Showing papers on "NQS published in 2013"

MOSFET Modeling & BSIM3 User's Guide

Abstract: Preface. 1. Introduction. 2. Significant Physical Effects In Modern MOSFETs. 3. Threshold Voltage Model. 4. I-V Model. 5. Capacitance Model. 6. Substrate Current Model. 7. Noise Model. 8. Source/Drain Parasitics Model. 9. Temperature Dependence Model. 10. Non-quasi Static (NQS) Model. 11. BSIM3v3 Model Implementation. 12. Model Testing. 13. Model Parameter Extraction. 14. RF and Other Compact Model Applications. Appendices. Index.

Trypanosoma cruzi mitochondrial swelling and membrane potential collapse as primary evidence of the mode of action of naphthoquinone analogues

Abstract: Naphthoquinones (NQs) are privileged structures in medicinal chemistry due to the biological effects associated with the induction of oxidative stress. The present study evaluated the activities of sixteen NQs derivatives on Trypanosoma cruzi. Fourteen NQs displayed higher activity against bloodstream trypomastigotes of T. cruzi than benznidazole. Further assays with NQ1, NQ8, NQ9 and NQ12 showed inhibition of the proliferation of axenic epimastigotes and intracelulluar amastigotes interiorized in macrophages and in heart muscle cells. NQ8 was the most active NQ against both proliferative forms of T. cruzi. In epimastigotes the four NQs induced mitochondrial swelling, vacuolization, and flagellar blebbing. The treatment with NQs also induced the appearance of large endoplasmic reticulum profiles surrounding different cellular structures and of myelin-like membranous contours, morphological characteristics of an autophagic process. At IC50 concentration, NQ8 totally disrupted the ΔΨm of about 20% of the parasites, suggesting the induction of a sub-population with metabolically inactive mitochondria. On the other hand, NQ1, NQ9 or NQ12 led only to a discrete decrease of TMRE + labeling at IC50 values. NQ8 led also to an increase in the percentage of parasites labeled with DHE, indicative of ROS production, possibly the cause of the observed mitochondrial swelling. The other three NQs behaved similarly to untreated controls. NQ1, NQ8, NQ9 and NQ12 induce an autophagic phenotype in T. cruzi epimastigoted, as already observed with others NQs. The absence of oxidative stress in NQ1-, NQ9- and NQ12-treated parasites could be due to the existence of more than one mechanism of action involved in their trypanocidal activity, leaving ROS generation suppressed by the detoxification system of the parasite. The strong redox effect of NQ8 could be associated to the presence of the acetyl group in its structure facilitating quinone reduction, as previously demonstrated by electrochemical analysis. Further experiments using biochemical and molecular approaches are needed to better characterize ROS participation in the mechanism of action of these NQs.

Development and validation of a presumptive colour spot test method for the detection of piperazine analogues in seized illicit materials

Abstract: The increasingly large quantities of potentially illicit samples received for confirmatory analysis highlights the importance and demand for preliminary testing procedures that are simple, rapid, selective, inexpensive and able to be used in the field. Colour testing fulfils the aforementioned requirements and is a technique frequently employed to achieve presumptive identification. Piperazine analogues (often marketed as ‘legal ecstasy’) are a group of psychoactive substances that have recently become established on the illicit drug market and are not effectively discriminated or identified by current colour testing methods. Herein, we report on the development and validation of a chemical spot test for piperazine analogues present in unknown seized materials using the spectrophotometric reagent, sodium 1,2-naphthoquinone-4-sulphonate (NQS). Primary testing revealed that NQS reacts almost instantly to form an intense, bright orange-red coloured complex with the representative piperazine 1-benzylpiperazine (BZP) at room temperature. The results of the test, assessed by colour development, were evaluated visually and variables affecting the coloured reaction were optimised. The colour test method was validated to meet requirements for use in preliminary screening, providing qualitative and reliable presumptive test results. Validation studies show that the characteristic colour change is unique to the piperazine class at room temperature, and is unaffected by the presence of common cutting agents, i.e. glucose and caffeine, in test samples of 5% purity, and other drugs such as N-methyl-3,4-methylenedioxyamphetamine (MDMA). The NQS reagent stability was found to be limited to storage in a refrigerated environment for no more than one week before results were affected. The operational limit of detection was found to be 40 μg.

New spectrophotometric methods for the determination of moxifloxacin in pharmaceutical formulations.

