The Experts below are selected from a list of 291 Experts worldwide ranked by ideXlab platform
Ji-ho Yoon - One of the best experts on this subject based on the ideXlab platform.
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Spectroscopic identification and conversion rate of gaseous guest-loaded hydroquinone clathrates
Chemical Physics Letters, 2012Co-Authors: Jong-won Lee, Ki Jong Choi, Yongjae Lee, Ji-ho YoonAbstract:Abstract The formation of hydroquinone clathrates with CO 2 , CH 4 , N 2 , and H 2 was investigated using X-ray diffraction, Raman spectroscopy, and solid-state 13 C NMR spectroscopy. Of the hydroquinones prepared at 5.0 MPa, the CH 4 - and CO 2 -loaded hydroquinones show complete conversion to β-form hydroquinone clathrates while the N 2 -loaded hydroquinone shows only partial conversion; there is no indication of the formation of hydroquinone clathrate with H 2 . The CO 2 -loaded hydroquinone is fully converted to the β-form hydroquinone clathrate even at 1.0 MPa. Solid-state 13 C NMR measurements of the hydroquinone clathrate samples prepared at different pressures reveal that the conversion rate for the formation of clathrate compounds from CH 4 and N 2 decreases with decreasing pressure.
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Characterization of hydroquinone clathrates by THz time-domain spectroscopy
2009 34th International Conference on Infrared Millimeter and Terahertz Waves, 2009Co-Authors: Ji-ho Yoon, Jin-seok Jang, Tae-in JeonAbstract:Using terahertz time-domain spectroscopy (THz-TDS), we have measured the absorption spectra of α-hydroquinone and methane- and methanol-loaded β-hydroquinone clathrates up to 3 THz frequency range. The α-hydroquinone exhibits 11 resonances whereas methane- and methanol-loaded β-hydroquinone clathrates show only 1 resonance. The observed THz resonances represent the intermolecular and lattice vibrations of the hydroquinone frameworks, but seem to be insensitive to the encaged guest species. The indices of refraction are found to be ca. 1.6 for α-hydroquinone and methane-loaded β-hydroquinone clathrate and 1.7 for methanol-loaded β-hydroquinone clathrate, and the anomalous dispersions are well defined at the resonance frequencies.
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Characterization of α-hydroquinone and β-hydroquinone clathrates by THz time-domain spectroscopy
Chemical Physics Letters, 2009Co-Authors: Jin-seok Jang, Tae-in Jeon, Ji-ho YoonAbstract:Abstract We have measured the absorption spectra of α-hydroquinone and methane- and methanol-loaded β-hydroquinone clathrates up to 3 THz frequency range using terahertz time-domain spectroscopy (THz-TDS). The α-hydroquinone exhibits 11 resonances whereas methane- and methanol-loaded β-hydroquinone clathrates show only 1 resonance. The observed THz resonances represent the intermolecular and lattice vibrations of the hydroquinone frameworks, but seem to be insensitive to the encaged guest species. The indices of refraction are found to be ca. 1.6 for α-hydroquinone and methane-loaded β-hydroquinone clathrate and 1.7 for methanol-loaded β-hydroquinone clathrate, and the anomalous dispersions are well-defined at the resonance frequencies.
