6,131 research outputs found
Corporate governance and the long-run performance of firms issuing seasoned equity: An Australian study
Corporate governance has been propelled to the forefront of contemporary business thinking by a string of high profile corporate collapses and dramatic regulatory responses in the United States, Australia and in other countries as well. A particularly extensive body of research has emerged surrounding the relationship between corporate governance and firm performance. We combine the governance literature with evidence on the long-term underperformance of firms issuing seasoned equity to examine the benefits of corporate governance in a setting where it is more likely to matter. That is, we address the question, Does good corporate governance mitigate post-issue underperformance? For a broad sample of Australian seasoned equity offerings and employing a comprehensive, self-constructed governance database, we first demonstrate that issuing firms substantially underperform a variety of benchmarks over the long term, confirming similar findings in the existing literature. We then find evidence that better-governed firms do not experience the same degree of post-issue underperformance. Our findings, which are robust to a variety of estimation methods and econometric specifications, are consistent with the windows of opportunity hypothesis and with equity raisings being an important channel through which better corporate governance can improve future performance
Skyrme Hartree-Fock Calculations for the Alpha Decay Q Values of Super-Heavy Nuclei
Hartree-Fock calculations with the SKX Skyrme interaction are carried out to
obtain alpha-decay Q values for deformed nuclei above Pb assuming axial
symmetry. The results for even-even nuclei are compared with experiment and
with previous calculations. Predictions are made for alpha-decay Q values and
half-lives of even-even super-heavy nuclei. The results are also compared for
the recently discovered odd-even chain starting at Z=112 and N=165.Comment: 17 pages, 8 figures, 1 tabl
Receptor protein tyrosine phosphatases control Purkinje neuron firing
Spinocerebellar ataxias (SCA) are a genetically heterogeneous family of cerebellar neurodegenerative diseases characterized by abnormal firing of Purkinje neurons and degeneration. We recently demonstrated the slowed firing rates seen in several SCAs share a common etiology of hyper-activation of the Src family of non-receptor tyrosine kinases (SFKs). However, the lack of clinically available neuroactive SFK inhibitors lead us to investigate alternative mechanisms to modulate SFK activity. Previous studies demonstrate that SFK activity can be enhanced by the removal of inhibitory phospho-marks by receptor-protein-tyrosine phosphatases (RPTPs). In this Extra View we show that MTSS1 inhibits SFK activity through the binding and inhibition of a subset of the RPTP family members, and lowering RPTP activity in cerebellar slices with peptide inhibitors increases the suppressed Purkinje neuron basal firing rates seen in two different SCA models. Together these results identify RPTPs as novel effectors of Purkinje neuron basal firing, extending the MTSS1/SFK regulatory circuit we previously described and expanding the therapeutic targets for SCA patients
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Gut thinking: the gut microbiome and mental health beyond the head
Background: In recent decades, dominant models of mental illness have become increasingly focused on the head, with mental disorders being figured as brain disorders. However, research into the active role that the microbiome-gut-brain axis plays in affecting mood and behaviour may lead to the conclusion that mental health is more than an internalised problem of individual brains.
Objective: This article explores the implications of shifting understandings about mental health that have come about through research into links between the gut microbiome and mental health problems such as depression and anxiety. It aims to analyse the different ways that the lines between mind and body and mental and physical health are re-shaped by this research, which is starting to inform clinical and public understanding.
Design: As mental health has become a pressing issue of political and public concern it has become increasingly constructed in socio-cultural and personal terms beyond clinical spaces, requiring a conceptual response that exceeds biomedical inquiry. This article argues that an interdisciplinary critical medical humanities approach is well positioned to analyse the impact of microbiome-gut-brain research on conceptions of mind.
Results: The entanglement of mind and matter evinced by microbiome-gut-brain axis research potentially provides a different way to conceptualise the physical and social concomitants of mental distress.