Abstract: Two rapid, simple and sensitive spectrophotometric methods for the quantitative analysis of moxifloxacin (MOX) in pharmaceutical formulations have been described. The first method (A) involves reaction of MOX with 1,2-naphthoquinone-4-sulphonate (NQS) in alkaline medium (pH 11.0) which results in an orange-coloured product exhibiting maximum absorption (lambda(max)) at 411 nm. The second method (B) is based on the oxidation of the MOX with a known excess of cerium (IV) sulfate and the residual oxidant is determined by treating with a fixed amount of methyl orange, and measuring the absorbance at 507 nm. The molar absorptivities for methods A and B were 4.9 x 10(3) and 6.5 x 10(4) L mol(-1) cm(-1), respectively. Under the optimized reaction conditions, Beer's law correlation of the absorbance with MOX concentration was obtained in the range of 2.5-20 and 0.5-30 microgmL(-1) for method A and B respectively. The intra-day precision expressed as relative standard deviation (RSD) was < 1.6% for both methods. The methods were validated in terms of accuracy and precision and were successfully applied to the determination of MOX in its pharmaceutical dosage form. The proposed methods are useful for routine analysis of MOX in quality control laboratories.

A New Spectrophotometric Method for Determination of Penicillamine inPharmaceutical Formulation Using 1, 2-naphthoquine-4-sulfonate (NQS)

Abstract: A rapid, simple and sensitive method for the determination of D-Penicillamine using sodium 1,2-naphthoquine- 4-sulfonate (NQS) has been developed. The method is based on the fact that a brown product can be formed by the reaction between D-Penicillamine and sodium NQS in a buffer solution of a pH 12.0. Beer’s law is obeyed in the range 10-30 μg/mL of D-Penicillamine at maximum wavelength of 425 nm. The linear regression equation of the calibration curve is A=0.1684+0.01624C (μg/mL), with a linear regression correlation coefficient of 0.997. The detection limit is 3.12 μg/mL and the recovery rate is in the range of 99.21-108.2%. The method has been successfully applied to the determination of D-Penicillamine in pharmaceutical formulation.

Nonquasi-Static Charge Model for Common Double-Gate MOSFETs Adapted to Gate Oxide Thickness Asymmetry

Abstract: With the unique quasi-linear relationship between the surface potentials along the channel, recently we have proposed a quasi-static terminal charge model for common double-gate MOSFETs, which might have asymmetric gate oxide thickness. In this brief, we extend this concept to develop the nonquasi-static (NQS) charge model for the same by solving the governing continuity equations. The proposed NQS model shows good agreement against TCAD simulations and appears to be useful for efficient circuit simulation.

Spectrophotometric determination of cefotaxime by using sodium 1,2-naphthoquinone-4-sulfonate

Abstract: A novel method is established to determine cefotaxime by using sodium 1,2-naphthoquinone-4-sulfonate (NQS) as a chromogenic reagent. A russety product can be formed owing to the nucleophilic substitution reaction between cefotaxime and NQS in 0.1 M solution of NaOH. The maximal absorption wavelength of the product is 489 nm. Absorbance is linear with the concentration of cefotaxime in the range of 3.8–114.6 mg/L, and the regression equation is A = 0.04481 + 0.00567c (mg/L), with a correlation coefficient of 0.9992. The detection limit and the RSD are 3 mg/L and 1.2%, respectively. The average recovery is in the range of 98.9–101.2%. The results indicate that the method could be applied to the determination of cefotaxime in injection.

A new spectrophotometric method for the determination of cardiovascular drugs in dosage forms

Abstract: A simple, accurate, and precise spectrophotometric method has been proposed for the determination of three cardiovascular drugs, namely: Atenolol (ATE), Doxazosin mesylate (DOX) and Lisinopril dihydrate (LID) in pharmaceutical formulations. Proposed method is based on the derivatization of drugs with 1,2-naphthoquinone-4-sulfonic (NQS). The optimum experimental conditions have been studied. Beer’s law is obeyed over the concentration of 0.5–3, 0.4–8, and 5–50 μg/mL for ATE, DOX, and LID, respectively. The detection limits were 0.11, 0.12, and 1.16 μg/mL for ATE, DOX, and LID, respectively, with a linear regression correlation coefficient of 0.9993, 0.9998, and 0.9997 and recovery in range from 98.25–102.57, 97.20–100.57, and 97.83–101.80for ATE, DOX, and LID, respectively. Effects of pH, temperature, reaction time, and NQS concentration on the determination of ATE, DOX, and LID, have been examined. This method is simple and can be applied for the determination of ATE, DOX, and LID in pharmaceutical formulations in quality control laboratories.

