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Showing papers on "Conductance published in 1994"


Journal ArticleDOI
TL;DR: A theoretical framework and global maps for relations between nitrogen-(N)-nutrition and stomatal conductance, gs' at the leaf scale and flUXe!1 of water vapor and carbon dioxide at the canopy scale are provided.
Abstract: This review provides a theoretical framework and global maps for relations between nitrogen-(N)-nutrition and stomatal conductance, gs' at the leaf scale and flUXe!1 of water vapor and carbon dioxide at the canopy scale. This theory defines the boundaries for observed rates of maximum surface conductance, Gsmax, and its relation to leaf area index, A, within a range of observed max­ imum stomatal conductances. gsmax. Soil evaporation compensates for the reduced contribution of plants to total ecosystem water loss at A < 4. Thus, Gsmax is fairly independent of changes in A for a broad range of vegetation types. The variation of Gsmax within these boundaries can be explained by effects of plant nutrition on stomatal conductance via effects on assimilation. Relations are established for the main global vegetation types among (i) maximum stomatal conductance and leaf nitrogen concentrations with a slope of 0.3 mm s-I per mg N g-I, (ii) maximum surface conductance and stomatal conductance with a slope of 3 mm s-I in G per mm S-I in g, and (iii) maximum surface CO2 uptake and surface conductance with a slope of 1 /lmol m-2 s-1 in A per mm S-1 in G. Based on the distribution of leaf nitrogen in different vegetation types, predictions are made for maximum surface conductance and assimilation of carbon dioxide at a global scale. The review provides a basis for modeling and predicting feedforward and feedback effects between terres­ trial vegetation and global climate.

634 citations


Journal ArticleDOI
TL;DR: The clearest signatures of the Kondo effect in transport through a quantum dot are the broadening, shift, and enhancement of the linear-response conductance peaks at low temperatures, and a peak in the nonlinear differential conductance around zero bias.
Abstract: The infinite-U Anderson model is applied to transport through a quantum dot. The current and density of states are obtained via the noncrossing approximation for two spin-degenerate levels weakly coupled to two leads. At low temperatures, the Kondo peak in the equilibrium density of states strongly enhances the linear-response conductance. Application of a finite voltage bias reduces the conductance and splits the peak in the density of states. The split peaks, one at each chemical potential, are suppressed in amplitude by a finite dissipative lifetime. We estimate this lifetime perturbatively as the time to transfer an electron from the higher-chemical-potential lead to the lower-chemical-potential one. At zero magnetic field, the clearest signatures of the Kondo effect in transport through a quantum dot are the broadening, shift, and enhancement of the linear-response conductance peaks at low temperatures, and a peak in the nonlinear differential conductance around zero bias.

417 citations


Journal ArticleDOI
TL;DR: Direct measurements at room temperature of the conductance of a point contact between a scanning tunneling microscope tip and Ni, Cu, and Pt surfaces and atomistic simulations show that the observed behavior is due to the quantization of the transverse electron motion in a contact which contains between one and ten atoms.
Abstract: We present direct measurements at room temperature of the conductance of a point contact between a scanning tunneling microscope tip and Ni, Cu, and Pt surfaces. As the contact is stretched the conductance jumps in units of 2${\mathit{e}}^{2}$/h. Atomistic simulations of the stretch of the contact combined with calculations of the conductance using the Landauer formula show that the observed behavior is due to the quantization of the transverse electron motion in a contact which contains between one and ten atoms.

316 citations


Journal ArticleDOI
TL;DR: It is found that the conductance fluctuation and weak-localization magnitudes are universal: they are independent of the size and shape of the cavity if the number of incoming modes, N, is large.
Abstract: We deduce the effects of quantum interference on the conductance of chaotic cavities by using a statistical ansatz for the S matrix. Assuming that the circular ensembles describe the S matrix, we find that the conductance fluctuation and weak-localization magnitudes are universal: they are independent of the size and shape of the cavity if the number of incoming modes, N, is large. The limit of small N is more relevant experimentally; here we calculate the full distribution of the conductance and find striking differences as N changes or a magnetic field is applied.

