An electron backscatter diffraction study of geesops: a broader view of trilobite vision?

The calcite eyes of trilobites have been studied for over 100 years using methods including light microscopy (e.g. Clarke 1889; Campbell 1975; Towe 1973; Clarkson 1979 and Bruton and Haas 2003) and more recently cathodoluminescence (CL) imaging coupled with scanning electron microscopy (SEM) of samples etched in EDTA (Miller and Clarkson 1980). This work has provided a great deal of information on the mechanisms by which lenses collected light, drawing attention to the importance of the crystallographic orientation of lens calcite for focusing, and leading to sophisticated models of trilobite vision (Clarkson and Levi-Setti, 1975; Gál et al., 2000). The morphology and mode of life of phacopids, in particular Geesops, are well understood (Bruton and Haas, 2003a; 2003b) but observations on the internal structure of their lenses contradict the generally accepted models for image formation by schizochroal eyes. Recent technological advances have given new impetus to the analysis of crystalline materials and especially important has been electron backscatter diffraction (EBSD). This is a SEM-based technique that can be used to accurately ‘map’ variations in the crystallographic orientation of a sample down to the sub-micrometre scale by recording on a sensitive camera Kikuchi patterns that are formed by diffraction of an electron beam when focused on a polished sample tilted at 70°. Although this technique has been understood for over 50 years (Alam et al., 1954) and has been extensively used in disciplines such as metallography (Humphreys, 2001), until recently its Earth Science applications were limited to studies of structural geology and petrology (Nuchter and Stockhert, 2007). Recent applications of EBSD to biomineralisation research (Dalbeck and Cusack, 2006; Griesshaber et al., 2007) have mapped the crystal orientation and microstructure of calcite shells and in 2006 Lee et al. were able to apply this technique to investigating the microstructure of lenses in the schizochroal eye of Dalmanites. This paper describes results of an EBSD study of eyes of Geesops schlotheimi (Bronn, 1825) combined with more traditional microscopy techniques to reveal new aspects of trilobite lens structure

Microstructure and growth of the lenses of schizochroal trilobite eyes

Lenses within the schizochroal eyes of phacopine trilobites are made principally of calcite and characterisation of them using light microscopy and high-resolution electron imaging and diffraction has revealed an array of microstructural arrangements that suggest a common original pattern across the suborder. The low convexity lenses of Odontochile hausmanni and Dalmanites sp. contain calcite fibres termed trabeculae. The c axis of trabecular calcite lies parallel to the lens axis, and adjacent trabeculae are distinguished by small differences in their a axis orientations. Despite the common alignment, the boundaries between trabeculae cross-cut the c axis as they fan out towards the lens base. Trabeculae are absent from the lens immediately beneath the visual surface and instead a radial fringe is present and is composed of micrometre-thick sheets of calcite whose c axes are oriented at a low angle to the visual surface. High convexity lenses are more common than those of lower convexity among the species studied, and they have a much thicker radial fringe. Beneath this fringe all of the lens calcite is oriented with its c axis parallel to the lens axis and it lacks trabeculae. We propose that both the high and low convexity lenses formed by rapid growth of calcite from a surface that migrated inwards from the cornea, and they may have had an amorphous calcium carbonate precursor. The trabeculae and radial fringes are unlikely to have had any beneficial effect on the transmission or focusing of light but rather are the outcomes of an elegant solution to the problem of how to construct a biconvex lens from a crystalline solid

Model waveform accuracy standards for gravitational wave data analysis

Model waveforms are used in gravitational wave data analysis to detect and then to measure the properties of a source by matching the model waveforms to the signal from a detector. This paper derives accuracy standards for model waveforms which are sufficient to ensure that these data analysis applications are capable of extracting the full scientific content of the data, but without demanding excessive accuracy that would place undue burdens on the model waveform simulation community. These accuracy standards are intended primarily for broadband model waveforms produced by numerical simulations, but the standards are quite general and apply equally to such waveforms produced by analytical or hybrid analytical-numerical methods

A critique of monetary protectionism

An argument against attempts to achieve current-account objectives through monetary manipulation of nominal exchange rates, with an explanation of why such tampering--which for various reasons might appear politically attractive--ultimately harms economic welfare.Foreign exchange - Law and legislation ; Monetary policy

Improved Time-Domain Accuracy Standards for Model Gravitational Waveforms

Model gravitational waveforms must be accurate enough to be useful for detection of signals and measurement of their parameters, so appropriate accuracy standards are needed. Yet these standards should not be unnecessarily restrictive, making them impractical for the numerical and analytical modelers to meet. The work of Lindblom, Owen, and Brown [Phys. Rev. D 78, 124020 (2008)] is extended by deriving new waveform accuracy standards which are significantly less restrictive while still ensuring the quality needed for gravitational-wave data analysis. These new standards are formulated as bounds on certain norms of the time-domain waveform errors, which makes it possible to enforce them in situations where frequency-domain errors may be difficult or impossible to estimate reliably. These standards are less restrictive by about a factor of 20 than the previously published time-domain standards for detection, and up to a factor of 60 for measurement. These new standards should therefore be much easier to use effectively.Comment: 10 pages, 5 figure