Coupling of soft-modeling methods with multivariate pattern recognition technique for the identification of nitroaniline isomers

Abstract: A new approach that takes advantage of both soft-modeling and pattern recognition methods is proposed to analyze kinetic data monitored spectrometrically to classify structurally similar nitroaniline isomers. The colorimetric condensation reaction of 1,2-naphthoquinone-4-sulfonate (NQS) with amines has been used to classify 2-, 3-, and 4-nitroaniline on the basis of their different kinetic properties. These nitroanilines react differentially with NQS at pH 7 to produce a colored product. Soft-modeling approaches such as multivariate curve resolution–alternating least squares (MCR–ALS) and simple-to-use interactive self-modeling mixture analysis (SIMPLISMA) followed by multiplicative signal correction have been used as preprocessing procedures to obtain patterns diagnostic for the analytes. Rank analysis was initially performed using determination of rank by augmentation to detect any species present during the course of the reaction in the system under investigation. The spectra and kinetic profiles of all absorbing species present in the raw measurements were obtained from SIMPLISMA and MCR–ALS resolution. The kinetic profiles were then used as input of the pattern recognition algorithm. The response patterns were systematically classified using linear discriminant analysis with high classification accuracy. Either all or one of the resolved profiles related to the components involved in the reaction can be used for identification of nitroaniline isomers. Copyright © 2013 John Wiley & Sons, Ltd.

Spectrophotometric determination of doripenem in bulk and injection formulations by 1,2-naphthoquinone 4-sulphonic acid sodium salt (NQS) reagent in alkalline medium

Abstract: A simple and cost effective spectrophotometric method was described for the determination of Doripenem(DP) in pure form and in pharmaceutical formulations. The method is based on the formation of dark yellow colored chromogen when the drug reacts with 1,2 naphtho quinone 4-sulphonic acid sodium salt (NQS) reagent in alkalline medium. The method involves the addition of excess NQS of known concentration in the presence of 0.5 mL NaOH for DP (Method A), the unreacted NQS is determined by the measurement of the λmax 449 nm, which was found to be the most suitable of several tests. This method was applied for the determination of drug contents in pharmaceutical formulations and enabled the determination of the drug in microgram quantities 0.5 to 3.0 mL for DP. No interference is observed from excipients and the validity of the method was tested against reference method. The colored species has an absorption maximum at 449 nm for DP (Method A) and obeys beer’s law in the concentration range 0.02 – 0.12 mg/mL of the drugs The apparent molar absorptivity is 0.0047, sandell’s sensitivitt is 8x10-4. The slope is 0.0997 ± 0.0017 and intercept of the equation of the regression line is -0.0003 ± 0.0033. The optimum experimental parameters for the reaction have been studied and the validity of the described procedure was assessed. Statistical analysis of the results has been carried out revealing high accuracy and good precision. The proposed method was successfully applied for the determination of Doripenem in pharmaceutical formulations

Spectrophotometric determination of tenofovir using 1, 2-napthaquinone-4-sulfonic acid sodium in pharmaceutical dosage form

Abstract: A new, simple and sensitive spectrophotometric method for the determination of tenofovir has been developed. The method is based on the condensation of tenofovir with 1, 2napthaquinone-4sulfonic acid sodium (NQS) in alkaline media to yield orange colored product. Tenofovir showed maximum absorbance at 334 nm with linearity was observed in the concentration range of 2-12 μg/ml (R2= 0.990). The relative standard deviation of 0.531% and recovery of tenofovir in tablet showed 99.33±0.52. The proposed method is simple, rapid, precise and convenient for the assay of tenofovir in pharmaceutical formulation.

New Colorimetric Method Development And Validation Of Sulfacetamide In Bulk And Formulation By Different Analytical Reagents

Abstract: Four simple, sensitive and reproducible spectrophotometric methods (Method A, Method B, Method C and Method D) were developed for the determination of sulfacetamide (SA) and its pharmaceutical formulation Method A was developed based on diaziatation of the SA by sodium nitrite in acidic medium followed by coupling with BM reagent having absorption maximum at 530 nm Method B was developed based on reaction of NQS with primary amine in SA in presence of alkaline medium having maximum absorption at 466nm Method C was based on reaction of primary amine with MBTH in presence of FeCl3 having maximum absorption at 562nm Method D was developed based on reduction of phosphomolybdotungstic acid in presence of alkali medium having an absorption maximum at 760 nm Beers law was obeyed in the range of 1 to 3 g/ml for Method A, 5 to 30 g/ml for Method B, 10 to 50 g/ml for Method C, and 100 to 300 g/ml for Method D These methods were successfully validated and estimated in bulk and pharmaceutical formulations

Compact modeling of the diode reverse recovery effect for leading developments of power electronic applications

Abstract: SPICE modeling of the diode reverse recovery effect is discussed. This effect is very important for the developments of power electronic circuit applications such as motor-drive inverters and power conditioners. With the dynamic carrier-distribution-based modeling approach, the reverse recovery behaviors are explained, where the nonquasi-static (NQS) behavior of carriers in the drift region is considered. Its reverse recovery modeling ability is verified with a two-dimensional (2D) device simulator, in comparison to the conventional lumped-charge modeling technique.

