CASPER: a computer program used for structural analysis of carbohydrates.

The computer program CASPER and its algorithms are described. The program is aimed at facilitating the determination of structures of oligosaccharides and regular polysaccharides, requiring as input either the one-dimensional 1H or 13C NMR spectrum or the 2D C,H-correlation NMR spectrum together with information on components and linkages. The databases, the method of simulating spectra, options of the program, and techniques for faster calculations are described as well as an example of a structural determination.     

A computer program for activation analysis

A computer program for calculating activation analysis results is described. The program comprises two gamma spectrum analysis programs, STOAV and SAMPO and one program for calculating elemental concentrations, KVANT. STOAV is based on a simple summation of channels and SAMPO is based on fitting of mathematical functions. The programs are tested by analyzing the IAEA G-1 test spectra. In the determination of peak location SAMPO is somewhat better than STOAV and in the determination of peak area SAMPO is more than twice as accurate as STOAV. On the other hand, SAMPO is three times as expensive to use with a Cyber 170 computer as STOAV.     

The computer processing and interpretation of mass spectral information. I—The reduction of raw mass spectra to monoisotopic form

An algorithm of the AELITA program (Atomic-Element Identification) is described which enables both low and high resulution mass spectra to be processed to give the elemental composition and ion abundances of the mass spectra in monoisotopic form. The program has no limitations in respect of the elemental composition and spectrum complexity. The criterion for the choice of the most probable solution is based either on the accuracy of measurement of the peak abundances and/or the masses. The program is written in ALGOL, run on a BESM-6 computer, and occupies about 19K core memory.     

An expert system for inferring structures of organic compounds from their mass spectra.

Development of an 'expert system' for elucidation of structures of acyclic organic compounds is described. An expert system is a computer program that embodies some of the heuristic problem-solving knowledge of human experts so that it can effectively be used as an aid to decision making. The expert system described in this paper is intended to assist a chemist in arriving at plausible structures, the input data being the mass spectrum, molecular formula and presence (if known) of functional groups. The program generates chemically possible structures for the given molecular formula and can use, where available, the constraints imposed by the mass spectrum of the compound and by any known functional groups. The program makes use of a new algorithm for obtaining a canonical representation of structures and a new heuristic for incorporating constraints of the mass spectrum. This work constitutes a case study of the application of artificial intelligence techniques in chemistry and the material presented highlights this motivation.     

A software package for the generation of noise with widely divergent spectral properties : The Simulation of Realistic Stationary Detector Noise

The computer program discussed is capable of generating stationary noise with optional statistical parameters. Five standard noise types can be generated: white, 1/f, first order, Gaussian, and damped cosine noise. The input to the program can be a measured or arbitrarily chosen autocovariance function (or power spectrum). The autocovariance function (power spectrum) computed from the generated noise will be in perfect agreement with the input autocovariance function, if an infinite number of noise data is generated. Some theoretical work on noise generation on the basis of the autocovariance function is described. The autocovariance function of 1/f noise is theoretically derived from the power spectrum, based on a model described earlier. A few examples of the use of the program and an example of a possible application are given. A peak-finding procedure is tested with a simulated chromatogram contaminated with different types of noise. Applications are possible in data processing, information extraction, simulation and automation.     

Computer analysis of amino acid chromatograms and other linear elution spectra

A computer-aided method of evaluation of amino acid column chromatograms is proposed and compared with the usual synchronous peak-integration method. Spectra and their backgrounds are digitized separately by a curve digitizer; this allows a better estimate of the background time courses. A computer program then fits a set of superimposed Gaussian distributions to each corrected spectrum, thus circumventing the problems arising from incompletely separated peaks. Samples of known composition, run intermittently through the analyzer between the unknown spectra, allow a determination of the time dependence of the ratios of “peak areas over amounts of amino acids”; hence, the amounts of amino acids can automatically be corrected for aging effects of the analyzing system. A modified version of the computer program allows resolution of any spectrum to a sum of Gaussians, with least squares fitting of their amplitudes, widths and locations.     

