Women in Physics Canada Conference - 2011

What is the Universe made of? Recent observations suggest surprising results: not only most of the matter in the Universe is dark and unconventional but, more surprisingly, the major component of the Universe may be in the form of 'dark energy' -- a form of energy that opposes the pull of gravity and causes the expansion of the universe to accelerate. By combining recent observations of clusters of galaxies, distant supernovae, and the cosmic microwave background, we find evidence for a Universe that has only 5% 'normal' baryonic matter, 20% non-baryonic dark matter, and 75% 'dark energy'. The observations suggest a Universe that is lightweight, with only 25% of the critical mass-density needed to halt the Universal expansion, and a geometry that is flat with no space curvature. The observations of the dark side of the Universe and their implications will be discussed.

In recent years there has been an increase in the number of women in all academic levels in physical and applied sciences in Canada. Despite the modern feminist movement the number of women in physics continues to be less than the number of men, particularly in higher and leadership positions. As there is no rational reason for women to trail men in achieving new scientific discoveries or excel in academic teaching, the cause of this is attributed to existing gender biases in the perception and practice of science. Thus increasing the number of women in physics as well as emphasising their relevance in physics has emerged as a women

Physics Education Research (PER) is a blossoming subfield of physics that is changing the way students become physicists. Our research involves the transformation of the lab portion of a first-year enriched physics course through the implementation of “invention activities:” discovery-learning activities that ask students to “invent” a solution to a problem before being taught the expert solution. The combination of invention activities and tell-and-practice methods has been shown to lead to better student learning and performance on transfer tasks, as compared to tell-and-practice methods alone (Roll, Aleven & Koedinger, 2009; Schwartz & Martin, 2004). In addition, scaffolding invention activities using domain-independent metacognitive prompts can support students through the invention process, leading them to attend to more features of the domain and reason at a deeper level (Roll, Holmes, Day & Bonn; submitted). Our current study further investigates this theory by expanding the treatment across a four-month term and using faded levels of scaffolding. Using interactive learning environments (ILE), five inventions in the domains of statistics and data-analysis were given to students and various assessments were administered to measure performance on domain-level knowledge and “invention skills.” I will present preliminary results from this and previous studies.

A gel that has similar thermodynamic properties to human tissue is necessary for determining the safety of implanted medical devices during magnetic resonance imaging (MRI). One particular gel recommended by the ASTM standard (F218209) is the polyacrylic acid (PAA) phantom. In this work, PAA mixtures were characterized by measuring viscosity (as a function of shear rate), electrical conductivity, thermal conductivity, and elastic and viscous moduli (as a function of frequency). Experiments compared samples with blend times between 30 seconds and 9 minutes, and measurements were taken over a period of weeks to document the aging process in the phantoms. Results suggest that 3 minutes or more of blending 500 mL quantities causes the sample to transform from a gel (which has a well-defined yield stress) into a viscous liquid. The same transformation was observed in a single sample over a  period of two weeks. These results are important because the current ASTM standard does not specify blending time in detail. It is therefore possible that variability in the gel preparation methods could affect the results of experiments to determine the safety of implanted medical devices. These results will help to strengthen the ASTM standard procedure in future revisions.

Molecular spectroscopy offers the tools and instrumentation needed to unveil the structure and characteristics of molecules that are found within planetary atmospheres. In order to do this we examine the frequencies of light that these molecules either absorb or emit. It is the fine structure of these absorption or emission features that give us information about their physical state.. In our lab we use a near-infrared source to probe various molecules and examine absorption features and their dependency on both temperature and pressure. In this study we plan to retrieve the N2-broadened widths, pressure-induces N2-shifts and N2-broadened line mixing coefficients for twenty two transitions in the P branch of the ν1+ν3 band of acetylene mixed with nitrogen. The gas mixture has been selected to be 10% acetylene and 90 % nitrogen. We will record spectra using a 3 channel tuneable diode laser spectrometer. The system contains a temperature controlled single pass absorption gas cell of fixed length, a room temperature cell filled with pure acetylene gas used to create a reference spectra and a third background cell. The system is controlled by LabVIEW software which will be discussed.Simulations have been performed on the v1+v3 band using data obtained from the HITRAN database and will be presented. . From the simulations we determined that we can measure twenty two lines in the P-branch of this band. These lines are all within the interval of P(1)-P(31). For each line we will record spectra at pressures of 100, 250, 400 and 500 torr and for each pressure we plan on measuring 7 different temperatures ranging from -60 to 60C. From these recorded spectra we hope to obtain line parameters using a nonlinear least squares fitting routine. The routine will allow for use of several different line shape models. This study will be the first one over a range of temperatures.

