Liqiang Ni

Sufficient Dimension Reduction via Inverse Regression: A Minimum Discrepancy Approach

A family of dimension-reduction methods, the inverse regression (IR) family, is developed by minimizing a quadratic objective function. An optimal member of this family, the inverse regression estimator (IRE), is proposed, along with inference methods and a computational algorithm. The IRE has at least three desirable properties: (1) Its estimated basis of the central dimension reduction subspace is asymptotically efficient, (2) its test statistic for dimension has an asymptotic chi-squared distribution, and (3) it provides a chi-squared test of the conditional independence hypothesis that the response is independent of a selected subset of predictors given the remaining predictors. Current methods like sliced inverse regression belong to a suboptimal class of the IR family. Comparisons of these methods are reported through simulation studies. The approach developed here also allows a relatively straightforward derivation of the asymptotic null distribution of the test statistic for dimension used in sliced average variance estimation.

U.S.-Based Fast-Food Restaurants: Factors Influencing the International Expansion of Franchise Systems

Studies of international franchising are scant but increasing and can be divided into two streams of research: those focusing on environmental predictors of internationalization and those focusing on strategic, firm-level characteristics. Examining the latter category, this study empirically explores a set of firm-level attributes as predictors of decision making on whether firms seek international expansion. Using longitudinal data from Bonds Franchise Guide 2001–2008, we draw on a sample of U.S.-based fast-food franchise systems to test our hypotheses. Specifically, our database is composed of 1,058 observations of 158 chains, and we estimate a semi-parametric logistic model for international franchising. The model contributes to the literature by being the first to examine the nonlinearity of international franchising determinants using agency theory. The results show that (a) bonding, (b) the percentage of franchised units, (c) the number of states within which the system operates, and (d) the provision of area development agreements and sub-franchising significantly contribute to the international expansion of U.S.-based fast-food franchisors.

Long-Term Exposure to Cigarette Smoke Extract Induces Hypomethylation at the RUNX3 and IGF2-H19 Loci in Immortalized Human Urothelial Cells

Cigarette smoking is the single most important epidemiological risk factor for bladder cancer but it is not known whether exposure of urothelial cells to the systemic soluble contents of cigarette smoke is directly causative to bladder cancer and the associated epigenetic changes such as tumor suppressor gene hypermethylation. We undertook this study to investigate if long-term treatment of human urothelial cells with cigarette smoke extract (CSE) results in tumor suppressor gene hypermethylation, a phenotype that was previously associated with long-term constant CSE treatment of airway epithelial cells. We chronically treated an immortalized human urothelial cell line UROtsa with CSE using a cyclic daily regimen but the cells were cultured in CSE-free medium between daily treatments. Bisulfite sequencing and real-time PCR array-based methylation profiling were employed to evaluate methylation changes at tumor suppressor gene loci in the chronically CSE-treated cells versus the passage-matched untreated control cells. The RUNX3 tumor suppressor gene promoter was hypomethylated with a significant increase in proportion of the completely unmethylated haplotype after the long-term CSE treatment; whereas RUNX3 promoter hypermethylation was previously reported for bladder cancers of smokers. Hypomethylation induced by the long-term CSE treatment was also observed for the IGF2-H19 locus. The methylation status at the PRSS8/prostasin and 16 additional loci however, was unaffected by the chronic CSE treatment. Transient CSE treatment over 1 daily regimen resulted in transcriptional down-regulation of RUNX3 and H19, but only the H19 transcription was down-regulated in the chronically CSE-treated urothelial cells. Transcription of a key enzyme in one-carbon metabolism, dihydrofolate reductase (DHFR) was greatly reduced by the long-term CSE treatment, potentially serving as a mechanism for the hypomethylation phenotype via a reduced supply of methyl donor. In conclusion, chronic cyclic CSE treatment of urothelial cells induced hypomethylation rather than hypermethylation at specific loci.

ELEVATED SOIL LEAD: STATISTICAL MODELING AND APPORTIONMENT OF CONTRIBUTIONS FROM LEAD-BASED PAINT AND LEADED GASOLINE

While it is widely accepted that lead-based paint and leaded gasoline are primary sources of elevated concentrations of lead in residential soils, conclusions regarding their relative contributions are mixed and generally study specific. We develop a novel nonlinear regression for soil lead concentrations over time. It is argued that this methodology provides useful insights into the partitioning of the average soil lead concentration by source and time over large residential areas. The methodology is used to investigate soil lead concentrations from the 1987 Minnesota Lead Study and the 1990 National Lead Survey. Potential litigation issues are discussed briefly.

Internationalization of Franchising

In the U.S. economy, the service sector has witnessed a tremendous growth in the past several decades, and the hospitality industry is one of the major components of this fast growth (Ketchen et al 2006). Different to most of the other service sectors, the hotel industry is usually capital intensive and its logistics and supply chain can be as complex as those of manufacturing operations (Chen and Dimou, 2005). For hotel companies, this can be a great obstacle to equity-based expansion models in various markets, particularly in the international market. This also raises the issue of the importance of the internationalization process through franchising for hotel companies.

Home Country Macroeconomic Determinants of Chinese OFDI

Compared with foreign direct investment (FDI) inflows, Chinese outward foreign direct investment (OFDI) used to be quite small. According to UN statistics, China’s FDI inflow-outflow ratio was 6.4:1 in 2005 (Cheung & Qian, 2008). However, Chinese investment abroad has increased dramatically since 2007. In 2008, Chinese OFDI outflow reached US

A note on shrinkage sliced inverse regression

52.1 billion, which equals China’s 2003 FDI inflow. In 2009, Chinese OFDI outflow was US

Examining the Determinants of Hotel Chain Expansion through International Franchising

48 billion, more than double 2007’s outflow (US

Using intraslice covariances for improved estimation of the central subspace in regression

22.5 billion) (UNCTAD, 2010). In 2010, it reached

Improving Dimension Reduction Via Contour-Projection

57.9 billion. According to recent statistics from the Department of Outward Investment and Economic Cooperation of the Ministry of Commerce in the People’s Republic of China, US