New applications of THz time-domain spectroscopy

This thesis was conducted to provide new applications to THz time-domain spectroscopy and to test alternative theories of conduction by precisely measuring the complex conductivity of doped silicon from low frequencies to frequencies higher than the plasma frequency and the carrier damping rate. I hope this thesis should be of interest to a wide audience of researchers who use thin film and doped silicon as an optical material at THz frequencies. I would like to sincerely thank Dr. Daniel Grischkowsky, my principal advisor, for his intelligent supervision, constructive guidance, scholarship, and encouragement

THz Sommerfeld wave propagation on a single metal wire

We report an experimental and theoretical study of THz Sommerfeld wave propagation on a single copper wire. THz pulses are optoelectronically generated and launched onto 0.52-mm-diam copper wire, and the guided THz pulses are detected at the end of the wire by a standard photoconductive antenna. Very low attenuation and group velocity dispersion are observed, and the measured radial field amplitude of the Sommerfeld wave is inversely proportional to the radial distance. These results are consistent with theoretical predictions. Experimental results from curved wires show the weakly guiding property of the THz Sommerfeld wave, which will limit its applications.Peer reviewedElectrical and Computer Engineerin

Electrical and optical characterization of conducting poly-3-methylthiophene film by THz time-domain spectroscopy

Using THz time-domain spectroscopy (THz-TDS), we have measured the absorption and dispersion of 7.5/(Ohm-cm) conducting poly-3-methylthiophene film from low frequencies up to 4 THz. From these measurements the complex conductance that increases with increasing frequency was obtained over this frequency range. The results do not follow simple Drude theory and are not comparable with normal metal and semiconductors; the results were well fit by the localization-modified Drude theory.Peer reviewedElectrical and Computer Engineerin

Impact of Socioeconomic Status on 30-Day and 1-Year Mortalities after Intensive Care Unit Admission in South Korea: A Retrospective Cohort Study

Background Socioeconomic status (SES) is closely associated with health outcomes, including mortality in critically ill patients admitted to intensive care unit (ICU). However, research regarding this issue is lacking, especially in countries where the National Health Insurance System is mainly responsible for health care. This study aimed to investigate how the SES of ICU patients in South Korea is associated with mortality. Methods This was a retrospective observational study of adult patients aged ≥20 years admitted to ICU. Associations between SES-related factors recorded at the time of ICU admission and 30-day and 1-year mortalities were analyzed using univariable and multivariable Cox regression analyses. Results A total of 6,008 patients were included. Of these, 394 (6.6%) died within 30 days of ICU admission, and 1,125 (18.7%) died within 1 year. Multivariable Cox regression analysis found no significant associations between 30-day mortality after ICU admission and SES factors (P>0.05). However, occupation was significantly associated with 1-year mortality after ICU admission. Conclusions Our study shows that 30-day mortality after ICU admission is not associated with SES in the National Health Insurance coverage setting. However, occupation was associated with 1-year mortality after ICU admission

Direct optoelectronic generation and detection of sub-ps-electrical pulses on sub-mm-coaxial transmission lines

We report efficient direct optoelectronic generation of sub-ps-THz pulses on 50 Ohm coaxial transmission lines with a 330 micro-m diameter solid copper outer tube filled with Teflon containing the 80 micro-m diameter inner conductor. The transmitted pulses after propagating as much as 105 mm were measured at the end of the line with an optoelectronic antenna having sub-ps-time resolution. We observed low-loss, single transverse electromagnetic mode propagation with very little group velocity dispersion. The experimentally derived values for the frequency-dependent absorption are consistent with the theoretical predictions.Peer reviewedElectrical and Computer Engineerin

Comparison of the effects of sugammadex and neostigmine on hospital stayin robot-assisted laparoscopic prostatectomy: a retrospective study

