the mechanism of action [Iwatsuki and Pertersen,... 

At these temperatures the distribution of occupied levels in the conduction bands ( the Fermi distributions ) in the two metal electrodes ( Fig.l ) are quite sharp, with a boundary between filled and empty states ( the Fermi level ) of characteristic width k T ( k =0.08617 meV/K=0.69503 cm Vk ). An applied bias voltage V between the two electrodes separates the Fermi levels by an energy eV. If the barrier oxide is sufficiently thin electrons can tunnel from one electrode to the other. This process is called tunneling since the electrons go through a potential barrier, rather than being excited over it. The barrier must be thin for an appreciable barrier to flow. For a typical 2 eV barrier the junction resistance is proportional to, where s is the barrier width in Angstroms (17). The... 

In this section, low resistance tunnel junctions prepared by natural oxidation [42-45] or remote plasma oxidation techniques [46] will be described, since up to now they have provided the lowest junction resistances, required to supplant spin valves for read head applications above 100-200 Gbit/in2. At the heart of tunnel junction fabrication lays the barrier fabrication. For read head applications, in the 100-300 Gbit/in2 region, junction resistance must be around 1 Qpm2 [47-51]. Figure 9(a) shows a TEM micrograph for a 1 nm thick AlHfOx low RA barrier [52],... 

Figure 22. (Top) measured zero field values of the junction resistance and (bottom) sequence of applied magnetic fields and the position of the 20 ns heating pulses of 2 V.

Now suppose an external electrical potential is applied by connecting the negative terminal of a battery to the p-type region and the positive terminal to the n-type region. The situation represented in Fig. 16.34(b) results. Electrons are drawn toward the positive terminal, and the resulting holes move toward the negative terminal—exactly opposite to the natural flow of electrons at the p-n junction. The junction resists the imposed current flow in this direction and is said to be under reverse bias. No current flows through the system. 

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