TODAY @ 2:00 p.m.
Department of Physics and Astronomy
MSc Public Lecture
Mykhaylo (Misha) Chavarha
Supervisor: Dr. Lyudmila Goncharova
“Defects and magnetism in SrTiO3 single crystals and ultra-thin films on Si”
DATE: WEDNESDAY, 4th April 2012
TIME: 1:30 p.m.2:00 p.m.
PLACE: Physics & Astronomy Room 22
All are welcome to attend.
Department of Physics and Astronomy
MSc Public Lecture
Mykhaylo (Misha) Chavarha
Supervisor: Dr. Lyudmila Goncharova
“Defects and magnetism in SrTiO3 single crystals and ultra-thin films on Si”
DATE: WEDNESDAY, 4th April 2012
TIME: 1:30 p.m.
PLACE: Physics & Astronomy Room 22
All are welcome to attend.
JOINT SEMINAR—the Department of Physics and Astronomy and the Centre for Planetary Science and Exploration (CPSX)
Date: Thursday, 5th April 2012
Time: 1:30 p.m.
Location: Physics & Astronomy Seminar Room 22
Dr. Nikku Madhusudhan
Yale Center for Astronomy and Astrophysics
Yale University
“Chemical Characterization of Exoplanetary Atmospheres”
ABSTRACT
Recent advances in exoplanetary science are leading to unprecedented constraints on chemical compositions of exoplanetary atmospheres. Molecular and elemental abundances derived from exoplanetary spectra provide critical clues on the chemical and dynamical processes in exoplanetary atmospheres, on the compositions of their interiors and formation environments, and on the potential habitability of rocky exoplanets. In this talk, I will present emerging constraints on chemical abundances for an ensemble of exoplanetary atmospheres, and their implications for atmospheric processes, interiors, and formation conditions of exoplanets. Strong constraints are emerging on mixing ratios of carbon and oxygen based molecules and on the elemental C/H, O/H, and C/O ratios in giant exoplanetary atmospheres. In particular, the C/O ratio critically influences the H2O abundance, with major repercussions on atmospheric chemistry and thermal inversions, and on the compositions of ices and rocks in planetary interiors and protoplanetary formation zones. Some of the first constraints span C/O ratios of unity or higher, opening the exotic possibility of carbon-rich planets (CRPs). The properties and formation scenarios of CRPs will be discussed in this talk. Such compositional estimates of extrasolar planets open new research avenues at the intersections of geosciences, planetary science, and astronomy. I will discuss some frontier areas in this direction, along with an overview of observational campaigns, from ground and space, and theoretical and experimental efforts.
Coffee & cookies will be available, courtesy of PASA.
Department of Physics and Astronomy
ASTRONOMY SEMINAR
Dr. Hua-bai Li
Dr. Hua-bai Li
Max-Planck-Institut für Astronomie
Heidelberg, Germany
Confronting Star-formation Models with Magnetic-field Observations
ABSTRACT
Self-gravity, turbulence and magnetic fields (B-fields) certainly all play a role in the star-formation process, which transforms just a small fraction of the mass of molecular clouds into stars. How exactly these forces interact with each other to regulate star formation is, however, still highly controversial. I will report recent sub-mm/optical observations of B-fields, which can put constraints on the competing models of cloud formation, cloud fragmentation, cloud core formation, and ambipolar diffusion.
Date: THURSDAY, 29th March 2012
Time: 10:30 a.m.
Location: Physics & Astronomy Room 22
Poster: http://www.physics.uwo.ca/colloquia/Colloquia%20Notices/2011_2012/CURIEL%20Colloquium.pdf
Western University
DEPARTMENT OF PHYSICS AND ASTRONOMY
PHYSICS & ASTRONOMY COLLOQUIUM
Date: Thursday, 29th March 2012
Time: 1:30 p.m.
Location: Physics & Astronomy Seminar Room 22
Dr. Erik Curiel
Rotman Institute of Philosophy
Department of Philosophy
Western University
“Are Black Holes Hot or Cold?”
ABSTRACT
In the early 1970s it was realized that there is a striking formal analogy between the so-called laws of black-hole mechanics and the laws of classical thermodynamics. Before the discovery of Hawking radiation, however, it was generally thought that the analogy was only formal, and did not reflect a deep connection between gravitational and thermodynamical phenomena. In particular, it is still commonly held that the surface gravity of a stationary black hole can be construed as a true physical temperature only when quantum effects are taken into account; in the context of classical general relativity alone, one cannot cogently construe it so. Does the use of quantum field theory in curved spacetime offer the only hope for taking the analogy seriously? I think the answer is ‘no.’ To attempt to justify that answer, I shall begin by arguing that the standard argument to the contrary begs the question. Looking at the various ways that the idea of “temperature” enters classical thermodynamics then will suggest arguments that, I claim, show the analogy between classical black-hole mechanics and classical thermodynamics should be taken more seriously, at least so far as temperature goes, without the need to rely on or invoke quantum mechanics. If this is correct, then there may be a deep connection between classical general relativity and classical thermodynamics on their own, independent of quantum mechanics.
Coffee & cookies will be available, courtesy of PASA.
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, 7th 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, 15th 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, 5th 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/BARMAN%20Colloquium.pdf
The University of Western Ontario
DEPARTMENT OF PHYSICS AND ASTRONOMY
PHYSICS & ASTRONOMY COLLOQUIUM
Date: Thursday, 8th March 2012
Time: 1:30 p.m.
Location: Physics & Astronomy Seminar Room 22
Dr. Travis Barman
Lowell Observatory
Flagstaff, Arizona
“Direct Imaging and Spectroscopy of Young Giant Planets”
ABSTRACT
Several young gas giants in wide orbits (> 10 AU) have now been directly imaged. These exciting discoveries provide new insights into the formation and early atmospheric properties of giant planets. This talk will focus on recent attempts to measure the near-infrared spectra of two planets orbiting the star HR8799. These data have aided in the characterization of the planets’ cloud and chemical properties, but also highlight the many difficulties we face when modeling planet atmospheres.
The few planets imaged so far are just the beginning. New instruments, tailor made for high-contrast imaging, are coming online this year and will reveal dozens of young planets. These instruments will also provide low resolution near-IR spectra of each new planet, revealing a wealth of information across a wide range of planet masses and ages. Given the lessons we are learning from systems like HR8799, interpreting these data will not be easy and significant observational and planet modeling obstacles must be overcome.
Coffee & Cookies will be available.
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, 1st 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