A. L. M. Verbeek - One of the best experts on this subject based on the ideXlab platform.
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Hydroquinine pharmacokinetics after oral administration in adult patients with muscle cramps
European Journal of Clinical Pharmacology, 2000Co-Authors: H. J. M. Van Kan, P. H. P. Jansen, C. Tuinte, P. Smits, A. L. M. VerbeekAbstract:Objective : This study was conducted to determine the pharmacokinetic properties of Hydroquinine after oral administration in adult patients with muscle cramps. The main reason for this study was the poor availability of pharmacokinetic data, hindering the design of studies to explore the possible relationship between Hydroquinine concentrations and effects. Methods : Sixteen adult patients with a clinical history of muscle cramps were given once-daily oral doses of 300 mg Hydroquinine hydrobromide for 4 days. Serum and saliva samples were taken following a predefined schedule until 24 h after the last dose. Urine was collected during the study period. Hydroquinine concentrations were measured, and calculations were made of pharmacokinetic parameters using non-linear curve fitting. Results : Pharmacokinetics of Hydroquinine could be best described using a one-compartment open model. After oral administration, Hydroquinine was rapidly absorbed (mean ± SD: maximum concentration 2.43 ± 0.68 mg/l; time to maximum concentration 1.4 ± 1.2 h; lag time 0.54 ± 0.50 h). With an elimination half-life of 10.9 ± 6.1 h, steady-state was reached in several days. The distribution volume was 1.24 ± 0.29 l/kg, total clearance was 6.7 ± 3.2 l/h. The measured unbound Hydroquinine fraction was 8.6 ± 3.0%. No correlation was found between saliva and serum concentrations. Cumulative urinary excretion of unchanged Hydroquinine 24 h after the first dose was 35.5 ± 9.2 mg. Conclusion : Pharmacokinetic properties of Hydroquinine are roughly similar to those of quinine. The unchanged fraction of Hydroquinine excreted in urine is higher than that reported for quinine. Saliva Hydroquinine concentrations could not be related to serum values. Steady-state trough or other fixed-time serum concentrations may prove useful for further optimisation of Hydroquinine dosage.
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randomised controlled trial of Hydroquinine in muscle cramps
The Lancet, 1997Co-Authors: P. H. P. Jansen, K C W Veenhuizen, A I M Wesseling, T M De Boo, A. L. M. VerbeekAbstract:Summary Background Although quinine and Hydroquinine are commonly prescribed for muscle cramps, controlled clinical trials of these drugs have reported mixed findings about efficacy. We investigated Hydroquinine therapy in otherwise healthy adults who had frequent, ordinary muscle cramps. Methods This randomised, double-blind, placebo-controlled, parallel-group trial consisted of three consecutive 2-week periods: qualification, treatment, and washout. 68 women and 44 men who had at least three muscle cramps per week were enrolled. During the treatment period, participants were randomly assigned 300 mg daily dose of Hydroquinine hydrobromide dihydrate (54 participants) or placebo (58). The frequency, severity (1–10), duration, and location of muscle cramps, as well as any side-effects, were recorded by participants in daily diaries. The primary outcome measures were the number of muscle cramps and the number of days during which the participants had muscle cramps (cramp-days). Findings We excluded five participants from both groups from the analysis. Thus, data from 49 Hydroquinine-group participants and 53 placebo-group participants were analysed. In both groups the total number of muscle cramps and the number of cramp-days decreased during the treatment period compared with the qualification period. However, these improvements were greater in the Hydroquinine group than in the placebo group. The Hydroquinine-group participants reported a median of 8 (95% CI 7–12) fewer cramps and median of 3 (1–4) fewer cramp-days, whereas those on placebo reported only 3 (0–5) fewer cramps and 1 (0–5) fewer cramp-days. 32 (65%) of participants in the Hydroquinine group had a 50% or greater reduction in the number of muscle cramps. After the onset of cramps, Hydroquinine did not reduce the severity or duration of cramps. We also found a sustained effect after treatment had stopped. Hydroquinine was well tolerated, and resulted in only mild side-effects. Interpretation In our study, 300 mg Hydroquinine was safe to take in the short-term and significantly more effective than placebo in the prevention of frequent, ordinary muscle cramps. This therapeutic effect outlasted the duration of treatment.
Akbar Bagheri - One of the best experts on this subject based on the ideXlab platform.
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simultaneous determination of hydroquinone and catechol at gold nanoparticles mesoporous silica modified carbon paste electrode
Journal of Hazardous Materials, 2016Co-Authors: J Tashkhourian, M Daneshi, F Namiana, Mohammad Behbahani, Akbar BagheriAbstract:A new electrochemical sensor based on gold nanoparticles mesoporous silica modified carbon paste electrode (AuNPs-MPS) was developed for simultaneous determination of hydroquinone and catechol. Morphology and structure of the AuNPs-MPS were characterized by transmission electron microscopy, X-ray diffraction and Fourier transform infrared spectroscopy. The electrochemical behavior of hydroquinone and catechol were investigated using square wave voltammetry and the results indicate that the electrochemical responses are improved significantly at the modified electrode. The observed oxidative peaks separation of about 120mV made possible the simultaneous determination of hydroquinone and catechol in their binary-mixture. Under the optimized condition, a linear dynamic range of 10.0μM-1.0mM range for hydroquinone with the detection limit of 1.2μM and from 30.0μM-1.0mM for catechol with the detection limit of 1.1μM were obtained. The applicability of the method was demonstrated by the recovery studies of hydroquinone and catechol in spiked tap water samples.
