Microwave-field sensing via electromagnetically induced absorption of Rb irradiated by three-color infrared lasers.

A microwave electric field sensing has been set up based on a three-color electromagnetically induced absorption in rubidium vapor cell via cascading transitions. All transitions are irradiated by infrared lasers: a 780 nm laser servers as probe to monitor the optical transmittancy via transition 5S1/2→P3/2;, a 776 nm laser and a 1260 nm laser are used to couple the states 5P3/2 and 5D5/2 and states 5D5/2 and 44F7/2, respectively. We find that a frequency detuning ∼2π × ( - 40) MHz of the 776 nm dressing beam prefers to a better signal-to-noise ratio for the probe beam. The off-resonance greatly depresses the double resonance pumping effect. A demonstration measurement for the electric field of microwave 1.18988 GHz, corresponding to the coupling resonance between two adjacent Rydberg states 44F7/2 and 44F9/2, gives a sensitivity of 55.79(23)nVcm-1/Hz and a smallest discernible electric field of 78.9(33) nVcm-1 in time scale of 500 ms.

Artificial modulation-free Pound-Drever-Hall method for laser frequency stabilization.

We have proposed an artificial modulation-free Pound-Drever-Hall (PDH) method for laser frequency stabilization and demonstrated it via two-color polarization spectroscopy of Rydberg electromagnetically induced transparency (EIT) resonance in a room-temperature rubidium vapor. Due to the unique error signal profile, the conventional PDH method owns a large capture range in laser frequency locking. Here we manually construct a PDH error signal via a linear combination of polarization spectroscopies of the Rydberg EIT resonances without and with a magnetic field applied. The artificial modulation-free PDH error signal owns a subnatural linewidth dispersion curve as well as a large capture range with which we successfully stabilize the laser to an absolute atomic frequency reference in a long running time, immune to environmental fluctuation and even manmade impulse perturbation. This method can provide an absolute frequency reference based on atomic transition while keeping similar locking ability to provide corrections for frequency fluctuations over a broad bandwidth as the conventional PDH.

Content and distribution of trace metals in surface sediments from the northern Bering Sea, Chukchi Sea and adjacent Arctic areas.

Concentrations of trace metals (Zn, Cr, Cu, V, Cd and Pb), total organic carbon (TOC), black carbon (BC) and their granulometry were examined in 25 surface sediment samples from the northern Bering Sea, Chukchi Sea and adjacent areas. Trace metal concentrations in the sediments varied from 21.06-168.21 mg kg(-1) for Zn, 8.91-46.94 mg kg(-1) for Cr, 2.69-49.39 mg kg(-1) for Cu, 32.46-185.54 mg kg(-1) for V, 0.09-0.92 mg kg(-1) for Cd, and 0.95-15.25 mg kg(-1) for Pb. The geoaccumulation index (Igeo) indicated that trace metal contamination (Zn and Cd) existed in some stations of the study area. The distribution of grain size plays an important role in influencing the distribution of trace metals (Zn, Cr, Cu, V, and Pb) in sediments from the Chukchi Sea and adjacent areas.

Time course of action and pharmacokinetics of ropivacaine in adult and elderly patients following combined lumbar plexus-sciatic nerve block.

OBJECTIVE: Large doses of local anesthetics are needed in combined lumbar plexus-sciatic nerve block. The safety of local anesthetics is important among elderly patients. This study investigates the pharmacokinetics of ropivacaine in elderly patients with combined lumbar plexus-sciatic nerve block. METHODS: Ropivacaine pharmacokinetics and the time of onset, duration of sensory and motor block were studied in adult patients (18 - 60 y) and elderly patients (>= 60 y). Combined lumbar plexus-sciatic nerve block was performed using a nerve stimulator. 0.375% ropivacaine was injected in patients. Plasma concentration of ropivacaine was determined by high performance liquid chromatography. RESULTS: There was no significant difference in onset time and time to peak (tmax1, tmax2) between elderly patients and adult patients. Half-life time (t1/2alpha, t1/2beta) and the duration of sensory and motor block were longer in elderly patients (p < 0.05). While the peak plasma concentrations of (double peaks, Cmax1, Cmax2) wer lower in elderly patients than that in adult patients. CONCLUSIONS: Age does not affect the onset time of ropivacaine after combined lumbar plexus-sciatic nerve block but can influence the motor and sensory recovery. Local absorption of ropivacaine is slower in elderly patients compared to adults.

Simultaneous modeling of pharmacokinetics and pharmacodynamics of propafenone in healthy subjects.

AIM: To study the simultaneous modeling of pharmacokinetics and pharmacodynamics (PK-PD) of propafenone (Pro) in healthy subjects. METHODS: Ten healthy Chinese volunteers, 5 extensive metabolizers (EM) and 5 intermediate metabolizers (IM) of CYP2D6, received a single dose (400 mg) of Pro hydrochloride. The blood samples and electrocardiogram (ECG) measurements were taken after administration over 15 h period. The concentrations of Pro in plasma were measured by a reverse-phase HPLC. PR interval was used as an average value of 10 PR interval measurements. RESULTS: There was a delay between Pro level and percentage of PR interval prolongation. After PK-PD simulating, the relationship between effect concentration (Ce) and the effect met the sigmoid E(max) model. CYP2D6 (EM & IM) played an important role in both pharmacokinetics and pharmacodynamics which produced by Pro. The AUC (microg . h . L-1) of IM group was significantly higher than that of EM group (5126 +/- 1030 vs 2948 +/- 1230, P < 0.05). Whereas Ce50 (microg/L) was also greater in IM group than in EM group (747 +/- 281 vs 359 +/- 123, P < 0.05). On the other hand, gamma of EM group was about one fold larger than that of IM group (P < 0.05). CONCLUSION: CYP2D6 phenotype of human may influence not only pharmacokinetic of Pro but also its pharmacological effects.

