180 research outputs found
Conductivity in a disordered one-dimensional system of interacting fermions
Dynamical conductivity in a disordered one-dimensional model of interacting
fermions is studied numerically at high temperatures and in the
weak-interaction regime in order to find a signature of many-body localization
and vanishing d.c. transport coefficients. On the contrary, we find in the
regime of moderately strong local disorder that the d.c. conductivity sigma0
scales linearly with the interaction strength while being exponentially
dependent on the disorder. According to the behavior of the charge stiffness
evaluated at the fixed number of particles, the absence of the many-body
localization seems related to an increase of the effective localization length
with the interaction.Comment: 4 pages, 5 figures, submitted to PR
Hidden Fermi-liquid charge transport in the antiferromagnetic phase of the electron-doped cuprates
Systematic analysis of the planar resistivity, Hall effect and cotangent of
the Hall angle for the electron-doped cuprates reveals underlying Fermi-liquid
behavior even deep in the antiferromagnetic part of the phase diagram. The
transport scattering rate exhibits a quadratic temperature dependence, and is
nearly independent of doping, compound and carrier type (electrons vs. holes),
and hence universal. Our analysis moreover indicates that the material-specific
resistivity upturn at low temperatures and low doping has the same origin in
both electron- and hole-doped cuprates.Comment: To appear in PR
Resistivity phase diagram of cuprates revisited
The phase diagram of the cuprate superconductors has posed a formidable
scientific challenge for more than three decades. This challenge is perhaps
best exemplified by the need to understand the normal-state charge transport as
the system evolves from Mott insulator to Fermi-liquid metal with doping. Here
we report a detailed analysis of the temperature (T) and doping (p) dependence
of the planar resistivity of simple-tetragonal HgBaCuO
(Hg1201), the single-CuO-layer cuprate with the highest optimal . The
data allow us to test a recently proposed phenomenological model for the
cuprate phase diagram that combines a universal transport scattering rate with
spatially inhomogeneous (de)localization of the Mott-localized hole. We find
that the model provides an excellent description of the data. We then extend
this analysis to prior transport results for several other cuprates, including
the Hall number in the overdoped part of the phase diagram, and find little
compound-to-compound variation in (de)localization gap scale. The results point
to a robust, universal structural origin of the inherent gap inhomogeneity that
is unrelated to doping-related disorder. They are inconsistent with the notion
that much of the phase diagram is controlled by a quantum critical point, and
instead indicate that the unusual electronic properties exhibited by the
cuprates are fundamentally related to strong nonlinearities associated with
subtle nanoscale inhomogeneity.Comment: 22 pages, 5 figure
Risk Factors for Neonatal Sepsis and Method for Reduction of Blood Culture Contamination
Background: False-positive blood cultures findings may lead to a falsely increased morbidity and increased hospital costs.Method: The survey was conducted as retrospective - prospective study and included 239 preterm infants (born before 37 weeks of gestation) who were treated in Neonatal Intensive Care Unit (NICU) in Institute for Child and Youth Health Care of Vojvodina during one year (January 1st, 2012 to December 31st, 2012). The retrospective part of the study focused on examination of incidence of neonatal sepsis and determination of risk factors. In the prospective part of the study infants were sub-divided into two groups: Group 1- infants hospitalized in NICU during the first 6 months of the study; blood cultures were taken by the āāclean techniqueāā and checklists for this procedure were not taken. Group 2- neonates hospitalized in NICU during last 6 months of the study; blood cultures were taken by āāsterile techniqueāā and checklists for this procedure were taken.Results: The main risk factors for sepsis were prelabor rupture of membranes, low gestational age, low birth weight, mechanical ventilation, umbilical venous catheter placement, and abdominal drainage. Staphylococcus aureus and coagulase negative Staphylococcus were the most frequently isolated microorganisms in false-positive blood samples.Conclusions: Education of employees, use of checklists and sterile sets for blood sampling, permanent control of false positive blood cultures, as well as regular and routine monthly reports are crucial for successful reduction of contamination rates
Microwave conductivity of thin YBCO film in magnetic field
The microwave response of a thin film of high temperature superconductor YBa_2Cu_3O_7 - Ī“ was measured for a wide region of temperatures and magnetic fields. From the measured complex frequency shift, the complex conductivity was calculated. The model for effective conductivity in the mixed state was fitted to the complex conductivity data and the values of upper critical fields B_c2(T) and depinning frequencies Ļ_0 (T) have been obtained as fitted parameters
Mikrovalna vodljivost tankih listova YBCO u magnetskom polju
The microwave response of a thin film of high temperature superconductor YBa2Cu3O7 - Ī“ was measured for a wide region of temperatures and magnetic fields. From the measured complex frequency shift, the complex conductivity was calculated. The model for effective conductivity in the mixed state was fitted to the complex conductivity data and the values of upper critical fields Bc2(T) and depinning frequencies Ļ0 (T) have been obtained as fitted parameters.Mjerili smo mikrovalni odziv tankog filma visokotemperaturnog supravodiÄa YBa2Cu3O7āĪ“ u Å”irokom podruÄju temperatura i magnetskih polja. Iz izmjerenog kompleksnog frekventnog pomaka izraÄunali smo kompleksnu vodljivost. NumeriÄkom prilagodbom modela efektivne vodljivosti u mijeÅ”anom stanju odredili smo vrijednosti gornjeg kritiÄnog polja Bc2 (T) i frekvencije opuÅ”tanja Ļ0(T)
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