Abstract Background Sugammadex reduces postoperative complications. We sought to determine whether it could reduce the length of hospital stay, post-anesthetic recovery time, unplanned readmission, and charges for patients who underwent robot-assisted laparoscopic prostatectomy (RALP) when compared to neostigmine. Methods This was a retrospective observational study of patients who underwent RALP between July 2012 and July 2017, in whom rocuronium was used as a neuromuscular blocker. The primary outcome was the length of hospital stay after surgery in patients who underwent reversal with sugammadex when compared to those who underwent reversal with neostigmine. The secondary outcomes were post-anesthetic recovery time, hospital charges, and unplanned readmission within 30 days after RALP. Results In total, 1430 patients were enrolled. Using a generalized linear model in a propensity score-matched cohort, sugammadex use was associated with a 6% decrease in the length of hospital stay (mean: sugammadex 7.7 days vs. neostigmine 8.2 days; odds ratio [OR] 0.94, 95% confidence interval [CI] [0.89, 0.98], P = 0.008) and an 8% decrease in post-anesthetic recovery time (mean: sugammadex 36.7 min vs. neostigmine 40.2 min; OR 0.92, 95% CI [0.90, 0.94], P < 0.001) as compared to neostigmine use; however, it did not reduce the 30-day unplanned readmission rate (P = 0.288). The anesthesia charges were higher in the sugammadex group than in the neostigmine group (P < 0.001); however, there were no significant differences between the groups in terms of postoperative net charges (P = 0.061) and total charges (P = 0.100). Conclusions Compared to the reversal of rocuronium effects with neostigmine, reversal with sugammadex after RALP was associated with a shorter hospital stay and post-anesthetic recovery time, and was not associated with 30-day unplanned readmission rates and net charges

THz Zenneck surface wave (THz surface plasmon) propagation on a metal sheet

We present an experimental study of the propagation of the THz Zenneck surface wave on an aluminum sheet, now more commonly denoted as the THz surface plasmon (TSP). Here, the TSP pulse is generated by coupling the THz pulse from a metal parallel-plate waveguide onto the aluminum sheet; the propagated TSP pulse is detected at the output end of the sheet using a standard photoconductive dipole antenna. We separate the associated free-space THz pulse from the TSP pulse using a curved sheet. The observed weakly guided TSP propagation has the expected low group velocity dispersion, but also has anomalously high attenuation and much tighter binding to the metal surface than predicted by Zenneck theory.Peer reviewedElectrical and Computer Engineerin

An accurate method for quantifying and analyzing copy number variation in porcine KIT by an oligonucleotide ligation assay

<p>Abstract</p> <p>Background</p> <p>Aside from single nucleotide polymorphisms, copy number variations (CNVs) are the most important factors in susceptibility to genetic disorders because they affect expression levels of genes. In previous studies, pyrosequencing, mini-sequencing, real-time PCR, invader assays and other techniques have been used to detect CNVs. However, the higher the copy number in a genome, the more difficult it is to resolve the copies, so a more accurate method for measuring CNVs and assigning genotype is needed.</p> <p>Results</p> <p>PCR followed by a quantitative oligonucleotide ligation assay (qOLA) was developed for quantifying CNVs. The accuracy and precision of the assay were evaluated for porcine <it>KIT</it>, which was selected as a model locus. Overall, the root mean squares of bias and standard deviation of qOLA were 2.09 and 0.45, respectively. These values are less than half of those in the published pyrosequencing assay for analyzing CNV in porcine <it>KIT</it>. Using a combined method of qOLA and another pyrosequencing for quantitative analysis of <it>KIT </it>copies with spliced forms, we confirmed the segregation of <it>KIT </it>alleles in 145 F₁animals with pedigree information and verified the correct assignment of genotypes. In a diagnostic test on 100 randomly sampled commercial pigs, there was perfect agreement between the genotypes obtained by grouping observations on a scatter plot and by clustering using the nearest centroid sorting method implemented in PROC FASTCLUS of the SAS package. In a test on 159 Large White pigs, there were only two discrepancies between genotypes assigned by the two clustering methods (98.7% agreement), confirming that the quantitative ligation assay established here makes genotyping possible through the accurate measurement of high <it>KIT </it>copy numbers (>4 per diploid genome). Moreover, the assay is sensitive enough for use on DNA from hair follicles, indicating that DNA from various sources could be used.</p> <p>Conclusion</p> <p>We have established a high resolution quantification method using an oligonucleotide ligation assay to measure CNVs, and verified the reliability of genotype assignment for random animal samples using the nearest centroid sorting method. This new method will make it more practical to determine <it>KIT </it>CNV and to genotype the complicated <it>Dominant White/KIT </it>locus in pigs. This procedure could have wide applications for studying gene or segment CNVs in other species.</p