The influence of CYP2D6 activity on the kinetics of propafenone enantiomers in Chinese subjects.

AIMS: To determine role of CYP2D6 activity in the pharmacokinetics of propafenone (PPF) enantiomers in native Chinese subjects. METHODS: Sixteen extensive metabolizers (EMs) and one poor metabolizer (PM), whose phenotype had been previously assessed with dextromethorphan metabolic phenotyping, were enrolled. Blood samples (0 approximately 15 h) were taken after oral administration of a single dose (400 mg) of racemic-propafenone hydrochloride. A reverse-phase h.p.l.c. method with pre-column derivatization was employed to quantitate enantiomeric concentrations of propafenone in plasma. RESULTS: For the EM subjects, S-PPF was less rapidly metabolized and had higher peak plasma concentrations than R-PPF (413+/-143 vs 291+/-109 ng ml-1, P<0.001). The AUC was markedly higher for S-PPF than for R-PPF (2214+/-776 vs 1639+/-630 microg h l-1, P<0.001), whereas the clearance of S-PPF was significantly lower than that of R-PPF (96.0+/-39.0 vs 138+/-78 l h-1, P<0.01). There were no differences in t1/2, and Cmax between the two isomers (P >0.05). In the one PM subject, not only did S-PPF appear to undergo less rapid metabolism than R-PPF, but the subject also showed 2 approximately 3 fold differences in Cmax, CL and AUC compared with EMs. The correlation coefficients (rs ) between dextromethorphan metabolic ratio (lg MR) and pharmacokinetic parameters (Cmax, CL and AUC) were 0.63, -0.87, 0.87 for S-PPF and 0. 57, -0.73, 0.86 for R-PPF, respectively. CONCLUSIONS: Our results suggest that CYP2D6 activity contributes to the pharmacokinetic variability of propafenone enantiomers in Chinese subjects.

CYP2D6 phenotype determines pharmacokinetic variability of propafenone enantiomers in 16 HAN Chinese subjects.

AIM: To determine the role of the CYP2D6 phenotype in the metabolism of propafenone (Pro) enantiomers in 16 HAN Chinese subjects. METHODS: Seven very extensive metabolizers (VEM) and nine intermediate metabolizers (IM) were enrolled from a Chinese population whose phenotype had been previously assessed with a dextromethorphan metabolic phenotyping. The blood samples (0-15 h) were taken after oral administration of a single dose (400 mg) of rac-Pro hydrochloride. Enantiomeric concentrations of propafenone in plasma were measured by a reverse-phase HPLC with precolumn derivatization. RESULTS: S-Pro was less metabolized and had higher plasma concentrations than R-Pro in both CYP2D6 phenotypes. Besides, the T1/2 of R-Pro was longer than that of S-Pro in IM, but not in VEM. However, there were significant differences in the metabolism of Pro enantiomers between VEM and IM. The Cmax and AUC of both isomers in the IM group were higher than those in the VEM group (P < 0.01). The Cl of Pro enantiomers in IM group was only about half of that in VEM group [(67 +/- 17) vs (133 +/- 28) L.h-1 for S-Pro, (90 +/- 24) vs (200 +/- 87) L.h-1 for R-Pro, P < 0.01]. The S/R ratios of T1/2, Tmax, Cmax, Cl, and AUC were not significantly different (P > 0.05). CONCLUSION: CYP2D6 phenotype determines the pharmacokinetic variability of propafenone enantiomers and existence of IM may be relevant to diminished capacity of CYP2D6 enzyme in Chinese subjects.

[NONMEM approach for estimating population pharmacokinetic parameters of phenytoin in Chinese epileptics].

Routine clinical pharmacokinetic data collected from epileptic out-patients who received phenytoin (PHT) were analysed to estimate population pharmacokinetic parameters. There were 258 steady-state serum phenytoin concentrations and associated dosage (mg.d-1) from 161 out-patients. The data were analysed using NONMEM program. The influence of body weight, drug combinations and sex on the maximum elimination rate (Vm) and age on the Michaelis-Menten constant (Km) were investigated. The Vm and Km of phenytoin in a 60 kg adult out-patient, without combination with other drugs (phenobarbital, clonazepam or diazepam) were estimated to be 439 mg.d-1 and 6.21 micrograms.ml-1, respectively. The best function adjusts Vm to the 0.57 power in proportion to body weight. The Km for patients less than 15 years old was 7% less than that for adults. The Vm of patients treated with phenytoin combined with phenobarbital, clonazepam or diazepam will increase 8.4 mg.d-1.