Showing papers on "NQS published in 2012"

1,2-Naphthoquinone-4-Sulphonic Acid Sodium Salt (NQS) as an Analytical Reagent for the Determination of Pharmaceutical Amine by Spectrophotometry

Abstract: Several papers have been presented in recent years regarding the field of application of 1,2-naphthoquinone-4-sulphonic acid sodium salt (NQS) as a chromogenic reagent for the determination of pharmaceutical amines using spectrophotometry. In this review article, various spectrophotometric methods using NQS as a labeling reagent for determination of pharmaceutical amines are presented. The application of these methods for the determination of drugs in pharmaceutical formulations and real samples is discussed.

Accurate RTA-Based Nonquasi-Static MOSFET Model for RF and Mixed-Signal Simulations

Abstract: A new relaxation-time-approximation-based nonquasi-static (NQS) MOSFET model, consistent between transient and small-signal simulations, has been developed for surface-potential-based MOSFET compact models. The new model is valid for all regions of operation and is compatible with, and at low frequencies recovers, the quasi-static description of the MOSFET. The model is implemented in two widely used circuit simulators and is tested for speed and convergence. It is verified by comparison with technology computer-aided design simulations and experimental data and by application of a recently developed benchmark test for NQS MOSFET models.

Spectophotometric methods for determination of cefdinir in pharmaceutical formulations via derivatization with 1,2-naphthoquinone-4-sulfonate and 4-chloro-7-nitrobenzo-2-oxa-1, 3-diazole.

Abstract: Two new simple, sensitive, accurate, and precise spectrophotometric methods have been developed and validated for the determination of cefdinir (CFD) in bulk drug and in its pharmaceutical formulations. The first method was based on the reaction of CFD with 1, 2- napthaquinone-4- sulfonic acid sodium (NQS) in an alkaline medium (pH 11) to form an orange-coloured product that was measured at 490 nm. The second method depends on hydrolysis of CFD using 0.5 M NaOH at 100 °C and subsequent reaction of the formed sulfide ions with 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl) to form a yellow-coloured chromogen measured at 390 nm. Different variables affecting the reactions of CFD with both NQS and NBD-Cl (e.g. NaOH concentration, hydrolysis time, NQS or NBD-Cl concentration and diluting solvent) were studied and optimized. Under optimum conditions, good linear relationships with good correlation coefficients (0.9990–0.9999) were found in the range of 10–80 and 5.0–30 µg ml−1 for NQS and NBD-Cl, respectively. The limits of assay detection and quantitation ranged from 1.097 and 0.280 and 3.656 and 0.934 µg ml−1 for NQS and NBD-Cl, respectively. The accuracy and precision of the proposed methods were satisfactory. The proposed method is simple, rapid, precise and convenient and was successfully applied for analysis of CFD in its pharmaceutical formulations and the recovery percentages ranged from 99.25 to 100.20%. Copyright © 2011 John Wiley & Sons, Ltd.

Small-Signal Modeling of Gate-All-Around (GAA) Junctionless (JL) MOSFETs for Sub-millimeter Wave Applications

Abstract: In this paper, we present the radiofrequency (RF) modeling for gate-all-around (GAA) junctionless (JL) MOSFETs with 30-㎚ channel length. The presented non-quasi-static (NQS) model has included the gate-bias-dependent components of the source and drain (S/D) resistances. RF characteristics of GAA junctionless MOSFETs have been obtained by 3-dimensional (3D) device simulation up to 1 ㎔. The modeling results were verified under bias conditions of linear region (VGS = 1 V, VDS = 0.5 V) and saturation region (VGS = VDS = 1 V). Under these conditions, the root-mean-square (RMS) modeling error of Y₂₂-parameters was calculated to be below 2.4%, which was reduced from a previous NQS modeling error of 10.2%.

Novel spectrophotometric method for determination of cinacalcet hydrochloride in its tablets via derivatization with 1,2-naphthoquinone-4-sulphonate.

Abstract: This study represents the first report on the development of a novel spectrophotometric method for determination of cinacalcet hydrochloride (CIN) in its tablet dosage forms. Studies were carried out to investigate the reaction between CIN and 1,2-naphthoquinone-4-sulphonate (NQS) reagent. In alkaline medium (pH 8.5), an orange red-colored product exhibiting maximum absorption peak (λmax) at 490 nm was produced. The stoichiometry and kinetic of the reaction were investigated and the reaction mechanism was postulated. This color-developing reaction was employed in the development of a simple and rapid visible-spectrophotometric method for determination of CIN in its tablets. Under the optimized reaction conditions, Beer's law correlating the absorbance with CIN concentration was obeyed in the range of 3 - 100 μg/ml with good correlation coefficient (0.9993). The molar absorptivity (e) was 4.2 × 105 l/mol/cm. The limits of detection and quantification were 1.9 and 5.7 μg/ml, respectively. The precision of the method was satisfactory; the values of relative standard deviations (RSD) did not exceed 2%. No interference was observed from the excipients that are present in the tablets. The proposed method was applied successfully for the determination of CIN in its pharmaceutical tablets with good accuracy and precisions; the label claim percentage was 100.80 - 102.23 ± 1.27 - 1.62%. The results were compared favorably with those of a reference pre-validated method. The method is practical and valuable in terms of its routine application in quality control laboratories.

