Poster: http://www.physics.uwo.ca/colloquia/Colloquia%20Notices/2011_2012/McNAB%20Research%20Talk.pdf

Western University
DEPARTMENT OF PHYSICS AND ASTRONOMY

PHYSICS & ASTRONOMY COLLOQUIUM

Date:          Wednesday, 7^th March 2012
Time:          1:30 p.m.
Location:    Physics & Astronomy Seminar Room 22

Dr. Jennifer McNab
Athinoula A. Martinos Center for Biomedical Imaging

Harvard Medical School

Massachusetts General Hospital, Boston, MA

“Developing Biomarkers of Neuroplasticity Using Diffusion MRI”

ABSTRACT

The human brain has a tremendous ability to adapt and compensate for injury. My research is centred on the development of non-invasive biomarkers of specific neuroplastic features implicated in the recovery process including: axonal branching, changing cortical cellular composition and changing axon diameter distributions. My approach is to map these non-invasive biomarkers using advanced diffusion MRI techniques that leverage recent advances in human MRI technology including 7x stronger encoding gradients, improved detectors and advanced diffusion acquisition and modeling techniques. For patients recovering from a brain injury (e.g. traumatic brain injury or stroke), biomarkers are needed in order to advance and refine neurorestorative treatments, to stratify patients in clinical trials and to guide individualized patient care.

Poster: http://www.physics.uwo.ca/colloquia/Colloquia%20Notices/2011_2012/STAROVEROV%20Colloquium.pdf

Western University
DEPARTMENT OF PHYSICS AND ASTRONOMY

PHYSICS & ASTRONOMY COLLOQUIUM

Date:          Thursday, 15^th March 2012
Time:          1:30 p.m.
Location:    Physics & Astronomy Seminar Room 22

Dr. Viktor Staroverov
Department of Chemistry
Western University

“Advances in Density-Functional Methods for Electronic Structure Calculations”

ABSTRACT

Density-functional theory (DFT) is the most successful though imperfect computational tool of chemistry and condensed-matter physics. Current research efforts in DFT concentrate on improving the existing density functionals and on developing new ideas that might lead to better approximations. In this talk, I will explain the challenges faced by theorists and show—by drawing upon the recent work in our group—how valuable physical insights and better numbers can be obtained by adopting a new approach to the problem. This approach consists of shifting the focus from exchange-correlation energy functionals to the corresponding effective potentials.

Coffee & cookies will be available, courtesy of PASA.

Poster: http://www.physics.uwo.ca/colloquia/Colloquia%20Notices/2011_2012/LEVESQUE%20Research%20Talk.pdf

Western University
DEPARTMENT OF PHYSICS AND ASTRONOMY

PHYSICS & ASTRONOMY COLLOQUIUM

Date:          Monday, 5^th March 2012
Time:          1:30 p.m.
Location:    Physics & Astronomy Seminar Room 22

Dr. Ives Levesque
Magnetic Resonance Systems Research Laboratory

Department of Electrical Engineering

Stanford University

“Quantitative mapping of brain tissue properties in vivo by magnetic resonance”

ABSTRACT

Magnetic resonance imaging (MRI) provides exquisite sensitivity to subtle variations in biological tissue structure, molecular composition, and physiological processes. Imaging data can be analyzed with biophysical models, resulting in a wide range of quantitative techniques to map fundamental parameters that relate, directly or indirectly, to tissue properties. Examples include relaxation times, water diffusion, and metabolic information. Quantitative MRI (QMRI) measurements can be validated directly in the laboratory, and facilitate inter-site comparisons and longitudinal studies. Validated metrics can become biomarkers, providing increased specificity for research and clinical use.

QMRI faces a number of challenges, notably the reproducibility and accuracy of methods, exam duration, and interpretation of observations. Acquisition sequences must be optimized for the desired measurement. Signal modeling must be realistic and reliable, and should seek a straightforward interpretation of the observations. Examples will be drawn from the study of multiple sclerosis (MS)—a neurological disease characterized by inflammation and neurodegeneration in the brain and spine—where methods based on magnetization transfer and T2 relaxation have been proposed to characterize myelin content and disease progression. Compensation of static and transmission field inhomogeneity and parallel transmit technology improve data quality and measurement accuracy, in particular for high field imaging (3 Tesla and up). Recent advances in image reconstruction, such as parallel imaging and compressed sensing, open new possibilities for faster data acquisition. These technological advances provide new avenues for the development and application of QMRI.

