6,405 research outputs found

    Short-term debt maturity, monitoring and accruals-based earnings management

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    Most prior studies assume a positive relation between debt and earnings management, consistent with the financial distress theory. However, the empirical evidence for financial distress theory is mixed. Another stream of studies argues that lenders of short-term debt play a monitoring role over management, especially when the firmā€™s creditworthiness is not in doubt. To explore the implications of these arguments on managersā€™ earnings management incentives, we examine a sample of US firms over the period 2003ā€“2006 and find that short-term debt is positively associated with accruals-based earnings management (measured by discretionary accruals), consistent with the financial distress theory. We also find that this relation is significantly weaker for firms that are of higher creditworthiness (i.e. investment grade firms), consistent with monitoring benefits outweighing financial distress reasons for managing earnings

    Characterization of highly-oriented ferroelectric Pb_xBa_(1-x)TiO_3

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    Pb_xBa_(1-x)TiO_3 (0.2 ā‰¾ x ā‰¾ 1) thin films were deposited on single-crystal MgO as well as amorphous Si_3N_4/Si substrates using biaxially textured MgO buffer templates, grown by ion beam-assisted deposition (IBAD). The ferroelectric films were stoichiometric and highly oriented, with only (001) and (100) orientations evident in x-ray diffraction (XRD) scans. Films on biaxially textured templates had smaller grains (60 nm average) than those deposited on single-crystal MgO (300 nm average). Electron backscatter diffraction (EBSD) has been used to study the microtexture on both types of substrates and the results were consistent with x-ray pole figures and transmission electron microscopy (TEM) micrographs that indicated the presence of 90Ā° domain boundaries, twins, in films deposited on single-crystal MgO substrates. In contrast, films on biaxially textured substrates consisted of small single-domain grains that were either c or a oriented. The surface-sensitive EBSD technique was used to measure the tetragonal tilt angle as well as in-plane and out-of-plane texture. High-temperature x-ray diffraction (HTXRD) of films with 90Ā° domain walls indicated large changes, as much as 60%, in the c and a domain fractions with temperature, while such changes were not observed for Pb_xBa_(1-x)TiO_3 (PBT) films on biaxially textured MgO/Si_3N_4/Si substrates, which lacked 90Ā° domain boundaries

    Graded ferroelectric capacitors with robust temperature characteristics

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    Ferroelectric thin films offer the possibility of engineering the dielectric response for tunable components in frequency-agile rf and microwave devices. However, this approach often leads to an undesired temperature sensitivity. Compositionally graded ferroelectric films have been explored as a means of redressing this sensitivity, but experimental observations vary depending on geometry and other details. In this paper, we present a continuum model to calculate the capacitive response of graded ferroelectric films with realistic electrode geometries by accurately accounting for the polarization distribution and long-range electrostatic interactions. We show that graded c-axis poled BaxSr_(1āˆ’xT)iO_3 BST parallel plate capacitors are ineffective while graded a-axis poled BST coplanar capacitors with interdigitated electrodes are extremely effective in obtaining high and temperature-stable dielectric properties

    Expression of O-linked N-acetylglucosamine modified proteins and production and characterization of chlamydia trachomatis CT663

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    O-linked Ć¢-N-acetylglucosamine is a regulatory post translational modification. This modification occurs on nearly all functional classes of proteins, in the nucleus and cytoplasm. O-GlcNAc is added to serine or threonine by O-GlcNAc transferase and removed by O-GlcNAcase. Previous attempts to study O-GlcNAc-modified proteins have resulted in low yields, making 3-dimensional structure determination impossible. In this dissertation O-GlcNAc transferase will be co-expressed with domains of human cAMP responsive element-binding protein (CREB1) and Abelson tyrosine-kinase 2 (ABL2) in E. coli, to produce O-GlcNAc-modified protein. The O-GlcNAc-modified protein was expressed in a variety of E. coli cell lines at a variety of conditions, but only small quantities of insoluble protein were produced. A glycosidase was suspected due to the disappearance of the O-GlcNAc modification from the protein. O-(2-acetamido-2-dexoy-dglucopyranosylidene) amino-N-phenylcarbamate (PUGNAc), a Ć¢-N-acetylglucosaminidase inhibitor, was added to the culture media and increased the production of O-GlcNAc-modified protein. This was the first evidence that Ć¢-N-acetylglucosaminidase (NagZ), an E. coli enzyme, cleaves O-GlcNAc from proteins in vivo. NagZ was isolated and shown to cleave O-GlcNAc from a synthetic O-GlcNAc-peptide in vitro. In E. coli, NagZ cleaves the GlcNAc-Ć¢1,4-N-acetylmuramic acid linkage to recycle peptidoglycan in the cytoplasm. A NagZ knockout showed no activity towards the O-GlcNAc-peptide, confirming NagZ as the enzyme responsible for cleaving O-GlcNAc from our glycoprotein expressed in vivo. O-GlcNAc-modified protein produced by the NagZ knockout (āˆ†NagZ) co-expression system is highly glycosylated and can be resolubilized from the pellet. The āˆ†NagZ is a step closer to production of milligram quantities of O-GlcNAc-modified protein for structure determination