269 citations


Journal ArticleDOI
01 Aug 1994-EPL
TL;DR: In this article, the conductance of a ballistic quantum dot (with chaotic classical dynamics and being coupled by ballistic point contacts to two electron reservoirs) is computed on the single assumption that its scattering matrix is a member of Dyson's circular ensemble.
Abstract: The conductance of a ballistic quantum dot (having chaotic classical dynamics and being coupled by ballistic point contacts to two electron reservoirs) is computed on the single assumption that its scattering matrix is a member of Dyson's circular ensemble. General formulae are obtained for the mean and variance of transport properties in the orthogonal (β = 1), unitary (β = 2), and symplectic (β = 4) symmetry class. Applications include universal conductance fluctuations, weak localization, sub-Poissonian shot noise, and normal-metal-superconductor junctions. The complete distribution P(g) of the conductance g is computed for the case that the coupling to the reservoirs occurs via two quantum point contacts with a single transmitted channel. The result P(g) ∝ g−1 + β/2 is qualitatively different in the three symmetry classes.

229 citations


Journal ArticleDOI
TL;DR: Observations suggest that the Cx45 pore diameter is approximately 10 A and is associated with a fixed negative charge within the junctional channel, suggesting that the chick connexin45 gap junctions are permeable to 2',7'-dichlorofluorescein but are not permeability to the more polar 6-carboxyfluoresce in dye.
Abstract: Gap junctions are thought to mediate the direct intercellular coupling of adjacent cells by the gating of an aqueous pore permeable to ions and molecules of up to 1 kD or 8 to 14 A in diameter. We performed ion-substitution and dye-transfer experiments to determine the relative Cl-/K+ conductance and dye permeability of anionic fluorescein derivatives in chick connexin45 (Cx45) channels. We demonstrate that Cx45 forms a 26 +/- 6-picosiemen (pS) channel with a maximum detectable Cl- permeability of 0.2 relative to K+ or Cs+. Although homogeneous channel conductances were observed in multichannel recordings, the open probability estimates were indicative of nonhomogeneous gating behavior and occasional cooperativity. A second conductance state of 19 +/- 4 pS begins to predominate at higher voltages. Cx45 gap junctions are permeable to 2',7'-dichlorofluorescein but are not permeable to the more polar 6-carboxyfluorescein dye. These observations suggest that the Cx45 pore diameter is approximately 10 A and is associated with a fixed negative charge within the junctional channel.

171 citations


Journal ArticleDOI
TL;DR: In this article, the impedance response of the Au/membrane/Au cell between 140 K and room temperature in the frequency range 10−2 to 106 Hz was measured for membranes aged either in air or in water after different pretreatments.

140 citations


Journal ArticleDOI
TL;DR: Poor man's renormalization group procedure allows us to calculate the renormalized transmission amplitudes at any energies and simple formulas that describe the conductance at any temperature are derived.
Abstract: Scattering from a localized potential of arbitrary strength is found for weakly interacting electrons. Poor man's renormalization group procedure allows us to calculate the renormalized transmission amplitudes at any energies. Simple formulas that describe the conductance at any temperature are derived. In the presence of the electron-electron backscattering, the low-temperature conductance deviates from the results of Luttinger liquid theory. In particular, the temperature dependence of the conductance may become nonmonotonic. In the presence of a magnetic field, backscattering gives rise to a peak in the differential conductance at bias equal to the Zeeman splitting.

122 citations


Journal ArticleDOI
TL;DR: The relationship of the activation of a voltage-sensitive chloride conductance to the chloride transmembrane equilibrium potential (ECl) and the consequent role of this conductance in determining the effect of the gamma-aminobutyric acid-A (GABAA) receptor-mediated trans Membrane chloride (Cl-) flux were investigated with the use of whole-cell recordings in the CA1 and dentate gyrus regions of adult rat hippocampal slice preparations.
Abstract: 1. The relationship of the activation of a voltage-sensitive chloride conductance [GCl(V)] to the chloride transmembrane equilibrium potential (ECl) and the consequent role of this conductance in d...

