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Norihiko Kohyama - One of the best experts on this subject based on the ideXlab platform.
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Frequent homozygous deletion of Cdkn2a/2b in Tremolite-induced malignant mesothelioma in rats.
Cancer Science, 2020Co-Authors: Yasumasa Okazaki, Norihiko Kohyama, Nobuaki Misawa, Shinya Akatsuka, Yoshitaka Sekido, Takashi Takahashi, Shinya ToyokuniAbstract:The onset of malignant mesothelioma (MM) is linked to exposure to asbestos fibers. Asbestos fibers are classified as serpentine (chrysotile) or amphibole, which includes the crocidolite, amosite, anthophyllite, Tremolite, and actinolite types. Although few studies have been undertaken, anthophyllite has been shown to be associated with mesothelioma, and Tremolite, a contaminant in talc and chrysotile, is a risk factor for carcinogenicity. Here, after characterizing the length and width of these fibers by scanning electron microscopy, we explored the cytotoxicity induced by Tremolite and anthophyllite in cells from an immortalized human mesothelial cell line (MeT5A), murine macrophages (RAW264.7), and in a rat model. Tremolite and short anthophyllite fibers were phagocytosed and localized to vacuoles, whereas the long anthophyllite fibers were caught on the pseudopod of the MeT5A and Raw 264.7 cells, according to transmission electron microscopy. The results from a 2-day time-lapse study revealed that Tremolite was engulfed and damaged the MeT5A and RAW264.7 cells, but anthophyllite was not cytotoxic to these cells. Intraperitoneal injection of Tremolite in rats induced diffuse serosal thickening, whereas anthophyllite formed focal fibrosis and granulomas on peritoneal serosal surfaces. Furthermore, the loss of Cdkn2a/2b, which are the most frequently lost foci in human MM, were observed in 8 cases of rat MM (homozygous deletion [5/8] and loss of heterozygosity [3/8]) by array-based comparative genomic hybridization techniques. These results indicate that Tremolite initiates mesothelial injury and persistently frustrates phagocytes, causing subsequent peritoneal fibrosis and MM. The possible mechanisms of carcinogenicity based on fiber diameter/length are discussed.
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frequent homozygous deletion of cdkn2a 2b in Tremolite induced malignant mesothelioma in rats
Cancer Science, 2020Co-Authors: Yasumasa Okazaki, Norihiko Kohyama, Nobuaki Misawa, Shinya Akatsuka, Yoshitaka Sekido, Takashi Takahashi, Shinya ToyokuniAbstract:The onset of malignant mesothelioma (MM) is linked to exposure to asbestos fibers. Asbestos fibers are classified as serpentine (chrysotile) or amphibole, which includes the crocidolite, amosite, anthophyllite, Tremolite, and actinolite types. Although few studies have been undertaken, anthophyllite has been shown to be associated with mesothelioma, and Tremolite, a contaminant in talc and chrysotile, is a risk factor for carcinogenicity. Here, after characterizing the length and width of these fibers by scanning electron microscopy, we explored the cytotoxicity induced by Tremolite and anthophyllite in cells from an immortalized human mesothelial cell line (MeT5A), murine macrophages (RAW264.7), and in a rat model. Tremolite and short anthophyllite fibers were phagocytosed and localized to vacuoles, whereas the long anthophyllite fibers were caught on the pseudopod of the MeT5A and Raw 264.7 cells, according to transmission electron microscopy. The results from a 2-day time-lapse study revealed that Tremolite was engulfed and damaged the MeT5A and RAW264.7 cells, but anthophyllite was not cytotoxic to these cells. Intraperitoneal injection of Tremolite in rats induced diffuse serosal thickening, whereas anthophyllite formed focal fibrosis and granulomas on peritoneal serosal surfaces. Furthermore, the loss of Cdkn2a/2b, which are the most frequently lost foci in human MM, were observed in 8 cases of rat MM (homozygous deletion [5/8] and loss of heterozygosity [3/8]) by array-based comparative genomic hybridization techniques. These results indicate that Tremolite initiates mesothelial injury and persistently frustrates phagocytes, causing subsequent peritoneal fibrosis and MM. The possible mechanisms of carcinogenicity based on fiber diameter/length are discussed.
