Asymptotic Behavior of a Viscous Liquid-Gas Model with Mass-Dependent Viscosity and Vacuum

In this paper, we consider two classes of free boundary value problems of a viscous two-phase liquid-gas model relevant to the flow in wells and pipelines with mass-dependent viscosity coefficient. The liquid is treated as an incompressible fluid whereas the gas is assumed to be polytropic. We obtain the asymptotic behavior and decay rates of the mass functions $n(x,t)$,\$m(x,t)$ when the initial masses are assumed to be connected to vacuum both discontinuously and continuously, which improves the corresponding result about Navier-Stokes equations in \cite{Zhu}.Comment: 24 page

The Permeation Behavior of Nanoparticles in Lipid Membranes

The number of engineered nanoparticles for applications in the biomedical arena has grown tremendously over the last years due to advances in the science of synthesis and characterization. For most applications, the crucial step is the transport through a physiological cellular membrane. However, the behavior of nanoparticles in a biological matrix is a very complex problem that depends not only on the type of nanoparticle, but also on its size, shape, phase, surface charge, chemical composition and agglomeration state. In this thesis, I introduce a streamlined theoretical model that predicts the average time of entry of nanoparticles in lipid membranes, using a combination of molecular dynamics simulations and statistical approaches. The uniqueness of the model lies in the ability to identify four parameters that separate the contributions of nanoparticle characteristics (i.e. size, shape, solubility) from the membrane properties (density distribution and dynamics). This factorization allows the inclusion of data obtained from both experimental and computational sources, as well as a rapid estimation of large sets of permutations in membranes. The robustness of the model is supported by experiments carried out in lipid vesicles encapsulating graphene quantum dots as nanoparticles. The model is applied to the study of various nanoparticles, biological membranes (i.e. mammalian cellular organelles, viral envelopes), and environmental conditions. Overall, this work contributes to the understanding and prediction of interactions between nanoparticles and lipid membranes, responding to the high level of interest across multiple areas of study in modulating intracellular targets, and the need to understand and improve the applications of nanoparticles and to assess their effect on human health (i.e. cytotoxicity, bioavailability).PHDBiophysicsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/163056/1/desmliu_1.pd

Co-movements of Shanghai and New York Stock prices by time-varying regressions

We estimate a time-varying regression model to study the relationship between returns in the Shanghai and New York stock markets, with possible inclusion of lagged returns. The parameters of the regressions reveal that the effect of the current stock return for New York on that for Shanghai steadily increases after the 1997 Asian financial crisis and turns significantly and persistently positive after 2002, when China entered WTO. The effect of the current return for Shanghai on New York also becomes significantly positive and increasing after 2002. The upward trend has been interrupted during the recent global financial crisis, but reaches the level of about 0.4 to 0.5 in 2010 for both markets. Our results show that China’s stock market has become more and more integrated into the world market in the past twenty years, with interruptions occurring during the recent global economic downturn.China; globalization; rate of return; stock markets; time-varying parameter regression

Effect of Graphene Oxide Nanosheets on Physical Properties of Ultra-High-Performance Concrete with High Volume Supplementary Cementitious Materials

Nanomaterials have been increasingly employed for improving the mechanical properties and durability of ultra-high-performance concrete (UHPC) with high volume supplementary cementitious materials (SCMs). Recently, graphene oxide (GO) nanosheets have appeared as one of the most promising nanomaterials for enhancing the properties of cementitious composites. To date, a majority of studies have concentrated on cement pastes and mortars with fewer investigations on normal concrete, ultra-high strength concrete, and ultra-high-performance cement-based composites with a high volume of cement content. The studies of UHPC with high volume SCMs have not yet been widely investigated. This paper presents an experimental investigation into the mini slump flow and physical properties of such a UHPC containing GO nanosheets at additions from 0.00 to 0.05% by weight of cement and a water−cement ratio of 0.16. The study demonstrates that the mini slump flow gradually decreases with increasing GO nanosheet content. The results also confirm that the optimal content of GO nanosheets under standard curing and under steam curing is 0.02% and 0.04%, respectively, and the corresponding compressive and flexural strengths are significantly improved, establishing a fundamental step toward developing a cost-effective and environmentally friendly UHPC for more sustainable infrastructure

CFO Promotion-based Incentives and Earnings Management

This study examines whether CFO promotion-based incentives induce opportunistic reporting activities. We find that CFO promotion-based incentives, measured by the pay gap between the CEO and the CFO, are positively associated with accruals management and accounting misconduct in the pre-SOX period and the probability of meeting or beating analysts’ forecasts in both the pre- and post-SOX periods. Further analysis shows that CFO promotion-based incentives are negatively associated with real earnings management in both the pre- and post-SOX periods. In addition, we find some evidence that the association between CFO promotion-based incentives and opportunistic reporting activities is stronger before CEO turnovers. We also document that CFOs engage in more opportunistic financial reporting when the pay gap between the CFO and other VPs is greater. Overall, our findings suggest that CFO promotion-based incentives may encourage CFOs to engage in opportunistic reporting activities but mitigate real earnings management

Probing short-range magnetic order in a geometrically frustrated magnet by spin Seebeck effect

Competing magnetic interactions in geometrically frustrated magnets give rise to new forms of correlated matter, such as spin liquids and spin ices. Characterizing the magnetic structure of these states has been difficult due to the absence of long-range order. Here, we demonstrate that the spin Seebeck effect (SSE) is a sensitive probe of magnetic short-range order (SRO) in geometrically frustrated magnets. In low temperature (2 - 5 K) SSE measurements on a model frustrated magnet \mathrm{Gd_{3}Ga_{5}O_{12}}, we observe modulations in the spin current on top of a smooth background. By comparing to existing neutron diffraction data, we find that these modulations arise from field-induced magnetic ordering that is short-range in nature. The observed SRO is anisotropic with the direction of applied field, which is verified by theoretical calculation.Comment: 5 pages, 4 figure