121 citations


Journal ArticleDOI
TL;DR: It is shown that quantum finite-size effects can be taken into account by a simple semiclassical correction to the Sharvin formula and that the conductance of a circular point contact deviates from the classical Sharvin result.
Abstract: An exact calculation of the quantum conduction through a curvilinear constriction in a three-dimensional electron gas is presented. We show that the conductance behavior presents significant differences with respect to the two-dimensional case. Importantly, we find that the conductance of a circular point contact deviates from the classical Sharvin result and the conductance per unit area is not constant except in the limit of macroscopic areas. We show that quantum finite-size effects can be taken into account by a simple semiclassical correction to the Sharvin formula. Recent experiments and calculations on quantum constrictions formed in atomic-scale point contacts are discussed.

121 citations


Journal ArticleDOI
TL;DR: Variation of the low threshold calcium conductance, gCa(LVA), shows that the ability to generate low-threshold spike bursts critically depends on the density of this conductance.
Abstract: 1. We have developed compartmental models of guinea-pig medial vestibular nuclei neurons (MVNns). The structure and the parameters of the model cells were chosen to reproduce the responses of type A and type B MVNns as described in electrophysiological recordings. 2. Dynamics of membrane potentials were modeled in 46 and 61 branched electrical compartments for Type A and Type B MVNns, respectively. Each compartment was allowed to contain up to nine active ionic conductances: a fast inactivating sodium conductance, gNa, a persistent sodium conductance, gNap, a low-voltage activated calcium conductance, gCa(LVA), a high-voltage activated calcium conductance, gCa(HVA), a fast-voltage activated potassium conductance, gK(fast), a slowly relaxing voltage activated potassium conductance, gK(slow), a fast transient potassium channel, gK(A), a slowly relaxing mixed sodium-potassium conductance activating at hyperpolarized membrane potentials, gH, and a calcium-activated potassium conductance gK(AHP). The kinetics of these conductances were derived from voltage-clamp studies in a variety of preparations. Kinetic parameters as well as distribution and density of ion channels were adjusted to yield the reported electrophysiological behavior of medial vestibular neurons. 3. Dynamics of intracellular free [Ca2]i were modeled by inclusion of a Ca(2+)-pump and a Na(+)-Ca2+ exchanger for extrusion of calcium. Diffusion of calcium between submembraneous sites and the center of an electrical compartment was modeled by 25 and 6 shell-like chemical compartments for the cell body and the proximal dendrites, respectively. These compartments also contained binding sites for calcium. 4. The dynamics of active conductances were the same in both models except for gK(fast). This was necessary to achieve the different shape of spikes and of spike afterhyperpolarization in type A and type B MVNns. An intermediate depolarizing component of the spike afterhyperpolarization of type B neurons in part depended on their dendritic cable structure. 5. Variation of the low threshold calcium conductance, gCa(LVA), shows that the ability to generate low-threshold spike bursts critically depends on the density of this conductance. Sodium plateaus were generated when increasing the density of gNap. 6. The type B model cell generated rhythmic bursts of spiking activity under simulation of two distinct experimental conditions.(ABSTRACT TRUNCATED AT 400 WORDS)

Journal ArticleDOI
TL;DR: A finite interdot repulsion is found to cause interesting rearrangements in the conductance spectrum.
Abstract: We apply the Hubbard Hamiltonian to describe quantum-dot arrays weakly coupled to two contacts. Exact diagonalization is used to calculate the eigenstates of the arrays containing up to six dots and the linear-response conductance is then calculated as a function of the Fermi energy. In the atomic limit the conductance peaks form two distinct groups separated by the intradot Coulomb repulsion, while in the band limit the peaks occur in pairs. The crossover is studied. A finite interdot repulsion is found to cause interesting rearrangements in the conductance spectrum.

Journal ArticleDOI
TL;DR: It is shown that quantization of conductance is realized for short wires, while for longer wires the effect of impurity scattering is important and a deviation from the quantized value becomes apparent especially at low temperatures.
Abstract: The way the quantized value of conductance in a quantum wire disappears is predicted as a function of temperature and length of the wire by taking account of both impurity scattering and mutual Coulomb interactions, i.e., in the case of a dirty Tomonaga-Luttinger liquid. It is shown that quantization of conductance is realized for short wires, while for longer wires the effect of impurity scattering is important and a deviation from the quantized value becomes apparent especially at low temperatures. In this case the conductance shows a distinctive temperature dependence.

