Ultrasound Matrix Imaging-Part II: The Distortion Matrix for Aberration Correction Over Multiple Isoplanatic Patches.

This is the second article in a series of two which report on a matrix approach for ultrasound imaging in heterogeneous media. This article describes the quantification and correction of aberration, i.e.

Ultrasound Matrix Imaging-Part I: The Focused Reflection Matrix, the F-Factor and the Role of Multiple Scattering.

This is the first article in a series of two dealing with a matrix approach for aberration quantification and correction in ultrasound imaging. Advanced synthetic beamforming relies on a double focusing operation at transmission and reception on each point of the medium. Ultrasound matrix imaging (UMI) consists in decoupling the location of these transmitted and received focal spots.

Distortion matrix approach for ultrasound imaging of random scattering media.

Focusing waves inside inhomogeneous media is a fundamental problem for imaging. Spatial variations of wave velocity can strongly distort propagating wave fronts and degrade image quality. Adaptive focusing can compensate for such aberration but is only effective over a restricted field of view.

Anderson Mobility Gap Probed by Dynamic Coherent Backscattering.

We use dynamic coherent backscattering to study one of the Anderson mobility gaps in the vibrational spectrum of strongly disordered three-dimensional mesoglasses. Comparison of experimental results with the self-consistent theory of localization allows us to estimate the localization (correlation) length as a function of frequency in a wide spectral range covering bands of diffuse transport and a mobility gap delimited by two mobility edges. The results are corroborated by transmission measurements on one of our samples.

Recurrent scattering and memory effect at the Anderson localization transition.

We report on ultrasonic measurements of the propagation operator in a strongly scattering mesoglass. The backscattered field is shown to display a deterministic spatial coherence due to a remarkably large memory effect induced by long recurrent trajectories. Investigation of the recurrent scattering contribution directly yields the probability for a wave to come back close to its starting spot.

A statistical approach to direct density of states measurements in disordered systems.

A statistical method for measuring the modal density of elastic waves through direct mode counting in strongly scattering disordered systems is presented. To illustrate this approach, the results of ultrasonic experiments in a highly porous sintered glass bead network are reported. This method is shown to yield a reliable and robust measurement of the density of states, enabling mode-counting techniques to be applied to increasingly complex systems, where modal overlap and sensitivity to experimental conditions have previously hampered definitive results.

Using blogs and wikis in a graduate public health course.

Blogs and wikis are examples of Web 2.0 technology that facilitate collaboration in the online world. In the health sciences, the emergence of these social tools potentially increases the risk of generating harmful or biased information.

Integrating information literacy into the education of public health professionals: roles for librarians and the library.

Objective: The paper reviews the core competencies for public health professionals presented in the Institute of Medicine's (IOM's) report, Who Will Keep the Public Healthy: Educating Public Health Professionals for the 21st Century; describes improving information literacy (IL) as a mechanism for integrating the core competencies in public health education; and showcases IL as an opportunity for solidifying partnerships between academic librarians and public health educators.

Methods: The IOM competencies, along with explicit examples of library support from a literature review of current IL trends in the health sciences, are analyzed.

Results: Librarians can play a fundamental role in implementing the IOM's core competencies in shaping public health education for the twenty-first century.

Comparison of ultrasonic velocities in dispersive and nondispersive food materials.

Ultrasonic techniques are increasingly being used to evaluate the properties of food materials. Interpretation of the structure and dynamics on the basis of measured ultrasonic parameters requires rigorous definition of ultrasonic parameters such as velocity, especially since many food materials can display considerable dispersive behavior (changes in velocity with frequency). Agar gel (2% w/v) and agar gel (2% w/v) with a regular array of bubbles (8% volume fraction) were chosen as nondispersive and dispersive materials, respectively.