The Experts below are selected from a list of 36603 Experts worldwide ranked by ideXlab platform
Rizwan Ahmed Malik - One of the best experts on this subject based on the ideXlab platform.
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giant strain thermally stable high energy storage properties and structural evolution of bi based lead free piezoceramics
Journal of Alloys and Compounds, 2016Co-Authors: Rizwan Ahmed Malik, Ali Hussain, Adnan Maqbool, Arif Zaman, T K SongAbstract:Abstract In this study, the mechanism of electric-field-induced phase transition in 0.96[Bi0.5(Na0.84K0.16)0.5Ti1-xTaxO3]–0.04SrTiO3, (where 0.00 ≤ x ≤ 0.030, abbreviated as BNKTT–ST) ceramics was discussed based on crystal structure and electromechanical properties. X-ray powder diffraction (XRD) showed a phase transition from mixed rhombohedral-tetragonal to single pseudocubic when x ≥ 0.020. Large electromechanical strain of ∼0.42% with a dynamic piezoelectric constant (Smax/Emax) of ∼700 pm/V at 6 kV/mm was recorded for 2 mol. % Ta content. Interestingly, at lower field of 4 kV/mm, the Smax/Emax attained the highest value of ∼830 pm/V. Poled, unpoled XRD analysis and electrical properties suggest that the relatively high Smax/Emax at x = 0.020 may be attributed to the combined effect of composition and ferroelectric (FE) to ergodic relaxor (ER) phase transition. Furthermore, the energy storage density was studied as a function of both composition and temperature to demonstrate the suitability for capacitor applications. This system also revealed improved energy storage properties. Particularly, for x = 0.020, a nearly temperature-invariant large recoverable energy density (W = 0.65 J/cm3) was achieved over a wide temperature range (75–150 °C). These properties demonstrate that the fabricated system might be a promising lead-free candidate for actuators and high temperature energy storage capacitor applications.
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high strain in lead free nb doped bi1 2 na0 84k0 16 1 2tio3 srtio3 incipient piezoelectric ceramics
Applied Physics Express, 2014Co-Authors: Rizwan Ahmed Malik, Jinkyu Kang, Ali Hussain, Chang Won Ahn, Hyoungsu Han, Jaeshin LeeAbstract:Lead-free 0.96[Bi1/2(Na0.84K0.16)1/2(Ti(1−x)Nbx)O3]–0.04SrTiO3 (BNKTN–ST, with x = 0–0.030) ceramics were synthesized by a conventional solid-state reaction technique. Polarization and strain hysteresis loops indicated a significant disruption of ferroelectric order accompanied by an enhanced field-induced strain (S = 0.438%) with a high normalized strain Smax/Emax of 876 pm/V at 5 kV/mm. Their reproducibility was confirmed by the fabrication of a 10-layered stack-type multilayer actuator, which demonstrated a normalized strain Smax/Emax of 720 pm/V.
David E Nix - One of the best experts on this subject based on the ideXlab platform.
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pharmacokinetics of rifampin under fasting conditions with food and with antacids
Chest, 1999Co-Authors: Charles A Peloquin, Rocsanna Namdar, Michael D Singleton, David E NixAbstract:Study objectives Determine the intrasubject and intersubject variability in, and the effects of food or antacids on, the pharmacokinetics of rifampin (RIF). Design Randomized, four-period crossover phase I study. Subjects Fourteen healthy male and female volunteers. Interventions Subjects ingested single doses of RIF, 600 mg, under fasting conditions twice, with a high-fat meal, and with aluminum-magnesium antacid. They also received standard doses of isoniazid, pyrazinamide, and ethambutol. Measurements and main results Serum was collected for 48 h and assayed by high-pressure liquid chromatography. Data were analyzed using noncompartmental methods and a compartmental analysis using nonparametric expectation maximization. Both fasting conditions produced similar results: a mean RIF maximal serum concentration (Cmax) of 10.54 ± 3.18 μg/mL, the time at which it occurred (Tmax) of 2.42 ± 1.32 h, and the area under the curve from time zero to infinity (AUC 0–∞ ) of 57.15 ± 13.41 μg · h/mL. These findings are similar to those reported previously. Antacids did not alter these parameters (Cmax of 10.89 ± 5.22 μg/mL, Tmax of 2.36 ± 1.28 h, and AUC 0–∞ of 58.37 ± 18.49μ g · h/mL). In contrast, the Food and Drug Administration high-fat meal reduced RIF Cmax by 36% (7.27 ± 2.29 μg/mL), nearly doubled Tmax (4.43 ± 1.09 h), but reduced AUC 0–∞ by only 6% (55.20 ± 14.48 μg · h/mL). Conclusions These changes in Cmax, Tmax, and AUC 0–∞ can be avoided by giving RIF on an empty stomach whenever possible.