Journal ArticleDOI
TL;DR: In this article, the Fourier analysis of the variance of the conductance of a wire was presented for any value of the parameter L/ξ, where L being the length of the wire and ξ the localization length.

Journal ArticleDOI
TL;DR: Permeability-ratio measurements in mixtures of monovalent and divalent cations indicated that local charges in or near the pore do not produce a large local surface potential in physiologic solutions, and the mechanism for the high Ca2+ conductance of the NMDA receptor channel is not the same as for the voltage-dependent Ca 2+ channel (VDCC).
Abstract: N-methyl-D-aspartate (NMDA) receptor channels in cultured CA1 hippocampal neurons were studied using patch-clamp techniques. The purpose of the research was to determine the occupancy of the channel by permeant cations and to determine the influence of charged residues in or near the pore. The concentration dependence of permeability ratios, the mole-fraction dependence of permeability ratios, the concentration dependence of the single-channel conductance, and a single-channel analysis of Mg2+ block all independently indicated that the NMDA receptor behaves as a singly-occupied channel. More precisely, there is one permeant cation at a time occupying the site or sites that are in the narrow region of the pore directly in the permeation pathway. Permeability-ratio measurements in mixtures of monovalent and divalent cations indicated that local charges in or near the pore do not produce a large local surface potential in physiologic solutions. In low ionic strength solutions, a local negative surface potential does influence the ionic environment near the pore, but in normal physiologic solutions the surface potential appears too small to significantly influence ion permeation. The results indicate that the mechanism for the high Ca2+ conductance of the NMDA receptor channel is not the same as for the voltage-dependent Ca2+ channel (VDCC). The VDCC has two high affinity, interacting binding sites that provide high Ca2+ selectivity and conductance. The binding site of the NMDA receptor is of lower affinity. Therefore, the selectivity for Ca2+ is not as high, but the lower affinity of binding provides a faster off rate so that interacting sites are not required for high conductance.

Journal ArticleDOI
TL;DR: In this article, a model has been developed for the sensing mechanism of metal oxide-based thick-film gas sensors to explain the behavior of sensor conductance as a function of the concentration of test gas and the operating temperature of the sensor.
Abstract: A model has been developed for the sensing mechanism of metal oxide-based thick-film gas sensors. The model explains the behaviour of the sensor conductance as a function of the concentration of test gas and the operating temperature of the sensor. Using the Schottky-barrier conduction mechanism through grain boundaries, a relationship between the degree of surface coverage θ and the conductance G has been obtained. To relate the conductance with the concentration of the gas, the Freundlich adsorption isotherm for gases and vapours on a solid surface has been used. The isotherm relates the degree of surface coverage θ with the partial pressure of the gas (concentration). By eliminating θ, an expression relating the variation of G with concentration has been obtained. To study the validity of the model, a thick-film Pd-doped tin oxide gas sensor has been fabricated and tested with propanol (C3H7OH). The variation in the conductance with changes in concentration and temperature has been observed. The observed data show an excellent fit with the developed model. Using the experimental data, the constants of the theoretical equation have also been evaluated.

Journal ArticleDOI
TL;DR: In this article, the effect of diagonal disorder on the conductance of molecular wires was investigated using a simple one-dimensional tight-binding picture, and it was shown that diagonal disorder affects three aspects of conductance: (i) it produces large conductance fluctuations from wire to wire.
Abstract: We present results for the effect of diagonal disorder on the conductance of molecular wires, using a simple one‐dimensional tight‐binding picture. We show that diagonal disorder affects three aspects of the conductance: (i) It produces large conductance fluctuations from wire to wire. (ii) It reduces the conductance in situations where the transfer would be resonant, and enhances the conductance when transfer is nonresonant. (iii) It gives near‐exponential conductance decays with wire length.

Journal ArticleDOI
TL;DR: In this paper, the energy distribution of trap time constants, capture cross sections, and interface state density of metaloxide-semiconductor (MOS) capacitors made on silicon carbide material was analyzed.
Abstract: Low‐frequency capacitance and conductance measurements have been extensively performed from 1 Hz to 100 kHz and in the 293–673 K temperature range, on metal‐oxide‐semiconductor (MOS) capacitors made on silicon carbide material. The energy distribution of the trap time constants, capture cross sections, and interface‐state density are presented. It is shown that only low‐frequency and high‐temperature measurements may provide the ability to scan the midgap region of the forbidden band gap. The experimental results fully confirm the feasibility of MOS devices on silicon carbide material. Furthermore, conductance measurements at high temperature indicate the presence of deep bulk levels.