Charge-Carrier Velocity Distributions in High-Mobility Polymer Dual-Gate Thin-Film Transistors

Abstract: We report charge-carrier velocity distributions in high-mobility polymer thin-film transistors (PTFTs) employing a dual-gate configuration. Our time-domain measurements of dual-gate PTFTs indicate higher effective mobility as well as fewer low-velocity carriers than in single-gate operation. Such nonquasi-static (NQS) measurements support and clarify the previously reported results of improved device performance in dual-gate devices by various groups. We believe that this letter demonstrates the utility of NQS measurements in studying charge-carrier transport in dual-gate thin-film transistors.

Optimized and validated spectrophotometric method for the determination of olanzapine in pharmaceutical formulations using 1,2,-naphthoquinone-4-sulphonate (nqs)

Abstract: Spectrophotometric study was carried out, for the first time, to investigate the reaction between the antipsychotic Olanzapine (OLP) and 1,2-naphthoquinone -4-sulphonate (NQS) reagent. In alkaline medium (pH 13), an orange-colored product exhibiting maximum absorption peak (λmax) at 454nm was produced. The stoichiometry of the reaction was determined and the reaction mechanism was postulated. This colordeveloping reaction was successfully employed in the development of simple and rapid spectrophotometric method for determination of OLP in its pharmaceutical dosage forms. Under the optimized reaction conditions, Beer’s law correlating the absorbance (A) with OLP concentration (C) was obeyed in the range of 0.4–4 µgml −1 . The regression equation for the calibration data was A = 0.0372 + 0.1637C, with good correlation coefficient (0.9997). The molar absorptivity (e) was 5.6×10 4 l mol −1 cm −1 . The limits of detection, quantification and Sandell sensitivity were 0.09, 0.29 µgml −1 and 0.006 µgcm −2 respectively. The intra-day precision (%RSD) and accuracy (%RE) ranged from 0.2 to 0.67 % and from 0.18 to 0.66 %, respectively, the inter-day (%RSD) and (%RE) values were within 0.12 % and 0.52 %, respectively. The proposed method was successfully applied to the determination of OLP in its pharmaceutical tablets with good accuracy and precisions; the label claim percentage was 100.67± 0.06. The method is practical and valuable for its routine application in quality control laboratories for analysis of OLP.

Modeling Non-Quasi-Static Effects in SiGe HBTs Using Improved Charge Partitioning Scheme

Abstract: The applicability of a partitioned-charge-based non-quasi-static (NQS) model is investigated using exact solutions for 1-D bipolar transistors. Limitations of the model to accurately predict $y_{21}(\omega)$ are overcome by further delaying the partitioned minority charge associated with the collector. A corresponding small-signal time-domain model is derived. The proposed model effectively includes the delays within both the quasi-neutral base and base–collector space-charge regions. Using only two extra nodes over the quasi-static bipolar transistor model HICUM, the NQS model is implemented using Verilog-A. The simplicity of the model yields straightforward parameter extraction techniques. Modeling results show excellent agreement with numerically simulated data.

Simple flow injection spectrophotometric determination of acetaminophen in pharmaceutical formulations using 1,2-naphthoquinone-4-sulphonate as chemical derivatization chromogenic reagent

Abstract: A simple method for the determination of paracetamol (acetaminophen) with sodium 1,2-naphthoquinone-4-sulphonate (NQS) in alkaline medium using flow injection analysis (FIA) was developed and validated. The effect of variables such as flow rate, NQS concentration, reaction coil length, NaOH concentration, and detection wavelength were studied. Linear response was found over the concentration range 3–35 mg L−1 (r2 = 0.9995), the relative standard deviation from replicate injections (n = 9) of 20 mg L−1 of paracetamol was 0.89%. A sampling rate of 82 samples h−1 was obtained. The method was applied for the determination of paracetamol in pharmaceutical tablets, and results have been compared with those obtained by the official method.

INVESTIGATION OF ft AND NON-QUASI-STATIC DELAY IN CONVENTIONAL AND JUNCTIONLESS MULTIGATE TRANSISTORS USING TCAD SIMULATIONS

Abstract: In this paper, a comparative study between conventional and junctionless multi-gate transistors is made with respect to unity gain cut-off frequency (ft) and non-quasi static (NQS) delay using TCAD simulations. The comparison is done with and without leakage current (IOFF) matching. Two structures, typical FinFET like trigate structure and gate all around structure with circular cross section, are considered in this study. It is found that compared to junctionless transistor, conventional devices show better ft and lesser NQS delay in both trigate and GAA transistors. When the IOFF matching constraint is met by adjusting the gate electrode work function, the conventional devices show no or weak IOFF dependency due to screening effect whereas junctionless devices show strong dependency on IOFF, with respect to ft and NQS delay.