A new approach to extracting the RF parameters of asymmetric DG MOSFETs with the NQS effect

Abstract: In analog circuit design an important parameter, from the perspective of superior device performance, is linearity. The DG MOSFET in asymmetric mode operation has been found to present a better linearity. In addition to that it provides, at the discretion of analog circuit designer, an additional degree of freedom, by providing independent bias control for the front and the back gates. Here a non-quasi-static (NQS) small signal model for DGMOSFET with asymmetric gate bias is proposed for extracting the parameters of the device using TCAD simulations. The parameters extracted here for analysis are the intrinsic front and back gate to drain capacitance, Cgd1 and Cgd2, the intrinsic front and back distributed channel resistance, Rgd1 and Rgd2 respectively, the transport delay, τm, and the inductance, Lsd. The parameter extraction model for an asymmetric DG MOSFET is validated with pre-established extracted parameter data, for symmetric DG MOSFET devices, from the available literature. The device simulation is performed with respect to frequency up to 100 GHz.

A new approach to extracting the RF parameters of asymmetric DG MOSFETs with the NQS effect

Abstract: In analog circuit design an important parameter,from the perspective of superior device performance,is linearity.The DG MOSFET in asymmetric mode operation has been found to present a better linearity.In addition to that it provides,at the discretion of analog circuit designer,an additional degree of freedom,by providing independent bias control for the front and the back gates.Here a non-quasi-static(NQS)small signal model for DGMOSFET with asymmetric gate bias is proposed for extracting the parameters of the device using TCAD simulations.The parameters extracted here for analysis are the intrinsic front and back gate to drain capacitance,Cgd1and Cgd2,the intrinsic front and back distributed channel resistance,Rgd1and Rgd2respectively,the transport delay,m,and the inductance,Lsd.The parameter extraction model for an asymmetric DG MOSFET is validated with pre-established extracted parameter data,for symmetric DG MOSFET devices,from the available literature.The device simulation is performed with respect to frequency up to 100 GHz.

Quantitative determination of tenofovirdisproxil fumarate as an active pharmaceuitcal ingradient in tablet formulations by visible spectrophotometry

Abstract: In the present investigation, a direct, simple and sensitive visible spectrophotometric method without using any buffer solution is described for the assay of tenofovir disproxil fumarate in pure and tablet dosage forms. The method is based on the formation of yellowish brown colored species by the drug with NQS reagent and exhibits absorption maxima at 451 nm. Regression analysis of Beer-Lambert plots showed good correlation in the concentration ranges (8-40) μg/ml. The proposed method is applied to commercial available tablets and the results are statistically compared with those obtained by the reported UV reference method and validated by recovery studies. The results are found satisfactory and reproducible. The method is applied successfully for the estimation of the tenofovir disproxil fumarate in the presence of other ingredients that are usually present in dosage forms. The method offers the advantages of rapidity, simplicity and sensitivity and normal cost and can be easily applied to resource-poor settings without the need for expensive instrumentation and reagents.

Novel visible spectrophotometric method development for the determination of oseltamivir phosphate in capsules using NQS as achromogenic reagent

Abstract: A direct, simple and sensitive visible spectrophotometric method is described for the assay of oseltamivir phosphate in pure and capsule forms. The method is based on the formation of yellowish brown colored species by the drug with Folin reagent and exhibits absorption maxima at 453 nm. Regression analysis of Beer-Lambert plots showed good correlation in the concentration ranges (16-48) µg/ml. The proposed method is applied to commercial available capsules and the results are statistically compared with those obtained by the UV reference method and validated by recovery studies. The results are found satisfactory and reproducible. The method is applied successfully for the estimation of the Oseltamivir phosphate in the presence of other ingredients that are usually present in dosage forms. The method offers the advantages of rapidity, simplicity and sensitivity and normal cost and can be easily applied to resource-poor settings without the need for expensive instrumentation and reagents