Giant 1/f noise in perovskite manganites: evidence of the percolation threshold

We discovered an unprecedented magnitude of the 1/f noise near the Curie temperature Tc in low-Tc manganites. The scaling behavior of the 1/f noise and the resistance provides strong evidence of the percolation nature of the ferromagnetic transition in the polycrystalline samples. The step-like changes of the resistance with temperature, observed for single crystals, suggest that the size of the ferromagnetic domains depends on the size of crystallites.Comment: 4 pages, 3 figure

Conduction of topologically-protected charged ferroelectric domain walls

We report on the observation of nanoscale conduction at ferroelectric domain walls in hexagonal HoMnO3 protected by the topology of multiferroic vortices using in situ conductive atomic force microscopy, piezoresponse force microscopy, and kelvin-probe force microscopy at low temperatures. In addition to previously observed Schottky-like rectification at low bias [Phys. Rev. Lett., 104, 217601 (2010)], conductance spectra reveal that negatively charged tail-to-tail walls exhibit enhanced conduction at high forward bias, while positively charged head-to-head walls exhibit suppressed conduction at high reverse bias. Our results pave the way for understanding the semiconducting properties of the domains and domain walls in small-gap ferroelectrics.Comment: 8 pages, 4 figure

A Comparison of the High-Frequency Magnetic Fluctuations in Insulating and Superconducting La2-xSrxCuO4

Inelastic neutron scattering performed at a spallation source is used to make absolute measurements of the dynamic susceptibility of insulating La2CuO4 and superconducting La2-xSrxCuO4 over the energy range 15<EN<350 meV. The effect of Sr doping on the magnetic excitations is to cause a large broadening in wavevector and a substantial change in the spectrum of the local spin fluctuations. Comparison of the two compositions reveals a new energy scale of 22 meV in La1.86Sr0.14CuO4.Comment: RevTex, 7 Pages, 4 postscript figure

One-parameter scaling theory for DNA extension in a nanochannel

Experiments measuring DNA extension in nanochannels are at odds with even the most basic predictions of current scaling arguments for the conformations of confined semiflexible polymers such as DNA. We show that a theory based on a weakly self-avoiding, one-dimensional "telegraph" process collapses experimental data and simulation results onto a single master curve throughout the experimentally relevant region of parameter space and explains the mechanisms at play.Comment: Revised version. 5 pages, 4 figures, revised version, supplementary informatio

Do Primary Care Doctors Behave the Same in Antibiotic Prescribing for Upper Respiratory Tract Infections?

Purpose: To compare the extent of using an evidence-based approach in managing upper respiratory tract infections (URTIs) among primary care doctors from two different government clinic settings in Malaysia. Method: This is a cross sectional, prospective study carried out in a teaching university primary care centre in Kuala Lumpur (KL) where doctors are constantly exposed to continuing medical education (CME) and seven health clinics in Seremban, Malaysia where doctors have less exposure to CME in the year 2000. Twelve primary care practitioners in KL and 13 in Seremban participated in the study. Each practitioner was asked to record clinical data and prescriptions given to twenty consecutive patients with URTIs using a structured questionnaire for each patient. The extent of usage of an evidence-based approach in managing URTIs among practitioners was assessed