Space-time fractional diffusions in Gaussian noisy environment

This paper studies the linear stochastic partial differential equation of fractional orders both in time and space variables $\left(\partial^\beta + \frac{\nu}{2} (-\Delta)^{\alpha/2} \right) u(t,x)= \lambda u(t,x) \dot{W}(t,x)$, where $\dot W$ is a general Gaussian noise and $\beta\in (1/2, 2)$, $\alpha\in (0, 2]$. The existence and uniqueness of the solution, the moment bounds of the solution are obtained by using the fundamental solutions of the corresponding deterministic counterpart represented by the Fox H-functions. Along the way, we obtain some new properties of the fundamental solutions

The Influences of Social Media on Chinese Start-up Stage Entrepreneurship

In today’s digital era, information is increasingly shared and distributed through online social networks. Online social media platforms like Twitter, Facebook, Youtube in the west and Sina Weibo, Wechat in China have not only greatly extended the reach of traditional social networks but also facilitated the information distribution process within the networks. With the rising popularity of such social media platforms, the channel where people obtain information has dramatically compared to traditional print media. Acknowledging the differences in social, culture and economic conditions and the uniqueness of Chinese economy, we argue there is a need to look at the influence of online social networks for Chinese start-up companies specifically. Therefore, in this research, we aim to investigate the influences of online social networks on Chinese young people’s perception on entrepreneurship and its impact on entrepreneurial activities for start-up companies. We collected survey data from 100 Chinese participants and carried out 25 interviews. The results revealed current status quo, opportunities and challenges on using online social networks. For instance, Weibo and Wechat are the most popular choices for business activities in China. The main entrepreneurial activities on social networks include information collection and analysis as part of the decision making process or facilitate the sales and promotion activities. Challenges include such as the overly populated false news and information distributed through the online social networks

Modified low-density lipoprotein from Mycobacterium tuberculosis induces foamy macrophage formation

Tuberculosis (TB) is one of the major causes of mortality in the world, causing approximately 1.5 million deaths every year, among which children take a great part. However, due to the perception that children are rarely infectious or they rarely develop severe disease, children with TB have always been neglected. What is worse, diagnosis of childhood TB is difficult, making it harder to control the disease. Foamy macrophages are a key component in the pathology of TB, and the formation of foamy macrophages foresees the progression of infection to active disease. Low-density lipoprotein (LDL) is one of the major lipoproteins that contain cholesterol, and important metabolism of cholesterol enables bacterial survival. After modification in the host, LDL could lead to foamy macrophage formation in the tubercular granuloma. We hypothesized that the modified LDL in patients with TB which induces foamy macrophage formation is different from other forms of LDL. Therefore, modified LDL in patients with TB could serve as a biomarker for TB diagnosis. Our long-term objective is to characterize modified LDL in TB patients and investigate its function in foamy macrophage formation. In this work, we first prepare Mtb-modified LDL, and then we set up macrophage experiment to investigate its function towards foamy macrophage formation. Then we focus on the characterization of Mtb-modified LDL using agarose gel electrophoresis, Western blot analysis, and MALDI-TOF analysis. | 65 page

Tunable Interface Non-linear Electron Transport in Semiconductor Nanowire Heterostructure and Its Application in Optoelectronics

Understanding the effects of finite size and dimensionality on the interaction of light with nanoscale semiconductor heterostructure is central to identifying and exploiting novel modes in optoelectronic devices. In type-I heterostructured core-shell GaAs/AlxGa1-xAs nanowires, the real space transfer (RST) of photogenerated hot electrons across the interface from the GaAs core to the AlxGa1-xAs shell forms the basis of a new family of optoelectronic devices by a carefully designed and optimized nanofabrication process. Due to the large mobility difference, we observed negative differential resistance (NDR) on single nanowire devices. External modulation of the transfer rates, manifested as a large tunability of the voltage onset of NDR, is achieved using three different modes: electrostatic gating, incident photon flux, and photon energy. In this dissertation, the physics of coupling of external control to transfer rate was investigated. The combined influences of geometric confinement, heterojunction shape and carrier scattering on hot-electron transfer is discussed. Temperature-dependent transport study under monochromatic tunable laser illumination reveals an ultrafast carrier dynamics related to RST of excess carriers, which provides an insight into hot carrier cooling. Device element showing adjustable phase shift and frequency doubling of ac modulation is demonstrated. For a full understanding, Carrier transport properties are probed through electron beam induced current, which is capable of imaging sub-surface feature in excess carrier transport. Along with simulation of injected electron trajectories, selective probing of core and shell by tuning electron beam energies reveals axial and bias dependent transport along parallel channels. The drift and diffusion component of the excess carrier current is deconvoluted from a coupled decay length, from which lower than bulk shell electron mobility is extracted. A precise knowledge of band edge discontinuities at heterostructure interface is inevitable to understand electronic and optoelectronic properties where real space transfer is involved. We used a combined photocurrent and photoluminescence spectroscopic study, in GaAs/AlxGa1-xAs and GaAs/AlAs core-shell nanowire systems, to construct a band diagram of an individual heterostructure nanowire with high spectral resolution, enabling quantification of conduction band offsets. The thesis outlines a promising novel device paradigm with a well-studied carrier transport physics at heterostructure nanowires, which can be further extended to a broad range of semiconductor material systems.Ph.D., Materials Science and Engineering -- Drexel University, 201

Research on Rural Revitalization and Governance From the Perspective of Sustainable Development

The Chinese government has long attached great importance to rural revitalization. The harmony and stability in rural areas are the fundamental guarantees of rural sustainable economic growth and farmers’ prosperity, and they rely on effective rural governance. Taking the Fu’an City in Fujian Province of China as an example, this paper analyzes the rural governance problems arising from the implementation of the rural revitalization strategy with the method of dynamic games with incomplete information after data collection by on-the-spot investigation and file inquiry, etc. The results show that the “solicitation” behavior of village B to increase its own income does not maximize the income of village B and village N; Even under the optimal state of income distribution is derived through the game model, the income distribution between the two villages is still unfair to village N, the investor of the “Waterlands Resort”. Therefore, in order to solve the rural governance problems caused by the distribution of benefits between village B and village N, government subsidies, property rights protection, village rules and regulations are required. Besides, the leading role of rural grassroots organizations should be given full play, and villagers’ self-governing system needs to be improved