Journal ArticleDOI
TL;DR: This paper uses a tight--binding Hamiltonian to describe the quantum wire, infinite perfect leads, a two--terminal Landauer--type formula for the conductance, and the recursive single-particle Green's function technique to find that conductance quantization is easily destroyed by strong scattering.
Abstract: In this paper we present and discuss our results for the conductance and conductance fluctuations of narrow quantum wires with two types of disorder: boundary roughness (hard wall confining potential) and islands of strongly scattering impurities within the bulk of the wire. We use a tight--binding Hamiltonian to describe the quantum wire, infinite perfect leads, a two--terminal Landauer--type formula for the conductance, and the recursive single-particle Green's function technique. We find that conductance quantization is easily destroyed by strong scattering. We also find that Anderson localization poses a serious restriction on the high carrier mobility predicted in quantum wires. Conductance fluctuations in narrow quantum wires are not, in general, universal (as in the metallic regime), but can be independent of the wire length over a short range of lengths.

Journal ArticleDOI
TL;DR: The findings indicate that the high affinity, essentially irreversible, interaction of ryanodine with the cardiac sarcoplasmic reticulum Ca(2+)-release channel produces a conformational alteration of the protein which results in modified ion handling.
Abstract: Under appropriate conditions, the interaction of the plant alkaloid ryanodine with a single cardiac sarcoplasmic reticulum Ca(2+)-release channel results in a profound modification of both channel gating and conduction. On modification, the channel undergoes a dramatic increase in open probability and a change in single-channel conductance. In this paper we aim to provide a mechanistic framework for the interpretation of the altered conductance seen after ryanodine binding to the channel protein. To do this we have characterized single-channel conductance with representative members of three classes of permeant cation; group 1a monovalent cations, alkaline earth divalent cations, and organic monovalent cations. We have quantified the change in single-channel conductance induced by ryanodine and have expressed this as a fraction of conductance in the absence of ryanodine. Fractional conductance seen in symmetrical 210 mM solutions is not fixed but varies with the nature of the permeant cation. The group 1a monovalent cations (K+, Na+, Cs+, Li+) have values of fractional conductance in a narrow range (0.60-0.66). With divalent cations fractional conductance is considerably lower (Ba2+, 0.22 and Sr2+, 0.28), whereas values of fractional conductance vary considerably with the organic monovalent cations (ammonia 0.66, ethylamine 0.76, propanolamine 0.65, diethanolamine 0.92, diethylamine 1.2). To establish the mechanisms governing these differences, we have monitored the affinity of the conduction pathway for, and the relative permeability of, representative cations in the ryanodine-modified channel. These parameters have been compared with those obtained in previous studies from this laboratory using the channel in the absence of ryanodine and have been modeled by modifying our existing single-ion, four-barrier three-well rate theory model of conduction in the unmodified channel. Our findings indicate that the high affinity, essentially irreversible, interaction of ryanodine with the cardiac sarcoplasmic reticulum Ca(2+)-release channel produces a conformational alteration of the protein which results in modified ion handling. We suggest that, on modification, the affinity of the channel for the group 1a monovalent cations is increased while the relative permeability of this class of cations remains essentially unaltered. The affinity of the conduction pathway for the alkaline earth divalent cations is also increased, however the relative permeability of this class of cations is reduced compared to the unmodified channel. The influence of modification on the handling by the channel of the organic monovalent cations is determined by both the size and the nature of the cation.(ABSTRACT TRUNCATED AT 400 WORDS)

Journal ArticleDOI
TL;DR: In this article, at fixed reverse bias voltages of a diode structure consisting of nanoscale silicon particles embedded in an amorphous SiO2 matrix, conductance oscillation in time is observed on some samples at room temperature.
Abstract: At fixed reverse bias voltages of a diode structure consisting of nanoscale silicon particles embedded in an amorphous SiO2 matrix, conductance oscillation in time is observed on some samples at room temperature. Possible mechanisms of the conductance oscillations include the exchange of electrons between the quantum confined states coupled to localized defects and the charge state of these defects. The precise origin of the observed oscillations has not been identified.