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pharmacokinetics of pyrazinamide under fasting conditions with food and with antacids
Pharmacotherapy, 1998Co-Authors: Charles A Peloquin, Gordon T James, Amy E Bulpitt, George S Jaresko, Roger W Jelliffe, David E NixAbstract:Study Objectives. To determine intrasubject and intersubject variability in, and the effects of food and antacids on, the pharmacokinetics of pyrazinamide (PZA). Design. Randomized, four-period, crossover phase I study. Subjects. Fourteen healthy men and women volunteers. Interventions. Subjects ingested single doses of PZA 30 mg/kg under fasting conditions twice, without a high-fat meal and with an aluminum-magnesium antacid. They also received standard dosages of isoniazid, rifampin, and ethambutol. Measurements and Main Results. Serum was collected for 48 hours and assayed by gas chromatography with mass selective detector. Data were analyzed by noncompartmental methods and a compartmental analysis using nonparametric expectation maximization. Both fasting conditions produced similar results: mean PZA Cmax 53.4 ± 10.4 μg/ml, Tmax 1.43 ± 1.06 hours, and AUC0-∞, 673 ± 79.7 μg·hr/ml. Fasting results are similar to those in previous reports. In the presence of antacids, subjects had a mean Cmax of 55.6 ± 9.0 μg/ml, Tmax of 1.43 ± 1.23 hours, and AUC0-∞ of 628 ± 88.4 μg·hr/ml. In the presence of the high-fat meal, mean Cmax was 45.6 ± 9.44 μg/ml, Tmax 3.09 ± 1.74 hours, and AUC0-∞ 687 ± 116 μg·hr/ml. Conclusions. These small changes in Cmax. Tmax, and AUC0-∞. can be avoided by giving PZA on an empty stomach whenever possible. Conclusion: Serum concentrations in this study were consistent with those described previously. In addition, PZA's kinetic behavior was consistent between fasting treatments. Antacids and food had minimal effects on the agent's absorption. Samples drawn between 0.5 and 3 hours after dosing approached Cmax for most subjects, with 1 hour being closest. Samples drawn as early as day 2 of daily PZA therapy will produce serum concentrations that approach steady-state values.
Helle Linnebjerg - One of the best experts on this subject based on the ideXlab platform.
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bioequivalence and comparative pharmacodynamics of insulin lispro 200 u ml relative to insulin lispro humalog 100 u ml
Clinical pharmacology in drug development, 2016Co-Authors: Amparo De La Pena, Patricia Brownaugsburger, Mary E Seger, Danny Soon, Adam Scott, Shobha Reddy, Michael Allen Dobbins, Helle LinnebjergAbstract:Insulin lispro 200 U/mL (IL200) is a new strength formulation of insulin lispro (Humalog®, IL100), developed as an option for diabetic patients on higher daily mealtime insulin doses. This phase 1, open-label, 2-sequence, 4-period crossover, randomized, 8-hour euglycemic clamp study aimed to demonstrate the bioequivalence of IL200 and IL100 after subcutaneous administration of 20 U (U) to healthy subjects (n = 38). Pharmacokinetic (PK) and pharmacodynamic (PD) responses were similar in both formulations. All 90%CIs for the ratios of area under the concentration-versus-time curve from time zero to the time of the last measurable concentration (AUC0–tlast) and maximum observed drug concentration (Cmax), as well as the total glucose infused throughout the clamp (Gtot) and the maximum glucose infusion rate (Rmax), were contained within 0.80 and 1.25. Time of maximum observed drug concentration (tmax) was similar between formulations, with a median difference of 15 minutes and a 95%CI of the difference that included zero. Inter- and intrasubject variability estimates were similar for both formulations. Both formulations were well tolerated. IL200 was bioequivalent to IL100 after subcutaneous administration of 20-U single doses, and PD responses were comparable between formulation strengths.
