Several Applications of Advanced Scientific Calculators: Nonlinear Least-Squares Analysis and Titration of a Weak Acid

Several advanced applications of scientific graphing calculators are demonstrated. These include (a) nonlinear least squares analysis and (b) construction of titration curves for weak acids with a strong base. Stepwise instructions for obtaining the titration curves with TI-80 Series Calculators are presented. Immediate display of graphical results of a solution from a quantitative chemical problem in a classroom setting is one of the advantages of the advanced scientific calculator.     

A Partial Least-Squares Multivariate Calibration Method for the Simultaneous Spectrophotometric Determination of Spironolactone,Canrenone and Hydrochlorothiazide

Abstract

An application of a partial least squares calibration method for the simultaneous spectrophotometric determination of spironolactone, canrenone and hydrochlorothiazide is suggested. The use of the PLS for the multicomponent spectrophotometric determination is demonstrated on the analysis of several synthetic mixtures. It was shown that is possible to resolve complex mixtures of     

Rapid and Simple Method for Simultaneous Determination of Escin and Diethylamine Salicylate in Pharmaceutical Preparations by Partial Least-Squares Multivariate Calibration

A partial least-squares calibration (PLS) method has been developed for simultaneous quantitative determination of escin (ES) and diethylamine salicylate (DAS) in pharmaceutical preparations. The resolution of these mixtures has been accomplished without prior separation or derivatisation, by using partial least-squares (PLS-2) regression analysis of electronic absorption spectral data. The experimental calibration matrix was constructed with 9 samples. The concentration ranges considered were 10, 20, 30 (ES) and 40, 50, 60 (DAS) μg cm⁻³. The absorbances were recorded between 200 and 325 nm every 5 nm. Proposed method was compared with conventional spectrophotometric method. The results show that PLS-2 is a simple, rapid, and accurate method applied to the determination of these compounds in pharmaceuticals.     

Gradients of the Exchange-repulsion Energy in the General Effective Fragment Potential Method

Formulae for calculating the analytic gradients of the exchange-repulsion energy in the general effective fragment potential (EFP2) method are derived and implemented using a direct differentiation approach. The timings for the exchange repulsion gradient evaluations are approximately three times longer than the energy evaluations, orders of magnitude faster than a previous implementation. Since the direct differentiation approach is not approximate, the gradients can be used with confidence in molecular dynamics and Monte Carlo simulations with the EFP2 method.     

Rapid and Simple Method for Simultaneous Determination of Escin and Diethylamine Salicylate in Pharmaceutical Preparations by Partial Least-Squares Multivariate Calibration

Summary. A partial least-squares calibration (PLS) method has been developed for simultaneous quantitative determination of escin (ES) and diethylamine salicylate (DAS) in pharmaceutical preparations. The resolution of these mixtures has been accomplished without prior separation or derivatisation, by using partial least-squares (PLS-2) regression analysis of electronic absorption spectral data. The experimental calibration matrix was constructed with 9 samples. The concentration ranges considered were 10, 20, 30 (ES) and 40, 50, 60 (DAS) μg cm⁻³. The absorbances were recorded between 200 and 325 nm every 5 nm. Proposed method was compared with conventional spectrophotometric method. The results show that PLS-2 is a simple, rapid, and accurate method applied to the determination of these compounds in pharmaceuticals.     

Energy band gaps and lattice parameters evaluated with the Heyd-Scuseria-Ernzerhof screened hybrid functional

This work assesses the Heyd-Scuseria-Ernzerhof (HSE) screened Coulomb hybrid density functional for the prediction of lattice constants and band gaps using a set of 40 simple and binary semiconductors. An extensive analysis of both basis set and relativistic effects is given. Results are compared with established pure density functionals. For lattice constants, HSE outperforms local spin-density approximation (LSDA) with a mean absolute error (MAE) of 0.037 A for HSE vs 0.047 A for LSDA. For this specific test set, all pure functionals tested produce MAEs for band gaps of 1.0-1.3 eV, consistent with the very well-known fact that pure functionals severely underestimate this property. On the other hand, HSE yields a MAE smaller than 0.3 eV. Importantly, HSE correctly predicts semiconducting behavior in systems where pure functionals erroneously predict a metal, such as, for instance, Ge. The short-range nature of the exchange integrals involved in HSE calculations makes their computation notably faster than regular hybrid functionals. The current results, paired with earlier work, suggest that HSE is a fast and accurate alternative to established density functionals, especially for solid state calculations.     

Local effects of atomizing analyte droplets on the plasma parameters of the inductively coupled plasma

Monodisperse droplets from aqueous analyte solutions with selected diameters in the range 35–67 µm are introduced into an inductively coupled plasma with frequencies between 1 to 10 droplets per second. The effect of desolvation and atomization in the ICP is studied end-on by optical emission spectroscopy employing simultaneously up to three calibrated monochromators with fast photomultipliers. The onsets of desolvation and analyte atomization and the extremely fast diffusion of hydrogen in the ICP and its effect on the plasma are studied by simultaneous measurements of hydrogen, analyte and Ar lines. The local cooling by analyte atomization as well as the recovering of the plasma excitation temperature after completed atomization is measured quantitatively in dependence on time applying the Boltzmann plot method to simultaneously recorded line intensities of atomized analyte atoms which act as plasma probes. Furthermore, it is shown that relatively small differences in analyte mass cause significant temperature changes during atomization and, as consequence, strong variations of the emission intensity of analyte lines during atomization if measured by end-on observation.     

