Spectral Filtration Research Articles

A new approach to computer-aided molecular structure elucidation: the expert system Structure Elucidator

This article concerns a new expert system for elucidating structures of organic compounds from their spectra, where two principally different molecular generators are used. The system is based on a database of 13C NMR spectra (135,000 structures), a library of molecular fragments and their 13C NMR subspectra (more than 400,000) and a library of spectrum-to-structure correlations for both NMR and IR spectra. At the first stage, the system tries to automatically determine the structure of the unknown compound using fragments taken from the library of 13C NMR spectra. The structures are generated by joining fragments that have common atoms. Knowledge of the molecular mass and the molecular formula is not needed for this stage. In case of failure the program automatically determines the molecular formula from the molecular mass (different formulas can have the same mass) and then forms the sets of fragments. The structures are generated with the help of another generator designed for constructing structures from non-overlapping fragments. The libraries of spectrum-to-structure correlations are used for determination of the molecular formula as well as for spectral filtration of fragments and structures. The most preferable structure is selected by predicting 13C and 1H NMR spectra. Some examples of problem solution are cited.

Resonant optoacoustic detector in nondispersive gas analyzer scheme

A nondispersive gas analyzer scheme is suggested, in which the resonant optoacoustic device is used for detection of air sample absorption, where modulation with the appropriate spectral filtration is carried out with the help of pure detecting gas cells. Analyzer performance for CO 2, CO, CH 4, SO 2 and NO is studied. The modulation depth for gas cells was found to be between 0.45 for NO and 0.84 for CO 2. Trace-gas detectivity is limited by acoustical noise, originating from light beam chopper at a level of 10 −2%. Information about the influence of spectral interference on detection selectivity was obtained.

Spectral and polarization analysis of optical images by means of acousto-optics

This paper presents results of a theoretical and experimental study of Bragg anisotropic diffraction. The diffraction may be used for filtration of optical radiation and processing of images. Special attention is devoted to the investigation of diffraction, which provides spectral filtration simultaneously with polarization analysis of divergent optical beams. A tunable tellurium dioxide acousto-optical filter for processing of optical images is described in the paper. Some experimental results of the image analysis in visible light and in the near-infrared region of the spectrum are discussed.

Geomagnetic solar flare effect on February 4 and 6, 1986 at the China Antarctic Great Wall Station

Taking the sampled every minute values of the horizontal, declination and vertical componentsH, D, Z and the intensity of total field F calculated fromH andZ on the magnetograms at ten geomagnetic observatories in China in the same periods, and at the China Antarctic Great Wall Station (CAGWS), the authors conducted the maximum entropy analysis and band-pass filtration of these data and obtained the following results: (1) At the periodT=10 − 90 min geomagnetic solar flare effect (sfe) is evident on the sunlit hemisphere. It is more pronounced at periods 15, 20, 25 and 30 min, and most prominent at 30 – 35 min. The solar X-ray spectra at the same time showed their peaks at 10 and 15 min; (2) The periodT=10 − 70 min of sfe at the CAGWS in the western Hemisphere was also recognizable after spectral analysis and filtration, but the corresponding period of the maximum amplitude was different from that in the sunlit hemisphere. The results further proved that the geomagnetic effect of solar flares could also be observed in the dark hemisphere; (3) The subsolar points of two solar flares were found around Lanzhou, and the associated current density in the ionosphere was about 24 A/km. The transitional zone from positive to negative sfe was found around the geographic latitudeϕ=22° − 24°N, where the sfe inH-crochet was almost illegible.

Anisotropic light diffraction on ultrasound in a tellurium dioxide single crystal

Various cases of Bragg anisotropic diffraction of an optical beam by ultrasound propagating in a TeO 2 single crystal are examined. Special attention is devoted to non-traditional diffraction with interaction lengths of light and ultrasound up to several centimetres. Possible applications of the examined cases of the diffraction for spectral filtration of collimated and non-collimated optical beams are discussed in the paper.

Physicochemical characteristics of ferric adriamycin complexes.

Ferric ions and adriamycin in solution interact to form complexes that can yield colloidal and flocculant mixtures. At high concentrations (Fe3+ greater than or equal to 10(-4) M, adriamycin greater than or equal to 10(-5) M) an absorption appears at 600 nm, indicating colloid formation, which is directly responsive to concentrations of the reactants. Evidence from dilution experiments by spectral analysis, ultracentrifugation, titration, and filtration indicate that phase transition that is sensitive to pH and time occurs with iron-adriamycin complexes to yield flocculated drug. We conclude that patients and animals treated with the iron-adriamycin preparations known as 'quelamycin' received flocculated iron-adriamycin, which accounts for the toxic and pharmacologic effects reported. It may be useful to utilize colloidal preparations of reactive or irritating drugs to avert acute toxic effects and to produce slower release of active drug.

Power spectral analysis of auditory brain stem responses to pure tone stimuli.

Power spectral analysis and digital filtration of the auditory brain stem responses to tone burst stimuli were carried out in three adult subjects with normal hearing. Three dominant peaks (peaks A. B, C), ranging in frequency 50-150, 500-600, and 1000-1100 Hz, were observed in the spectrograms of the responses to 4 kHz at 80 dB SL. Power of higher frequency components (peaks B and C) decreased markedly or disappeared completely with decreased intensity as well as decreased frequency of stimulus, while peak A around 100 Hz consistently appeared regardless of stimulus intensity or frequency. Main spectral components of the individual waves in the ABR were determined as follows: peak A for the slow positive deflection in the response, peak B for waves VI and VII, peak C for waves II and IV, and peaks B and C for waves I, III and V.

Edge Acuity Improvement by Spectral Filtration in the Deep U.V.

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Effect of photon synchronization in intensity interference: New effect and new possibilities

A new optical photon-correlation effect is predicted, which appears when short light pulses are subjected to a narrow-band spectral filtration. The effect allows to study the temporal form and photon statistics of short optical pulses and to measure their length in nanosecond to subpicosecond range without use of fast photodetectors.

Spectral effects on three-dimensional reconstruction from rays.

Continuous bremsstrahlung spectra were calculated for 120 kVp for constant and sinusoidal potentials. Fluorescent radiation for the tungsten target was added to the bremsstrahlung, and the spectra were attenuated through various filter materials. A drawing of an object to be scanned was divided into an array of small squares in which the composition was assumed to be constant. Transmission data for 120 rays at each of 120 angles spanning a range of 180 degrees were calculated. Two algorithms for the reconstruction of attenuation coefficients from projection data, an algebraic reconstruction technique (ART) and the convolution method, were utilized to reconstruct effective coefficients. The effect of spectral filtration on the quality of the reconstruction was evaluated. Lightly filtered x-ray beams give rise to severe distortions in image quality, with values of the reconstructed coefficients rising toward the periphery of the object. Highly filtered beams give rise to images with less pronounced distortion.

Optical Unit for Reflection Densitometry

An optical unit for the measurement of reflection density is described. In conjunction with a sensitive densitometer, optical densities up to 4.0 can be measured with highly selective spectral filtration. The unit utilizes 45° incident radiation with measurement of normally reflected radiation as specified for use with photographic materials. The stray light level amounts to less than 1 part in 100 000, and the unwanted specular radiation to less than 1 part in 10 000. Problems in the design and evaluation of this unit are reviewed.