Reflection - quantifying a rare good

Based on a literature review, reflections in written text are rare. The reported proportions of reflection are based on different baselines, making comparisons difficult. In contrast, this research reports on the proportion of occurrences of elements of reflection based on sentence level. This metric allows to compare proportions of elements of reflection. Previous studies are based on courses tailored to foster reflection. The reported proportions represent more the success of a specific instruction than informing about proportions of reflections occurring in student writings in general. This study is based on a large sample of course forum posts of a virtual learning environment. In total 1000 sentences were randomly selected and manually classified according to six elements of reflection. Five raters rated each sentence. Agreement was calculated based on a majority vote. The proportions of elements of reflection are reported and its potential application for course analytics demonstrated. The results indicate that reflections in text are indeed rare, and that there are differences within elements of reflection

IDENTIFICATION OF RELEVANT TIME-SCALES IN NONEQUILIBRIUM COMMUNITY DYNAMICS - CONCLUSIONS FROM PHYTOPLANKTON SURVEYS

This paper is a reflection on J.B. Wilson's (1990) publication which presents an attempt to understand the development of terrestrial plant communities of New Zealand against twelve different explanations of Hutchinson's Paradox. I make a rough comparison between terrestrial and planktonic communities; then I briefly review Hutchinson's Paradox and some of the later relevant phytoplankton results. I summarize the relevance of the IDH in phytoplankton dynamics, assessing its strengths and weaknesses; and finally, try to project our conclusions to terrestrial plant communities; this concerns chiefly the need for appropriate spatial and temporal scaling

Calibrating evanescent-wave penetration depths for biological TIRF microscopy

Roughly half of a cells proteins are located at or near the plasma membrane. In this restricted space the cell senses its environment, signals to its neighbors and ex-changes cargo through exo- and endocytotic mechanisms. Ligands bind to receptors, ions flow across channel pores, and transmitters and metabolites are transported against con-centration gradients. Receptors, ion channels, pumps and transporters are the molecular substrates of these biological processes and they constitute important targets for drug discovery. Total internal reflection fluorescence microscopy suppresses background from cell deeper layers and provides contrast for selectively imaging dynamic processes near the basal membrane of live-cells. The optical sectioning of total internal reflection fluorescence is based on the excitation confinement of the evanescent wave generated at the glass-cell interface. How deep the excitation light actually penetrates the sample is difficult to know, making the quantitative interpretation of total internal reflection fluorescence data problematic. Nevertheless, many applications like super-resolution microscopy, colocalization, fluorescence recovery after photobleaching, near-membrane fluorescence recovery after photobleaching, uncaging or photo-activation-switching, as well as single-particle tracking require the quantitative interpretation of evanescent-wave excited images. Here, we review existing techniques for characterizing evanescent fields and we provide a roadmap for comparing total internal reflection fluorescence data across images, experiments, and laboratories.Comment: 18 text pages, 7 figures and one supplemental figur

Large Deviations and Exit-times for reflected McKean-Vlasov equations with self-stabilizing terms and superlinear drifts

We study a class of reflected McKean-Vlasov diffusions over a convex domain with self-stabilizing coefficients. This includes coefficients that do not satisfy the classical Wasserstein Lipschitz condition. Further, the process is constrained to a (not necessarily bounded) convex domain by a local time on the boundary. These equations include the subclass of reflected self-stabilizing diffusions that drift towards their mean via a convolution of the solution law with a stabilizing potential. Firstly, we establish existence and uniqueness results for this class and address the propagation of chaos. We work with a broad class of coefficients, including drift terms that are locally Lipschitz in spatial and measure variables. However, we do not rely on the boundedness of the domain or the coefficients to account for these non-linearities and instead use the self-stabilizing properties. We prove a Freidlin-Wentzell type Large Deviations Principle and an Eyring-Kramer's law for the exit-time from subdomains contained in the interior of the reflecting domain.Comment: 41 page

Keywords of written reflection - a comparison between reflective and descriptive datasets

This study investigates reflection keywords by contrasting two datasets, one of reflective sentences and another of descriptive sentences. The log-likelihood statistic reveals several reflection keywords that are discussed in the context of a model for reflective writing. These keywords are seen as a useful building block for tools that can automatically analyse reflection in texts

Exploring the 'hidden' in organisations: methodological challenges in construction management research

There has been recognition of the limitations of technocratic approaches to construction management research, and critical theorists in the field have often rejected prescriptive explanations of social phenomena. Thus, there has been a rise in the use of interpretive methodological approaches and a proliferation of qualitative research methods in the construction management literature. Still, interpretive research that requires interaction between the researcher and her informants often confronts the age-old, fundamental challenge that is posed to social science research: that is, what really does go on in organisations, beyond what is (and can be) said and seen? Through post-hoc reflection of a recent study into innovation in construction, it was found that multiple perspectives matter in shaping our understanding of how innovative practices manifests in construction. An observation was also made regarding the hidden agendas of senior management participants in recognising, rewarding and promoting innovation, which potentially contribute to disconnections between theory and practice of innovation in construction. Questions are raised as to how researchers can help articulate these ‘hidden’ agendas and methodological challenges discussed here points to the virtues and limitations of the ethnographic approach

Quantifying protein densities on cell membranes using super-resolution optical fluctuation imaging

Surface molecules, distributed in diverse patterns and clusters on cell membranes, influence vital functions of living cells. It is therefore important to understand their molecular surface organisation under different physiological and pathological conditions. Here, we present a model-free, quantitative method to determine the distribution of cell surface molecules based on TIRF illumination and super-resolution optical fluctuation imaging (SOFI). This SOFI-based approach is robust towards single emitter multiple-blinking events, high labelling densities and high blinking rates. In SOFI, the molecular density is not based on counting events, but results as an intrinsic property due to the correlation of the intensity fluctuations. The effectiveness and robustness of the method was validated using simulated data, as well as experimental data investigating the impact of palmitoylation on CD4 protein nanoscale distribution in the plasma membrane of resting T cells.Comment: 9 pages, 3 figures plus Supplementary Informatio

A high-fidelity photon gun: intensity-squeezed light from a single molecule

A two-level atom cannot emit more than one photon at a time. As early as the 1980s, this quantum feature was identified as a gateway to "single-photon sources", where a regular excitation sequence would create a stream of light particles with photon number fluctuations below the shot noise. Such an intensity squeezed beam of light would be desirable for a range of applications such as quantum imaging, sensing, enhanced precision measurements and information processing. However, experimental realizations of these sources have been hindered by large losses caused by low photon collection efficiencies and photophysical shortcomings. By using a planar metallo-dielectric antenna applied to an organic molecule, we demonstrate the most regular stream of single photons reported to date. Measured intensity fluctuations reveal 2.2 dB squeezing limited by our detection efficiency, equivalent to 6.2 dB intensity squeezing right after the antenna.Comment: 9 pages, 3 figure