826 research outputs found
Determinants of board composition in Australia and the impact of corporate governance regulation
This study investigates the relation between firm characteristics and board composition in Australia for a sample of the same 432 listed firms in 2001 and 2007 and the impact of the Principles of Good Corporate Governance and Best Practice issued by the Australian Stock Exchange in 2003. Two feature of this regulation were (a) it recommended independent boards for all firms, without regard to firm characteristics (an approach commonly described as `one size fits all) and (b) it allowed non-compliance through `if not why not reporting. Using various designations of independence and firm size subsamples we find for `Top 100 firms in 2001 up to 49% (Adjusted R2 48.8) of variation in board independence may be explained by firm characteristics, but generally the explanatory power was much lower. Evidence is provided that although more firms had majority independent boards the relation between board composition and firm characteristics may have weakened over the period. This highlights a potential concern that the regulation has imposed unnecessary costs or inappropriate governance mechanisms on Australian firms
Voxel-wise comparisons of cellular microstructure and diffusion-MRI in mouse hippocampus using 3D Bridging of Optically-clear histology with Neuroimaging Data (3D-BOND)
A key challenge in medical imaging is determining a precise correspondence between image properties and tissue microstructure. This comparison is hindered by disparate scales and resolutions between medical imaging and histology. We present a new technique, 3D Bridging of Optically-clear histology with Neuroimaging Data (3D-BOND), for registering medical images with 3D histology to overcome these limitations. Ex vivo 120 × 120 × 200 μm resolution diffusion-MRI (dMRI) data was acquired at 7 T from adult C57Bl/6 mouse hippocampus. Tissue was then optically cleared using CLARITY and stained with cellular markers and confocal microscopy used to produce high-resolution images of the 3D-tissue microstructure. For each sample, a dense array of hippocampal landmarks was used to drive registration between upsampled dMRI data and the corresponding confocal images. The cell population in each MRI voxel was determined within hippocampal subregions and compared to MRI-derived metrics. 3D-BOND provided robust voxel-wise, cellular correlates of dMRI data. CA1 pyramidal and dentate gyrus granular layers had significantly different mean diffusivity (p > 0.001), which was related to microstructural features. Overall, mean and radial diffusivity correlated with cell and axon density and fractional anisotropy with astrocyte density, while apparent fibre density correlated negatively with axon density. Astrocytes, axons and blood vessels correlated to tensor orientation
In vivo fluorescence lifetime tomography of a FRET probe expressed in mouse
Förster resonance energy transfer (FRET) is a powerful biological tool for reading out cell signaling processes. In vivo use of FRET is challenging because of the scattering properties of bulk tissue. By combining diffuse fluorescence tomography with fluorescence lifetime imaging (FLIM), implemented using wide-field time-gated detection of fluorescence excited by ultrashort laser pulses in a tomographic imaging system and applying inverse scattering algorithms, we can reconstruct the three dimensional spatial localization of fluorescence quantum efficiency and lifetime. We demonstrate in vivo spatial mapping of FRET between genetically expressed fluorescent proteins in live mice read out using FLIM. Following transfection by electroporation, mouse hind leg muscles were imaged in vivo and the emission of free donor (eGFP) in the presence of free acceptor (mCherry) could be clearly distinguished from the fluorescence of the donor when directly linked to the acceptor in a tandem (eGFP-mCherry) FRET construct
Ecological and Behavioural Correlates of Intracellular Buffering Capacity in the Muscles of Antarctic Fishes
Five species of antarctic fishes can be arranged in order of increasing anaerobic capacity of the white muscles for burst swimming: Rhigophila dearborni (Zoarcidae), icefish (Channichthyidae), Dissostichus mawsoni, Trematomus centronotus, and Pagothenia borchgrevinki (Nototheniidae). This order reflects in-creasing dependence on anaerobic work done during short bursts of speed during prey capture or predator avoidance. Buffer capacity (beta) for white muscle was lower than that of behaviourally equivalent fish from lower latitudes and beta is itself temperature-dependent
Percentile reference values for anthropometric body composition indices in European children from the IDEFICS study
INTRODUCTION: To characterise the nutritional status in children with obesity or wasting conditions, European anthropometric reference values for body composition measures beyond the body mass index (BMI) are needed. Differentiated assessment of body composition in children has long been hampered by the lack of appropriate references.
