SURFACE MODES AT A FERRITE-SEMICONDUCTOR INTERFACE

Nous déterminons le comportement d'ondes magnétostatiques de surface à une interface ferrite-semiconducteur. Nous établissons des formules donnant le comportement du champ électrique dans le semiconducteur, et l'influence que la densité de porteurs libres du semiconducteur a sur la ferrite. L'étude approchée des ondes de surface se propageant dans une direction faisant un grand angle avec le champ magnétique appliqué montre que les affirmations antérieures prétendant l'existence d'onde hélicon de surface sont sans fondement, dans les conditions normales.The behaviour of oblique magnetostatic surface waves at a ferrite semiconductor is determined. New formulae are derived for the electric field behaviour in the semiconductor, and for the influence on the ferrite of carrier density of the semiconductor. The approximate behaviour of the surface waves travelling at a large angle to the applied magnetic field shows that previous claims for the existence of surface helicons are unsubstantiated, for normal conditions

Microfluidic advances in phenotypic antibiotic susceptibility testing

A strong natural selection for microbial antibiotic resistance has resulted from the extensive use and misuse of antibiotics. Though multiple factors are responsible for this crisis, the most significant factor – widespread prescription of broad-spectrum antibiotics – is largely driven by the fact that the standard process for determining antibiotic susceptibility includes a 1–2-day culture period, resulting in 48–72 h from patient sample to final determination. Clearly, disruptive approaches, rather than small incremental gains, are needed to address this issue. The field of microfluidics promises several advantages over existing macro-scale methods, including: faster assays, increased multiplexing, smaller volumes, increased portability for potential point-of-care use, higher sensitivity, and rapid detection methods. This Perspective will cover the advances made in the field of microfluidic, phenotypic antibiotic susceptibility testing (AST) over the past two years. Sections are organized based on the functionality of the chip – from simple microscopy platforms, to gradient generators, to antibody-based capture devices. Microfluidic AST methods that monitor growth as well as those that are not based on growth are presented. Finally, we will give our perspective on the major hurdles still facing the field, including the need for rapid sample preparation and affordable detection technologies

Rapid detection of bacteria from blood with surface-enhanced Raman spectroscopy

Traditional methods for identifying pathogens in bacteremic patients are slow (24-48+ h). This can lead to physicians making treatment decisions based on an incomplete diagnosis and potentially increasing the patient's mortality risk. To decrease time to diagnosis, we have developed a novel technology that can recover viable bacteria directly from whole blood and identify them in less than 7 h. Our technology combines a sample preparation process with surface-enhanced Raman spectroscopy (SERS). The sample preparation process enriches viable microorganisms from 10 mL of whole blood into a 200 μL aliquot. After a short incubation period, SERS is used to identify the microorganisms. We further demonstrated that SERS can be used as a broad detection method, as it identified a model set of 17 clinical blood culture isolates and microbial reference strains with 100% identification agreement