927 research outputs found
Causal effects of stock market on corporate decisions, disclosure mandates, and informational feedback
No full textThe accounting literature has long recognized that maintaining or increasing stock prices isone of the most important factors for managers’ reporting and disclosure decisions, how-ever, the extant literature mainly examines the reverse causality (i.e., the effect of voluntaryearnings forecasts or earnings management on stock prices), due to endogeneity concerns.Chapter 1 examines managers’ decisions on information disclosure in response to stock-underpricing. Using mutual fund fire sales as an exogenous source of market-disruption,we find some managers increase frequency/precision of earnings guidance in response tostock-underpricing. Other managers, especially those in firms with poorer performanceand more short-term-oriented investors, engage in accrual-based earnings management.The passage of SOX, however, affects firms’ response to fire sales, with firms increasingtheir reliance on guidance as opposed to earnings management. The shift is associatedwith faster post-fire-sales price recovery, suggesting that enhancing information disclosurerather than information manipulation is effective in correcting stock-underpricing.The SEC promulgated Regulation Fair Disclosure (Reg FD) to establish a “level play-ing field”for investors through prohibiting the use of selective disclosure. In Chapter 2, weuse Reg FD as a plausibly natural experiment to evaluate links between disclosure, privateinformation production, and real efficiency. We find that the rule has an adverse impact onprice informativeness, investment-to-price sensitivity, and firm valuewith stronger effectsfor firms with greater prior reliance on selective disclosure. Analyst forecast quality alsoappears to decline following the rule change. Interestingly, the impact of Reg FD on priceinformativeness and the sensitivity of investment-to-price diminishes over time, while the deterioration in analyst forecasts tends to persist. Collectively, the results highlight unin-tended consequences of Reg FD in inhibiting private information acquisition and, thereby,the informational feedback from stock prices to real decisions.Ph.D.Includes bibliographical referencesby Jinglin Jian
Onset timing of significant unroofing around Qaidam basin, northern Tibet, China: constraints from 40Ar/39Ar and FT thermochronology on granitoids
No full textFunctional significance of adaption in optic flow-based spatial vision in flies
No full textLi J. Functional significance of adaption in optic flow-based spatial vision in flies. Bielefeld: Universität Bielefeld; 2019
Diversity survey of Pholcus spiders (Araneae, Pholcidae) from eastern Sichuan and neighboring areas, with descriptions of six new species
Full text linkThirteen spider species of the genus Pholcus Walckenaer, 1805 are reported from a diversity survey in eastern Sichuan and neighboring areas (northeastern Yunnan and western Guizhou). They belong to three species groups and include six newly described species: Pholcus qiaojia Li, Li & Yao, sp. nov. (♂♀, Yunnan) in the bidentatus group; P. aba Li, Li & Yao, sp. nov. (♂♀, Sichuan) and P. wenchuan Li, Li & Yao, sp. nov. (♂♀, Sichuan) in the crypticolens group; P. mengding Li, Li & Yao, sp. nov. (♂♀, Sichuan), P. miyi Li, Li & Yao, sp. nov. (♂♀, Sichuan) and P. yaan Li, Li & Yao, sp. nov. (♂♀, Sichuan) in the yichengicus group. P. bidentatus Zhu, Zhang, Zhang & Chen, 2005 is recorded from Yunnan for the first time and P. kunming Zhang & Zhu, 2009 is recorded from Guizhou and Sichuan for the first time. Detailed diagnoses, descriptions, photomicroscope images, and DNA barcodes of all newly described species are provided
Threshold voltage reliability and trap modelling in silicon carbide MOS capacitor under high temperature
No full textTo extend Moore’s law, silicon carbide devices attend the researcher’s attention due to their irreplaceable advantages such as high critical breakdown electrical field, wide bandgap and excellent thermal conductivity without sacrificing too much charge carrier mobility. However, the defects on the SiC-oxide interface degrades the performance of the device and even get worse at high temperature, such as the threshold voltage shifting problems, limiting the design of the integrated circuits. The thesis models, characterise, analyses, measures and extracts the traps of SiC MOSCAP, to understand the trapped charge transportation and unreliability mechanism under high temperature.Effectively using SiC materials necessitates the need to understand the physical properties itself. Due to the large bandgap, the inversion layer cannot be observable in low frequency C-V measurement. The electrical field, space charge region, surface potential and C-V curve in SiC devices all differ from Si devices. More importantly, the trapped charges fluctuate the surface potential of the SiC devices. To give insight into the mechanism governing the trapped charges, the mathematical solution of the trapped charges in the whole bandgap is solved.To be specific, the trap behaviour at a single energy level is then followed. A nonzero transient current is generated due only to the capture and release of the trapped charges when the equilibrium condition is broken. The trapped charges with high energy are thermalized and an equivalent admittance is obtained which further be split into a capacitance and a conductance.Rising temperature activates the dopant atoms that are not ionised, and the Fermi level shifts towards the midband. The variation of equivalent circuit components and physical parameters responds to the temperature. High temperature expands the SiC crystal and the trapped charges are easy to receive energy from phonons so that the interaction between traps and the conduction band is enhanced and more empty states are waiting for the recombination of the charge carriers.Electrical Engineerin
Peptide-modified surfaces for enzyme immobilization.
