Thermal Enhancement of Interference Effects in Quantum Point Contacts

We study an electron interferometer formed with a quantum point contact and a scanning probe tip in a two-dimensional electron gas. The images giving the conductance as a function of the tip position exhibit fringes spaced by half the Fermi wavelength. For a contact opened at the edges of a quantized conductance plateau, the fringes are enhanced as the temperature T increases and can persist beyond the thermal length l_T. This unusual effect is explained assuming a simplified model: The fringes are mainly given by a contribution which vanishes when T -> 0 and has a decay characterized by a T-independent scale

Supplemental parenteral nutrition in intensive care patients: A cost saving strategy.

The Swiss supplemental parenteral nutrition (SPN) study demonstrated that optimised energy provision combining enteral nutrition (EN) and SPN reduces nosocomial infections in critically ill adults who fail to achieve targeted energy delivery with EN alone. To assess the economic impact of this strategy, we performed a cost-effectiveness analysis using data from the SPN study. Multivariable regression analyses were performed to characterise the relationships between SPN, cumulative energy deficit, nosocomial infection, and resource consumption. The results were used as inputs for a deterministic simulation model evaluating the cost-effectiveness of SPN administered on days 4-8 in patients who fail to achieve ≥60% of targeted energy delivery with EN by day 3. Cost data were derived primarily from Swiss diagnosis-related case costs and official labour statistics. Provision of SPN on days 4-8 was associated with a mean decrease of 2320 ± 338 kcal in cumulative energy deficit compared with EN alone (p < 0.001). Logistic regression analysis showed that each 1000 kcal decrease in cumulative energy deficit was associated with a 10% reduction in the risk of nosocomial infection (odds ratio 0.90; 95% confidence interval 0.83-0.99; p < 0.05). The incremental cost per avoided infection was -63,048 CHF, indicating that the reduction in infection was achieved at a lower cost. Optimisation of energy provision using SPN is a cost-saving strategy in critically ill adults for whom EN is insufficient to meet energy requirements

Failure of single-parameter scaling of wave functions in Anderson localization

We show how to use properties of the vectors which are iterated in the transfer-matrix approach to Anderson localization, in order to generate the statistical distribution of electronic wavefunction amplitudes at arbitary distances from the origin of $L^{d-1} \times \infty$ disordered systems. For $d=1$ our approach is shown to reproduce exact diagonalization results available in the literature. In $d=2$, where strips of width $L \leq 64$ sites were used, attempted fits of gaussian (log-normal) forms to the wavefunction amplitude distributions result in effective localization lengths growing with distance, contrary to the prediction from single-parameter scaling theory. We also show that the distributions possess a negative skewness $S$, which is invariant under the usual histogram-collapse rescaling, and whose absolute value increases with distance. We find $0.15 \lesssim -S \lesssim 0.30$ for the range of parameters used in our study, .Comment: RevTeX 4, 6 pages, 4 eps figures. Phys. Rev. B (final version, to be published

Length-dependent oscillations of the conductance through atomic chains: The importance of electronic correlations

We calculate the conductance of atomic chains as a function of their length. Using the Density Matrix Renormalization Group algorithm for a many-body model which takes into account electron-electron interactions and the shape of the contacts between the chain and the leads, we show that length-dependent oscillations of the conductance whose period depends on the electron density in the chain can result from electron-electron scattering alone. The amplitude of these oscillations can increase with the length of the chain, in contrast to the result from approaches which neglect the interactions.Comment: 7 pages, 4 figure

Scanning Gate Microscopy of a Nanostructure where Electrons Interact

We show that scanning gate microscopy can be used for probing electron-electron interactions inside a nanostructure. We assume a simple model made of two non-interacting strips attached to an interacting nanosystem. In one of the strips, the electrostatic potential can be locally varied by a charged tip. This change induces corrections upon the nanosystem Hartree-Fock self-energies which enhance the fringes spaced by half the Fermi wavelength in the images giving the quantum conductance as a function of the tip position

Role of a parallel magnetic field in two dimensional disordered clusters containing a few correlated electrons

An ensemble of 2d disordered clusters with a few electrons is studied as a function of the Coulomb energy to kinetic energy ratio r_s. Between the Fermi system (small r_s) and the Wigner molecule (large r_s), an interaction induced delocalization of the ground state takes place which is suppressed when the spins are aligned by a parallel magnetic field. Our results confirm the existence of an intermediate regime where the Wigner antiferromagnetism defavors the Stoner ferromagnetism and where the enhancement of the Lande g factor observed in dilute electron systems is reproduced.Comment: 4 pages, 3 figure

Transport properties of one-dimensional Kronig-Penney models with correlated disorder

Transport properties of one-dimensional Kronig-Penney models with binary correlated disorder are analyzed using an approach based on classical Hamiltonian maps. In this method, extended states correspond to bound trajectories in the phase space of a parametrically excited linear oscillator, while the on site-potential of the original model is transformed to an external force. We show that in this representation the two probe conductance takes a simple geometrical form in terms of evolution areas in phase-space. We also analyze the case of a general N-mer model.Comment: 16 pages in Latex, 12 Postscript figures include

The Anderson Transition in Two-Dimensional Systems with Spin-Orbit Coupling

We report a numerical investigation of the Anderson transition in two-dimensional systems with spin-orbit coupling. An accurate estimate of the critical exponent $\nu$ for the divergence of the localization length in this universality class has to our knowledge not been reported in the literature. Here we analyse the SU(2) model. We find that for this model corrections to scaling due to irrelevant scaling variables may be neglected permitting an accurate estimate of the exponent $\nu=2.73 \pm 0.02$

Post-international adoption medical follow-up at the Angers university hospital between 2009 and 2012.

OBJECTIVE: The authors had for aim to describe infectious diseases in internationally adopted child at arrival in France. PATIENTS AND METHODS: We made a retrospective descriptive study of the children\u27s files having undergone medical check-ups between 2009 and 2012. RESULTS: One hundred and eighty-two files were included: 80% of the children came from Africa, 15% from South America and the Caribbean, 3% from Asia, and 2% from Europe. Forty-three percent were diagnosed with tinea. HIV, hepatitis C, and syphilis blood tests were all negative. Six children presented with acute or chronic hepatitis B, another 5 children with acute hepatitis A. One blood test for cysticercosis was positive. Two children presented with malaria. 58% of the children carried an intestinal parasite; the most prevalent was Giardia duodenalis. Bacteriological stool culture was positive for 17 children, for 9 with an antibiotic resistant bacterium. Twenty-seven children had a positive virological stool culture, 2 for a poliovirus. CONCLUSION: A systematic infectious check-up should be performed for a child adopted internationally when he/she arrives in France. This allows diagnosing diseases requiring an emergency treatment, or asymptomatic but severe diseases when chronic. Some blood tests must be double-checked when the child arrives, because of possible false negative initial tests results in the country of origin. Screening, early treatment, and implementing prophylaxis can decrease the risk of transmission to relatives. It also allows monitoring the antimicrobial resistance of some pathogens and the reintroduction of the poliovirus in France