ABSTRACT
OBJECTIVES: Serrated polyps compromise both typical hyperplastic polyps as well as sessile serrated adenomas and dysplastic serrated polyps. Hyperplastic polyps exhibit two histological patterns: microvesicular hyperplastic polyps (MVHPs) and goblet cell hyperplastic polyps (GCHPs). MVHPs and GCHPs differ in their molecular signature. MVHPs have been frequently found to have the BRAF(V600E) mutation as well as aberrant methylation. In contrast, GCHPs have been associated with the KRAS mutation (KRAS-mut), which are infrequently seen in dysplastic serrated sessile adenomas. The particular risk factors that are associated with development of the types of hyperplastic polyps have not been previously studied. The purpose of this study is to characterize the associations between particular risk factors and the development of goblet cell or microvesicular hyperplastic polyps. METHODS: We conducted a cross-sectional analysis of 3,543 asymptomatic, mostly average risk patients 50 and 79 years of age undergoing open-access screening colonoscopy between March 2005 and January 2012. Each patient was given a survey regarding 25 reputed risk factors for colorectal neoplasia and the responses were correlated with findings at colonoscopy. Associations between putative risk factors for colorectal neoplasia and MVHPs and GSHPs were examined using multiple logistic regression. RESULTS: MVHPS and GCHPs were identified in 5.3% and 8.7% of patients, respectively. The results of the statistical analysis indicate that a history of smoking greater than 20 years is associated with an increased risk of MVHPs (P<0.005) and GCHPs (P<0.005). An elevated BMI >30 kg/m(2) was also associated with the presence of MVHP at colonoscopy (P<0.005). Blacks and Asians appear to be protected from the development of MVHPs. In contrast, there was a positive association with the presence of GCHP at colonoscopy in blacks. CONCLUSIONS: The study suggests that the development of the distinct histological types of hyperplastic polyps are associated with distinct modifiable and non-modifiable lifestyle factors.
Subject(s)
Adenoma/epidemiology , Colonic Neoplasms/epidemiology , Colonic Polyps/epidemiology , Goblet Cells/pathology , Hyperplasia/epidemiology , Adenoma/genetics , Adenoma/pathology , Black or African American/statistics & numerical data , Aged , Asian/statistics & numerical data , Asymptomatic Diseases , Colonic Neoplasms/genetics , Colonic Neoplasms/pathology , Colonic Polyps/genetics , Colonic Polyps/pathology , Colonoscopy , Cross-Sectional Studies , Early Detection of Cancer , Female , Humans , Hyperplasia/genetics , Hyperplasia/pathology , Male , Middle Aged , Obesity/epidemiology , Proto-Oncogene Proteins/genetics , Proto-Oncogene Proteins B-raf/genetics , Proto-Oncogene Proteins p21(ras) , Risk Factors , Smoking/epidemiology , United States/epidemiology , White People/statistics & numerical data , ras Proteins/geneticsABSTRACT
A dimensionless thermoelectric figure-of-merit (ZT) of 0.95 in p-type nanostructured bulk silicon germanium (SiGe) alloys is achieved, which is about 90% higher than what is currently used in space flight missions, and 50% higher than the reported record in p-type SiGe alloys. These nanostructured bulk materials were made by using a direct current-induced hot press of mechanically alloyed nanopowders that were initially synthesized by ball milling of commercial grade Si and Ge chunks with boron powder. The enhancement of ZT is due to a large reduction of thermal conductivity caused by the increased phonon scattering at the grain boundaries of the nanostructures combined with an increased power factor at high temperatures.