Novel MOSFET (metal-oxide-semiconductor field effect transistor) NQS (network queuing system) model and circuit simulation method

Abstract: The invention provides a novel MOSFET (metal-oxide-semiconductor field effect transistor) NQS (network queuing system) model based on charge relaxation time approximation and a circuit simulation method. By the aid of a calculating balance value at the current moment and a practical value at the last moment of charge of a device and relaxation time factors, the model directly solves node charge at the current moment, and a simulation result of the model is completely consistent with that of a Bsim3 (Berkeley short-channel IGFET model 3) NQS model. Additionally, the NQS model takes effect of intrinsic charge at all ends of an MOSFET into consideration. Compared with the Bsim3 NQS model, the novel MOSFET NQS model has the advantages that memory consumed by circuit simulation is reduced, simulation time is saved, and transient analysis of a high-frequency circuit is more accurate. The model can not only transiently simulate for strong-inversion devices, but also can accurately analyze substrate current and gate current of the MOSFET positioned in a sub-threshold region.

Simultaneous Spectrophotometric Determination of o-Aminophenol and p-Aminophenol Using H-Point Standard Addition Method -Application to Real Waters

Abstract: H-point standard addition method (HPSAM) has been applied to the simultaneous determination of o-aminophenol (oA) and p-aminophenol (pA) isomers in binary mixtures. The method is based on the Schiff's base formation of aminophenols with 1,2-naphoquinone sulphonate (NQS) as a chromogenic reagent in the presence of micellar cityltrimethyl ammonium bromide (CTAB) and sodium carbonate. The results showed that simultaneous determinations could be performed with the ratios 0.4 : 2.0 and 4.0 : 2.0 measured at pair of wavelengths (480 and 610) nm with recovery % range 94.75-104.37 % and precision better than 4.0 % when oA considered as analyte and pA as interferent, and a ratio 0.4 : 0.2 and 4.0 : 2.0 measured at 455 and 540 nm with recovery % range 95.37-105.0 % and precision better than 4.0 % when pA considered as analyte and oA as interferent.

Validated spectrophotometric method for the determination, spectroscopic characterization and thermal structural analysis of duloxetine with 1,2-naphthoquinone-4-sulphonate

Abstract: A novel, selective, sensitive and simple spectrophotometric method was developed and validated for the determination of the antidepressant duloxetine hydrochloride in pharmaceutical preparation. The method was based on the reaction of duloxetine hydrochloride with 1,2-naphthoquinone-4-sulphonate (NQS) in alkaline media to yield orange colored product. The formation of this complex was also confirmed by UV-visible, FTIR, 1H NMR, Mass spectra techniques and thermal analysis. This method was validated for various parameters according to ICH guidelines. Beer’s law is obeyed in a range of 5.0–60 μg/mL at the maximum absorption wavelength of 480 nm. The detection limit is 0.99 μg/mL and the recovery rate is in a range of 98.10–99.57%. The proposed methods was validated and applied to the determination of duloxetine hydrochloride in pharmaceutical preparation. The results were statistically analyzed and compared to those of a reference UV spectrophotometric method.

Efficient models for non-quasi-static effects and correlated noise in SiGe HBTs

Abstract: The capability of a single CR sub-circuit to model a wide range of non-quasi-static (NQS) delays in silicon germanium heterojunction bipolar transistors is explored. A comparative study is carried out to show that the suitable use of a single CR sub-circuit following the partitioned-charge-based approach can replace the popularly used CR-LCR combination to model both the input and output NQS effects. Based on this NQS model, a correlated noise model is developed, which requires only three additional nodes for implementation in Verilog-A. Results show excellent agreement with numerically simulated data.

Impact of the emitter stored charge on RF noise of junction bipolar transistors

Abstract: In this paper a new noise model is presented which accounts for the effect of the emitter stored charge on the RF noise behavior of bipolar junction transistors. The model is derived combining the general Van Vliet noise model for bipolar transistors and the non-quasi-static (NQS) theory in quasi-neutral base and emitter regions. Model equations are then interpreted with the help of a small-signal equivalent circuit of a bipolar transistor which includes additional circuit elements in order to take the NQS effects in the base and in the emitter into account. It is shown finally that the emitter diffusion charge can have a considerable impact on the noise FOM's of bipolar transistors, compared to the impact of the NQS effects in the quasi-neutral base region.

Parameter extraction for relaxation-time based non-quasi-static MOSFET models

Abstract: This paper presents a new extraction technique for non-quasi-static (NQS) delay time and gate resistance for relaxation-time-approximation based MOS transistor models. The technique is based on analysis of y dg in strong inversion, as a function of both V GS and frequency, for V DS = 0. An effective delay τ eff is computed from measured data, and a plot of τ eff versus the theoretical NQS-only delay allows the NQS relaxation time parameter and the gate resistance to be determined self-consistently.