TOMORROW @ 1:30

Western University
DEPARTMENT OF PHYSICS AND ASTRONOMY

PHYSICS & ASTRONOMY COLLOQUIUM

Date:           Friday, 29^th June 2012
Time:          1:30 p.m.
Location:    Physics & Astronomy Seminar Room 22

Dr. Gautier Mathys
Joint ALMA Observatory
& European Southern Observatory, CHILE

“Rotation, Magnetism, Binarity, and Chemical Peculiarities in A-type Stars”

ABSTRACT

In recent years, growing evidence has been collected for the existence of a number of dependences between rotation rate, magnetic field strength and structure, and binary orbital properties, of magnetic chemically peculiar stars of spectral type A (Ap stars). One of the most recent and intriguing results suggests the existence of a connection between rotation and orbital periods in Ap binaries. I shall discuss the nature of this connection and its potential implications for the origin of the magnetic fields of Ap stars.

TODAY @ 3 p.m.

Western University
PHYSICS & ASTRONOMY COLLOQUIUM

< COFFEE & COOKIES will be available>

Date:           Wednesday, 27^th June 2012
Time:          3:00 p.m.
Location:    Physics & Astronomy Seminar Room 22

Dr. Samaya Nissanke
Astronomy Department
California Institute of Technology (Caltech)

“Seeing and hearing the Violent Universe”

ABSTRACT

The strongest gravitational waves in the universe are expected to arise from violent events such as the mergers of neutron star or black hole binaries. Decades of theoretical and experimental efforts could result in the first direct detection of gravitational waves. Subsequent measurements should offer us an unprecedented view of strong-field gravity in action. A subset of neutron star binary mergers could be associated with a transient electromagnetic (EM) counterpart, and EM follow-up using radio, optical and high-energy facilities of these events are critical for improving our understanding of the physics underlying strong-field gravity astrophysics, and compact objects. I will outline the challenges that lie ahead in pinpointing the sky location of neutron star binary mergers using worldwide networks of gravitational-wave interferometers and electromagnetic synoptic wide-field surveys.

TODAY @ 1:30

Western University
DEPARTMENT OF PHYSICS AND ASTRONOMY

PHYSICS & ASTRONOMY COLLOQUIUM

Date:           Thursday, 21^st June 2012
Time:          1:30 p.m.
Location:    Physics & Astronomy Seminar Room 22

Dr. Duncan Forgan
Institute for Astronomy
Royal Observatory, Edinburgh

“Numerical Astrobiology and the Search for ExtraTerrestrial Life”

ABSTRACT

Traditionally, theoretical studies of extraterrestrial intelligence have been founded on simple calculations such as Drake’s Equation. While a useful first step, these approaches do not fully incorporate the statistical richness of the Galaxy’s stellar and planetary populations. I will review my attempts to improve SETI calculations using Monte Carlo Realisation techniques. This allows us to compare hypotheses for the origin of life and intelligence, using mock galaxies as a playing field.

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

Western University
PHYSICS & ASTRONOMY COLLOQUIUM

Date:           Wednesday, 27^th June 2012
Time:          3:00 p.m.
Location:    Physics & Astronomy Seminar Room 22

Dr. Samaya Nissanke
Astronomy Department
California Institute of Technology (Caltech)

“Seeing and hearing the Violent Universe”

ABSTRACT

The strongest gravitational waves in the universe are expected to arise from violent events such as the mergers of neutron star or black hole binaries. Decades of theoretical and experimental efforts could result in the first direct detection of gravitational waves. Subsequent measurements should offer us an unprecedented view of strong-field gravity in action. A subset of neutron star binary mergers could be associated with a transient electromagnetic (EM) counterpart, and EM follow-up using radio, optical and high-energy facilities of these events are critical for improving our understanding of the physics underlying strong-field gravity astrophysics, and compact objects. I will outline the challenges that lie ahead in pinpointing the sky location of neutron star binary mergers using worldwide networks of gravitational-wave interferometers and electromagnetic synoptic wide-field surveys.

TODAY @ 2:30

Western University
DEPARTMENT OF PHYSICS AND ASTRONOMY

PHYSICS & ASTRONOMY COLLOQUIUM

Date:           Wednesday, 20^th June 2012
Time:          2:30 p.m.
Location:       Physics & Astronomy Seminar Room 22

Dr. B. G. Sidharth
B. M. Birla Science Centre
Director, International Institute for Applicable Mathematics & Information Sciences
Hyderabad, INDIA

“A model for the cosmological constant (dark energy)”

ABSTRACT

A dark energy driven expanding universe with a small acceleration was theoretically predicted in 1997 and observed in 1998 and then reconfirmed. This went against the then prevailing view of a decelerating dark energy dominated universe. But the exact characterization of dark energy has remained elusive. Several models have been constructed for it. We discuss one such model based on the neutrino background which gives the correct order of the cosmological constant.

