3,918 research outputs found
Insights into business confidence from firm-level panel data
Business confidence announcements attract widespread attention, yet relatively little is known about the series itself. What, for example, does an improvement or deterioration in business confidence mean? We consider this question using a panel of firm-level responses to a business opinion survey that includes a question on business confidence. We relate the confidence responses of the firms to microeconomic and macroeconomic variables that have a direct interpretation and, as a result, determine the variables that firms associate with business confidence. Our analysis of firm-level data reveals that what firms associate with business confidence changes over time and means different things to different firms. Consequently, it is not immediately apparent what a change in business confidence actually means
RXTE Observation of Cygnus X-1: II. Timing Analysis
We present timing analysis for a Rossi X-ray Timing Explorer observation of
Cygnus X-1 in its hard/low state. This was the first RXTE observation of Cyg
X-1 taken after it transited back to this state from its soft/high state.
RXTE's large effective area, superior timing capabilities, and ability to
obtain long, uninterrupted observations have allowed us to obtain measurements
of the power spectral density (PSD), coherence function, and Fourier time lags
to a decade lower in frequency and half a decade higher in frequency than
typically was achieved with previous instruments. Notable aspects of our
observations include a weak 0.005 Hz feature in the PSD coincident with a
coherence recovery; a `hardening' of the high-frequency PSD with increasing
energy; a broad frequency range measurement of the coherence function,
revealing rollovers from unity coherence at both low and high frequency; and an
accurate determination of the Fourier time lags over two and a half decades in
frequency. As has been noted in previous similar observations, the time delay
is approximately proportional to f^(-0.7), and at a fixed Fourier frequency the
time delay of the hard X-rays compared to the softest energy channel tends to
increase logarithmically with energy. Curiously, the 0.01-0.2 Hz coherence
between the highest and lowest energy bands is actually slightly greater than
the coherence between the second highest and lowest energy bands. We carefully
describe all of the analysis techniques used in this paper, and we make
comparisons of the data to general theoretical expectations. In a companion
paper, we make specific comparisons to a Compton corona model that we have
successfully used to describe the energy spectral data from this observation.Comment: To Be Published in the Astrophysical Journal. 18 pages. Uses
emulatepaj.st
RXTE Observation of Cygnus X-1: Spectral Analysis
We present the results of the analysis of the broad-band spectrum of Cygnus
X-1 from 3.0 to 200 keV, using data from a 10 ksec observation by the Rossi
X-ray Timing Explorer. The spectrum can be well described phenomenologically by
an exponentially cut-off power law with a photon index Gamma = 1.45 +/- 0.02 (a
value considerably harder than typically found), e-folding energy E_fold = 162
+/- 9 keV, plus a deviation from a power law that formally can be modeled as a
thermal blackbody with temperature kT_bb = 1.2 +/1 0.2 keV. Although the 3 - 30
keV portion of the spectrum can be fit with a reflected power law with Gamma =
1.81 +/- 0.01 and covering fraction f = 0.35 +/- 0.02, the quality of the fit
is significantly reduced when the HEXTE data in the 30 - 100 keV range is
included, as there is no observed hardening in the power law within this energy
range. As a physical description of this system, we apply the accretion disc
corona models of Dove, Wilms & Begelman (1997) --- where the temperature of the
corona is determined self-consistently. A spherical corona with a total optical
depth tau = 1.6 +/- 0.1 and an average temperature kT_c = 87 +/- 5 keV,
surrounded by an exterior cold disc, does provide a good description of the
data (reduced chi-squared = 1.55). These models deviate from the data by up to
7% in the 5 - 10 keV range, and we discuss possible reasons for these
discrepancies. However, considering how successfully the spherical corona
reproduces the 10 - 200 keV data, such ``photon-starved'' coronal geometries
seem very promising for explaining the accretion processes of Cygnus X-1.Comment: Revised version (added content). 8 pages, 6 figures, 1 table.tex
file, latex, uses mn.sty. Accepted for publication in MNRA
Oxygen and its control over structural and electronic properties of Pb based 1212 superconductors