Poster: http://www.physics.uwo.ca/colloquia/Colloquia%20Notices/2011_2012/GONCHAROVA%20Colloquium.pdf

Western University
DEPARTMENT OF PHYSICS AND ASTRONOMY

PHYSICS & ASTRONOMY COLLOQUIUM

Date:          Thursday, 1^st March 2012
Time:         1:30 p.m.
Location:   Physics & Astronomy Seminar Room 22

Dr. Lyudmila Goncharova
Department of Physics & Astronomy
Western University

“Ion beam analysis in modern materials science”

ABSTRACT

Modern synthetic approaches and nanofabrication are providing us the means of creating material structures controlled at the atomic scale. Familiar examples include the formation of hetero-structures grown with atomic precision, nanoparticles with designed electronic properties, and new carbon-based devices. The forefront of such materials research includes creation of novel materials for energy and electronics applications. One of the challenges here is that electron transport properties of these diverse materials are closely linked to the basic interactions at the interface.

Ion scattering has been very successfully applied in our group to study interfaces of devices based on silicon and higher-mobility semiconductors, as well as to prepare arrays of nanocrystals for photonic applications. Among quantum emitters semiconductor quantum dots (QD) have the highest emission rates and can be easily integrated with semiconductor technology. QD emission properties often degrade because of various imperfections at the QD-dielectric interface. I will review the electronic states and optical properties of Si and Ge quantum dots with variable size prepared by ion implantation in a dielectric matrix studied by ion beam analysis and complementary techniques. Our results for QDs will be compared with other studies for Si-QDs prepared by alternative methods, and discrepancies in the interfacial compositions will be analyzed.

Finally, ion beam analysis, and its role in interfacial characterization will be described in the context of a number of projects underway in our group. These include: 1) interfacial analysis of complex oxide thin film stacks, 2) diffusion and oxidation processes with sub-nm resolution, 3) origin of ferromagnetic contribution to the magnetization of commercial single crystal substrates and thin films. Their understanding requires detailed analysis by high-resolution methods including ion beam analysis..

Coffee & cookies will be available, courtesy of PASA

by Prof. Harald Pfeiffer of the Canadian Institute for Theoretical Astrophysics, 1:30 pm PAB 22.

Gravitational waves are expected to be detected later this decade by the Advanced LIGO experiment. Today’s talk should give us a look ahead. Harald tells me there are already searches on to detect signatures of a population of low mass (less than the mass of the Sun) black holes in the halo of the Milky Way. How such things could possibly have formed is another issue! There is also apparently an uncertainty of a factor of 50(!) in the expected rate of GW signals measurable by Advanced LIGO.

Poster: http://www.physics.uwo.ca/colloquia/Colloquia%20Notices/2011_2012/KOAY%20Research%20Talk.pdf

Western University
DEPARTMENT OF PHYSICS AND ASTRONOMY

PHYSICS & ASTRONOMY COLLOQUIUM

Date:          Thursday, 9^th February 2012
Time:          1:30 p.m.
Location:    Physics & Astronomy Seminar Room 22

Dr. Cheng Guan Koay
University of Wisconsin School of Medicine & Public Health

Madison, Wisconsin

“Diffusion Magnetic Resonance Imaging: From optimal acquisition design to signal extraction”

ABSTRACT

Diffusion Magnetic Resonance Imaging (MRI) in combination with functional MRI promises a whole new vista for scientists to investigate noninvasively the structural and functional connectivity of the human brain—the human connectome, which had heretofore been out of reach. As with other imaging modalities, diffusion MRI data are inherently noisy and its acquisition time-consuming. Further, a faithful representation of the human connectome that can serve as a predictive model requires a robust and accurate data-analytic pipeline. This talk will touch on recent advances on two important segments of a complex diffusion MRI data-analytic pipeline: temporally and spatially optimal acquisition design via deterministic approaches, and accurate signal extraction through a framework that is capable of breaking the noise floor.

