FABRICATION AND FRACTURE TEST OF FUNCTIONALIZED GRAPHENE-PETI 5 COMPOSITE

ABSTRACT The development of a composite cryogenic fuel tank is desirable for the creation of a reusable single-stage launch vehicle. The cyclic loading and temperature changes experienced during launch and re-entry conditions result in the microcracking of conventional composites. To increase the fracture strength of this composite, a property often limited by the matrix, the nanoplatelet known as graphene or exfoliated graphite, has been introduced. Three nanocomposites were produced using graphene and Phenylethynyl Terminated Imide oligomer (PETI-5). The nanocomposites were machined in to flexure samples and tested at room temperature. Results from these tests indicate that the ideal concentration of graphene in our PETI-5 nanocomposite is 0.08%

Labor leverage, financial statement comparability, and corporate employment

We examine how labor-induced operating leverage shapes managers' decision to adopt more comparable financial statement. We hypothesize that firms subject to higher labor-induced operating leverage are more likely to adopt more comparable financial statements in order to facilitate more timely employment adjustment which reduces firm risk related to labor leverage. Consistent with our hypothesis, we find that proxies for labor-induced operating leverage, such as labor unions, labor intensity, and labor share are positively related to financial statement comparability. We also find that financial statement comparability increases the sensitivity of hiring to performance change, particularly, for negative operating performance, supporting our notion that financial statement comparability helps managers' timelier labor adjustment. Last, we examine whether the improved comparability prevents massive layoffs thanks to continuously more timely employment adjustment. Consistent with our prediction, we find that comparability reduces the likelihood of large-scale layoffs

Enhanced Water Oxidation Catalytic Performance of Graphene Oxide by Gamma Ray Irradiation Post-Treatment

Herein, we report the influence of γ-ray irradiation process on the physicochemical properties of partially reduced graphene oxide (PRGO) thin films. It is found that γ-ray irradiation at 25KGy alters the surface, chemical environment, and wettability properties of PRGO via inducing edge sites and oxygen moieties, resulting in increased water oxidation performance

Information Content of Credit Rating Affirmations

We examine whether the reiteration of past credit ratings (i.e., credit rating affirmation) provides value-relevant information to equity analysts and stock investors. While a large body of accounting and finance research provides evidence on the informational role of credit rating downgrades and upgrades, the informational effects of credit rating affirmations remain unexplored, despite the fact that the frequency of issuing rating affirmations is 1.6 times greater than that of issuing both rating downgrades and upgrades. Using a sample of US corporate credit rating reports that reiterate the previous credit ratings over the period of April 1995-June 2018, we find that equity analysts’ earnings forecast dispersion and stock return volatility—proxies for information uncertainty—decrease within a 30-day window following the credit rating affirmation announcements. The reduction in information uncertainty after rating affirmation is mainly driven by firms with non-investment grade bonds, whereas such reduction is not statistically significant for firms with investment grade bonds. We next find that the stock market reaction to affirmations is significantly positive on average and the positive reaction is most pronounced for firms with non-investment grade bonds. Taken together, our findings suggest that credit rating affirmations reduce information uncertainty and stock market investors find it useful for their investment decisions, particularly for firms with non-investment grade bonds. This study enhances our under-standing of the non-trivial informational value of the credit rating affirmations for equity market participants

Endoscopic and histological patchiness in treated ulcerative colitis

Traditionally, contiguous distribution of inflammation (endoscopic and histological) with rectal involvement is thought to be important in distinguishing ulcerative colitis (UC) from Crohn's disease of the colon. Little long-term data are available that prove whether this rule holds during the course of disease as it is modified by time and treatment. The aim of this study was to investigate the prevalence of endoscopic and histological patchiness and rectal sparing in treated UC over time and to correlate these findings with treatment at the time of endoscopy. Methods : Patients with well-established UC who underwent sequential colonoscopy or flexible sigmoidoscopy with biopsies were included in this study. Patients’ medical records including endoscopy/biopsy reports and clinical status/symptoms/treatment at the time of endoscopy were reviewed retrospectively. Results : A total of 32 patients (14 men, 18 women; median age, 45 yr; median UC duration, 15 yr) underwent 175 sequential endoscopies with biopsies (161 colonoscopies, 14 sigmoidoscopies; median, five endoscopies per patient; range, 3–10). Endoscopic and/or histological patchiness was present in 20 of 175 (11%) sequential endoscopies with biopsies over time from 12 of 32 (38%) patients. Endoscopic and/or histological rectal sparing was present in 27 of 175 (15%) of sequential endoscopies with biopsies over time from 14 of 32 (44%) patients. Seven patients had both patchiness and rectal sparing. Therefore, in 47 (27%) follow-up endoscopies in 19 (59%) patients, there was either patchy disease, rectal sparing, or both sometime during the course of disease with treatment. There was no significant difference in treatment, including steroid use and rectal therapy, between those with patchiness and/or rectal sparing and those without. Conclusions : Contrary to traditional teaching, endoscopic and histological patchiness of inflammation and rectal sparing are common during the course of disease in treated UC and seem to be unrelated to specific therapy.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74642/1/j.1572-0241.1999.01533.x.pd

Miniaturized Diffraction Based Interferometric Distance Measurement Sensor

In this thesis, new metrology hardware is designed, fabricated, and tested to provide improvements over current MEMS metrology. The metrology system is a micromachined scanning interferometer having a sub-nm resolution in a compact design. The proposed microinterferometer forms a phase sensitive diffraction grating with interferometric sensitivity, while adding the capability of better lateral resolution by focusing the laser to a smaller spot size. A detailed diffraction model of the microinterferometer was developed to simulate the device performance and to suggest the location of photo detectors for integrated optoelectronics. A particular device is fabricated on a fused silica substrate using aluminum to form the deformable diffraction grating fingers and AZ P4620 photo resist (PR) for the microlens. The details of the fabrication processes are presented. The structure also enables optoelectronics to be integrated so that the interferometer with photo detectors can fit in an area that is 1mm x 1mm. The scanning results using a fixed grating micromachined scanning interferometer demonstrated that it could measure vibration profile as well as static vertical(less than a half wave length) and lateral dimension of MEMS. The SI, which is integrated with photo diodes, demonstrated its operation by scanning a cMUT. The PID control has been tested and resulted in improvement in scanned images. The integrated micromachined scanning interferometer demonstrated that the deformable grating could be used to tune the measurement keep the interferometer in quadrature for highest sensitivity.Ph.D.Committee Co-Chair: Degertekin, F. Levent; Committee Co-Chair: Kurfess, Thomas; Committee Member: Ayazi, Farrokh; Committee Member: Gaylord, Thomas; Committee Member: Hesketh, Pete