Retrieving definitional content for ontology development

Ontology construction requires an understanding of the meaning and usage of its encoded concepts. While definitions found in dictionaries or glossaries may be adequate for many concepts, the actual usage in expert writing could be a better source of information for many others. The goal of this paper is to describe an automated procedure for finding definitional content in expert writing. The approach uses machine learning on phrasal features to learn when sentences in a book contain definitional content, as determined by their similarity to glossary definitions provided in the same book. The end result is not a concise definition of a given concept, but for each sentence, a predicted probability that it contains information relevant to a definition. The approach is evaluated automatically for terms with explicit definitions, and manually for terms with no available definition.     

Spectrophotometric determination of aluminum and iron in calcium

A simple, rapid, and accurate method is described whereby micro amounts of aluminum and iron can be determined in calcium metal. The iron is determined spectrophotometrically by measuring the absorbency of the reddish-orange color of the tris(1,10-phenanthroline)iron(II)ion, [(C₁₂H₈N₂)₃Fe]⁺⁺. This complex effectively removes the iron interference, and the aluminum is determined spectrophotometrically in the solution remaining from the iron determination by extracting it with a chloroform solution of 8-quinolinol and measuring the absorbency of the yellow color of the tris(8-quinolinolo)aluminum(III) in the chloroform solution.     

Isotonic Regression under Lipschitz Constraint

The pool adjacent violators (PAV) algorithm is an efficient technique for the class of isotonic regression problems with complete ordering. The algorithm yields a stepwise isotonic estimate which approximates the function and assigns maximum likelihood to the data. However, if one has reasons to believe that the data were generated by a continuous function, a smoother estimate may provide a better approximation to that function. In this paper, we consider the formulation which assumes that the data were generated by a continuous monotonic function obeying the Lipschitz condition. We propose a new algorithm, the Lipschitz pool adjacent violators (LPAV) algorithm, which approximates that function; we prove the convergence of the algorithm and examine its complexity. The authors were supported by the Intramural Research Program of NIH, National Library of Medicine.     

High resolution proton magnetic resonance spectroscopy of human brain and liver

Water-suppressed and slice-selective proton spectra of live human brain exhibited several resonances that were tentatively assigned to metabolites such as N-acetylaspartate, glutamate, phosphocreatine and creatine, choline derivatives, and taurine. In the liver spectrum of a healthy volunteer, the major resonance was tentatively assigned to a fatty acyl methylene and the minor resonances to protons in carnitine, taurine, glutamate, and glutamine. In the spectrum of a cancerous liver, resonances in addition to those present in the normal liver were seen. Protein degradation in the liver with cancer was indicated by resonances from urea and from the ring protons in tryptophan, tyrosine, and phenylalanine. Furthermore, increased nucleic acid synthesis was indicated by resonances from nucleotide protons.     

微波消解-电感耦合等离子体质谱法测定丙烯腈-丁二烯-苯乙烯共聚物塑料中的铅、镉、汞、铬、砷

建立了微波消解技术-电感耦合等离子体质谱(ICP-MS)法同时测定丙烯腈-丁二烯-苯乙烯共聚物(ABS)塑料中的铅、镉、汞、铬、砷五种元素的方法。对仪器的参数设置、进样系统进行了优化,并对此类塑料样品中上述元素分析的前处理条件,如消解体系、消解温度、恒温时间以及酸用量等进行了优化。方法检出限为0.7～6.5 ng·g-1;用加标回收的方法评价了该方法的准确性,加标回收率为89.8%～110.8%;样品测定相对标准偏差为2.8%～11.3%。该方法检出限低、精确度好、准确度高、简单快速、无需基体匹配。     

A 3D QSAR pharmacophore model and quantum chemical structure--activity analysis of chloroquine(CQ)-resistance reversal

Using CATALYST, a three-dimensional QSAR pharmacophore model for chloroquine(CQ)-resistance reversal was developed from a training set of 17 compounds. These included imipramine (1), desipramine (2), and 15 of their analogues (3-17), some of which fully reversed CQ-resistance, while others were without effect. The generated pharmacophore model indicates that two aromatic hydrophobic interaction sites on the tricyclic ring and a hydrogen bond acceptor (lipid) site at the side chain, preferably on a nitrogen atom, are necessary for potent activity. Stereoelectronic properties calculated by using AM1 semiempirical calculations were consistent with the model, particularly the electrostatic potential profiles characterized by a localized negative potential region by the side chain nitrogen atom and a large region covering the aromatic ring. The calculated data further revealed that aminoalkyl substitution at the N5-position of the heterocycle and a secondary or tertiary aliphatic aminoalkyl nitrogen atom with a two or three carbon bridge to the heteroaromatic nitrogen (N5) are required for potent "resistance reversal activity". Lowest energy conformers for 1-17 were determined and optimized to afford stereoelectronic properties such as molecular orbital energies, electrostatic potentials, atomic charges, proton affinities, octanol-water partition coefficients (log P), and structural parameters. For 1-17, fairly good correlation exists between resistance reversal activity and intrinsic basicity of the nitrogen atom at the tricyclic ring system, frontier orbital energies, and lipophilicity. Significantly, nine out of 11 of a group of structurally diverse CQ-resistance reversal agents mapped very well on the 3D QSAR pharmacophore model.     

Development and Certification of NIST Standard Reference Materials for Relative Raman Intensity Calibration

In analytical Raman spectroscopy it becomes increasingly important to employ a procedure for the correction of the relative intensity of Raman spectra. The determination of the intensity response function of a Raman instrument traditionally has been carried out through a white light source that has been calibrated for its relative spectral irradiance. While this method will furnish a correction curve to yield spectra corrected to relative Raman intensity, it is often cumbersome and fraught with experimental difficulties that can profoundly affect the reliability of the correction procedure. An alternate methodology that permits a simplified calibration of the Raman instrument response function is based on the use of luminescent glass standards that transfer a white light calibration onto the Raman measurement system. In this procedure, a measurement of the luminescence of an intensity standard, whose relative irradiance has been determined, provides a means to establish the instrument response function. Correction of measured spectra by this function furnishes spectra that are free of instrumental intensity artifacts. Based on this approach, NIST is developing a series of Standard Reference Materials (SRMs) for the calibration of Raman intensity. This process, and the results obtained thereby, is described for Raman spectroscopy measurements employing 785nm excitation. The procedure is valid for both macro-sampling and micro-sampling Raman work.     

Structural determinations of some chloroazepine-2,5-diones using a lanthanide shift reagent

The use of a lanthanide shift reagent, Eu(fod)₃, to aid in the structural assignments of some chloroazepine-2,5-diones is described. The chloroazepine-2,5-diones, synthesized via the Schmidt reactions of chloro-1,4-benzoquinones, could not readily have their structures assigned by other spectroscopic methods. Correlations of plotted lanthanide induced shifts in pmr studies demonstrated that there was a large positional dependence on the magnitude of induced shifts. The large difference in the magnitude of induced shifts made it possible to assign protons and methyl substituents to specific positions on the azepine ring, thus assigning the structure of the compound.