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Oh, Seong Y.,Singh, Jagdish P.,Lim, Changhwan The Optical Society 2014 Applied Optics Vol.53 No.17
<P>An interferometric analysis was performed to investigate the influence of argon (Ar) buffer gas on the characteristics of laser-induced aluminum (Al) plasma at atmospheric pressure. The plasma was produced by focusing a Q-switched Nd:YAG laser pulse (λ=1064??nm, pulse duration 5??ns, E=6.0??mJ) onto an Al target. The interference patterns were constructed using a Nomarski interferometer incorporated with a frequency-doubled, Q-switched Nd:YAG laser (λ=532??nm, pulse duration 10??ns) that generates an interferometric probe beam. The interferometric measurements were carried out as a function of the elapsed time after the onset of breakdown under the conditions of open air and an Ar gas jet flow (5??l/min). With the injection of an Ar buffer gas jet in the ablation process, an increase in electron density and a preferential axial plasma expansion of the plasma plume were observed during the early stages of plasma formation as a consequence of increased inverse-Bremsstrahlung (IB) absorption efficiency.</P>
Baek Moon Seong,Baek Ae-Rin,Hong Sang-Bum,Bae Soohyun,Park Hye Kyeong,Kim Changhwan,Lee Hyun-Kyung,Cho Woo Hyun,Kim Jin Hyoung,Chang Youjin,Lee Heung Bum,Gil Hyun-Il,Shin Beomsu,Yoo Kwang Ha,Moon Jae 대한의학회 2023 Journal of Korean medical science Vol.38 No.41
Background: There is insufficient data on the benefits of empiric antibiotic combinations for hospital-acquired pneumonia (HAP). We aimed to investigate whether empiric antipseudomonal combination therapy with fluoroquinolones decreases mortality in patients with HAP. Methods: This multicenter, retrospective cohort study included adult patients admitted to 16 tertiary and general hospitals in Korea between January 1 and December 31, 2019. Patients with risk factors for combination therapy were divided into anti-pseudomonal non-carbapenem β-lactam monotherapy and fluoroquinolone combination therapy groups. Primary outcome was 30-day mortality. Propensity score matching (PSM) was used to reduce selection bias. Results: In total, 631 patients with HAP were enrolled. Monotherapy was prescribed in 54.7% (n = 345) of the patients, and combination therapy was prescribed in 45.3% (n = 286). There was no significant difference in 30-day mortality between the two groups (16.8% vs. 18.2%, P = 0.729) or even after the PSM (17.5% vs. 18.2%, P = 0.913). After the PSM, adjusted hazard ratio for 30-day mortality from the combination therapy was 1.646 (95% confidence interval, 0.782–3.461; P = 0.189) in the Cox proportional hazards model. Moreover, there was no significant difference in the appropriateness of initial empiric antibiotics between the two groups (55.0% vs. 56.8%, P = 0.898). The proportion of multidrug-resistant (MDR) pathogens was high in both groups. Conclusion: Empiric anti-pseudomonal fluoroquinolone combination therapy showed no survival benefit compared to β-lactam monotherapy in patients with HAP. Caution is needed regarding the routine combination of fluoroquinolones in the empiric treatment of HAP patients with a high risk of MDR.
