Use of computerized pattern recognition in the study of the cuticular hydrocarbons of imported fire ants. II. Comparison of the cuticular hydrocarbon patterns between different colonies of Solenopsis richteri

Gas chromatography (GC) data obtained from the cuticular hydrocarbons of the black imported fire ants are treated by methods of pattern recognition. Based on a recently described sample preparation procedure, GC data are normalized to eliminate slight variations in chromatographic conditions, and converted to the proper format for discriminant analysis by computer. The results of several methods of data treatment and display are discussed, based on the chemometrics system package, ARTHUR.     

Analysis of chemical signals in red fire ants by gas chromatography and pattern recognition techniques

Gas chromatographic (GC) profiles of cuticular hydrocarbon extracts obtained from individual and pooled ant samples were analyzed using pattern recognition techniques. Clustering according to the biological variables of social caste and colony were observed. Pooling individual extracts enhanced the recognition of patterns in the GC profile data characteristic of colony. Evidently, the contribution of the ant's individual pattern to the overall hydrocarbon profile pattern can obscure information about colony in the GC traces of cuticular hydrocarbon extracts obtained from red fire ants. Re-analysis of temporal caste and time period data on the cuticular hydrocarbon patterns demonstrates that sampling time and social caste must be taken into account to avoid unnecessary variability and possible confounding. This and the fact that foragers could not be separated from reserves and brood-tenders in all five laboratory colonies studied suggests that cuticular hydrocarbons as a class of sociochemicals cannot model every facet of nestmate recognition in Solenopsis invicta which in turn suggests a potential role for other compounds in the discrimination of alien conspecifics from nestmates.     

Analysis of chemical signals in red fire ants by gas chromatography and pattern recognition techniques

Gas chromatographic (GC) profiles of cuticular hydrocarbon extracts obtained from individual and pooled ant samples were analyzed using pattern recognition techniques. Clustering according to the biological variables of social caste and colony were observed. Pooling individual extracts enhanced the recognition of patterns in the GC profile data characteristic of colony. Evidently, the contribution of the ant's individual pattern to the overall hydrocarbon profile pattern can obscure information about colony in the GC traces of cuticular hydrocarbon extracts obtained from red fire ants. Re-analysis of temporal caste and time period data on the cuticular hydrocarbon patterns demonstrates that sampling time and social caste must be taken into account to avoid unnecessary variability and possible confounding. This and the fact that foragers could not be separated from reserves and brood-tenders in all five laboratory colonies studied suggests that cuticular hydrocarbons as a class of sociochemicals cannot model every facet of nestmate recognition in Solenopsis invicta which in turn suggests a potential role for other compounds in the discrimination of alien conspecifics from nestmates.     

Use of computerized pattern recognition in the analysis of stress induced changes in coffee aroma

The aim of the study was to evaluate changes in the aroma of coffee that has been exposed to heat for some time. Coffee grinds were extracted with water. The coffee was kept hot and sampled periodically using a continuous gas phase extraction method. Gas chromatography/mass spectrometry was used to follow changes in chromatographic profiles. Data were subjected to pattern recognition. About 20 substances were found that significantly changed when exposed to heat.     

Study of the direct detection of crosslinks in hydrocarbons by 13C-NMR. I. Preparation and characterization of model compound 1,1,2,2-tetra(tridecyl) ethane

The present series of papers is the commencement of a study aimed at the direct detection and quantification of crosslinking in hydrocarbons with the ultimate objective of a precise study of radiation-induced crosslinking in polyethylene. The subject of the present paper is the synthesis of a model compound containing a crosslink in a well-defined position sufficiently remote from the chain ends to be representative of an average crosslink in polyethylene. Such a compound in the form of 1,1,2,2-tetra(tridecyl) ethane has been synthetized and isolated in pure form in the course of the present work. Melting points and x-ray spacings of the new compound have been determined, and a comparison with the corresponding linear paraffins has been made. Effects are noted relating to the influence of molecular shape on the GPC elution volume, in which context an observation on a cyclic paraffin is also quoted.     

A study of the globulin of cottonseeds. XXIV. Isolation and characterization of a glycopeptide of the 7S globulin

From a pronase hydrolysate of the 7S globulin of cottonseeds, using a column containing Sephadex G-25 and paper chromatography, a glycopeptide has been isolated which contains in its molecule residues of aspartic acid, glucosamine, and mannose in a ratio of 1:2:5. It has been shown by an analysis of the products of the methylation of the glycopeptide that the carbohydrate chain has a branched structure.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 215–217, March–April, 1981.     

Regularities in the retention of isomeric aromatic hydrocarbons in liquid chromatography. Part I. Analysis of polymethyl-and monoalkyl benzenes and polynuclear aromatic hydrocarbons on hydroxylated silica gel

Summary The retention on hydroxylated silica gel surface upon elution with n-hexane increases in the series of polymethylbenzenes and decreases in the series of mono-alkylbenzenes (after toluene) All iosmers of xylenes, trimethyl- and tetramethylbenzenes are separated as well as isomers of tert.-phenyls, isomers of several dimethylnaphthalenes, anthracene, phenanthrene and poly aromatic hydrocarbons with five condensed rings. These separations are based on the influence of the corresponding molecule structures on the intermolecular interaction with both the adsorbent (strengthening or weakening the energy of hydrogen bonds) and the eluent (intermolecular interaction with n-hexane increases upon lengthening the alkyl group). The effect of orientation at the surface of the investigated hydrocarbon molecules on their retention is also discussed.     

