350 research outputs found

    A one-channel conductor in an ohmic environment: mapping to a TLL and full counting statistics

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    It is shown that a one-channel mesoscopic conductor in an ohmic environment can be mapped to the problem of a backscattering impurity in a Tomonaga-Luttinger liquid (TLL). This allows to determine non perturbatively the effect of the environment on I−VI-V curves, and to find an exact relationship between dynamic Coulomb blockade and shot noise. We investigate critically how this relationship compares to recent proposals in the literature. The full counting statistics is determined at zero temperature.Comment: 5 pages, 2 figures, shortened version for publication in Phys. Rev. Let

    Transport properties of single atoms

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    We present a systematic study of the ballistic electron conductance through sp and 3d transition metal atoms attached to copper and palladium crystalline electrodes. We employ the 'ab initio' screened Korringa-Kohn-Rostoker Green's function method to calculate the electronic structure of nanocontacts while the ballistic transmission and conductance eigenchannels were obtained by means of the Kubo approach as formulated by Baranger and Stone. We demonstrate that the conductance of the systems is mainly determined by the electronic properties of the atom bridging the macroscopic leads. We classify the conducting eigenchannels according to the atomic orbitals of the contact atom and the irreducible representations of the symmetry point group of the system that leads to the microscopic understanding of the conductance. We show that if impurity resonances in the density of states of the contact atom appear at the Fermi energy, additional channels of appropriate symmetry could open. On the other hand the transmission of the existing channels could be blocked by impurity scattering.Comment: RevTEX4, 9 pages, 9 figure

    Dynamical Coulomb blockade of multiple Andreev reflections

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    We analyze the dynamical Coulomb blockade of multiple Andreev reflections (MAR) in a superconducting quantum point contact coupled to a macroscopic impedance. We find that at very low transmission the blockade scales as n2n^2 with n=Int(2Δ/eV)n = {Int}(2\Delta/eV), where VV is the bias voltage and Δ\Delta is the superconducting gap, as it would correspond to the occurrence of "shots" of charge nene. For higher transmission the blockade is reduced both due to Pauli principle and to elastic renormalization of the MAR probability, and for certain voltage regions it may even become an "antiblockade", i.e. the current is enhanced due to the coupling with the electromagnetic environment.Comment: 5 pages, 4 figures, submitted to Phys. Rev. Let

    Experimental Test of the Dynamical Coulomb Blockade Theory for Short Coherent Conductors

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    We observed the recently predicted quantum suppression of dynamical Coulomb blockade on short coherent conductors by measuring the conductance of a quantum point contact embedded in a tunable on-chip circuit. Taking advantage of the circuit modularity we measured most parameters used by the theory. This allowed us to perform a reliable and quantitative experimental test of the theory. Dynamical Coulomb blockade corrections, probed up to the second conductance plateau of the quantum point contact, are found to be accurately normalized by the same Fano factor as quantum shot noise, in excellent agreement with the theoretical predictions.Comment: 4 pages, 4 figures, accepted for publication in Physical Review Letter

    Inelastic Interaction Corrections and Universal Relations for Full Counting Statistics

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    We analyze in detail the interaction correction to Full Counting Statistics (FCS) of electron transfer in a quantum contact originating from the electromagnetic environment surrounding the contact. The correction can be presented as a sum of two terms, corresponding to elastic/inelastic electron transfer. Here we primarily focus on the inelastic correction. For our analysis, it is important to understand more general -- universal -- relations imposed on FCS only by quantum mechanics and statistics with no regard for a concrete realization of a contact. So we derive and analyze these relations. We reveal that for FCS the universal relations can be presented in a form of detailed balance. We also present several useful formulas for the cumulants. To facilitate the experimental observation of the effect, we evaluate cumulants of FCS at finite voltage and temperature. Several analytical results obtained are supplemented by numerical calculations for the first three cumulants at various transmission eigenvalues.Comment: 10 pages, 3 figure

    Proposed treatment strategy for reactive hypoglycaemia

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    Background/aim: Managing reactive hypoglycaemia (RH) poses challenges due to limited and often ineffective treatment options. We report a case series and draw on this to propose a stepwise treatment approach consisting of lifestyle modifications, metformin, GLP-1 analogues, and the use of flash glucose monitoring technology. Method: A retrospective review was conducted to analyse the management of 11 cases presenting with recurrent RH symptoms. Result: Two patients experienced successful resolution of symptoms through lifestyle modifications. Metformin alone was effective in treating seven out of nine patients who received pharmacological treatment. Two patients with previous upper gastrointestinal surgery showed a partial response to metformin and benefited further from additional long-acting GLP-1 analogue. Pharmacological intervention led to significant reductions in insulin and C-peptide levels in repeat mixed meal tolerance tests (P-values 0.043 for insulin and 0.006 for C-peptide). Finally, flash glucose monitoring technology was useful in early detection and preventing episodes of hypoglycaemia in one of these patients with persistent symptoms. Conclusion: These findings highlight the potential efficacy of escalated treatment strategies for RH, including the use of metformin, GLP-1 analogues, and flash glucose monitoring technology

    An Assessment of the Human Papillomavirus Immunization Knowledge, Practices, and Prevention Among a Cohort of Urban College Students

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    Human papillomavirus (HPV) is the most common sexually transmitted disease, yet little is known about the college-age knowledge and prevention practices related to HPV. Although sample vaccination rates mirrored national known vaccination rates, a majority of participants did not complete the three dose vaccine schedule. HPV knowledge was similar between males and females while males were more likely to engage in preventative practices. This information can help healthcare providers reinforce vaccination schedule and prevention practices
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