NMR study of tetrahydrofuran oriented in a nematic phase

The H-1 NMR spectrum of tetrahydrofuran (THF) dissolved in the nematic phase IV (Merck) has been analysed by used of a computer program which incorporates symmetry. A satisfactory fit for the spectrum could be obtained under the assumption that the spin Hamiltonian has effective C(2v)symmetry. Comparison of the empirical values of the direct dipolar couplings with the predictions of different theoretical models shows that agreement is better for free pseudorotation than for interconversion between two equivalent conformation.     

PIAD — A computer code for peak identification and activity determination

A Peak Identification and Activity Determination (PIAD) computer program has been developed. A new concept of peak significance is introduced and a great change has been made to the currently used associated gamma lines technique in calculating the confidence index; confidence factor is also given to the gamma line of a nuclide that is not seen in the spectrum. The program is written in Fortran IV under the operating system of RSX-11M.     

Computer-assisted qualitative analysis of gamma-ray spectra

A computer program is described to perform the identification of isotopes in neutron activated samples. The γ-ray energies as obtained from a Ge(Li) γ-ray spectrum are compared with those of a library, containing data for about 250 isotopes. Isotopes whose γ-ray energies match closely with the unknowns are selected as possible constituents. Unlikely attributions are then eliminated by a careful inspection of the γ-rays found. Further exploitation of half-life, the way of production and the sensitivity for the given irradiation and measurement conditions, allow the selection of the most likely constituents in the source. The results of the automated identification agree closely to those obtained by an experienced investigator. The program is written in FORTRAN IV for a PDP-9 computer with a 16 K word memory.     

Computer-assisted multicomponent spectral analysis with fuzzy data sets

A new approach to the interpretation of spectra with “fuzzy sets” is described. A computer program CIF (Compound Identification with Fuzzy sets) is applied. This program is capable of finding components in a mixture by comparing the sample spectrum with reference spectra in a library. The applications discussed involve the interpretation of infrared spectra. The problems of spectral library search are discussed, an elementary introduction to fuzzy set theory is given, and applications to spectral library search are demonstrated.     

Using computers to interpret IR spectra of complex molecules

IR spectroscopy provides a unique fingerprint of compounds and has proven to be extremely valuable in the study of antibiotics. To interpret a spectrum effectively, one often employs an aid, such as a correlation chart or a computer program. This paper describes a program (PAIRS) that automatically interprets IR spectra.     

Spectroscopic studies and normal coordinate analysis of bilirubin

The infrared spectrum of bilirubin has been recorded in the spectral region 200-4000 cm(-1). The Raman spectrum has also been recorded using the second harmonic (530 nm) radiation of a 200 mW Nd-YAG laser. In order to confirm the vibrational assignment of the bands obtained from experimental observation, a normal coordinate analysis has been carried out using the semi-empirical AM1 method through MOPAC 5.1 computer program. Electronic absorption spectrum of bilirubin dissolved in CHCl3 has been recorded in the spectral region 300-600 nm. A broad spectrum is observed with peak maxima at 454.2 nm. The photoacoustic spectrum of this molecule (in the powder form) has also been recorded for the first time which shows certain discrete features.     

Qualitative and quantitative interpretation of gamma-ray spectra in activation analysis

A method is presented for the automatic identification of the elements present in a sample and the calculation of the corresponding concentrations from the energies and peak areas determined by a spectrum analysis computer program. A preliminary interpretation list is produced in which the possible isotopes are given for each peak in the spectrum. This list is based only on the gamma-ray energies and half-lives of the isotopes. A careful analysis of this list yields groups of identified elements at four different significance levels. The determination of the corresponding concentration is based on the single-comparator method. The procedure is included in an automatic activation analysis system but can also be used separately.     

The computer processing and interpretation of mass spectral information. VII—identification of ions in terms of structural symbols

A new version of the AELITA-F program for computation of a monoisotopic spectrum and identification of the ion composition as a collection of elements or as structural fragments is described. A technique is proposed for specifying a priori information on the compound in a ‘hybrid’ form which combines structural fragments of the molecule and individual chemical elements. This version permits the elimination of redundant information and reduces the requirements of computer resources. The program effectiveness is increased by reducing the number of ions to be generated. The format in which the mass spectral information is read out is more comprehensible to a chemist.     

