The Quest for the Most Spherical Bubble

We describe a recently realized experiment producing the most spherical cavitation bubbles today. The bubbles grow inside a liquid from a point-plasma generated by a nanosecond laser pulse. Unlike in previous studies, the laser is focussed by a parabolic mirror, resulting in a plasma of unprecedented symmetry. The ensuing bubbles are sufficiently spherical that the hydrostatic pressure gradient caused by gravity becomes the dominant source of asymmetry in the collapse and rebound of the cavitation bubbles. To avoid this natural source of asymmetry, the whole experiment is therefore performed in microgravity conditions (ESA, 53rd and 56th parabolic flight campaign). Cavitation bubbles were observed in microgravity (~0g), where their collapse and rebound remain spherical, and in normal gravity (1g) to hyper-gravity (1.8g), where a gravity-driven jet appears. Here, we describe the experimental setup and technical results, and overview the science data. A selection of high-quality shadowgraphy movies and time-resolved pressure data is published online.Comment: 18 pages, 14 figures, 1 tabl

Experimental Design: Design Experimentation

This paper was selected for publication in MIT’s Design Issues. The research takes an original approach by positioning experimentation as a comprehensive design methodology, rather than using the traditional industrial design approach of employing experimentation as a problem-solving tool within a standard design model. It is an evolution of design thinking on non-linear design methods first developed by Hall and presented to the ‘International Association of Societies of Design Research Conference’, Seoul, South Korea (2009), and in a paper entitled ‘Innovation design engineering: Non-linear progressive education for diverse intakes’ presented at the ‘International Conference on Engineering and Product Design Education’, University of Brighton, UK, which offered a non-linear pedagogy (Hall and Childs 2009) that uniquely supports a diverse interdisciplinary intake. Experimental design is well known in the science domain but very little evidence has been recorded of experimentation in industrial design and its position in relation to work in other science and research domains. Connections are made with theories on research methods, an analysis of case studies and comparisons of literature on experimentation from science disciplines, especially that of Kuhn (1962), Galison (1987), Pasteur’s quadrant for scientific research in Stokes (1997) and Borgdorff (2007). Hall makes significant claims in exploring and articulating a model of design experimentation that highlights the differences between scientific and design experimentation. This work was original in describing an experimental design model for the increasing activity in early phases of design development by recording and enhancing knowledge in this important area for future design research and practice. The methods researched in the paper were later used in experimental design workshops in Daegu, South Korea (2011) and Busan, South Korea (2012)

Non-perturbative solutions in the electro-weak theory with tˉt\bar t t condensate and the tt-quark mass

We apply Bogoliubov compensation principle to the gauge electro-weak interaction to demonstrate a spontaneous generation of anomalous three-boson gauge invariant effective interaction. The non-trivial solution of compensation equations uniquely defines the form-factor of the anomalous interaction and parameters of the theory including value of gauge electro-weak coupling $g(M_W^2)$ in satisfactory agreement with its experimental value. A possibility of spontaneous generation of effective four-fermion interaction of heavy quarks is also demonstrated. This interaction defines an equation for a scalar bound state of heavy quarks which serve as a substitute for the elementary scalar Higgs doublet. As a result we calculate the $t$-quark mass $m_t\,=\,177\,GeV$ in satisfactory agreement with the experimental value. The results strongly support idea of $\bar t\,t$ condensate as a source of the electro-weak symmetry breaking.Comment: 16 pages, 5 figures. arXiv admin note: substantial overlap with arXiv:1103.395

Polarization experiments

Possible instrumental set--ups for the measurement of CMB polarization are reviewed in this article. We discuss existing and planned instruments, putting special emphasis on observational, instrumental, and data processing issues for the detection of very low polarization signals of prime cosmological interest. A short prospective summary is included