Journal ArticleDOI
20 May 1994-EPL
TL;DR: In this paper, the influence of excited levels on the nonlinear transport properties of a quantum dot weakly coupled to ideal leads is studied using a master-equation approach using a quantum-mechanical model for interacting electrons.
Abstract: The influence of excited levels on the non-linear-transport properties of a quantum dot weakly coupled to ideal leads is studied using a master-equation approach. A quantum-mechanical model for interacting electrons is used to determine the spectrum of the dot. The current-voltage characteristic shows Coulomb blockade and additional fine structure that is related to the excited states of the correlated electrons. Asymmetric coupling to the leads causes asymmetric conductance peaks. It is demonstrated that spin selection rules can lead to regions of negative differential conductance.

Journal ArticleDOI
TL;DR: The conductance caused by translocation of various phosphonium cations across phospholipid (from soybean) bilayer membrane was measured and a "odd and even" pattern was observed in a variety of phenomena such as solubility in water, equivalent ionic conductivity inWater, and 31P NMR chemical shift.
Abstract: The conductance caused by translocation of various phosphonium cations across phospholipid (from soybean) bilayer membrane was measured. Phosphonium cations used were tetraphenylphosphonium (TPP+) and triphenylalkylphosphonium cations formulated as (Phe)3-P(+)-(CH2)nCH3 (n = 0-5). The conductance was dependent on voltage applied externally to the membrane in accordance with a theory developed by previous authors. Using the theory, values of beta K(i) were determined, where beta and k(i) are a linear partition coefficient and a rate constant of transmembrane ion transport, respectively. Since beta k(i) depended on the phosphonium ion concentration, values extrapolated to infinite dilution, (beta k(i))0, were determined. Temperature dependence of (beta k(i))0 allowed us to estimate the activation energy of transport, Ea. For TPP+ thermodynamic values obtained were consistent with values calculated by Flewelling and Hubbell [(1986) Biophys. J. 49, 541-552]. When (Phe)3-P(+)-(CH2)nCH3 (n = 0-5) were used, E(a) depended on the odd or even of n. This "odd and even" pattern was observed in a variety of phenomena such as solubility in water, equivalent ionic conductivity in water, and 31P NMR chemical shift.


Journal ArticleDOI
TL;DR: The shape of the conductance-concentration curve observed in the ROMK1 channel implies that it has multiple K(+)-occupied binding sites in its conduction pathway.
Abstract: One prediction of a multi-ion pore is that its conductance should reach a maximum and then begin to decrease as the concentration of permeant ion is raised equally on both sides of the membrane. A conductance maximum has been observed at the single-channel level in gramicidin and in a Ca(2+)-activated K+ channel at extremely high ion concentration (> 1,000 mM) (Hladky, S. B., and D. A. Haydon. 1972. Biochimica et Biophysica Acta. 274:294-312; Eisenmam, G., J. Sandblom, and E. Neher. 1977. In Metal Ligand Interaction in Organic Chemistry and Biochemistry. 1-36; Finkelstein, P., and O. S. Andersen. 1981. Journal of Membrane Biology. 59:155-171; Villarroel, A., O. Alvarez, and G. Eisenman. 1988. Biophysical Journal. 53:259a. [Abstr.]). In the present study we examine the conductance-concentration relationship in an inward-rectifier K+ channel, ROMK1. Single channels, expressed in Xenopus oocytes, were studied using inside-out patch recording in the absence of internal Mg2+ to eliminate blockade of outward current. Potassium, at equal concentrations on both sides of the membrane, was varied from 10 to 1,000 mM. As K+ was raised from 10 mM, the conductance increased steeply and reached a maximum value (39 pS) at 300 mM. The single-channel conductance then became progressively smaller as K+ was raised beyond 300 mM. At 1000 mM K+, the conductance was reduced to approximately 75% of its maximum value. The shape of the conductance-concentration curve observed in the ROMK1 channel implies that it has multiple K(+)-occupied binding sites in its conduction pathway.