Full text linkBACKGROUND: Chemistry and particularly enzymology at surfaces is a topic of rapidly growing interest, both in terms of its role in biological systems and its application in biocatalysis. Existing protein immobilization approaches, including noncovalent or covalent attachments to solid supports, have difficulties in controlling protein orientation, reducing nonspecific absorption and preventing protein denaturation. New strategies for enzyme immobilization are needed that allow the precise control over orientation and position and thereby provide optimized activity. METHODOLOGY/PRINCIPAL FINDINGS: A method is presented for utilizing peptide ligands to immobilize enzymes on surfaces with improved enzyme activity and stability. The appropriate peptide ligands have been rapidly selected from high-density arrays and when desirable, the peptide sequences were further optimized by single-point variant screening to enhance both the affinity and activity of the bound enzyme. For proof of concept, the peptides that bound to β-galactosidase and optimized its activity were covalently attached to surfaces for the purpose of capturing target enzymes. Compared to conventional methods, enzymes immobilized on peptide-modified surfaces exhibited higher specific activity and stability, as well as controlled protein orientation. CONCLUSIONS/SIGNIFICANCE: A simple method for immobilizing enzymes through specific interactions with peptides anchored on surfaces has been developed. This approach will be applicable to the immobilization of a wide variety of enzymes on surfaces with optimized orientation, location and performance, and provides a potential mechanism for the patterned self-assembly of multiple enzymes on surfaces
G-quadruplex: a multifunction DNA structure with great potential
No full textG-quadruplex DNA has great potential for use in many biochemical applications. In the field of nucleic acid nanotechnology, G-quadruplexes can facilitate chemical reactions, mimicking the function of an enzyme when bound to hemin, collectively referred to as G-quadruplex/hemin (abbv. GQH). However, in many published studies, GQH shows unstable and inconsistent catalytic activities, especially regarding the suicide inactivation of GQH, often observed when using it as a peroxidase replacement in reactions. The unstable catalysis of GQH limits its biotechnological applications. Here, we report how varied environmental conditions and the use of different substrates influence inactivation kinetics of GQH, while posing potential solutions to improve the catalytic stability of GQH over long reaction periods. These solutions include optimization of pH condition, protection of hemin through the utilization of polyhistidine chains, and generation of H2O2 utilizing enzyme cascades. Specifically in a cascade reaction of GOx – GQH, GOx converts glucose to H2O2, which can then be utilized by GQH for oxidation of Amplex Red, rather than using high concentration of H2O2. The residual activity of GQH is more stable over time in this cascade, presumably due to the low intermediate H2O2 concentration reducing oxidative damage done to hemin. We also report and confirm previously demonstrated results of protection of hemin from damage through utilization of polypeptide-DNAzyme aggregates. Interestingly, we demonstrate a trade-off in overall initial reaction rate with long-term catalytic activity. That is, unprotected GQH had higher initial velocities at the reaction onset than protected complexes, but protected complexes significantly outperformed the unprotected DNAzyme after only 15 minutes of incubation with H2O2. Overall, our results characterize the inherent inactivation kinetics of the peroxidase-mimicking GQH DNAzyme caused by product color depletion and hemin inactivation in the presence of H2O2 across a variety of environmental conditions. We also explored potential options as detailed above to improve the stability of GQH catalysis. With these results, we hope to provide potentially useful kinetic information for future applications of GQH in biomimetic systems, DNA-based nanotechnologies, and other future applications. We also report a potentially useful future application of the GQ structure in the assembly of DNA nanowires for the efficient transfer of photon energy across nanodevices.Presented at the annual Celebration of Undergraduate Research and Creative Activity while the author was an undergraduate student at Rutgers University-Camden
Motion adaptation facilitates optic flow-based spatial vision
No full textLi J. Motion adaptation facilitates optic flow-based spatial vision. Bielefeld University; 2017.Neuronal representation and extraction of spatial information are essential for
behavioral control. For flying insects, a plausible way to gain spatial information is to
exploit distance-dependent optic flow that is generated during translational self-motion.