Estimation of Intramolecular Hydrogen- bonding Energy via the Substitution Method

The intramolecular hydrogen-bonding energies for eighteen molecules were calculated based on the substitution method, and compared with those predicted by the cis-trans method. The energy values obtained from two methods are close to each other with a correlation coefficient of 0.96. Furthermore, the hydrogen-bonding energies based on the substitution method are consistent with the geometrical features of intramolecular hydrogen bonds. Both of them demonstrate that the substitution method is capable of providing a good estimation of intramolecular hydrogen-bonding energy.     

Hydrogenation and Fluorination of Graphene Models: Analysis via the Average Local Ionization Energy

We have investigated the use of the average local ionization energy, I?(S)(r), as a means for rapidly predicting the relative reactivities of different sites on two model graphene surfaces toward the successive addition of one, two, and three hydrogen or fluorine atoms. The I?(S)(r) results were compared with directly computed interaction energies, at the B3LYP/6-311G(d,p) level. I?(S)(r) correctly predicts that the edges of graphene sheets are more reactive than the interior portions. It shows that added hydrogens activate the adjoining (ortho) sites and deactivate those that are separated by one site (meta). Overall, I?(S)(r) is effective for rapidly (single calculations) estimating the relative site reactivities of these large systems, although it reflects only the system prior to an interaction and cannot take into account postinteraction factors, e.g., structural distortion.     

Simulation of Molecular Weight Distribution After Polymer Breakdown. I. A Least-Squares Parameter Estimation Method on Monte Carlo Models

The degradation index (DI) has been used in previous work for Monte Carlo simulation of breakdown of polymers with narrow initial molecular weight distribution. However, the definition of DI is inadequate for polymers of broader molecular weight distribution. A least-squares method for estimating DI for such systems is described.     

Method to generate surfaces with desired roughness parameters

A surface engineering method based on the electrostatic deposition of microparticles and dry etching is described and shown to be able to independently tune both amplitude and spatial roughness parameters of the final surface. Statistical models were developed to connect process variables to the amplitude parameters (center line average and root-mean-square) and a spatial parameter (autocorrelation length) of the final surfaces. Process variables include particle coverage, which affects both amplitude and spatial roughness parameters, particle size, which affects only spatial parameters, and etch depth, which affects only amplitude parameters. Correlations between experimental data and model predictions are discussed.     

Nonlinear Standard Addition Method in the Determination of Dimethyl Sulfide in Beer by Headspace Gas Chromatography

ABSTRACT

Nonlinear standard addition method was studied for determination of DMS in beer with a laboratory-assembled headspace gas chromatographic system with flame photometric detector. The sample concentration and the detector response exponent can be obtained simultaneously without preparation of the blank sample, and the reliability of the results can be evaluated by the self-integrity of the data. The method introduced here is easier to carry out and more cost-effective.     

Correction for Fluctuations of Local Molecular Field in the Debye Method of Dilute Solutions

A simple method for evaluating the correction for the effect of solvent on the dipole moments of molecules, determined using the Debye method of dilute solutions, is proposed.     

Energy Propagation Through a Protometabolism Leading to the Local Emergence of Singular Stationary Concentration Profiles

Living systems rely on chains of energy transfer from an energy source to maintain their metabolism. This task requires functionally identified components and organizations. However, propagation of a sustained energy flux through a cascade of reaction cycles has never been reproduced at a steady state in a simple chemical system. By using energy patterning and a diffusing hub reactant, we achieved the transfer of energy through an abiotic protometabolism. Patterned illumination was applied to a liquid solution of a reversible photoacid. It resulted in the local onset of a proton pump, which subsequently drove an extended reaction–diffusion cycle that involved pH‐sensitive reactants. Thus, light has been used for locally setting out of chemical equilibrium a reaction involving “blind” reactants. The spontaneous onset of an energy‐transfer chain notably drives the local generation of singular dissipative chemical structures; continuous matter fluxes are dynamically maintained at boundaries between spatially and chemically segregated zones, in the absence of any membrane or predetermined material structure.     

能量色散X射线荧光法快速测定高冰镍中铁的含量

应用能量色散ｘ射线荧光法快速测定高冰镍中铁的含量。以一次射线的康普顿散射射线作内标，同时采用“负补偿法”校正干扰元素Ｃｕ和Ｎｉ对铁特征荧光的增强作用，取得较好效果，试验表明：本法具有操作简单、速度快、精度耘高等优点。对由￣２３８Ｐｕ放射性同位素源、闪烁探测器和双道谱仪组成的测量系统，测定铁含量的精度（ＲＳＤ）达到１．８％，平均绝对误差为０．１６％，单样分析时间为９６ｓ。     

Method for calculating the parameters of formation of hydrates from multicomponent gases

A model of hydrate formation in multicomponent gas–liquid water or ice systems including the exo- and endothermic processes has been suggested. Based on this model, a method for calculating the molecular and energy parameters such as the hydration number, amount of moles of hydrate, amount of gas and water in it, its density and molar mass, and the energy and rate of hydrate formation was developed. A comparison of the calculated and experimental values of the parameters revealed that the difference between them varied from 0 to 5.46%.     

Simultaneous Determination of Acetaminophen and Phenobarbital in Suppositories by Partial Least-Squares Spectrophotometric Calibration

Abstract

The use of partial least-squares spectrophotometric calibration for the simultaneous determination of suppositories in a multicomponent formulation is presented. This method is applied to the deternination of acetaminophen and phenobarbital in suppository preparations. The results show that these components in a molar ratio of about 61:1 in suppositories have been determined simultaneously with high precision.