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

Western University
DEPARTMENT OF PHYSICS AND ASTRONOMY

PHYSICS & ASTRONOMY COLLOQUIUM

Date:           Friday, 29^th June 2012
Time:          1:30 p.m.
Location:    Physics & Astronomy Seminar Room 22

Dr. Gautier Mathys
Joint ALMA Observatory
& European Southern Observatory, CHILE

“Rotation, Magnetism, Binarity, and Chemical Peculiarities in A-type Stars”

ABSTRACT

In recent years, growing evidence has been collected for the existence of a number of dependences between rotation rate, magnetic field strength and structure, and binary orbital properties, of magnetic chemically peculiar stars of spectral type A (Ap stars). One of the most recent and intriguing results suggests the existence of a connection between rotation and orbital periods in Ap binaries. I shall discuss the nature of this connection and its potential implications for the origin of the magnetic fields of Ap stars.

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

Western University
DEPARTMENT OF PHYSICS AND ASTRONOMY

PHYSICS & ASTRONOMY COLLOQUIUM

Date:           Thursday, 21^st June 2012
Time:          1:30 p.m.
Location:    Physics & Astronomy Seminar Room 22

Dr. Duncan Forgan
Institute for Astronomy
Royal Observatory, Edinburgh

“Numerical Astrobiology and the Search for ExtraTerrestrial Life”

ABSTRACT

Traditionally, theoretical studies of extraterrestrial intelligence have been founded on simple calculations such as Drake’s Equation. While a useful first step, these approaches do not fully incorporate the statistical richness of the Galaxy’s stellar and planetary populations. I will review my attempts to improve SETI calculations using Monte Carlo Realisation techniques. This allows us to compare hypotheses for the origin of life and intelligence, using mock galaxies as a playing field.

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

Western University
DEPARTMENT OF PHYSICS AND ASTRONOMY

PHYSICS & ASTRONOMY COLLOQUIUM

Date:           Wednesday, 20^th June 2012
Time:          2:30 p.m.
Location:       Physics & Astronomy Seminar Room 22

Dr. B. G. Sidharth
B. M. Birla Science Centre
Director, International Institute for Applicable Mathematics & Information Sciences
Hyderabad, INDIA

“A model for the cosmological constant (dark energy)”

ABSTRACT

A dark energy driven expanding universe with a small acceleration was theoretically predicted in 1997 and observed in 1998 and then reconfirmed. This went against the then prevailing view of a decelerating dark energy dominated universe. But the exact characterization of dark energy has remained elusive. Several models have been constructed for it. We discuss one such model based on the neutrino background which gives the correct order of the cosmological constant.

TODAY

Western University
DEPARTMENT OF PHYSICS AND ASTRONOMY

PHYSICS & ASTRONOMY COLLOQUIUM

Date:           Thursday, 31^st May 2012
Time:          1:30 p.m.
Location:    Physics & Astronomy Seminar Room 22

Dr. Jeff Hutter
Department of Physics & Astronomy
Western University

“Examining the role of crystallization inhibitors using atomic-force microscopy”

ABSTRACT

Kinetic inhibitors are additives that affect crystallization kinetics without altering thermodynamic properties, such as the melting point. Based on their effectiveness at exceedingly small concentrations, models for the mechanism by which such additives operate have assumed adsorption to crystal growth faces. A well-known model proposed in 1958 by Cabrera and Vermilyea (the C-V model) suggests that impurities adsorb to growth faces and pin growth steps, forcing them to curve, and thus decreasing the effective supersaturation via the Gibbs-Thomson effect. Despite considerable effort, direct evidence for this mechanism has only been offered for a few systems, while significant objections have been raised: How can the irreversible adsorption required to pin growth steps be reconciled with the observed dependence on inhibitor concentration? How can growth proceed at all in the presence of strongly adsorbed inhibitor molecules?

The main example of kinetic inhibition that will be discussed here involves the crystallization of calcium oxalate monohydrate (COM), which is the main mineral component of kidney stones. Certain proteins, such as osteopontin (OPN), are known to inhibit stone formation, but the details of the process are not well understood. In order to determine the role of such inhibitors, we have examined the growth of COM at the molecular level and in real time using the atomic force microscope (AFM). We find that the presence of OPN, as well as synthesized peptides corresponding to portions of the OPN molecule, results in clear changes in the morphology and propagation speed of growth steps. By observing the subsequent recovery of COM growth when the inhibitor is flushed from solution, we can test the validity of the assumptions of the C-V model. An improved understanding of this inhibitor mechanism may result in the design of therapeutic agents for the prevention of kidney stones, as well as an improved ability to tailor additives for a variety of commercial processes.