Journal ArticleDOI
TL;DR: In this article, the conductance of Si/p+-Ge/Si epitaxial heterostructure associated with hole tunnelling into isolated ultrasmall (approximately 10 nm) quantum dots p+Ge has been studied.
Abstract: The conductance of the Si/p+-Ge/Si epitaxial heterostructure associated with hole tunnelling into isolated ultrasmall ( approximately 10 nm) quantum dots p+-Ge has been studied. Quantum dots have been obtained after islanding of 1.3 nm Ge film during MBE growth by the Stransky-Krastanov mode method. Conductance oscillations as a function of bias voltage were observed. The experimental data are analysed in terms of a model that involves the interplay of single-electron charging effects and resonant tunnelling through individual energy levels.

Journal ArticleDOI
TL;DR: It is shown that the magnitude of the persistent current in a loop depends on the direction of the direct current flow from one reservoir to another, a feature that can be experimentally verified.
Abstract: We have calculated the persistent current and the conductance of a normal metal loop connected to two electron reservoirs in the presence of magnetic flux. The geometry considered here facilitates simultaneous measurement of the persistent current and the conductance. We show that, in general, the magnitude of the persistent current in a loop depends on the direction of the direct current flow from one reservoir to another, a feature that can be experimentally verified.

Journal ArticleDOI
TL;DR: The instantaneous current/voltage relation of this ductal Cl− conductance is inwardly rectifying with a slope conductance, and the inward rectification seen in the steady-state I/V relation is due, not only to voltage activation of the Cl− Conductance, but also to the intrinsic conductance properties of the channel.
Abstract: We have previously shown that mouse mandibular granular ducts contain a hyperpolarization-activated Cl- conductance. We now show that the instantaneous current/voltage (I/V) relation of this Cl- conductance is inwardly rectifying with a slope conductance of 15.4 +/- 1.8 nS (n = 4) at negative potentials and of 6.7 +/- 0.9 nS (n = 4) at positive potentials. Thus, the inward rectification seen in the steady-state I/V relation is due, not only to voltage activation of the Cl- conductance, but also to the intrinsic conductance properties of the channel. We show further that the ductal Cl- conductance is not activated by including ATP (10 mmol/l) in the pipette solution. Finally, we show that the conductance is not blocked by the addition of any of the following compounds to the extracellular solution: anthracene-9-carboxylate (A9C, 1 mmol/l), diphenylamine-2-carboxylate (DPC, 1 mmol/l), 5-nitro-2-(3-phenylpropylamino)-benzoate (NPPB, 100 mumol/l), 4,4'-diisothiocyanato-stilbene-2,2'-disulphonate (DIDS, 100 mumol/l), indanyloxyacetic acid (IAA-94, 100 mumol/l), verapamil (100 mumol/l), glibenclamide (100 mumol/l) and Ba2+ (5 mmol/l). The properties of the ductal Cl- conductance most nearly resemble those of the ClC-2 channel. Both channel types have instantaneous I/V relations that are slightly inwardly rectifying, are activated by hyperpolarization with a time-course in the order of hundreds of milliseconds, have a selectivity sequence of Br- > Cl- > I-, and are insensitive to DIDS. The only identified difference between the two is that the ClC-2 channel is 50% blocked both by DPC and A9C (1 mmol/l), whereas the ductal Cl- conductance is insensitive to these compounds.

Journal ArticleDOI
TL;DR: In this article, the effect of quasiparticle interference on the conductance of hybrid mesoscopic systems composed of a quasi-one-dimensional normal (N) wire of a different topology contiguous with S (superconducting) and N-regions is studied.

Journal ArticleDOI
TL;DR: It is discussed how dc conductance measurements can provide information on the location and width of the bands of extended states and can be used to demonstrate experimentally that structural correlations inhibit the localization of disorder.
Abstract: We study how the in8uence of structural correlations in disordered systems manifests itself in experimentally measurable magnitudes, focusing on dc conductance of semiconductor superlattices with general potential pro6les. We show that the existence of bands of extended states in these structures gives rise to very noticeable peaks in the 6nite-temperature dc conductance as the chem ical potential is moved through the bands or as the temperature is increased from zero. On the basis of these results we discuss how dc conductance measurements can provide information on the location and width of the bands of extended states. Our predictions can be used to demonstrate experimentally that structural correlations inhibit the localization eKects of disorder.