My apologies for having the wrong year in the previous notice!              

Poster: http://www.physics.uwo.ca/colloquia/Colloquia%20Notices/2011_2012/STEVENS%20Research%20Talk.pdf

Western University
DEPARTMENT OF PHYSICS AND ASTRONOMY

PHYSICS & ASTRONOMY COLLOQUIUM

Date:          Tuesday, 7^th February 2012
Time:          1:30 p.m.
Location:    Physics & Astronomy Seminar Room 22

Dr. Todd Stevens
Robarts Research Institute
Imaging Research Laboratories

“Accelerated high angular resolution diffusion imaging using compressed sensing: Crossing fiber data you can trust in a time you can afford”

ABSTRACT

There are a large number of neuroscience and neurology applications that would benefit from robust functional brain connectivity information. To substantiate and enhance functional MRI (fMRI) analyses of neural circuitry, diffusion–weighted MRI can provide information about the underlying white matter connectivity architecture. However, conventional diffusion tensor imaging (DTI) techniques are not capable of characterizing the diffusion of voxels that contain multiple crossing fibers—a situation that is known to occur in up to 30% of voxels acquired with typical diffusion imaging resolutions. Consequently, network tractography information generated from DTI data is prone to inaccuracies.

High angular resolution diffusion imaging (HARDI) schemes more finely sample the diffusion field to allow for more complete characterization of intra–voxel crossing fibers. The principal drawback of HARDI techniques is long scan times that preclude the acquisition of both fMRI and diffusion data in a reasonable exam time. Advantageously, diffusion information is amenable to dramatic acquisition accelerations using a new approach called compressed sensing (CS). Using CS–based acquisitions, accurate tractography maps based on HARDI information can be acquired at the lower acquisition costs of typical DTI.

This talk will introduce the concepts of CS-HARDI as well as provide details on the development roadmap for establishing and validating this technique, and will briefly describe some potential applications of this technique in the context of existing research interests at Western.

Poster: http://www.physics.uwo.ca/colloquia/Colloquia%20Notices/2011_2012/STEVENS%20Research%20Talk.pdf

Western University
DEPARTMENT OF PHYSICS AND ASTRONOMY

PHYSICS & ASTRONOMY COLLOQUIUM

Date:          Tuesday, 7^th February 2011
Time:          1:30 p.m.
Location:    Physics & Astronomy Seminar Room 22

Dr. Todd Stevens
Robarts Research Institute
Imaging Research Laboratories

“Accelerated high angular resolution diffusion imaging using compressed sensing: Crossing fiber data you can trust in a time you can afford”

ABSTRACT

There are a large number of neuroscience and neurology applications that would benefit from robust functional brain connectivity information. To substantiate and enhance functional MRI (fMRI) analyses of neural circuitry, diffusion–weighted MRI can provide information about the underlying white matter connectivity architecture. However, conventional diffusion tensor imaging (DTI) techniques are not capable of characterizing the diffusion of voxels that contain multiple crossing fibers—a situation that is known to occur in up to 30% of voxels acquired with typical diffusion imaging resolutions. Consequently, network tractography information generated from DTI data is prone to inaccuracies.

High angular resolution diffusion imaging (HARDI) schemes more finely sample the diffusion field to allow for more complete characterization of intra–voxel crossing fibers. The principal drawback of HARDI techniques is long scan times that preclude the acquisition of both fMRI and diffusion data in a reasonable exam time. Advantageously, diffusion information is amenable to dramatic acquisition accelerations using a new approach called compressed sensing (CS). Using CS–based acquisitions, accurate tractography maps based on HARDI information can be acquired at the lower acquisition costs of typical DTI.

This talk will introduce the concepts of CS-HARDI as well as provide details on the development roadmap for establishing and validating this technique, and will briefly describe some potential applications of this technique in the context of existing research interests at Western.