Hyun Hana - Academia.edu (original) (raw)

Papers by Hyun Hana

Bulletin of the Korean Chemical Society, 2008

Second-order rate constants (kN) have been measured spectrophotometrically for reactions of Y-sub... more Second-order rate constants (kN) have been measured spectrophotometrically for reactions of Y-substituted phenyl benzoates (1a-h) with azide ion (N3-) in 80 mol % H2O/20 mol % DMSO at 25.0 ± 0.1 o C. The Brønstedtype plot for the azidolysis exhibits a downward curvature, i.e., the slope (βlg) changes from-0.97 to-0.20 as the basicity of the leaving group decreases. The pKa o (defined as the pKa at the center of the Brønsted curvature) is 4.8, which is practically identical to the pKa of the conjugate acid of N3ion (4.73). Hammett plots correlated with σ o and σconstants exhibit highly scattered points for the azidolysis. On the contrary, the corresponding Yukawa-Tsuno plot results in an excellent linear correlation with ρ = 2.45 and r = 0.40, indicating that the leaving group departs in the rate-determining step. The curved Brønsted-type plot has been interpreted as a change in the rate-determining step in a stepwise mechanism. The microscopic rate constants (k1 and k2/k-1 ratio) have been calculated for the azidolysis and found to be consistent with the proposed mechanism.

Journal of Back and Musculoskeletal Rehabilitation, 2016

BACKGROUND: Hamstring tightness induces posterior pelvic tilt and decreased lumbar lordosis, whic... more BACKGROUND: Hamstring tightness induces posterior pelvic tilt and decreased lumbar lordosis, which can result in low back pain OBJECTIVE: We investigated effects of hamstring stretch with pelvic control on pain and work ability in standing workers. METHODS: One hundred adult volunteers from a standing workers were randomly assigned to pelvic control hamstring stretching (PCHS) (n = 34), general hamstring stretching (GHS) (n = 34), control (n = 32) groups. The control group was performed self-home exercise. All interventions were conducted 3 days per week for 6 weeks, and included in the hamstring stretching and lumbopelvic muscle strengthening. Outcomes were evaluated through the visual analog scale (VAS), straight leg raise test (SLR), sit and reach test (SRT), Oswestry disability index (ODI), and work ability index (WAI). RESULTS: Significant difference in VAS, SLR, SRT, ODI, and WAI were found in the PCHS and GHS groups. The control group was a significant difference only in ODI. The PCHS group showed a greater difference than the GHS group and control group in VAS, SLR, SRT, and ODI. CONCLUSIONS: The pelvic control hamstring stretch exercise would be more helpful in back pain reduction and improvement of work ability in an industrial setting.

Bulletin of the Korean Chemical Society, 2008

Second-order rate constants (kN) have been measured spectrophotometrically for reactions of Y-sub... more Second-order rate constants (kN) have been measured spectrophotometrically for reactions of Y-substituted phenyl benzoates (1a-h) with azide ion (N3-) in 80 mol % H2O/20 mol % DMSO at 25.0 ± 0.1 o C. The Brønstedtype plot for the azidolysis exhibits a downward curvature, i.e., the slope (βlg) changes from-0.97 to-0.20 as the basicity of the leaving group decreases. The pKa o (defined as the pKa at the center of the Brønsted curvature) is 4.8, which is practically identical to the pKa of the conjugate acid of N3ion (4.73). Hammett plots correlated with σ o and σconstants exhibit highly scattered points for the azidolysis. On the contrary, the corresponding Yukawa-Tsuno plot results in an excellent linear correlation with ρ = 2.45 and r = 0.40, indicating that the leaving group departs in the rate-determining step. The curved Brønsted-type plot has been interpreted as a change in the rate-determining step in a stepwise mechanism. The microscopic rate constants (k1 and k2/k-1 ratio) have been calculated for the azidolysis and found to be consistent with the proposed mechanism.

Journal of Back and Musculoskeletal Rehabilitation, 2016

BACKGROUND: Hamstring tightness induces posterior pelvic tilt and decreased lumbar lordosis, whic... more BACKGROUND: Hamstring tightness induces posterior pelvic tilt and decreased lumbar lordosis, which can result in low back pain OBJECTIVE: We investigated effects of hamstring stretch with pelvic control on pain and work ability in standing workers. METHODS: One hundred adult volunteers from a standing workers were randomly assigned to pelvic control hamstring stretching (PCHS) (n = 34), general hamstring stretching (GHS) (n = 34), control (n = 32) groups. The control group was performed self-home exercise. All interventions were conducted 3 days per week for 6 weeks, and included in the hamstring stretching and lumbopelvic muscle strengthening. Outcomes were evaluated through the visual analog scale (VAS), straight leg raise test (SLR), sit and reach test (SRT), Oswestry disability index (ODI), and work ability index (WAI). RESULTS: Significant difference in VAS, SLR, SRT, ODI, and WAI were found in the PCHS and GHS groups. The control group was a significant difference only in ODI. The PCHS group showed a greater difference than the GHS group and control group in VAS, SLR, SRT, and ODI. CONCLUSIONS: The pelvic control hamstring stretch exercise would be more helpful in back pain reduction and improvement of work ability in an industrial setting.