Optic flow is computed by arrays of local motion detectors retinotopically arranged in
the second neuropile layer of the insect visual system. These motion detectors have
adaptive response characteristics, i.e. their responses to motion with a constant or only
slowly changing velocity decrease, while their sensitivity to rapid velocity changes is
maintained or even increases. We analyzed by a modeling approach how motion
adaptation affects signal representation at the output of arrays of motion detectors
during simulated flight in artificial and natural 3D environments. We focused on
translational flight, because spatial information is only contained in the optic flow
induced by translational locomotion. Indeed, flies, bees and other insects segregate
their flight into relatively long intersaccadic translational flight sections interspersed with
brief and rapid saccadic turns, presumably to maximize periods of translation (80% of
the flight). With a novel adaptive model of the insect visual motion pathway, we could
show that the motion detector responses to background structures of cluttered
environments are largely attenuated as a consequence of motion adaptation, while
responses to foreground objects stay constant or even increase. This conclusion even
holds under the dynamic flight conditions of insects
Into the Dream Land: Fengshui and the Ideal Landscape in Wang Ximeng’s A Thousand Li of Rivers and Mountains
No full textSince the establishment of the People’s Republic of China in 1949, fengshui (风水, often translated as “geomancy”) has been considered “feudal superstition” (Ch. fengjian mixin 封建迷 信) by the government, so research on geomantic influences on ancient Chinese landscape painting has been neglected in the past century. Fengshui study (Ch. fengshuixue 风水学) includes the analysis of Chinese peoples’ conceptions of the ideal state of land and the proper relationships between the human community and its surroundings. Landscape paintings have long played an important role in the fengshui of interior architecture spaces of Chinese society and culture as a whole. This thesis is the first scholarly attempt to analyze the fengshui features in a specific painted scroll, as well as how fengshui theory shares the same philosophical foundations as ancient Chinese landscape painting. Thus, by influencing the cultural backgrounds of many artists, fengshui has also affected traditional painting styles, directly and indirectly. Traditional Chinese artists had a unique view of the natural environment, and from the paintings and literary works from the Southern and Northern Dynasties (420-589) onward, it is obvious that these landscape renderings are composed of the attitude and spirit of the artist himself, while the traditional landscape painting is just an objective description of external objects. This thesis focuses on Northern Song artist Wang Ximeng’s A Thousand Li of Rivers and Mountains (1113 CE) as an example of how the sentimental and naturalistic characteristics of ancient Chinese landscape painting involve a high degree of syncretism between fengshui theory and landscape painting
The jingling Geordie: community arts and the regional culture of the North East of England
Full text linkIn the light of the massive economic and social changes which have affected the North East of England over the last 25 years, the author assesses the vitality of the indigenous culture and reflects upon current cultural trends and the North East’s future, particularly in relation to a regional Europe. He traces the folk-tradition of the region and looks at ways in which this can be drawn upon to develop a meaningful link between past and present. He looks closely at the changing nature of class-relationships in the North East and reflects upon how a valid local culture can survive in a multi-cultural society. He draws upon his own extensive experience in Community Arts, looking at definitions of the term in the new political climate and arguing for its positive contribution to the cultural debate. He dwells on the issue of regionalism and devolution in a new Europe, comparing the situation in the North East of England with political and cultural changes in Scotland and other parts of the United Kingdom
- …
