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Universal Gas-Uptake Behavior of a Zeolitic Imidazolate Framework ZIF-8 at High Pressure
Choi, Jinhyuk,Im, Junhyuck,Noh, Kyungkyou,Kim, Jaheon,Vogt, Thomas,Lee, Yongjae American Chemical Society 2019 The Journal of Physical Chemistry Part C Vol.123 No.42
<P>We report the pressure-induced insertion (PII) of gases in a zeolitic imidazolate framework (ZIF) at high pressure. ZIF-8 crystals were compressed in the presence of nonpolar CO<SUB>2</SUB> and SF<SUB>6</SUB> as well as polar CHClF<SUB>2</SUB> (<I>aka</I> R22) up to 4.07, 0.81, and 2.06 GPa, respectively, in a diamond anvil cell, and their X-ray powder diffraction data were analyzed by Rietveld methods. ZIF-8 showed pressure-induced amorphization in SF<SUB>6</SUB> but maintained its crystallinity in the presence of other gases. In general, the unit cell volume of ZIF-8 expanded via PII of CO<SUB>2</SUB> or R22 up to ca. 0.5 GPa and contracted linearly after completion of the PII processes. The total volumes of the inserted guest molecules, which were estimated from the residual electron densities, indicated that the inserted guest molecules fully occupy the pores of ZIF-8. The relationship between the total occupied volumes by guests and applied pressures was best represented with an asymptotic logarithmic curve regardless of the type of molecules. These results reveal the universal gas-uptake behavior of ZIF-8 at high pressure, which requires only the penetration of molecules into the pores of the framework of ZIF-8.</P> [FIG OMISSION]</BR>
Energy Spread Effects in the PAL XFEL
Jinhyuk Choi,Heung Sik Kang,이태연 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.48 No.4
Pohang Accelerator Laboratory has recently launched a X-ray free electron laser project called PAL-XFEL. The goal of PAL-XFEL is to produce hard X-rays of 0.3 nm as well as soft X-rays. There exist strict requirements which should be satisfied for successful X-ray lasings. Among them, we will discuss the effects of the energy spread, such as micro-bunching instability and transverse coherency, in this paper. Also, simulation results will be presented.
Jinhyuk Choi,김정율,이혜승,최유진,김하연,이진환,장혜윤,김애리 대한병리학회 2016 Journal of Pathology and Translational Medicine Vol.50 No.6
Background: Human papillomavirus (HPV) is a well-established oncogenic virus of cervical, anogenital, and oropharyngeal cancer. Various subtypes of HPV have been detected in 0% to 60% of breast cancers. The roles of HPV in the carcinogenesis of breast cancer remain controversial. This study was performed to determine the prevalence of HPV-positive breast cancer in Korean patients and to evaluate the possibility of carcinogenic effect of HPV on breast. Methods: Meta-analysis was performed in 22 case-control studies for HPV infection in breast cancer. A total of 123 breast cancers, nine intraductal papillomas and 13 nipple tissues of patients with proven cervical HPV infection were tested by real-time polymerase chain reaction to detect 28 subtypes of HPV. Breast cancers were composed of 106 formalin-fixed and paraffin embedded (FFPE) breast cancer samples and 17 touch imprint cytology samples of breast cancers. Results: The overall odds ratio between breast cancer and HPV infection was 5.43 (95% confidence interval, 3.24 to 9.12) with I2 = 34.5% in meta-analysis of published studies with case-control setting and it was statistically significant. HPV was detected in 22 cases of breast cancers (17.9%) and two cases of intaductal papillomas (22.2%). However, these cases had weak positivity. Conclusions: These results failed to serve as significant evidence to support the relationship between HPV and breast cancer. Further study with larger epidemiologic population is merited to determine the relationship between HPV and breast cancer.
Photon polarization in charged-pion radiative decay
Choi, Jinhyuk,Lee, Ung Won,Song, H. S.,Kim, Jung Hong 全北大學校 基礎科學硏究所 1991 基礎科學 Vol.14 No.1
We discuss the dependence of the photon polarization in the radiative pion decay π^+ →e^+ ν_eγ on the parameter γ= F^A/F^V, the ratio of the axial-vector to vector pion form factor for the decay, and show that the measurement of the outgoing photon polarization provides an additional information in determining a unique value of γ.
Comparison of Sonochemistry Method and Sol-Gel Method for the Fabrication of TiO<sub>2</sub> Powder
Choi, Jinhyuk,Cho, Sung Hun,Kim, Tae Ho,Lee, Soo Wohn Trans Tech Publications, Ltd. 2011 Materials science forum Vol.695 No.-
<P>Sol-gel with sonochemical process and sol-gel method were used for the fabrication of photocatalytic TiO2 powder and the properties of the TiO2 powder thus prepared were examined and compared. For the synthesis of TiO2 powder, the starting material was Ti-butoxide and H2O and the reaction was carried out at 80 °C in a sol-gel method. On the other hand, Ti-butoxide was reacted with H2O in an ultrasonic frequency of 23 kHz with ultrasonic powers of 800 W for two hours. After evaporation, 24 hours aging time was kept at 400 °C in both cases, the final product appeared was the anatase phase. Ultrasonic chemical method was found to be excellent for flocculation and crushing effects where as in sol-gel method, the product obtained was of high purity and high homogeneity. Sol-gel with sonochemical process has found to be excellent for flocculation and crushing effects. From Sol-gel method, the size of TiO2 particles produced were found to be about 20 nm, spherical, homogeneous while severe agglomeration. In contrast, by sonochemistry method, the size of TiO2 particles produced were about 10 ~ 22 nm size and it has shown more photocatalytic activity than sol-gel sample which is about 28.7 % greater efficiency</P>
X-선 자유전자레이저를 이용한 철과 휘발성 물질의 반응 연구와 이의 초기 지구에서의 환원성 대기 형성 과정에 대한 함의
최진혁(Jinhyuk Choi),Rachel J. Husband,황희정(Huijeong Hwang),김태현(Taehyun Kim),방윤아(Yoonah Bang),윤서희(Seohee Yun),이정민(Jeongmin Lee),심희현(Heehyeon Sim),김상수(Sangsoo Kim),남대웅(Daewoong Nam),채복남(Boknam Chae),Hanns- 한국암석학회 2023 한국암석학회 학술발표회 논문집 Vol.2023 No.6