A wider audience: Turning VLBI into a survey instrument

Radio observations using the Very Long Baseline Interferometry (VLBI) technique typically have fields of view of only a few arcseconds, due to the computational problems inherent in imaging larger fields. Furthermore, sensitivity limitations restrict observations to very compact and bright objects, which are few and far between on the sky. Thus, while most branches of observational astronomy can carry out sensitive, wide-field surveys, VLBI observations are limited to targeted observations of carefully selected objects. However, recent advances in technology have made it possible to carry out the computations required to target hundreds of sources simultaneously. Furthermore, sensitivity upgrades have dramatically increased the number of objects accessible to VLBI observations. The combination of these two developments have enhanced the survey capabilities of VLBI observations such that it is now possible to observe (almost) any point in the sky with milli-arcsecond resolution. In this talk I review the development of wide-field VLBI, which has made significant progress over the last three years.Comment: Invited review at the General Assembly of the Astronomische Gesellschaf

Listening to reporter proteins: how loud does the message need to be?

Optical imaging as non-invasive modality has tremendous research applications in the area of biomedical sciences such as characterization of cancerous cells. However, this imaging modality is limited by depth of light penetration of around 1 mm in living tissues obscuring visualization in vivo. Optoacoustic imaging is a potential solution of this problem based on detection of ultrasound produced by light-absorbing molecules exposed to laser radiation resulting in a tissue contrast. The image contrast relies on absorption of laser emission, however providing ultrasound resolution in living tissues. This study characterized properties of colorectal adenocarcinoma cells expressing Near-infrared Fluorescent proteins (iRFPs) for detection and visualization in Multispectral Optoacoustic Tomography (MSOT) settings in both tissue-mimicking phantoms and mice. We estimated variables affecting MSOT imaging of 3D multicellular tissue spheroids such as size, expression of iRFP in vitro. We tested MSOT for detection of subcutaneously implanted tumours expressing iRFPs in BALB/C nude mice in vivo

Addressing student models of energy loss in quantum tunnelling

We report on a multi-year, multi-institution study to investigate student reasoning about energy in the context of quantum tunnelling. We use ungraded surveys, graded examination questions, individual clinical interviews, and multiple-choice exams to build a picture of the types of responses that students typically give. We find that two descriptions of tunnelling through a square barrier are particularly common. Students often state that tunnelling particles lose energy while tunnelling. When sketching wave functions, students also show a shift in the axis of oscillation, as if the height of the axis of oscillation indicated the energy of the particle. We find inconsistencies between students' conceptual, mathematical, and graphical models of quantum tunnelling. As part of a curriculum in quantum physics, we have developed instructional materials to help students develop a more robust and less inconsistent picture of tunnelling, and present data suggesting that we have succeeded in doing so.Comment: Originally submitted to the European Journal of Physics on 2005 Feb 10. Pages: 14. References: 11. Figures: 9. Tables: 1. Resubmitted May 18 with revisions that include an appendix with the curriculum materials discussed in the paper (4 page small group UW-style tutorial

Listening to reporter proteins: how loud does the message need to be?

Optical imaging as non-invasive modality has tremendous research applications in the area of biomedical sciences such as characterization of cancerous cells. However, this imaging modality is limited by depth of light penetration of around 1 mm in living tissues obscuring visualization in vivo. Optoacoustic imaging is a potential solution of this problem based on detection of ultrasound produced by light-absorbing molecules exposed to laser radiation resulting in a tissue contrast. The image contrast relies on absorption of laser emission, however providing ultrasound resolution in living tissues. This study characterized properties of colorectal adenocarcinoma cells expressing Near-infrared Fluorescent proteins (iRFPs) for detection and visualization in Multispectral Optoacoustic Tomography (MSOT) settings in both tissue-mimicking phantoms and mice. We estimated variables affecting MSOT imaging of 3D multicellular tissue spheroids such as size, expression of iRFP in vitro. We tested MSOT for detection of subcutaneously implanted tumours expressing iRFPs in BALB/C nude mice in vivo

Anisotropic Scaling in Layered Aperiodic Ising Systems

The influence of a layered aperiodic modulation of the couplings on the critical behaviour of the two-dimensional Ising model is studied in the case of marginal perturbations. The aperiodicity is found to induce anisotropic scaling. The anisotropy exponent z, given by the sum of the surface magnetization scaling dimensions, depends continuously on the modulation amplitude. Thus these systems are scale invariant but not conformally invariant at the critical point.Comment: 7 pages, 2 eps-figures, Plain TeX and epsf, minor correction