Strain and phase identification of the U.S. category B agent Coxiella burnetii by matrix assisted laser desorption/ionization time-of-flight mass spectrometry and multivariate pattern recognition

Accurate bacterial identification is important in diagnosing disease and in microbial forensics. Coxiella burnetii, a highly infective microorganism causative of the human disease Q fever, is now considered a U.S. category B potential bioterrorism agent. We report here an approach for the confirmatory identification of C. burnetii at the strain level which involves the combined use of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and supervised pattern recognition via Partial Least Squares-Discriminant Analysis (PLS-DA). C. burnetii isolates investigated in this study included the following prototype strains from different geographical and/or historical origins and with different antigenic properties: Nine Mile I, Australian QD, M44, KAV, PAV, Henzerling, and Ohio. After culture and purification following standard protocols, linear MALDI-TOF mass spectra of pure bacterial cultures were acquired in positive ion mode. Mass spectral data were normalized, baseline-corrected, denoised, binarized and modeled by PLS-DA under crossvalidation conditions. Robustness with respect to uncontrolled variations in the sample preparation and MALDI analysis protocol was assessed by repeating the experiment on five different days spanning a period of 6 months. The method was validated by the prediction of unknown C. burnetii samples in an independent test set with 100% sensitivity and specificity for five out of six strain classes.     

The determination of losses in the fire assay of gold: Part I. Cupellation and parting losses

The losses in the cupellation and parting procedures of the fire assay for gold were evaluated with simulated buttons of lead foil. Variation in weight of lead, silver-gold ratio, and cupel size did not affect gold losses. Removal of cupel material from the bead increased the gold loss. Flattening the bead and increasing the parting acid strength reduced the gold losses somewhat. No evidence of losses by volatilization was observed.     

Polymerization of 1,3,5-trithiane in the solid state initiated by UV-irradiation. I. Polymerization conditions and polymer characterization

The solid-state 1,3,5-trithiane polymerization initiated by UV-irradiation was studied at various irradiation times and various polymerization temperatures. The conversion of monomer to polymer reaches limiting values (at longest) in about 30 min of reaction. The apparent activation energy of this process is somewhat higher than in the chemically initiated polymerization. Generated by UV, active centers, which initiate the polymerization, are stable. On the basis of X-ray diffraction studies it was found that the prepared polythiomethylene has a hexagonal structure and high degree of crystallinity. In the polymer investigated, a new additional crystal phase is formed, which is not stable.     

The role of chemometrics in single and sequential extraction assays: a review: part I. Extraction procedures, uni- and bivariate techniques and multivariate variable reduction techniques for pattern recognition

Element mobility and availability in natural solid matrices can be studied with single and sequential extraction procedures; such procedures provide reliable and useful information only if the experiments are correctly planned and executed and the results are properly interpreted. Chemometrics can be a valuable tool for these aims, especially taking into account the large amounts of data generated with extraction essays and the complexity of the processes under investigation. This review deals with the application of chemometrics in research studies involving single and sequential extractions on soils or sediments, for several purposes: the development and optimization of the extraction conditions, the calculation of element fractionation, the visual illustration of the experimental results, the acquisition of different areas of information, including relationships among variables, similarities and differences among samples, causes of the observed behaviour (e.g. source identification), risk assessment, models and predictions of future events. In Part I of the review, following an overview on extraction procedures, the applications of univariate and bivariate chemometric methods are reported; then the principles of multivariate techniques for pattern recognition based on variable reduction, their applications and the main findings obtained are addressed.     

Diffusion Structural Analysis for characterization of ceramics and glasses from gels: I. Principle of the method and its use in the study of silica gels preparation

The Diffusion Structural Analysis (DSA) is described as a new tool for characterization of the processes taking place during preparation of ceramics and glasses from gels. Examples of the DSA application in the silica gels preparation from TEOS are demonstrated. The DSA results are compared with the results of optical transparency and pH measurements during sol-gel transition.     

A study on the synthesis,characterization and properties of polyaniline using acrylic acid as a primary dopant. I: polymerization and polymer

In the presence of acrylic acid (AA) as a primary dopant, polyaniline (PANI) doped with poly(acrylic acid) was successfully synthesized by using ammonium persulfate (APS) as initiator and oxidizing agent. The effect of experimental conditions on the polymer yields was systematically studied. It was found that the polymer yield can be as high as 65%, and this value strongly depends on synthesis conditions, such as the reaction time, the molar ratio of oxidizing agent to aniline monomer, the concentration of reactants and reaction temperature. The molecular weight ( ) of main chains of the de‐doped PANI is estimated to be 32,000–53,000. Based on the data of FT‐IR, UV‐vis, ¹³C‐nuclear magnetic resonance (NMR), elemental analysis and electrical conductivity measurement, the emeraldine salt form of PANI was confirmed and the molecular structure of the resulting PANI‐AA was proposed. Accordingly the reaction mechanism was discussed and it was convinced that the polymerization reaction of AA is initiated by APS. Copyright © 2004 John Wiley & Sons, Ltd.     

An ab initio study of S(N)2 reactivity at C6 in hexopyranose derivatives. I. Influence of dipole-dipole interactions in the transition structure

It is widely accepted that dipole-dipole interactions in the S(N)2 transition structure can play a dominant role in determining reaction rates. A model of this type was proposed some years ago to explain the remarkably low reactivity of galactopyranose-6-O-sulfonates toward S(N)2 displacement, and similar arguments have recently been restated in the context of gas-phase reactions. In this paper, we present ab initio calculations (B3LYP/6-31+G(d,p)) on model structures and an analysis of charge densities using the theory of atoms in molecules. We find that the maximum possible impact of local dipole-dipole interactions is insufficient to account for the observed reactivity differences.