GMM Estimation of the Number of Latent Factors

We propose a generalized method of moment (GMM) estimator of the number of latent factors in linear factor models. The method is appropriate for panels a large (small) number of cross-section observations and a small (large) number of time-series observations. It is robust to heteroskedasticity and time series autocorrelation of the idiosyncratic components. All necessary procedures are similar to three stage least squares, so they are computationally easy to use. In addition, the method can be used to determine what observable variables are correlated with the latent factors without estimating them. Our Monte Carlo experiments show that the proposed estimator has good finite-sample properties. As an application of the method, we estimate the number of factors in the US stock market. Our results indicate that the US stock returns are explained by three factors. One of the three latent factors is not captured by the factors proposed by Chen Roll and Ross 1986 and Fama and French 1996.Factor models; GMM; number of factors; asset pricing

Large-N and Large-T Properties of Panel Data Estimators and the Hausman Test

This paper examines the asymptotic properties of the popular within, GLS estimators and the Hausman test for panel data models with both large numbers of cross-section (N) and time-series (T) observations. The model we consider includes the regressors with deterministic trends in mean as well as time invariant regressors. If a time-varying regressor is correlated with time invariant regressors, the time series of the time varying regressor is not ergodic. Our asymptotic results are obtained considering the dependence of such non-ergodic time-varying regressors. We find that the within estimator is as efficient as the GLS estimator. Despite this asymptotic equivalence, however, the Hausman statistic, which is essentially a distance measure between the two estimators, is well defined and asymptotically \chi^2-distributed under the random effects assumption.

A study of leadership development programme for gifted primary school students in South Korea

This thesis investigates leadership development in the gifted primary school students of South Korea. It ultimately aims to make suggestions toward the formulation and implementation of a model leadership gifted curriculum and programme specific to the Korean cultural and educational setting. The bases of the suggestions were assembled from three sources: literature pertaining to the relevant topics of the thesis, available leadership gifted curricula and programmes, and the perspectives of Korean gifted educators. The views of the Korean gifted teachers were investigated using mixed methods or methodological triangulation; the measurement instruments employed in this study were a tripartite questionnaire survey and complementary semi-structured interviews. Fifty Korean gifted teachers teaching at mainstream national and state primary schools, Centres for the Gifted, and specialised gifted schools partook in the questionnaire survey. Two Korean gifted teachers from mainstream state primary schools and the director of the Korean Educational Development Institute (KEDI) were interviewed to supplement the data collected through the questionnaires. The results illuminated the Korean gifted educational context and highlighted the lack and the need for leadership development for the gifted. Through the comprehensive review of the literature review, available curricula/programmes, and results of this study, final suggestions for a prospective leadership gifted curriculum and programme were made. Three main guidelines were proposed; firstly, a model of the prospective contents of leadership gifted education, named the Four Areas Leadership Model (FALM); secondly, the suggestions for the implementation of the FALM in a curriculum format; finally, the suggestions for the implementation of the FALM in a programme format. The FALM adopted the framework of Parker's (1983) Leadership Training Model, and its implementation as a programme was adapted from Renzulli's (1976, 1986) Enrichment Triad Model's implementation scheme which was considered appropriate to the Korean context

Factors associated with nosocomial fungal sepsis among patients in the paediatric intensive care unit at the Chris Hani Baragwanath academic hospital

