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Coal–rock interface recognition is one of the key unaddressed problems in unmanned mining, so a novel method for it is proposed. Firstly, electron spin resonance (ESR) is used to directly measure 10 kinds of coals/rocks common in China. Secondly, the free radical characteristics of different particle coals/rocks such as the Lande factor g, line width ΔH, and the concentration of the free radical Ng in the X-band ESR are studied. Lastly, the statistical classifier method of support-vector machine is employed to build a classification model with the input of the parameters of the ESR absorption spectra. Based on the ESR-SVM model, the recognition rate of coals/rocks reaches 100%, the recognition rate of different coals reaches 100%, and the recognition rate of different bituminous coals reaches 88.3%. The experimental results demonstrate that the proposed method is fast, stable, and accurate for the detection of the coal–rock interface and can be a promising tool for the classification of different coals. [ABSTRACT FROM AUTHOR]

• Correlations between trace Mn2+ and calcite polymorph in gallstones were discovered. • ESR provides a probe to detect trace Mn2+ in gallstone due to sextet characteristics. • The XRD technique revealed the crystal habit of calcite in gallstones. • Prevalence of calcium carbonate in the gallstones from the northeast China is 35.7 %. • Relation between the levels of Mn2+ and the type of gallstones are discussed. Gallstones containing calcium carbonate (GCCC) from the northeast China were analyzed using X-ray diffraction (XRD), infrared spectroscopy (IR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and electron spin resonance (ESR). The sextet signal arising from the allowed transitions of the trace Mn2+ ions in GCCC was found to be ESR-detectable and strong. The XRD technique revealed the crystal habit of calcite in GCCC. Of the three polymorphs of calcium carbonate, no calcite was present as a solitary crystallization form, accompanied by aragonite or vaterite or both. The sextet ESR signal and the (104) main XRD peak at 2 θ = ∼29.4° were employed as two probes to explore the relationship between trace Mn2+ and calcite. The Mn content can be considered as an indicator of the amount of calcite in GCCC because of the existence of a correlation between Mn2+ and calcite. The correlation between Mn2+ and calcite, the relation between the levels of Mn2+ and the type of gallstones, the structural preference of Mn2+ to the calcite polymorph, and the influence of dietary habits on calcite in calcium carbonate gallstones are discussed. [ABSTRACT FROM AUTHOR]

Gallstones containing calcium carbonate (GCCC) from the northeast China were analyzed using X-ray diffraction (XRD), infrared spectroscopy (IR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and electron spin resonance (ESR). The sextet signal arising from the allowed transitions of the trace Mn 2+ ions in GCCC was found to be ESR-detectable and strong. The XRD technique revealed the crystal habit of calcite in GCCC. Of the three polymorphs of calcium carbonate, no calcite was present as a solitary crystallization form, accompanied by aragonite or vaterite or both. The sextet ESR signal and the (104) main XRD peak at 2θ = ∼29.4° were employed as two probes to explore the relationship between trace Mn 2+ and calcite. The Mn content can be considered as an indicator of the amount of calcite in GCCC because of the existence of a correlation between Mn 2+ and calcite. The correlation between Mn 2+ and calcite, the relation between the levels of Mn 2+ and the type of gallstones, the structural preference of Mn 2+ to the calcite polymorph, and the influence of dietary habits on calcite in calcium carbonate gallstones are discussed., Competing Interests: Declaration of Competing Interest All authors declare that: we have no conflict of interest, financial or otherwise. There are no other relationships or activities that could appear to have influenced the submitted work. Informed consent has been obtained from all patients included in this study., (Copyright © 2020 Elsevier GmbH. All rights reserved.)