Conclusion: Mental health is not narrowly located in the head but is assimilated by the physical body and intermingled with the natural world, requiring different methods of research to unfold the meanings and implications of gut thinking for conceptions of human selfhood
Weakened magnetic braking as the origin of anomalously rapid rotation in old field stars
A knowledge of stellar ages is crucial for our understanding of many
astrophysical phenomena, and yet ages can be difficult to determine. As they
become older, stars lose mass and angular momentum, resulting in an observed
slowdown in surface rotation. The technique of 'gyrochronology' uses the
rotation period of a star to calculate its age. However, stars of known age
must be used for calibration, and, until recently, the approach was untested
for old stars (older than 1 gigayear, Gyr). Rotation periods are now known for
stars in an open cluster of intermediate age (NGC 6819; 2.5 Gyr old), and for
old field stars whose ages have been determined with asteroseismology. The data
for the cluster agree with previous period-age relations, but these relations
fail to describe the asteroseismic sample. Here we report stellar evolutionary
modelling, and confirm the presence of unexpectedly rapid rotation in stars
that are more evolved than the Sun. We demonstrate that models that incorporate
dramatically weakened magnetic braking for old stars can---unlike existing
models---reproduce both the asteroseismic and the cluster data. Our findings
might suggest a fundamental change in the nature of ageing stellar dynamos,
with the Sun being close to the critical transition to much weaker magnetized
winds. This weakened braking limits the diagnostic power of gyrochronology for
those stars that are more than halfway through their main-sequence lifetimes.Comment: 25 pages, 3 figures in main paper, 6 extended data figures, 1 table.
Published in Nature, January 2016. Please see https://youtu.be/O6HzYgP5uyc
for a video description of the resul
Practical computational toolkits for dendrimers and dendrons structure design
Dendrimers and dendrons offer an excellent platform for developing novel drug delivery systems and medicines. The rational design and further development of these repetitively branched systems are restricted by difficulties in scalable synthesis and structural determination, which can be overcome by judicious use of molecular modelling and molecular simulations. A major difficulty to utilise in silico studies to design dendrimers lies in the laborious generation of their structures. Current modelling tools utilise automated assembly of simpler dendrimers or the inefficient manual assembly of monomer precursors to generate more complicated dendrimer structures. Herein we describe two novel graphical user interface (GUI) toolkits written in Python that provide an improved degree of automation for rapid assembly of dendrimers and generation of their 2D and 3D structures. Our first toolkit uses the RDkit library, SMILES nomenclature of monomers and SMARTS reaction nomenclature to generate SMILES and mol files of dendrimers without 3D coordinates. These files are used for simple graphical representations and storing their structures in databases. The second toolkit assembles complex topology dendrimers from monomers to construct 3D dendrimer structures to be used as starting points for simulation using existing and widely available software and force fields. Both tools were validated for ease-of-use to prototype dendrimer structure and the second toolkit was especially relevant for dendrimers of high complexity and size.Peer reviewe
From counting to construction of BPS states in N=4 SYM
We describe a universal element in the group algebra of symmetric groups,
whose characters provides the counting of quarter and eighth BPS states at weak
coupling in N=4 SYM, refined according to representations of the global
symmetry group. A related projector acting on the Hilbert space of the free
theory is used to construct the matrix of two-point functions of the states
annihilated by the one-loop dilatation operator, at finite N or in the large N
limit. The matrix is given simply in terms of Clebsch-Gordan coefficients of
symmetric groups and dimensions of U(N) representations. It is expected, by
non-renormalization theorems, to contain observables at strong coupling. Using
the stringy exclusion principle, we interpret a class of its eigenvalues and
eigenvectors in terms of giant gravitons. We also give a formula for the action
of the one-loop dilatation operator on the orthogonal basis of the free theory,
which is manifestly covariant under the global symmetry.Comment: 41 pages + Appendices, 4 figures; v2 - refs and acknowledgments adde
Separation between coherent and turbulent fluctuations. What can we learn from the Empirical Mode Decomposition?
The performances of a new data processing technique, namely the Empirical
Mode Decomposition, are evaluated on a fully developed turbulent velocity
signal perturbed by a numerical forcing which mimics a long-period flapping.