Interferometric Analysis of 1064-nm Nanosecond Laser Induced Copper Plasma
Young June Hong,Oh, Seong Y.,Sung Yong Ha,Hee-Jin Kim,Changhwan Lim IEEE 2014 IEEE transactions on plasma science Vol.42 No.3
<P>This paper reports on the interferometric analysis of laser-induced plasma performed to investigate the spatial and temporal dynamics of a plasma column as a function of the time elapsed after laser-induced ablation on the surface of a copper target. The plasma was driven by focusing Q-switched Nd:YAG laser pulse ( λ = 1064 nm, τ = ~ 5 ns, and E=12. 5 mJ) onto a copper target and the interference patterns were constructed using a Nomarski interferometer. Phase information of the interference patterns was extracted using a fast Fourier-transform method. With the phase information obtained thus the spatial distribution of electron density was inferred from the Abel inversion equation. For the infrared nanosecond pulsed ablation regime, we observed that the resulting plasma expands preferentially toward the incoming laser beam at the early stage of plasma formation. The maximum plasma density was measured to be of the order of ~ 10<SUP>20</SUP> cm<SUP>-3</SUP>. As time elapses, the rapid radial expansion of plasma plume and significant reduction of electron density were observed.</P>
Carbon ion radiotherapy in the treatment of hepatocellular carcinoma
Hwa Kyung Byun,Changhwan Kim,Jinsil Seong 대한간학회 2023 Clinical and Molecular Hepatology(대한간학회지) Vol.29 No.4
Hepatocellular carcinoma (HCC) is a highly lethal cancer with limited treatment options and poor prognosis. Carbon ion radiotherapy (CIRT) has emerged as a promising treatment modality for HCC due to its unique physical and biological properties. CIRT uses carbon ions to target and destroy cancer cells with a high precision and efficacy. The Bragg Peak phenomenon allows precise dose delivery to the tumor while minimizing damage to healthy tissues. In addition, the high relative biological effectiveness of carbon ions can be shown against radioresistant and hypoxic tumor areas. CIRT also offers a shorter treatment schedule than conventional radiotherapy, which increases patient convenience and compliance. The clinical outcomes of CIRT for HCC have shown excellent local control rates with minimal side effects. Considering its physical and biological properties, CIRT may be a viable option for complex clinical scenarios such as patients with poor liver function, large tumors, re-irradiation cases, and tumors close to critical organs. Further research and larger studies are needed to establish definitive indications for CIRT and to compare its efficacy with that of other treatment modalities. Nevertheless, CIRT offers a potential breakthrough in HCC management, providing hope for improved therapeutic outcomes and reduced treatment-related toxicities.
Construction of <i>Bacillus thuringiensis</i> Simulant Strains Suitable for Environmental Release
Park, Sangjin,Kim, Changhwan,Lee, Daesang,Song, Dong Hyun,Cheon, Ki Cheol,Lee, Hong Suk,Kim, Seong Joo,Kim, Jee Cheon,Lee, Sang Yup American Society for Microbiology 2017 Applied and environmental microbiology Vol.83 No.9
<P>IMPORTANCE B. thuringiensis has recently been receiving increasing attention as a good spore simulant in biodefense research. However, few studies were done to properly address many important features of B. thuringiensis as a simulant in environmental studies. Since spores can persist in the environment for years after release, environmental contamination is a big problem, especially when genetically engineered strains are used. To solve these problems, we report here the development of B. thuringiensis simulant strains that are capable of forming yellow colonies for easy detection, incapable of forming spores more than once due to a genetic circuit, and lacking in two major SASP genes. The genetic circuit to produce a spore without sporulation capability, together with the deletion of SASP genes, ensures the environmental and human safety of the simulant strains developed in this study. All of these features will allow wider use of B. thuringiensis as a simulant for Bacillus anthracis in environmental release studies.</P>
금속관 내부의 음압유량 향상을 위한 기하학적 디자인 및 SLIPS 윤활
김동근(Dong Geun Kim),장창환(Changhwan Jang),김성재(Seong Jae Kim),김대겸(Daegyoum Kim),김산하(Sanha Kim) 한국트라이볼로지학회 2021 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.37 No.6
Metal pipes are used in a wide range of applications, from plumbing systems of large construction sites to small devices such as medical tools. When a liquid is enforced to flow through a metal pipe, a higher flow rate is beneficial for higher efficiency. Using high pressures can enhance the flow rate yet can be harmful for medical applications. Thus, we consider an optimal geometrical design to increase the flow rate in medical devices. In this study, we focus on cannulas, which are widely used small metal pipes for surgical procedures, such as liposuction. We characterize the internal flow rate driven by a negative pressure and explore its dependence on the key design parameters. We quantitatively analyze the suction characteristics for each design variable by conducting computational fluid dynamics simulations. In addition, we build a suction performance measurement system which enables the translational motion of cannulas with pre-programmed velocity for experimental validation. The inner diameter, section geometry, and hole configuration are the design factors to be evaluated. The effect of the inner diameter dominates over that of section geometry and hole configuration. In addition, the circular tube shape provides the maximum flow rate among the elliptical geometries. Once the flow rate exceeds a critical value, the rate becomes independent of the number and width of the suction holes. Finally, we introduce a slippery liquid-infused nanoporous surface (SLIPS) coating using nanoparticles and hydrophobic lubricants that effectively improves the flow rate and antifouling property of cannulas without altering the geometrical design parameter.