On the inward drift of runaway electrons during the plateau phase of runaway current

The well observed inward drift of current carrying runaway electrons during runaway plateau regime after disruption is studied by considering the phase space dynamic of runaways in a large aspect ratio toroidal system. We consider the case where the toroidal field is unperturbed and the toroidal symmetry of the system is preserved. The balance between the change in canonical angular momentum and the input of mechanical angular momentum in such system requires runaways to drift horizontally in configuration space for any given change in momentum space. The dynamic of this drift can be obtained by taking the variation of canonical angular momentum. It is then found that runaway electrons will always drift inward as long as they are decelerating. This drift motion is essentially non-linear, since the current is carried by runaways themselves, and any runaway drift relative to the magnetic axis will cause further displacement of the axis itself. A simplified analytical model is constructed to describe such inward drift both in ideal wall case and no wall case, and the runaway current center displacement as a function of parallel momentum variation is obtained. The time scale of such displacement is estimated by considering effective radiation drag, which shows reasonable agreement with observed displacement time scale. This indicates that the phase space dynamic studied here plays a major role in the horizontal displacement of runaway electrons during plateau regime.Comment: 25 pages, 9 figures, submitted to Physics of Plasma

Doctor of Philosophy

dissertationThe United States is a leader in internationalizing its higher education and has witnessed a tremendous increase in recruiting international students. International students, however, encounter a host of challenges, including language and cultural barriers. Additionally, many come to the United States with a need for strong career development and guidance. Due to the complexity of cultural, social, legal, and personal factors, college career counselors require adequate training and education to appropriately assist international students. Specifically, the need to develop career counselors’ sense of efficacy and multicultural competence is paramount. This study was conducted to assess college career counselors’ perceived level of multicultural counseling competence and self-efficacy in working with international students, as well as the relationship between these two variables. Factors promoting cultural competence and counselor self-efficacy were also explored. In addition, using hierarchical linear regression analysis, this study explored the degree to which multicultural competence influences counselor self-efficacy above and beyond their training and experience. A total number of 145 college counselors completed the online survey. Results suggest counselors rate themselves as possessing an average level of self-efficacy in working with international students, as well as moderate to high multicultural counseling competence. Graduate degree in counseling, counseling classes, on-the-job training, and supervision were positively associated with higher counselor self-efficacy. Similarly, counselors who took more multicultural classes and attended more multicultural training reported higher multicultural counseling competence. Multicultural counseling competence was found to be significantly correlated with career counselors’ self-efficacy in working with international students as well as a significant predictor of counselor self-efficacy. The current study supports the importance of recruiting college career counselors with a graduate level of education in counseling. On-the-job training, supervision, and multicultural training were also crucial in counselors’ perceived level of cultural competence and self-efficacy in working with international students. The findings of this study have important implications for career counselor recruitment, supervision, and training

Dynamical Studies of Model Membrane and Cellular Response to Nanosecond, High-Intensity Pulsed Electric Fields

The dynamics of electroporation of biological cells subjected to nanosecond, high intensity pulses are studied based on a coupled scheme involving the current continuity and Smoluchowski equations. The improved pore formation energy model includes a dependence on pore population and density. It also allows for variable surface tension and incorporates the effects of finite conductivity on the electrostatic correction term, which was not considered by the simple energy models in the literature. It is shown that E(r) becomes self-adjusting with variations in its magnitude and profile. The whole scheme is self-consistent and dynamic. An electromechanical analysis based on thin-shell theory is presented to analyze cell shape changes in response to external electric fields. The calculations demonstrate that at large fields, the spherical cell geometry can be modified, and even ellipsoidal forms may not be appropriate to account for the resulting shape. It is shown that, in keeping with reports in the literature, the final shape depends on membrane thickness. This has direct implications for tissues in which significant molecular restructuring can occur. This study is also focused on obtaining qualitative predictions of pulse width dependence to apoptotic cell irreversibility that has been observed experimentally. The analysis couples a distributed electrical model for current flow with the Smoluchowski equation to provide self-consistent, time-dependent transmembrane voltages. The model captures the essence of the experimentally observed pulse-width dependence, and provides a possible physical picture that depends only on the electrical trigger. Different cell responses of normal and malignant (Farage) tonsillar B-cell are also compared and discussed. It is shown that subjecting a cell to an ultrashort, high-intensity electric pulse is the optimum way for reversible intracellular manipulation. Finally, a simple but physical atomistic model is presented for molecular motion within biological membranes subjected to electric fields. The dynamical, stochastic aspects are treated at the molecular level, without including each and every atom of the complex molecular system. The membrane lipid molecules are represented by a ball-spring model, with pair-wise Lennard-Jones interacting potentials. Predictions include pore formation times of around 1 ns, relatively low ionic throughput in keeping with recent observations, and currents of about 5 nA (at 500 kV/cm). It is also shown that ions facilitate pore formation and that membrane poration may be the principle route for phosphatidylserine externalization