A research report submitted to the Faculty of Health Sciences, University of the Witwatersrand, Johannesburg in partial fulfillment of the requirements for the degree of Master of Medicine in the branch of Paediatrics and Child Health 29 May 2017Introduction Sepsis, and in particular, severe sepsis, remains a major cause of death in children worldwide. One of the areas where the burden of sepsis is keenly felt is in the paediatric intensive care unit (PICU) setting, contributing significantly to childhood mortality. Fungal organisms have emerged as a major organism contributing to nosocomial sepsis in PICU. No local data regarding nosocomial fungal sepsis in the non-neonatal, PICU population exists regarding this matter. This study describes the characteristics of patients with nosocomial fungal sepsis in the PICU at South Africa’s largest hospital Chris Hani Baragwanath Academic Hospital (CHBAH). Methods This study was a retrospective review of patient records. All patients aged 0-16 years admitted to the PICU at Chris Hani Baragwanath Academic Hospital (CHBAH) from January 2008 through December 2011 were assessed. A total of seventeen patients who developed nosocomial fungal sepsis were included in this study. Results The incidence of candidaemia was reported to be 3.2 per 100 cases. The major age group affected by nosocomial fungal sepsis was the under one age group. The most common diagnoses on admission were lower respiratory tract infection (LRTI) followed by haematology-oncology and acute gastroenteritis cases. ICU factors found to commonly co-­‐exist with proven nosocomial fungal sepsis were presence of a central venous catheter (100%), mechanical ventilation (82%), arterial line (70%), and systemic corticosteroid use (47%). The penicillin class was the most common antimicrobial that patients were found to be on at the time of nosocomial sepsis. The most common fungal organism as a cause for nosocomial sepsis was C. parapsilosis rather than C. albicans. Furthermore, the majority of this study’s isolates were susceptible to voriconazole rather the current empiric antifungal of choice, namely fluconazole. Conclusion The presence of central venous catheters, arterial lines, mechanical ventilation and systemic corticosteroid use is common in paediatric patients with nosocomial fungal sepsis. However, this study was unable to determine statistically significant factors associated with fungal sepsis in a tertiary PICU due to the surprisingly small number of cases (n=35) detected over a four-year period. This perhaps represents the most striking finding of the study together with a concerning pattern of fluconazole resistance (14%) among isolated organisms.MT201

Panel Data Models with Multiple Time-Varying Individual Effects

This paper considers a panel data model with time-varying individual effects. The data are assumed to contain a large number of cross-sectional units repeatedly observed over a fixed number of time periods. The model has a feature of the fixed-effects model in that the effects are assumed to be correlated with the regressors. The unobservable individual effects are assumed to have a factor structure. For consistent estimation of the model, it is important to estimate the true number of factors. We propose a generalized methods of moments procedure by which both the number of factors and the regression coefficients can be consistently estimated. Some important identification issues are also discussed. Our simulation results indicate that the proposed methods produce reliable estimates.panel data, time-varying individual effects, factor models

The UDP-Glycosyltransferase Family in Drosophila melanogaster: Nomenclature Update, Gene Expression and Phylogenetic Analysis.

UDP-glycosyltransferases (UGTs) are important conjugation enzymes found in all kingdoms of life, catalyzing a sugar conjugation with small lipophilic compounds and playing a crucial role in detoxification and homeostasis. The UGT gene family is defined by a signature motif in the C-terminal domain where the uridine diphosphate (UDP)-sugar donor binds. UGTs have been identified in a number of insect genomes over the last decade and much progress has been achieved in characterizing their expression patterns and molecular functions. Here, we present an update of the complete repertoire of UGT genes in Drosophila melanogaster and provide a brief overview of the latest research in this model insect. A total of 35 UGT genes are found in the D. melanogaster genome, localized to chromosomes 2 and 3 with a high degree of gene duplications on the chromosome arm 3R. All D. melanogaster UGT genes have now been named in FlyBase according to the unified UGT nomenclature guidelines. A phylogenetic analysis of UGT genes shows lineage-specific gene duplications. Analysis of anatomical and induced gene expression patterns demonstrate that some UGT genes are differentially expressed in various tissues or after environmental treatments. Extended searches of UGT orthologs from 18 additional Drosophila species reveal a diversity of UGT gene numbers and composition. The roles of Drosophila UGTs identified to date are briefly reviewed, and include xenobiotic metabolism, nicotine resistance, olfaction, cold tolerance, sclerotization, pigmentation, and immunity. Together, the updated genomic information and research overview provided herein will aid further research in this developing field