Cortical recording with conducting polymer electrodes

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008.Includes bibliographical references (leaves 39-41).The ability to record from the same neuron for extended periods of time is essential to understanding how the brain reorganizes during motor learning. Conventional chronic recording microelectrodes are made from metal or silicon. However, the large stiffness mismatch between the electrodes and brain tissue causes shear-induced inflammation, limiting long-term recording stability. The flexibility of a polypyrrole microwire has the potential to improve the chronic recording stability by minimizing the stiffness mismatch. This thesis shows the fabrication of conducting polymer electrodes and the stability of their impedance in physiological saline. The initial impedance was as low as 70 k[omega], but the electrode impedance increased by a factor of 10 when immersed in saline over 370 hours. This conducting polymer microwire electrode was implanted in a rodent brain and successfully used to record neuronal action potentials.by Woong Jin Bae.S.M

The development of sociomathematical norms in the transition to tertiary exam-oriented individualistic mathematics education in an East Asian context

This study investigates social, mathematical, and sociomathematical norms perceived by college students in an engineering mathematics course and examines the students’ sense of mathematics as signals of individual merit. Data sources include a survey and one-on-one interviews with 38 students. The findings help illustrate student perceptions of academic social norms in a large-lecture course represented by the acquisition model of learning in college, detached from communal and collaborative disciplinary practices. Findings provide insights into the local educational context of an East Asian country as a case study when exam-oriented mathematics is institutionalized as normalcy

A Case Study on Safe Blast Design with Vibration Analysis

Safe delicacy blasting is necessarily to decrease safe problems resulting from blasting but if designs to consider only safety, it is a problem not to ensure economical gains because the effect of blasting is decreased. Therefore, blasting vibration must be predicted to consider given circumstances and ground conditions before blasting work, and then a design based on predicted result must be done. In this study, the testing blasting was carried out in two fields within a country, and then measured data for testing blasting were collected. The effect for blasting vibration was analyzed as the property of distance, charging gunpowder capacity, surrounding conditions, and measured points. The test results were performed by back-analysis, and compared with previous research results. Therefore, it will be proposed an effective prediction and design

The role of adjuvant pelvic radiotherapy in rectal cancer with synchronous liver metastasis: a retrospective study

<p>Abstract</p> <p>Background</p> <p>Synchronous liver metastases are detected in approximately 25% of colorectal cancer patients at diagnosis. The rates of local failure and distant metastasis are substantial in these patients, even after undergoing aggressive treatments including resection of primary and metastatic liver tumors. The purpose of this study was to determine whether adjuvant pelvic radiotherapy is beneficial for pelvic control and overall survival in rectal cancer patients with synchronous liver metastasis after primary tumor resection.</p> <p>Methods</p> <p>Among rectal cancer patients who received total mesorectal excision (TME) between 1997 and 2006 at Yonsei University Health System, eighty-nine patients diagnosed with synchronous liver metastasis were reviewed. Twenty-seven patients received adjuvant pelvic RT (group S + R), and sixty-two patients were managed without RT (group S). Thirty-six patients (58%) in group S and twenty patients (74%) in group S+R received local treatment for liver metastasis. Failure patterns and survival outcomes were analyzed.</p> <p>Results</p> <p>Pelvic failure was observed in twenty-five patients; twenty-one patients in group S (34%), and four patients in group S+R (15%) (<it>p </it>= 0.066). The two-year pelvic failure-free survival rates (PFFS) of group S and group S+R were 64.8% and 80.8% (<it>p </it>= 0.028), respectively, and the two-year overall survival rates (OS) were 49.1% and 70.4% (<it>p </it>= 0.116), respectively. In a subgroup analysis of fifty-six patients who received local treatment for liver metastasis, the two-year PFFS were 64.9% and 82.9% (<it>p </it>= 0.05), respectively; the two-year OS were 74.1% and 80.0% (<it>p </it>= 0.616) in group S (n = 36) and group S+R (n = 20), respectively.</p> <p>Conclusions</p> <p>Adjuvant pelvic RT significantly reduced the pelvic failure rate but its influence on overall survival was unclear. Rectal cancer patients with synchronous liver metastasis may benefit from adjuvant pelvic RT through an increased pelvic control rate and improved quality of life.</p

Strength of Footing with Punching Shear Preventers

The punching shear failure often governs the strength of the footing-to-column connection. The punching shear failure is an undesirable failure mode, since it results in a brittle failure of the footing. In this study, a new method to increase the strength and ductility of the footing was proposed by inserting the punching shear preventers (PSPs) into the footing. The validation and effectiveness of PSP were verified through a series of experimental studies. The nonlinear finite element analysis was then performed to demonstrate the failure mechanism of the footing with PSPs in depth and to investigate the key parameters that affect the behavior of the footing with PSPs. Finally, the design recommendations for the footing with PSPs were suggested

Rejuvenating Star Formation Activity in an Early-type Dwarf Galaxy, LEDA 1915372, with Accreted HI Gas

We report a rare astrophysical phenomenon, in which an early-type dwarf galaxy (dE), LEDA 1915372, is accreting gas from a nearby star-forming dwarf galaxy, MRK 0689, and is rejuvenating star-formation activity at the center. Both LEDA 1915372 and MRK 0689 have similar brightness of $M_{r}$ = $-$16.99 and $-$16.78 mag, respectively. They are located in a small group environment, separated by a sky-projected distance of 20.27 kpc (up to 70 kpc in three dimension), and have a relative line-of-sight radial velocity of 6 km/s. The observation of 21 cm emission with the Giant Metrewave Radio Telescope provides strong evidence of interaction between the pair dwarf galaxies in terms of neutral hydrogen (HI) morphology and kinematics. In particular, the HI map reveals that the two galaxies are clearly connected by a gas bridge, and the gas components of both LEDA 1915372 and MRK 0689 share a common direction of rotation. We also find that the HI emission peak deviates from LEDA 1915372 toward its optical blue plume, suggesting a tidal origin of ongoing central star formation. Our findings provide a new path to the formation of blue-cored dEs.Comment: Accepted for publication in ApJ

Identification of novel peptides that stimulate human neutrophils

Neutrophils play a key role in innate immunity, and the identification of new stimuli that stimulate neutrophil activity is a very important issue. In this study, we identified three novel peptides by screening a synthetic hexapeptide combinatorial library. The identified peptides GMMWAI, MMHWAM, and MMHWFM caused an increase in intracellular Ca2+ in a concentration-dependent manner via phospholipase C activity in human neutrophils. The three peptides acted specifically on neutrophils and monocytes and not on other non-leukocytic cells. As a physiological characteristic of the peptides, we observed that the three peptides induced chemotactic migration of neutrophils as well as stimulated superoxide anion production. Studying receptor specificity, we observed that two of the peptides (GMMWAI and MMHWFM) acted on formyl peptide receptor (FPR)1 while the other peptide (MMHWAM) acted on FPR2. Since the three novel peptides were specific agonists for FPR1 or FPR2, they might be useful tools to study FPR1- or FPR2-mediated immune response and signaling