A heuristic computer program for automatic spectrum assignment in microwave spectroscopy

A heuristic computer program has been written in fortran IV to do the automatic assignment of the microwave spectrum of a rigid, asymmetric rotor with no centrifugal or hyperfine effects. Given certain guidelines, the program needs only the observed lines and the transitions for which frequencies are to be assigned. It does not need any other physically observed effect (e.g. the Stark effect).     

GAMANAL-PC: A program for gamma-ray spectrum analysis using a microcomputer

The gamma-ray spectrum analysis program, GAMANAL, has been modifed to operate on a microcomputer. The program uses an algorithm involving a Gaussian and a tailing term for fitting and resolving peaks obtained from spectrometers using germanium semiconductor detectors. Gamma-ray energies, intensities and absolute photon emission rates can be determined. A graphical output showing the original and fitted data can also be obtained. The results generated by the program are stored on disk as ASCII files for futher analysis. This allows the use of other computer programs and languages in tasks such as decay curve analysis, radionuclide activity measurements and neutron activation analysis.     

Enhanced spectrum matching of mixed mass spectra by means of quality factors

A system of computer programs for recognizing impure or mixed spectra was assembled that provided automatic subtraction of reference mass spectra from a mixed spectrum. The software was 99% successful in recognizing pure spectra for the cases tested. Subtractions were done on mixed spectra in 70% of the cases tested. Spectrum subtraction enhanced the ability of the matching program to match components of a multicomponent mixture correctly, whereas quality factors were a great aid in the evaluation of the overall match validity.     

The computer-assisted interpretation of copolymer mass spectra

A computer program called MSCOPOL has been developed to aid in the interpretation of copolymer mass spectra. The program reads the mass spectrum, calculates the most likely monomer masses via correlation or Fourier transform methods, determines possible end group masses based on the monomer masses, and can then search monomer and end group data bases for likely chemical moieties. Refinement of the end group result is possible by calculation of the monomer ratio and degree of polymerization as a function of end group mass. The program is written in Microsoft Visual Basic and runs on an IBM compatible PC. Applications are shown for polystyrene, poly(N-vinyl pyrrolidone/vinyl acetate), and poly(ethylene oxide/propylene oxide).     

Methods for preparing comparative standards and field samples for neutron activation analysis of soil

One of the more difficult problems associated with comparative neutron activation analysis (CNAA) is the preparation of standards which are tailor-made to the desired irradiation and counting conditions. Frequently, there simply is not a suitable standard available commercially, or the resulting gamma spectrum is convoluted with interferences. In a recent soil analysis project, the need arose for standards which contained about 35 elements. In response, a computer spreadsheet was developed to calculate the appropriate amount of each element so that the resulting gamma spectrum is relatively free of interferences. Incorporated in the program are options for calculating all of the irradiation and counting parameters including activity produced, necessary flux/bombardment time, counting time, and appropriate source-to-detector distance. The result is multi-element standards for CNAA which have optimal concentrations. The program retains ease of use without sacrificing capability. In addition to optimized standard production, a novel soil homogenization technique was developed which is a low cost, highly efficient alternative to commercially available homogenization systems. Comparative neutron activation analysis for large scale projects has been made easier through these advancements. This paper contains details of the design and function of the NAA spreadsheet and innovative sample handling techniques.     

Programmierte gemeinsame Auswertung charakteristischer Banden in den Raman- und Infrarotspektren organischer Substanzen

The presence or absence of skeletal elements and substituents of an “unknown” sample may be determined by a sequence of yes/no decisions, concerning frequency and relative intensity of the characteristic bands in its infrared and Raman spectrum. The decision criteria given as a table may also be used in a graphical form or as a computer program for automatical interpretation. This simultaneous evaluation of both spectra is more reliable than the usual procedure of treating the spectra separately.