The phase stability, electronic properties and crystal structure of the Pb based 1212 cuprate superconductor (Pb[1+x]/2Cu[1-x]/2)Sr2(Y1-xCax)Cu2O7+/-s were studied using a number of techniques. Since synthetic difficulties limited study of these materials, sol-gel techniques incorporating mixed metal nitrate precursors were applied. Novel synthesis techniques improved reaction rate but did not entirely overcome synthesis difficulties. The effects of Ca content; reaction temperature, and oxygen content in controlling product phase formation and phase stability under synthesis conditions were investigated. X-ray and neutron diffraction were used to probe structural disorder within samples as Ca levels increased and sample oxygen content was varied. The subsequent Rietveld refinements revealed that the levels of cation site disorder increase in line with increasing Ca levels. Under oxidising conditions, annealing temperature and thus oxygen content of the sample plays a critical role in controlling superconducting properties. Optimal Tc and superconducting volume are only achieved over the oxygen content range 6.99-7.00. Low pO2 annealing conditions were used to control sample oxygen content; however, these were not significantly better than standard techniques. Low pO2 environments facilitate the removal of oxygen from samples and allowed the study of phase stability. It was possible to show that decomposition of the 1212 phase leads to formation of new superconducting phases that might well account for contentious literature claims. EXAFS and NMR measurements show that on a local scale, the structure of the 1212 phase rocksalt layer is quite different to the average structure generated from diffraction measurements. The Pb atoms tend to form a PbO4+x molecular type cluster, in which x can increase up to 0.5 to accommodate the inclusion of an excess 0.1 oxygens into the structure. Solid-state NMR measurements reveal in Ca containing samples that up to 20% of the Y within the structure is dimerised
Rotation of Coulomb crystals in a magnetized inductively coupled complex plasma
Under suitable conditions, micron-sized dust particles introduced into inductively coupled argon plasma form a stable microscopic crystal lattice, known as a Coulomb (or plasma) crystal. In the experiment described, an external axial magnetic field was applied to various configurations of Coulomb crystal, including small crystal lattices consisting of one to several particles, and large crystal lattices with many hundreds of particles. The crystals were observed to rotate collectively under the influence of the magnetic field. This paper describes the experimental procedures and the preliminary results of this investigation
Ccdc11 is a novel centriolar satellite protein essential for ciliogenesis and establishment of left-right asymmetry
The establishment of left–right (L-R) asymmetry in vertebrates is dependent on the sensory and motile functions of cilia during embryogenesis. Mutations in CCDC11 disrupt L-R asymmetry and cause congenital heart disease in humans, yet the molecular and cellular functions of the protein remain unknown. Here we demonstrate that Ccdc11 is a novel component of centriolar satellites—cytoplasmic granules that serve as recruitment sites for proteins destined for the centrosome and cilium. Ccdc11 interacts with core components of satellites, and its loss disrupts the subcellular organization of satellite proteins and perturbs primary cilium assembly. Ccdc11 colocalizes with satellite proteins in human multiciliated tracheal epithelia, and its loss inhibits motile ciliogenesis. Similarly, depletion of CCDC11 in Xenopus embryos causes defective assembly and motility of cilia in multiciliated epidermal cells. To determine the role of CCDC11 during vertebrate development, we generated mutant alleles in zebrafish. Loss of CCDC11 leads to defective ciliogenesis in the pronephros and within the Kupffer’s vesicle and results in aberrant L-R axis determination. Our results highlight a critical role for Ccdc11 in the assembly and function of motile cilia and implicate centriolar satellite–associated proteins as a new class of proteins in the pathology of L-R patterning and congenital heart disease
RXTE Observation of Cygnus X-1
We present timing analysis for a Rossi X-ray Timing Explorer (RXTE) observation of Cygnus X-1 in its hard/low state. This was the first RXTE observation of Cyg X-1 taken after it transited back to this state from its soft/high state. RXTE's large effective area, superior timing capabilities, and ability to obtain long, uninterrupted observations have allowed us to obtain measurements of the power spectral density (PSD), coherence function, and Fourier time lags to a decade lower in frequency and half a decade higher in frequency than typically was achieved with previous instruments. Notable aspects of our observations include a weak 0.005 Hz feature in the PSD coincident with a coherence recovery; a 'hardening' of the high-frequency PSD with increasing energy; a broad frequency range measurement of the coherence function, revealing rollovers from unity coherence at both low and high frequency; and an accurate determination of the Fourier time lags over two and a half decades in frequency. As has been noted in previous similar observations, the time delay is approximately proportional to f(exp -0.7), and at a fixed Fourier frequency the time delay of the hard X-rays compared to the softest energy channel tends to increase logarithmically with energy. Curiously, the 0.01-0.2 Hz coherence between the highest and lowest energy bands is actually slightly greater than the coherence between the second highest and lowest energy bands. We carefully describe all of the analysis techniques used in this paper, and we make comparisons of the data to general theoretical expectations. In a companion paper, we make specific comparisons to a Compton corona model that we have successfully used to describe the energy spectral data from this observation
