Berry Phase Effects on Electronic Properties

Ever since its discovery, the Berry phase has permeated through all branches of physics. Over the last three decades, it was gradually realized that the Berry phase of the electronic wave function can have a profound effect on material properties and is responsible for a spectrum of phenomena, such as ferroelectricity, orbital magnetism, various (quantum/anomalous/spin) Hall effects, and quantum charge pumping. This progress is summarized in a pedagogical manner in this review. We start with a brief summary of necessary background, followed by a detailed discussion of the Berry phase effect in a variety of solid state applications. A common thread of the review is the semiclassical formulation of electron dynamics, which is a versatile tool in the study of electron dynamics in the presence of electromagnetic fields and more general perturbations. Finally, we demonstrate a re-quantization method that converts a semiclassical theory to an effective quantum theory. It is clear that the Berry phase should be added as a basic ingredient to our understanding of basic material properties.Comment: 48 pages, 16 figures, submitted to RM

Evaluation of the energy-based runoff concept for a subalpine tundra hillslope

A major challenge to cold regions hydrology and northern water resources management lies in predicting runoff dynamically in the context of warming-induced changes to the rates and patterns of ground thaw and drainage. Meeting this challenge requires new knowledge of the mechanisms and rates of ground thaw and their implications to water drainage and storage patterns and processes. The study carries out to evaluate the concept of energy-based runoff in the perspective of ground heat flux, soil thaw and liquid moisture content, tortuosity of snow-free area, preferential flow and discharge of the hillslope. Based on field measurements, coupled energy and water flow is simulated in the Area of Interest (AOI) with a half-hour time interval by the distributed hydrological model, GEOtop. In the field, the saturated hydraulic conductivity varies exponentially between the superficial organic layer and the underlying mineral layer. In the simulation, the parameters of the soil physical properties are input by fourteen uneven layers below the ground surface. Starting from the initially frozen state, the process of soil thaw is simulated with dynamic variables such as soil liquid moisture and ice content, hydraulic conductivity, thermal conductivity and heat capacity. The simulated frost table depths are validated by 44-point measurements and the simulation of point soil temperature is also compared to data measured in an excavated soil pit. As a result, the frost table topography is dominated by both the snow-free pattern and the energy fluxes on the ground surface. The rate and magnitude of runoff derived from snow drift and the ice content of frozen soil is greatly influenced by the frost table topography. According to the simulation, the frost table depth is closely regressed with the ground surface temperature by a power function. As soil thawing progresses, ground heat flux reduces gradually and the rate of soil thaw becomes small when the frost table descends. Along with the snow-free area expanding, the average soil moisture of the AOI increases prior to that time when the average frost table is less than 25 cm deep. The snow-free patches expand heterogeneously in the AOI, which causes the spatial and temporal variation of hydraulic conductivity due to the non-uniform frost table depth. According to the simulation, the transit time of the flow through the AOI decreases to the shortest span on May 13 with the average frost table of 10 cm. Before this date, the time lag between snowmelt percolation and slope runoff is about 8-10 hours; while after this date, the time lag is no more than 5 hours. The pattern of the preferential flow in the AOI highly depends on the frost table topography. When the snow-free patches are widely scattered and the average frost table is between 0 and 10 cm, the preferential flow paths are inhibited. With soil thaw progresses, the preferential flow paths are prominent with the largest single contributing area occurring when the average frost table is between 10 cm to 15 cm. When the average frost table reaches 25 cm, the importance of preferential flow is not apparent, and matrix flow prevails

Effects of caffeoylxanthiazonoside on airway inflammation in an allergic asthma mice model

Purpose: To investigate the inhibitory effects of caffeoylxanthiazonoside (CYT) on airway inflammation in mice and its mechanism of action. Methods: An allergic asthma mice model was established by intraperitoneal injection and aerosol nebulization with ovalbumin (OVA). After treatment with CYT, the blood and bronchoalveolar lavage fluid (BALF) were collected from the mice. The leukocytes were classified and counted with Giemsa solution. Enzyme-linked immunosorbent assay (ELISA) was used to determine the serum levels of IgE, and IL-4, IL-5, IL-13 and IFN-γ in the BALF of mice. Lung tissues were obtained from the mice and MUC5AC protein expression was measured by western blot. Results: CYT significantly decreased the serum level of IgE in asthmatic mice. Inflammatory cells in BALF of mice were markedly reduced (p < 0.05) by CYT treatment at varying doses (10, 20, and 40 mg/kg). Treatment with CYT also significantly suppressed the cytokines of IL-4, IL-5 and IL-13 and increased the IFN-γ in the BLAF of OVA-induced allergic asthma mice (p < 0.05). Western blot results indicate that CYT treatment significantly decreased the expression of MUC5AC protein in the lung tissues of asthmatic mice. In addition, no significant effects on the body weight of the mice were found after CYT treatment. Conclusion: Caffeoylxanthiazonoside inhibits airway inflammation in allergic asthma mice by altering Th1/Th2 via re-balancing of related cytokines and downregulation of lung MUC5AC protein expression. Therefore, this compound can potentially be developed for the therapeutic management of inflammation in allergic asthma

A low-frequency noise model with carrier generation-recombination process for pentacene organic thin-film transistor

published_or_final_versio

High-performance pentacene thin-film transistor with ZrLaO gate dielectric passivated by fluorine incorporation

postprin

Insecure Property rights and Government Ownership of Firms

China's remarkable economic growth occurred despite (1) the lack of rule of law to secure property rights against state encroachment; and (2) government ownership of most new and successful non-state firms. We develop a theory of ownership under state predation that incorporates these two considerations. In our theory, "private ownership" leads to excessive revenue hiding and "state ownership" fails to provide incentives for managers and local governments in a credible way. In contrast, "local government ownership" integrates local government activities and business activities together, which may not only provide incentives for local governments, but also involves less revenue hiding from the local government and less predation from the state. Furthermore, ownership diversity across localities and within a locality is possible. Our theory is consistent with empirical evidence from China. We thus interpret local government ownership as an organizational response to imperfect state institutions.http://deepblue.lib.umich.edu/bitstream/2027.42/39442/3/wp52.pd

Institutional Environment, Community Government, and Corporate Governance: Understanding China's Township-Village Enterprises

We study China's township-village enterprises (TVES) from an organizational perspective with a focus on governance. Unlike most previous studies, we interpret the firm boundaries of TVEs at the community level rather than the enterprise level. From this perspective, we analyze the central role that community governments play in TVE governance as an organizational response to the imperfect institutional environment of both state and market. Specifically, we show that the community government's involvement in TVEs helps overcome the problems of state predation and under-financing of private enterprises. We also explain why TVE governance leads to harder budget constraints than state-owned enterprises.http://deepblue.lib.umich.edu/bitstream/2027.42/39449/3/wp59.pd

Insecure Property rights and Government Ownership of Firms

China's remarkable economic growth occurred despite (1) the lack of rule of law to secure property rights against state encroachment; and (2) government ownership of most new and successful non-state firms. We develop a theory of ownership under state predation that incorporates these two considerations. In our theory, "private ownership" leads to excessive revenue hiding and "state ownership" fails to provide incentives for managers and local governments in a credible way. In contrast, "local government ownership" integrates local government activities and business activities together, which may not only provide incentives for local governments, but also involves less revenue hiding from the local government and less predation from the state. Furthermore, ownership diversity across localities and within a locality is possible. Our theory is consistent with empirical evidence from China. We thus interpret local government ownership as an organizational response to imperfect state institutions.