G Scaglioni - One of the best experts on this subject based on the ideXlab platform.
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effect of ageing on the electrical and mechanical properties of human soleus motor units activated by the h reflex and m wave
The Journal of Physiology, 2003Co-Authors: Nicola A Maffiuletti, G Scaglioni, Marco V Narici, Manuela Pensini, A MartinAbstract:This study was designed to investigate the effect of ageing on the mechanical and electromyographic (EMG) characteristics of the soleus motor units (MUs) activated by the maximal Hoffmann reflex (Hmax) and by the direct muscle compound action potential (Mmax). Eleven young (mean age 25 ± 4 years) and ten elderly (mean age 73 ± 5 years) males took part in this investigation. The senior group presented lower amplitudes of Mmax (−57 %, P < 0.001) and Hmax (−68 %, P < 0.001) waves compared to the younger population. These were associated with a depression of relative twitch torque of the plantar flexors. The average values of the Hmax/Mmax ratio did not statistically differ between the two populations, despite a tendency for lower values (∼23 %) in the senior group. However, the older adults showed a greater relative amplitude of the sub-maximal M wave evoked at Hmax (MatHmax) than did the younger males (young 5 % vs. elderly 29 % of the Mmax, P < 0.01). This finding suggests an increased homogeneity between the excitability threshold of sensory and motor axons. The twitch torque at Hmax (PtH–M) was subsequently calculated by subtraction from the total twitch torque of the mechanical contamination associated with MatHmax. The resulting PtH–M was significantly lower in the elderly (−59 %, P < 0.001). Despite a discrepancy of 20 % between the two groups, the mechanical ratio (PtH–M/PtM; PtM, twitch tension related to the Mmax compound action potential), like the EMG ratio, did not statistically differ between the young and older individuals. Nevertheless, the senior subjects exhibited a higher twitch/EMG ratio for the reflexively activated MUs (PtH–M/Hmax) than the younger individuals (+40 %, P < 0.05). This finding suggests an on-going neuromuscular remodelling, resulting in an increased innervation ratio. The neural rearrangement may be viewed as a compensatory adaptation of the motor system to preserve the mechanical efficiency of the surviving MUs, despite the age-related impairment of the segmental reflex system. This phenomenon is confirmed by the maintenance, with senescence, of the approximately constant values of the twitch/EMG ratio for the entire motor pool (PtM/Mmax).
Jiwei Zhai - One of the best experts on this subject based on the ideXlab platform.
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effect of different templates on structure evolution and large strain response under a low electric field in textured lead free bnt based piezoelectric ceramics
Journal of The European Ceramic Society, 2015Co-Authors: Junhua Xi, Jun Zhang, Bo Shen, Jiwei ZhaiAbstract:Abstract -textured 0.83Na0.5Bi0.5TiO3–0.17Bi0.5K0.5TiO3 (BNT–BKT) ceramics with high degree of texturing (>80%) were synthesized by templated grain growth using different perovskite plate-like BaTiO3, SrTiO3 and NaNbO3 as template particles to develop lead-free piezoelectric materials with an excellent actuating performance. The effects of different template particles addition to BNT–BKT ceramics on the grain orientation, structure evolution, phase stability and macroscopic functional properties was systematically investigated. BaTiO3 template particles addition to form -textured BNT–BKT–BT textured ceramics suppresses an electric-field-induced long-range ferroelectric order, giving rise to a high field-induced Smax/Emax of 710 pm/V under a relatively low driving field of 45 kV/cm compared with existing lead-free Bi-perovskite ceramics. In particular, temperature-dependent strain response reveals that -textured BNT–BKT–5BT ceramics exhibit not only large Smax/Emax at a low driving field of 45 kV/cm at room temperature but also enhanced the temperature stability of Smax/Emax featured by large Smax/Emax of 517 pm/V at high temperature.