A practical approach to managing patients with HCV infection.

Hepatitis C virus (HCV) infection is a major worldwide public health concern. It is a common cause of chronic liver disease and hepatocellular carcinoma. HCV antibody and HCV RNA testing are available diagnostic studies that offer high degree of accuracy. Current standard therapy includes a combination of pegylated interferon and ribavirin. Response rate is approximately 40% for genotype 1 and 80% for genotypes 2 and 3, respectively. Successful treatment can stop the progression of chronic liver disease, reduce the need for liver transplantation, and possibly decrease the risk for Hepatocellular carcinoma (HCC). Evaluating for potential treatment candidacy is an important initial step in the management of chronic HCV infection as not all individuals may need or qualify for the treatment. Understanding the natural history, the different diagnostic modalities, the current therapeutic options and, the treatment response and adverse effect profiles can help the practitioners better manage chronic HCV infection

Asymptotic-preserving exponential methods for the quantum Boltzmann equation with high-order accuracy

In this paper we develop high-order asymptotic-preserving methods for the spatially inhomogeneous quantum Boltzmann equation. We follow the work in Li and Pareschi, where asymptotic preserving exponential Runge-Kutta methods for the classical inhomogeneous Boltzmann equation were constructed. A major difficulty here is related to the non Gaussian steady states characterizing the quantum kinetic behavior. We show that the proposed schemes work with high-order accuracy uniformly in time for all Planck constants ranging from classical regime to quantum regime, and all Knudsen numbers ranging from kinetic regime to fluid regime. Computational results are presented for both Bose gas and Fermi gas

A STATISTICAL RESEARCH ON THE TYPICAL PATTERNS OF MODERN HOUSING FABRICS, CASE STUDY OF NANJING, CHINA

Proceedings of the XXV ISUF International Conference “Urban Form and Social Context: from Traditions to Newest Demands” (Krasnoyarsk, July 5–9, 2018)After nearly 20 years of massive social housing construction and another 20 years of housing real estate development, Chinese cities basically solved the citizen’s housing problem in the second decade of the 21st century. As a consequence, the major physical component of contemporary cities is modern housing fabrics, which cover over 30% urban land. It is generally believed this magnitude housing development is dominated by modernism residential building with a standard image of a slab apartment. However, as revealed in this research, the real situation is far more diversified and complicated, with various building types, like villas, slabs, towers, and different spatial arrangements, like parallel, zigzag, enclosure. How to classify these diversified realities and what are the typical patterns of different housing fabrics? To answer these questions, this research collected more than 200 housing fabric samples across the city of Nanjing. The latter is the Capital of Jiangsu Province, and a typical modern mega-city in Yangzi River Delta area. To get the reasonable categories of fabric types, a comprehensive classification system is applied. Different from the too simplified classification based on single parameter, building height, adopted in the national housing standard, this classification system is based on the matrix of various parameters, including building height, arrangement, and a building type. The various parameters and their intricate combinations guarantee the classification to be capable to seize and distinguish the formal features of different fabrics. Spacemate, a charting tool developed by B.M. Pont and et al. in TU Delft, is used to testify the classification. After the classification, the samples are divided into 21 categories. For each category, data samples, like spacing, dimension of building footprint, height, density, land coverage, and et al. are collected and a statistical analysis are conducted. Based on this qualitative sample studies, the typical patterns and their statistical models are built up. In the application part, a bioclimatic performance study of these typical patterns is presented. Due to the typicality and statistical precision, the complicated co-relation between urban fabric and bioclimatic performance could be discovered, efficiently and convincingly