Gravitational radiation from the r-mode instability

The instability in the r-modes of rotating neutron stars can (in principle) emit substantial amounts of gravitational radiation (GR) which might be detectable by LIGO and similar detectors. Estimates are given here of the detectability of this GR based the non-linear simulations of the r-mode instability by Lindblom, Tohline and Vallisneri. The burst of GR produced by the instability in the rapidly rotating 1.4 solar mass neutron star in this simulation is fairly monochromatic with frequency near 960 Hz and duration about 100 s. A simple analytical expression is derived here for the optimal S/N for detecting the GR from this type of source. For an object located at a distance of 20 Mpc we estimate the optimal S/N to be in the range 1.2 to about 12.0 depending on the LIGO II configuration.Comment: 8 pages, 4 figure

Which older women could benefit from interventions to decrease sitting time and increase physical activity? [Letter to the Editor]

In addition to the well-known health risks associated with lack of physical activity (PA), evidence is emerging about the health risks of sedentary behaviour (sitting). Research about patterns and correlates of sitting and PA in older women is scarce. METHODS: Self-report data from 6,116 women aged 76-81 years were collected as part of the Australian Longitudinal Study on Woman’s Health. Linear regression models were computed to examine whether demographic, social and health factors were associated with sitting and PA. RESULTS: Women who did no PA sat more than women who did any PA (p<0.001). Seven correlates were associated with sitting and PA (p<0.05). Five of these were associated with more sitting and less PA: three health-related (BMI, chronic conditions, anxiety/depression) and two social correlates (caring duties, volunteering). One demographic (being from another English-speaking country) and one social correlate (more social interaction) were associated with more sitting and more PA. Four correlates, two demographic (living in a city; post-high school education), one social (being single), and one health-related correlate (dizziness/loss of balance) were associated with more sitting only. Two other health-related correlates (stiff/painful joints; feet problems) were associated with less PA only. CONCLUSION: Sedentary behaviour and PA are distinct behaviours in older Australian women. Information about the correlates of both behaviours can be used to identify population groups who might benefit from interventions to reduce sedentary behaviour and/or increase PA

Regional Integration in Asia and Its Effects on the EU and North America

Consequences of free trade agreements (FTAs) among the ASEAN+3 countries and ASEAN+6 countries are explored using a dynamic computable general equilibrium (CGE) model. Quantitative assessments of intra and extra-regional effects on welfare, trade and output are offered. When both trade facilitation and endogenously determined productivity are included in the FTA scenarios, Singapore, other ASEAN countries and China would be able to realize relatively large welfare gains, while the welfare effects on the EU and North America are negligible. The trade and output effects on the latter two regions are also relatively small, with the notable exception of crops, other than rice, in North America.Regional integration, FTA, East Asia, welfare effects, CGE model

Learning the Meets Life: The Lived Experience of Teaching with Secular Spiritual Pedagogy

Spirituality is an elusive, hard-to-define quality that is impossible to measure. Spirituality is often conflated with religion, even though the two have different definitions and purposes. For these reasons and more, spirituality is regularly an overlooked or taboo topic in K-12 education. Likewise, spiritual pedagogy, which considers spirituality a central aspect of education, is often ignored. Yet empirical research is revealing that humans, at our core, are spiritual beings. Studies indicate that when education affirms the animating life force of humans and focuses on the development of people’s inner lives, humans thrive. Thus, the phenomenon of teaching with secular spiritual pedagogy is well worth investigating. First, however, the phenomenon needs to be understood. Therefore, this study explored the following research question: What is the lived experience of teaching with secular spiritual pedagogy? The research employed a hermeneutic phenomenological methodology to illuminate the essence of the lived experience of teaching with secular spiritual pedagogy. I conducted two in-depth interviews with each of seven K-12 teachers who employ secular spiritual pedagogical practices. Interviews were conducted as open-ended guided conversations, asking teachers to describe what spirituality looks and feels like in their classrooms and to reflect on how they make meaning of their experience. In addition, four of the teachers participated in a focus group to reflect on the early findings. The findings indicated that teaching with spiritual pedagogy is an extra-ordinary spiritual learning opportunity that some teachers consider to be a spiritual path. Findings are organized into The Path of Spiritual Learning, a conceptual map with six essential themes. The Path is framed by the theme of Meaning and Purpose, has Connection as a foundation, and moves toward Authenticity. The themes on The Path are synthesized with transformative learning theory, Heron’s theory of personhood, whole person learning, and the developing theoretical understanding of authenticity within the field of adult learning. Recommendations for K-12 and adult education are to evolve toward a participatory, or relational, epistemology, where the interconnectedness of life is the guiding ontological framework – one that values the flourishing of all human life as the central goal of education