We are doing research on the chemical reaction of the hydrogen atom with water under sub- and supercritical conditions. Supercritical water is water above the critical point (373.9 C and 220.6 bar). This reaction is one of the most important reactions in the next generation of nuclear reactors called Gen IV, where supercritical water will be used as a coolant. We have been studying this reaction by the SR experimental technique. SR is the only technique that is able to work under these extreme conditions to provide kinetics data and it can be a billion times more sensitive than other techniques. TRIUMF, the particle accelerator in Vancouver is the facility that we used to collect data.

The DEAP-3600 single-phase liquid argon detector at SNOLAB will increase the sensitivity to spin-independent WIMP-nucleon scatters by two orders of magnitude, allowing for the possibility of dark matter particle detection. The spherical detector will contain 3600 kg of liquid argon in an 85 cm radius acrylic vessel surrounded by 255 photomultiplier tubes (PMTs). After a collision between a WIMP and an Ar-40 nucleus, the scintillation light from the recoiling nucleus will be collected by PMTs. The separation of background events from WIMP events is critical. Detector materials contain levels of uranium and thorium, and these decay chains contain alpha, beta, and gamma decays. Alpha particles near the surface of the acrylic vessel are perhaps the most difficult background. A fraction of the alpha energy, or the recoiling nucleus from the alpha decay, could misreconstruct in the fiducial volume and result in a false candidate dark matter event. The maximum concentrations in the DEAP-3600 acrylic are 0.3 ppt, 1.3 ppt, and 1.1 x 10^-8 ppt for U-238, Th-232, and Pb-210, respectively. The concentrations of U-238, Th-232, and Pb-210 in the bulk acrylic will be measured by vaporizing acrylic, collecting the residue, and counting the contamination in a high-purity germanium well detector.

Study of rare decays is an important approach for exploring physics beyond the Standard Model (SM). The branching ratio of the helicity suppressed p ? e? decay, is one of the most accurately calculated decay process involving hadrons and has so far provided the most stringent test of the hypothesis of electron-muon universality in weak interactions. The branching ratio has been calculated in the SM to better than 0.01% accuracy to be R = 1.2353(1).10^4 .The PIENU experiment at TRIUMF, which started taking physics data in September 2009, aims to reach an accuracy five times better than the previous PSI and TRIUMF experiments so as to confront the theoretical calculation at the level of 0.1%. If a deviation from the SM branching ratio is found, “new physics” beyond the SM, at potentially very high mass scales (up to 1000 TeV), could be revealed. Alternatively, sensitive constraints on hypotheses can be obtained for pseudoscalar or scalar interactions, or on the mass and couplings of heavy neutrinos.So far, around five millions pion to electron decay events have been accumulated by the PIENU experiment. Data taking will continue in 2011 to increase the statistics to the 10^7 level.The presentation will outline the physics motivations, describe the apparatus and techniques designed to achieve high precision and present the status of the analysis.

The goal of Total Body Irradiation (TBI) is to deliver a uniform dose of radiation to the entire body, to destroy cancerous cells. Since the human body is not uniform in either density or thickness, it is difficult to deliver a uniform dose. A novel, Aperture Modulated, Total Body Irradiation (AMTBI) technique was introduced by researchers at the Tom Baker Cancer Centre to address this problem. The AMTBI technique reduces the dose deviation along the midline in the longitudinal direction to less than 5%, as compared to 15% with conventional TBI. This improvement in dose homogeneity is achieved by dynamically changing the apertures of the Multi-Leaf Collimator (MLC) according to the radiative area

This research focuses on finding analytical solutions to the mechanical bidomain model of cardiac tissue. In particular, a perturbation expansion is used to analyze the equations, with the perturbation parameter being inversely proportional to the spring constant coupling the intracellular and extracellular spaces. The results indicate that the intracellular and extracellular pressures are not equal, and that the two spaces move relative to each other. This calculation is complicated enough to illustrate the implications of the mechanical bidomain model, but is nevertheless simple enough to solve analytically. The zeroth-order of the perturbation expansion reveals that the intracellular and extracellular displacements are equal, thus making it unnecessary to account for either space on an individual basis. Yet, in the first-order of the expansion we see a shift and the intracellular and extracellular displacements are unequal. One application of the calculation is to the mechanical behavior of active cardiac tissue surrounding an ischemic region. Also, a hypothesis for the physical meaning of the pressure inequality is if this inequality is held for an extended period of time it may cause fluid to flow across the cell membrane and in the tissue.