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Joel E. Abbott,Daniel L. Miller,William Shi,David Wenzler,Fuad F. Elkhoury,Nishant D. Patel,Roger L. Sur 대한비뇨의학회 2017 Investigative and Clinical Urology Vol.58 No.5
Purpose: Accurate measurement of pH is necessary to guide medical management of nephrolithiasis. Urinary dipsticks offer a convenient method to measure pH, but prior studies have only assessed the accuracy of a single, spot dipstick. Given the known diurnal variation in pH, a single dipstick pH is unlikely to reflect the average daily urinary pH. Our goal was to determine whether multiple dipstick pH readings would be reliably comparable to pH from a 24-hour urine analysis. Materials and Methods: Kidney stone patients undergoing a 24-hour urine collection were enrolled and took images of dipsticks from their first 3 voids concurrently with the 24-hour collection. Images were sent to and read by a study investigator. The individual and mean pH from the dipsticks were compared to the 24-hour urine pH and considered to be accurate if the dipstick readings were within 0.5 of the 24-hour urine pH. The Bland-Altman test of agreement was used to further compare dipstick pH relative to 24-hour urine pH. Results: Fifty-nine percent of patients had mean urinary pH values within 0.5 pH units of their 24-hour urine pH. Bland-Altman analysis showed a mean difference between dipstick pH and 24-hour urine pH of -0.22, with an upper limit of agreement of 1.02 (95% confidence interval [CI], 0.45–1.59) and a lower limit of agreement of -1.47 (95% CI, -2.04 to -0.90). Conclusions: We concluded that urinary dipstick based pH measurement lacks the precision required to guide medical management of nephrolithiasis and physicians should use 24-hour urine analysis to base their metabolic therapy.
Ahreum Min,Seung Jun Lee,최명룡,Roger E. Miller 대한화학회 2009 Bulletin of the Korean Chemical Society Vol.30 No.12
We report the first electric field dependence IR spectra of three cytosine tautomers solvated in helium nanodroplets. By using an electric field dependence on the three lowest energy tautomers of cytosine and ab initio calculations, we are able to measure the vibrational transition moment angles (VTMAs), specifically for the NH2 symmetric stretch (SS) mode in this study, with more precision; thus we have reassigned the previous NH2 (SS) VTMA of 74o for the C1 tautomer to 85o, which the latter is in excellent agreement with the ab initio value. Nonplanarity of the three lowest energy tautomers of cytosine has been investigated by measuring the VTMA of each vibrational mode for the tautomers.
Vibrational spectroscopy of xanthine in superfluid helium nanodroplets
Lee, Seung Jun,Choi, Myong Yong,Miller, Roger E. Elsevier 2009 Chemical physics letters Vol.475 No.1
<P><B>Graphical abstract</B></P><P>Ab initio vibrational transition moment angles for N1H, N3H and N7H of xanthine are compared with those obtained from experiments.</P><ce:figure></ce:figure> <P><B>Abstract</B></P><P>Mid-infrared spectra are employed to identify and characterize the structure and specific vibrational modes of xanthine monomer in helium nanodroplets. The predicted NH vibrational frequencies of xanthine show strong dependence on the level of theory and the basis set used in this study. However, the measurement of the angle between the permanent and corresponding vibrational transition dipole moment, called the vibrational transition moment angle (VTMA), gives unambiguous and straightforward assignments to the specific vibrational bands of xanthine. In this work, the global minimum tautomer of xanthine is observed and characterized using ab initio calculations and VTMAs for the various vibrational modes of the xanthine monomer.</P>
Infrared Spectroscopy of Imidazole Trimer in Helium Nanodroplets: Free NH Stretch Mode
Seulki Lee,Seung Jun Lee,Ahreum Ahn,Yusic Kim,민아름,최명룡,Roger E. Miller 대한화학회 2011 Bulletin of the Korean Chemical Society Vol.32 No.3
We report the first vibrational band assignment of imidazole trimer (IMT) solvated in helium nanodroplets. Several congested vibrational bands of imidazole (IM) clusters were obtained in the frequency region of 3513-3515 cm^(−1) and vibrationally resolved due to the extremely low temperature (0.37 K) and very weak solutesolvent interaction environments of helium droplets. The unambiguous free NH band assignment was achieved with an aid of pick-up oven temperature dependence and vibrational transition moment angle (VTMA)experiments as well as density functional theory (DFT) calculations. The band at 3514.3 cm^(−1) is attributed to the free NH stretching mode of linear IMT clusters, easily formed by the dipole-dipole interactions of IM in ultracold helium nanodroplets.
Min, Ah-Reum,Lee, Seung-Jun,Choi, Myong-Yong,Miller, Roger E. Korean Chemical Society 2009 Bulletin of the Korean Chemical Society Vol.30 No.12
We report the first electric field dependence IR spectra of three cytosine tautomers solvated in helium nanodroplets. By using an electric field dependence on the three lowest energy tautomers of cytosine and ab initio calculations, we are able to measure the vibrational transition moment angles (VTMAs), specifically for the $NH_2$ symmetric stretch (SS) mode in this study, with more precision; thus we have reassigned the previous $NH_2$ (SS) VTMA of 74$^{\circ}$ for the C1 tautomer to 85$^{\circ}$, which the latter is in excellent agreement with the ab initio value. Nonplanarity of the three lowest energy tautomers of cytosine has been investigated by measuring the VTMA of each vibrational mode for the tautomers.
Infrared Spectroscopy of Imidazole Trimer in Helium Nanodroplets: Free NH Stretch Mode
Lee, Seul-Ki,Lee, Seung-Jun,Ahn, Ah-Reum,Kim, Yu-Sic,Min, Ah-Reum,Choi, Myong-Yong,Miller, Roger E. Korean Chemical Society 2011 Bulletin of the Korean Chemical Society Vol.32 No.3
We report the first vibrational band assignment of imidazole trimer (IMT) solvated in helium nanodroplets. Several congested vibrational bands of imidazole (IM) clusters were obtained in the frequency region of $3513-3515\;cm^{-1}$ and vibrationally resolved due to the extremely low temperature (0.37 K) and very weak solutesolvent interaction environments of helium droplets. The unambiguous free NH band assignment was achieved with an aid of pick-up oven temperature dependence and vibrational transition moment angle (VTMA) experiments as well as density functional theory (DFT) calculations. The band at $3514.3\;cm^{-1}$ is attributed to the free NH stretching mode of linear IMT clusters, easily formed by the dipole-dipole interactions of IM in ultracold helium nanodroplets.
Imidazole Trimer-Water Complexes in Superfluid Helium Nanodroplets: Water Stretching Modes
Ahn, Ah-Reum,Lee, Seung-Jun,Lee, Seul-Ki,Min, Ah-Reum,Kim, Yu-Sic,Jung, Hyeon-Jin,Hong, Seong-Min,Lee, Joon-Hwa,Choi, Myong-Yong,Miller, Roger E. Korean Chemical Society 2011 Bulletin of the Korean Chemical Society Vol.32 No.4