Nonequilibrium fluctuation-dissipation relations for one- and two-particle correlation functions in steady-state quantum transport.

We study the non-equilibrium (NE) fluctuation-dissipation (FD) relations in the context of quantum thermoelectric transport through a two-terminal nanodevice in the steady-state. The FD relations for the one- and two-particle correlation functions are derived for a model of the central region consisting of a single electron level. Explicit expressions for the FD relations of the Green's functions (one-particle correlations) are provided. The FD relations for the current-current and charge-charge (two-particle) correlations are calculated numerically. We use self-consistent NE Green's functions calculations to treat the system in the absence and in the presence of interaction (electron-phonon) in the central region. We show that, for this model, there is no single universal FD theorem for the NE steady state. There are different FD relations for each different class of problems. We find that the FD relations for the one-particle correlation function are strongly dependent on both the NE conditions and the interactions, while the FD relations of the current-current correlation function are much less dependent on the interaction. The latter property suggests interesting applications for single-molecule and other nanoscale transport experiments.

Dynamical equations for time-ordered Green's functions: from the Keldysh time-loop contour to equilibrium at finite and zero temperature.

We study the dynamical equation of the time-ordered Green's function at finite temperature. We show that the time-ordered Green's function obeys a conventional Dyson equation only at equilibrium and in the limit of zero temperature. In all other cases, i.e. finite temperature at equilibrium or non-equilibrium, the time-ordered Green's function obeys instead a modified Dyson equation. The derivation of this result is obtained from the general formalism of the non-equilibrium Green's functions on the Keldysh time-loop contour. At equilibrium, our result is fully consistent with the Matsubara temperature Green's function formalism and also justifies rigorously the correction terms introduced in an ad hoc way with Hedin and Lundqvist. Our results show that one should use the appropriate dynamical equation for the time-ordered Green's function when working beyond the equilibrium zero-temperature limit.

Nonequilibrium charge susceptibility and dynamical conductance: identification of scattering processes in quantum transport.

We calculate the nonequilibrium charge transport properties of nanoscale junctions in the steady state and extend the concept of charge susceptibility to the nonequilibrium conditions. We show that the nonequilibrium charge susceptibility is related to the nonlinear dynamical conductance. In spectroscopic terms, both contain the same features versus applied bias when charge fluctuation occurs in the corresponding electronic resonances. However, we show that, while the conductance exhibits features at biases corresponding to inelastic scattering with no charge fluctuations, the nonequilibrium charge susceptibility does not. We suggest that measuring both the nonequilibrium conductance and charge susceptibility in the same experiment will permit us to differentiate between different scattering processes in quantum transport.

Functionality in single-molecule devices: model calculations and applications of the inelastic electron tunneling signal in molecular junctions.

We analyze how functionality could be obtained within single-molecule devices by using a combination of non-equilibrium Green's functions and ab initio calculations to study the inelastic transport properties of single-molecule junctions. First, we apply a full non-equilibrium Green's function technique to a model system with electron-vibration coupling. We show that the features in the inelastic electron tunneling spectra (IETS) of the molecular junctions are virtually independent of the nature of the molecule-lead contacts. Since the contacts are not easily reproducible from one device to another, this is a very useful property. The IETS signal is much more robust versus modifications at the contacts and hence can be used to build functional nanodevices. Second, we consider a realistic model of a organic conjugated molecule. We use ab initio calculations to study how the vibronic properties of the molecule can be controlled by an external electric field which acts as a gate voltage. The control, through the gate voltage, of the vibron frequencies and (more importantly) of the electron-vibron coupling enables the construction of functionality: nonlinear amplification and/or switching is obtained from the IETS signal within a single-molecule device.

Profile of mixed species (Plasmodium vivax and falciparum) malaria in adults.

OBJECTIVE: Studies on malaria due to co-existent P. falciparum and P. vivax infections are negligible in India. Therefore, this study was undertaken to find out the clinical profile, prognostic factors, and outcome of mixed species malaria and to compare it with P. falciparum malaria. METHODS: This prospective, comparative study has been conducted in a tertiary health care institution with high prevalence of malaria. A cohort of 888 patients of malaria was enrolled in this study. The diagnosis of malaria was made either by Giemsa stained peripheral blood smear or RDT. Mixed species (MS) malaria was diagnosed when both P. vivax and P. falciparum were detected either from peripheral blood smear or RDT. Patients with P. falciparum malaria were grouped in to Pf group. The differences in clinical presentation, biochemical and haematological findings, occurrence of severe malaria, and outcome were recorded, compared, and analyzed. The severity of complication was assessed and Malaria Severity Score (MSS) was calculated. All the patients were treated according to WHO guidelines. RESULTS: Of them MS and Pf malaria constituted 118 (13.2%) and 770 (86.7%) patients respectively. Severe malaria was found in 17.8% (21 of 118) patients of MS and 57.1% (440 of 770) patients Pf malaria. Pf constituted 440 (95.5%) cases where as MS constituted 21 (4.5%) respectively. The number of severe malaria was significantly (p < 0.001) more in Pf than MS. Out of 21 cases of severe malaria in MS infection, 14 (66.6%) had single complication and 7 (33.3%) cases had multiple complication. However, in Pf mono infection there were 200 (45.5%) patients with single and 240 (54.5%) with multiple complication. There were 4 independent risk factors for a patient of developing complicated malaria. They were: presenting without fever, high parasite count, Pf mono infection, and fever to treatment interval. Multiple complications and high MSS are associated with increased death in Pf malaria. The outcome of patients of MS was good. CONCLUSION: In conclusion mixed species infection is not uncommon in the locality where both species coexists. Mixed species infection can complicate with severe malaria. However, its incidence and severity is less than severe falciparum malaria. In mixed infection, P.vivax malaria has a protective effect against the severity of falciparum malaria.

Nonequilibrium electronic structure of interacting single-molecule nanojunctions: vertex corrections and polarization effects for the electron-vibron coupling.

We consider the interaction between electrons and molecular vibrations in the context of electronic transport in nanoscale devices. We present a method based on nonequilibrium Green's functions to calculate both equilibrium and nonequilibrium electronic properties of a single-molecule junction in the presence of electron-vibron interactions. We apply our method to a model system consisting of a single electronic level coupled to a single vibration mode in the molecule, which is in contact with two electron reservoirs. Higher-order diagrams beyond the usual self-consistent Born approximation (SCBA) are included in the calculations. In this paper we consider the effects of the double-exchange diagram and the diagram in which the vibron propagator is renormalized by one electron-hole bubble. We study in detail the effects of the first- and second-order diagrams on the spectral functions for a large set of parameters and for different transport regimes (resonant and off-resonant cases), both at equilibrium and in the presence of a finite applied bias. We also study the linear response (linear conductance) of the nanojunction for all the different regimes. We find that it is indeed necessary to go beyond the SCBA in order to obtain correct results for a wide range of parameters.