University of Central Florida

About: University of Central Florida is a education organization based out in Orlando, Florida, United States. It is known for research contribution in the topics: Laser & Population. The organization has 18822 authors who have published 48679 publications receiving 1234422 citations. The organization is also known as: UCF.

Applications of the FIB lift-out technique for TEM specimen preparation.

Abstract: A site-specific technique for cross-section transmission electron microscopy specimen preparation of difficult materials is presented. A focused ion beam was used to slice an electron transparent membrane from a specific area of interest within a bulk sample. Micromanipulation lift-out procedures were then used to transport the electron-transparent specimen to a carbon-coated copper grid for subsequent TEM analysis. The FIB (focused ion beam) lift-out technique is a fast method for the preparation of site-specific TEM specimens. The versatility of this technique is demonstrated by presenting cross-sectioned TEM specimens from several types of materials systems, including a multi-layered integrated circuit on a Si substrate, a galvanized steel, a polycrystalline SiC ceramic fiber, and a ZnSe optical ceramic. These specimens have both complex surface geometry and interfaces with complex chemistry. FIB milling was performed sequentially through different layers of cross-sectioned materials so that preferential sputtering was not a factor in preparing TEM specimens. The FIB lift-out method for TEM analysis is a useful technique for the study of complex materials systems for TEM analysis.

Underwriter Reputation, Initial Returns, and the Long-Run Performance of IPO Stocks

Abstract: Explores the relationship between the short-term and long-term returns of initial public offerings (IPOs) and the reputation of the underwriters associated with the IPOs. Previous work in this area has shown that use of reputable underwriters for the IPO leads to less short-run underpricing. Data used in this analysis were collected from 2,292 IPOs that were issued between January 1979 and December 1991. The sample includes only firm commitment, domestic offerings of at least $2 million. Three ways of measuring underwriter reputation are considered: the measure developed by Johnson and Miller, the Megginson-Weiss measure, and the Carter-Manaster measure. Results show that larger and more established firms are marketed by the most prestigious investment banks for the initial IPO. In both short-term and long-term performance, the Carter-Manaster measure has the most significance. Further, the analysis shows less negative performance over the three-year period considered for IPOs that are underwritten by more prestigious investment banks. Although it is costly to compile the Carter-Manaster measure, it is shown to be the best of the three measures at controlling for underwriter prestige in IPO studies. Included in this work are the Carter-Manaster measures and the corresponding Megginson-Weiss measures for a large number of investment banks. (SRD)

Dynamic Changes in the Structure, Chemical State and Catalytic Selectivity of Cu Nanocubes during CO2 Electroreduction: Size and Support Effects

Abstract: In situ and operando spectroscopic and microscopic methods were used to gain insight into the correlation between the structure, chemical state, and reactivity of size- and shape-controlled ligand-free Cu nanocubes during CO2 electroreduction (CO2 RR). Dynamic changes in the morphology and composition of Cu cubes supported on carbon were monitored under potential control through electrochemical atomic force microscopy, X-ray absorption fine-structure spectroscopy and X-ray photoelectron spectroscopy. Under reaction conditions, the roughening of the nanocube surface, disappearance of the (100) facets, formation of pores, loss of Cu and reduction of CuOx species observed were found to lead to a suppression of the selectivity for multi-carbon products (i.e. C2 H4 and ethanol) versus CH4 . A comparison with Cu cubes supported on Cu foils revealed an enhanced morphological stability and persistence of CuI species under CO2 RR in the former samples. Both factors are held responsible for the higher C2 /C1 product ratio observed for the Cu cubes/Cu as compared to Cu cubes/C. Our findings highlight the importance of the structure of the active nanocatalyst but also its interaction with the underlying substrate in CO2 RR selectivity.