OBJECTIVES: The aim of our study is to provide percentiles for body composition indices in normal weight European children, based on the IDEFICS cohort (Identification and prevention of Dietary-and lifestyle-induced health Effects in Children and infantS).
METHODS: Overall 18 745 2.0-10.9-year-old children from eight countries participated in the study. Children classified as overweight/obese or underweight according to IOTF (N = 5915) were excluded from the analysis. Anthropometric measurements (BMI (N = 12 830); triceps, subscapular, fat mass and fat mass index (N = 11 845-11 901); biceps, suprailiac skinfolds, sum of skinfolds calculated from skinfold thicknesses (N = 8129-8205), neck circumference (N = 12 241); waist circumference and waist-to-height ratio (N = 12 381)) were analysed stratified by sex and smoothed 1st, 3rd, 10th, 25th, 50th, 75th, 90th, 97th and 99th percentile curves were calculated using GAMLSS.
RESULTS: Percentile values of the most important anthropometric measures related to the degree of adiposity are depicted for European girls and boys. Age-and sex-specific differences were investigated for all measures. As an example, the 50th and 99th percentile values of waist circumference ranged from 50.7-59.2 cm and from 51.3-58.7 cm in 4.5-to < 5.0-year-old girls and boys, respectively, to 60.6-74.5 cm in girls and to 59.9-76.7 cm in boys at the age of 10.5-10.9 years.
CONCLUSION: The presented percentile curves may aid a differentiated assessment of total and abdominal adiposity in European children
Groupwise Multimodal Image Registration using Joint Total Variation
In medical imaging it is common practice to acquire a wide range of
modalities (MRI, CT, PET, etc.), to highlight different structures or
pathologies. As patient movement between scans or scanning session is
unavoidable, registration is often an essential step before any subsequent
image analysis. In this paper, we introduce a cost function based on joint
total variation for such multimodal image registration. This cost function has
the advantage of enabling principled, groupwise alignment of multiple images,
whilst being insensitive to strong intensity non-uniformities. We evaluate our
algorithm on rigidly aligning both simulated and real 3D brain scans. This
validation shows robustness to strong intensity non-uniformities and low
registration errors for CT/PET to MRI alignment. Our implementation is publicly
available at https://github.com/brudfors/coregistration-njtv
Extending Phenomenological Crystal-Field Methods to C1 Point-Group Symmetry: Characterization of the Optically Excited Hyperfine Structure of Er1673+:Y2SiO5
We show that crystal-field calculations for C1 point-group symmetry are possible, and that such
calculations can be performed with sufficient accuracy to have substantial utility for rare-earth based
quantum information applications. In particular, we perform crystal-field fitting for a C1-symmetry site in
167Er3þ∶Y2SiO5. The calculation simultaneously includes site-selective spectroscopic data up to
20 000 cm−1, rotational Zeeman data, and ground- and excited-state hyperfine structure determined from
high-resolution Raman-heterodyne spectroscopy on the 1.5 μm telecom transition. We achieve an
agreement of better than 50 MHz for assigned hyperfine transitions. The success of this analysis opens
the possibility of systematically evaluating the coherence properties, as well as transition energies and
intensities, of any rare-earth ion doped into Y2SiO5
A comprehensive understanding of ground and optically-excited hyperfine structure of ¹⁶⁷Er³+:Y2SiO5
Using high-performance computing techniques and targeted experimental
investigation we have developed a predictive crystal-field model of the complex
hyperfine structure of ¹⁶⁷Er³+:Y2SiO5 We simultaneously match
site-selective spectroscopic data up to 20,000 cm-¹, rotational Zeeman
data, and ground- and excited-state hyperfine structure determined from
high-resolution Raman-heterodyne spectroscopy on the 1.5 μm telecom
transition. We achieve agreement of better than 50 MHz for assigned hyperfine
transitions. The successful analysis of the complex hyperfine patterns opens
the possibility of systematically searching this whole class of materials for
the ZEFOZ transitions that have proved so useful in quantum information
applications
When contributions make a difference: Explaining order effects in responsibility attribution
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