First, we introduce a "resemblance" criterion to discriminate between the
polluted and the unpolluted modes extracted from the perturbed velocity signal
by means of the Empirical Mode Decomposition algorithm. A rejection procedure,
playing, somehow, the role of a high-pass filter, is then designed in order to
infer the original velocity signal from the perturbed one. The quality of this
recovering procedure is extensively evaluated in the case of a "mono-component"
perturbation (sine wave) by varying both the amplitude and the frequency of the
perturbation. An excellent agreement between the recovered and the reference
velocity signals is found, even though some discrepancies are observed when the
perturbation frequency overlaps the frequency range corresponding to the
energy-containing eddies as emphasized by both the energy spectrum and the
structure functions. Finally, our recovering procedure is successfully
performed on a time-dependent perturbation (linear chirp) covering a broad
range of frequencies.Comment: 23 pages, 13 figures, submitted to Experiments in Fluid
Activation of the innate immune receptor Dectin-1 upon formation of a 'phagocytic synapse'.
Innate immune cells must be able to distinguish between direct binding to microbes and detection of components shed from the surface of microbes located at a distance. Dectin-1 (also known as CLEC7A) is a pattern-recognition receptor expressed by myeloid phagocytes (macrophages, dendritic cells and neutrophils) that detects β-glucans in fungal cell walls and triggers direct cellular antimicrobial activity, including phagocytosis and production of reactive oxygen species (ROS). In contrast to inflammatory responses stimulated upon detection of soluble ligands by other pattern-recognition receptors, such as Toll-like receptors (TLRs), these responses are only useful when a cell comes into direct contact with a microbe and must not be spuriously activated by soluble stimuli. In this study we show that, despite its ability to bind both soluble and particulate β-glucan polymers, Dectin-1 signalling is only activated by particulate β-glucans, which cluster the receptor in synapse-like structures from which regulatory tyrosine phosphatases CD45 and CD148 (also known as PTPRC and PTPRJ, respectively) are excluded (Supplementary Fig. 1). The 'phagocytic synapse' now provides a model mechanism by which innate immune receptors can distinguish direct microbial contact from detection of microbes at a distance, thereby initiating direct cellular antimicrobial responses only when they are required
Web-based measure of life events using computerized life events and assessment record (CLEAR): preliminary cross-sectional study of reliability, validity, and association with depression
Background: Given the criticisms of life event checklists and the costs associated with interviews, life event research requires a sophisticated but easy-to-use measure for research and clinical practice. Therefore, the Computerised Life Events and Assessment Record (CLEAR), based on the Life Events and Difficulties Schedule (LEDS), was developed.
Objectives: To test CLEAR’s reliability, validity, and association with depression.
Methods: CLEAR, the General Health Questionnaire, and the List of Threatening Experiences Questionnaire (LTE-Q) were completed by 328 participants (126 students; 202 matched midlife sample: 127 unaffected controls, 75 recurrent depression cases). Test-retest reliability over 3-4 weeks was examined, and validity determined by comparing CLEAR with LEDS and LTE-Q. Both CLEAR and LTE-Q were examined in relation to depression.
Results: CLEAR demonstrated good test-retest reliability for overall number of life events (.89) and severe life events (.60). Long-term problems showed similar findings. In terms of validity, CLEAR severe life events had moderate sensitivity (59.1%) and specificity (65.4%) when compared to LEDS. CLEAR demonstrated moderate sensitivity (43.1%) and specificity (78.6%) when compared to LTE-Q. CLEAR severe life events and long term problems were significantly associated with depression (OR = 3.50, 95% CI: 2.10-5.85, P < .001; OR = 3.38, 95% CI: 2.02-5.67, P < .001, respectively) whereas LTE-Q events were not (OR=1.06, 95% CI: .43-2.60, P =.90).
Conclusions: CLEAR has acceptable reliability and validity and predicts depression. It therefore has great potential for effective use in research and clinical practice identifying stress-related factors for the onset and maintenance of depression and related disorders
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