    The Long-term Dynamical Evolution of Disk-fragmented Multiple Systems in the Solar Neighborhood

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    The origin of very low-mass hydrogen-burning stars, brown dwarfs (BDs), and planetary-mass objects (PMOs) at the low-mass end of the initial mass function is not yet fully understood. Gravitational fragmentation of circumstellar disks provides a possible mechanism for the formation of such low-mass objects. The kinematic and binary properties of very low-mass objects formed through disk fragmentation at early times (<10 Myr) were discussed in our previous paper. In this paper we extend the analysis by following the long-term evolution of diskfragmented systems up to an age of 10 Gyr, covering the ages of the stellar and substellar populations in the Galactic field. We find that the systems continue to decay, although the rates at which companions escape or collide with each other are substantially lower than during the first 10 Myr, and that dynamical evolution is limited beyond 1 Gyr. By t = 10 Gyr, about one third of the host stars are single, and more than half have only one companion left. Most of the other systems have two companions left that orbit their host star in widely separated orbits. A small fraction of companions have formed binaries that orbit the host star in a hierarchical triple configuration. The majority of such double-companion systems have internal orbits that are retrograde with respect to their orbits around their host stars. Our simulations allow a comparison between the predicted outcomes of disk fragmentation with the observed low-mass hydrogen-burning stars, BDs, and PMOs in the solar neighborhood. Imaging and radial velocity surveys for faint binary companions among nearby stars are necessary for verification or rejection of the formation mechanism proposed in this paper

    Numerical Modeling of Single-Chamber SOFCs with Hydrocarbon Fuels

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    The effect of the dynamical state of clusters on gas expulsion and infant mortality

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    The star formation efficiency (SFE) of a star cluster is thought to be the critical factor in determining if the cluster can survive for a significant (>50 Myr) time. There is an often quoted critical SFE of ~30 per cent for a cluster to survive gas expulsion. I reiterate that the SFE is not the critical factor, rather it is the dynamical state of the stars (as measured by their virial ratio) immediately before gas expulsion that is the critical factor. If the stars in a star cluster are born in an even slightly cold dynamical state then the survivability of a cluster can be greatly increased.Comment: 6 pages, 2 figures. Review talk given at the meeting on "Young massive star clusters - Initial conditions and environments", E. Perez, R. de Grijs, R. M. Gonzalez Delgado, eds., Granada (Spain), September 2007, Springer: Dordrecht. Replacement to correct mistake in a referenc

    Highly neurotic never-depressed students have negative biases in information processing

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    BACKGROUND: Cognitive theories associate depression with negative biases in information processing. Although negatively biased cognitions are well documented in depressed patients and to some extent in recovered patients, it remains unclear whether these abnormalities are present before the first depressive episode. METHOD: High neuroticism (N) is a well-recognized risk factor for depression. The current study therefore compared different aspects of emotional processing in 33 high-N never-depressed and 32 low-N matched volunteers. Awakening salivary cortisol, which is often elevated in severely depressed patients, was measured to explore the neurobiological substrate of neuroticism. RESULTS: High-N volunteers showed increased processing of negative and/or decreased processing of positive information in emotional categorization and memory, facial expression recognition and emotion-potentiated startle (EPS), in the absence of global memory or executive deficits. By contrast, there was no evidence for effects of neuroticism on attentional bias (as measured with the dot-probe task), over-general autobiographical memory, or awakening cortisol levels. CONCLUSIONS: These results suggest that certain negative processing biases precede depression rather than arising as a result of depressive experience per se and as such could in part mediate the vulnerability of high-N subjects to depression. Longitudinal studies are required to confirm that such cognitive vulnerabilities predict subsequent depression in individual subjects
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