Jin-seok Jang - One of the best experts on this subject based on the ideXlab platform.
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Characterization of hydroquinone clathrates by THz time-domain spectroscopy
2009 34th International Conference on Infrared Millimeter and Terahertz Waves, 2009Co-Authors: Ji-ho Yoon, Jin-seok Jang, Tae-in JeonAbstract:Using terahertz time-domain spectroscopy (THz-TDS), we have measured the absorption spectra of α-hydroquinone and methane- and methanol-loaded β-hydroquinone clathrates up to 3 THz frequency range. The α-hydroquinone exhibits 11 resonances whereas methane- and methanol-loaded β-hydroquinone clathrates show only 1 resonance. The observed THz resonances represent the intermolecular and lattice vibrations of the hydroquinone frameworks, but seem to be insensitive to the encaged guest species. The indices of refraction are found to be ca. 1.6 for α-hydroquinone and methane-loaded β-hydroquinone clathrate and 1.7 for methanol-loaded β-hydroquinone clathrate, and the anomalous dispersions are well defined at the resonance frequencies.
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Characterization of α-hydroquinone and β-hydroquinone clathrates by THz time-domain spectroscopy
Chemical Physics Letters, 2009Co-Authors: Jin-seok Jang, Tae-in Jeon, Ji-ho YoonAbstract:Abstract We have measured the absorption spectra of α-hydroquinone and methane- and methanol-loaded β-hydroquinone clathrates up to 3 THz frequency range using terahertz time-domain spectroscopy (THz-TDS). The α-hydroquinone exhibits 11 resonances whereas methane- and methanol-loaded β-hydroquinone clathrates show only 1 resonance. The observed THz resonances represent the intermolecular and lattice vibrations of the hydroquinone frameworks, but seem to be insensitive to the encaged guest species. The indices of refraction are found to be ca. 1.6 for α-hydroquinone and methane-loaded β-hydroquinone clathrate and 1.7 for methanol-loaded β-hydroquinone clathrate, and the anomalous dispersions are well-defined at the resonance frequencies.
Tae-in Jeon - One of the best experts on this subject based on the ideXlab platform.
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Characterization of hydroquinone clathrates by THz time-domain spectroscopy
2009 34th International Conference on Infrared Millimeter and Terahertz Waves, 2009Co-Authors: Ji-ho Yoon, Jin-seok Jang, Tae-in JeonAbstract:Using terahertz time-domain spectroscopy (THz-TDS), we have measured the absorption spectra of α-hydroquinone and methane- and methanol-loaded β-hydroquinone clathrates up to 3 THz frequency range. The α-hydroquinone exhibits 11 resonances whereas methane- and methanol-loaded β-hydroquinone clathrates show only 1 resonance. The observed THz resonances represent the intermolecular and lattice vibrations of the hydroquinone frameworks, but seem to be insensitive to the encaged guest species. The indices of refraction are found to be ca. 1.6 for α-hydroquinone and methane-loaded β-hydroquinone clathrate and 1.7 for methanol-loaded β-hydroquinone clathrate, and the anomalous dispersions are well defined at the resonance frequencies.
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Characterization of α-hydroquinone and β-hydroquinone clathrates by THz time-domain spectroscopy
Chemical Physics Letters, 2009Co-Authors: Jin-seok Jang, Tae-in Jeon, Ji-ho YoonAbstract:Abstract We have measured the absorption spectra of α-hydroquinone and methane- and methanol-loaded β-hydroquinone clathrates up to 3 THz frequency range using terahertz time-domain spectroscopy (THz-TDS). The α-hydroquinone exhibits 11 resonances whereas methane- and methanol-loaded β-hydroquinone clathrates show only 1 resonance. The observed THz resonances represent the intermolecular and lattice vibrations of the hydroquinone frameworks, but seem to be insensitive to the encaged guest species. The indices of refraction are found to be ca. 1.6 for α-hydroquinone and methane-loaded β-hydroquinone clathrate and 1.7 for methanol-loaded β-hydroquinone clathrate, and the anomalous dispersions are well-defined at the resonance frequencies.