RXTE Observation of Cygnus X-1: III. Implications for Compton Corona and ADAF Models
We have recently shown that a 'sphere + disk' geometry Compton corona model provides a good description of Rossi X-ray Timing Explorer (RXTE) observations of the hard/low state of Cygnus X-1. Separately, we have analyzed the temporal data provided by RXTE. In this paper we consider the implications of this timing analysis for our best-fit 'sphere + disk' Comptonization models. We focus our attention on the observed Fourier frequency-dependent time delays between hard and soft photons. We consider whether the observed time delays are: created in the disk but are merely reprocessed by the corona; created by differences between the hard and soft photon diffusion times in coronae with extremely large radii; or are due to 'propagation' of disturbances through the corona. We find that the time delays are most likely created directly within the corona; however, it is currently uncertain which specific model is the most likely explanation. Models that posit a large coronal radius [or equivalently, a large Advection Dominated Accretion Flow (ADAF) region] do not fully address all the details of the observed spectrum. The Compton corona models that do address the full spectrum do not contain dynamical information. We show, however, that simple phenomenological propagation models for the observed time delays for these latter models imply extremely slow characteristic propagation speeds within the coronal region
Outcomes of the chemistry discipline network mapping exercises
Standards, threshold learning outcomes and generic graduate outcomes are increasingly important at Australian Universities. The Chemistry Discipline Network has begun developing approaches to these issues and in this paper, we report our experiences and outcomes thus far. One Chemistry Discipline Network working group has completed the first snapshot map of all chemistry units of study offered in twelve universities across Australia, including content, delivery and assessment. We report some general patterns found and more possible questions that can be asked of the information base (http://www.chemnet.edu.au/?q=node/39). In addition, we have mapped the chemistry units offered in six universities against the chemistry TLOs (http://www.chemnet.edu.au/sites/default/files/files/Chemistry%20Threshold%20Learning%20Outcomes%20May%202011.pdf) while simultaneously identifying exemplar learning activities / objects and related assessment for each TLO. This process establishes possible practices and systems which will enable universities to demonstrate that the subjects and degrees meet TLO and standards audits, and also which systems ideally fit seamlessly within normal course development and review. The results of the two mapping exercises are proving invaluable as sources of both information and discussion of issues, including what does a student have to achieve to deserve a BSc in chemistry, and what sort of diversity should be encouraged between universities with different sub-discipline specialities. Using these results, we plan a good practice guide to help ensure that degrees will pass an audit. In conjunction with this we are working towards possible discipline agreed standards to submit to the standards authority
Application of long-term cultured interferon-γ enzyme-linked immunospot assay for assessing effector and memory T cell responses in cattle
doi:10.3791/52833 (2015). Effector and memory T cells are generated through developmental programing of naïve cells following antigen recognition. If the infection is controlled up to 95 % of the T cells generated during the expansion phase are eliminated (i.e., contraction phase) and memory T cells remain, sometimes for a lifetime. In humans, two functionally distinct subsets of memory T cells have been described based on the expression of lymph node homing receptors. Central memory T cells express C-C chemokine receptor 7 and CD45RO and are mainly located in T-cell areas of secondary lymphoid organs. Effector memory T cells express CD45RO, lack CCR7 and display receptors associated with lymphocyte homing to peripheral or inflamed tissues. Effector T cells do not express either CCR7 or CD45RO but upon encounter with antigen produce effector cytokines, such as interferon-γ. Interferon-γ release assays are used for the diagnosis of bovine and human tuberculosis and detect primaril
- …