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mesothelioma in a worker who spun chrysotile asbestos at home during childhood
American Journal of Industrial Medicine, 2009Co-Authors: Eiji Yano, Ayako Takata, Norihiko Kohyama, Mianzheng Wang, Zhiming Wang, Xiaorong Wang, Yasunosuke SuzukiAbstract:Background Malignant mesothelioma has a long latency period and more commonly found in those exposed to amphibole than chrysotile asbestos. Method A 35 years old asbestos worker in an asbestos textile plant in Chongqing, China, developed mesothelioma after only 4 years of employment. He was born and bred in a company residence of an asbestos plant and manually spun asbestos thread during school age. In the plant, not amphibole but only chrysotile has been used. Results Diagnosis of malignant mesothelioma was confirmed by comprehensive approaches including gross appearance, histology, histochemistry, and immunocytochemistry. In the lung and tumor tissues, huge number of Tremolite with exceptional chrysotile was observed despite the reverse proportion in the work environment. Discussion Residential exposure and home spinning of asbestos seemed contributed to the early development of mesothelioma in this subject. Although only chrysotile was used and contamination of Tremolite was low in the work environment, chrysotile seemed to be cleared leaving Tremolite remain in the tissue. Conclusion Chrysotile with little contamination of Tremolite can lead to early development of malignant mesothelioma when heavily exposed from childhood at a company residence with household exposure. There can be several mechanisms for Tremolite to remain in the lung tissue, far exceeding chrysotile in number. Am. J. Ind. Med. 52:282–287, 2009. © 2009 Wiley-Liss, Inc.
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airborne fiber concentration and size distribution of mineral fibers in area with serpentinite outcrops in aichi prefecture japan
Industrial Health, 2001Co-Authors: Kiyoshi Sakai, Norihiko Kohyama, Naomi Hisanaga, Eiji Shibata, Yasuhiro TakeuchiAbstract:Airborne fiber concentrations and size distributions of both asbestos and nonasbestos fibers were determined at property boundaries of 4 serpentinite quarries producing crushed stone (quarry property boundary), 10 sites within 10 km of the area with serpentinite outcrops (serpentinite area), and 2 sites in a reference area. The asbestos was identified in 7 rock and 3 soil samples collected in the serpentinite area. The geometric means of airborne concentrations of asbestos and nonasbestos fibers longer than 0.2 μm in length were: 384 and 447 fibers/liter (f/L) in the quarry property boundary (in operation), 12 and 124 f/L in the quarry property boundary (in closed), 5 and 103 fibers/liter in the serpentinite area, and less than 2 and 59 fibers/liter in the reference area, respectively. There was a significant difference in airborne concentrations of both asbestos and nonasbestos fibers among the areas. TTremolite/actinolite were found with chrysotile in the stones. Airborne concentrations of Tremolite/actinolite were higher than those of chrysotile at the quarry property boundary and in the serpentinite area. Tremolite/actinolite were also found in the soils. There was no significant difference among the areas in the arithmetic means of fiber size distribution of both asbestos and nonasbestos fibers.
Ben Armstrong - One of the best experts on this subject based on the ideXlab platform.
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mortality in a cohort of vermiculite miners exposed to fibrous amphibole in libby montana
Occupational and Environmental Medicine, 2004Co-Authors: J C Mcdonald, Jessica M Harris, Ben ArmstrongAbstract:Background: Fibrous Tremolite is a widespread amphibole asbestiform mineral, airborne fibres of which constitute an environmental hazard in Libby, Montana, northern California, and elsewhere. Aims: To determine excess risk from lung cancer, mesothelioma, and all-cause mortality in a cohort of men exposed to Tremolite, but no other form of asbestos. Methods: Mortality by certified cause and various measures of exposure to Tremolite and related amphibole fibres was assessed in a cohort of 406 vermiculite mineworkers in Libby, Montana, employed before 1963 and followed until 1999. Results: Total deaths were: lung cancer 44 (SMR 2.40), non-malignant respiratory disease (NMRD) 51 (SMR 3.09), all causes 285 (SMR 1.27); included among the total were 12 deaths ascribed to mesothelioma (4.21% of all deaths). Adjusted linear increments in relative risks (per 100 f/ml.y), estimated by Poisson regression, were: lung cancer (0.36, 95% CI 0.03 to 1.20), NMRD (0.38, 95% CI 0.12 to 0.96), and all deaths (0.14, 95% CI 0.05 to 0.26). Conclusions: The all-cause linear model would imply a 14% increase in mortality for mine workers exposed occupationally to 100 f/ml.y or about 3.2% for a general population exposed for 50 years to an ambient concentration of 0.1 f/ml. Amphibole fibres, Tremolite in particular, are likely to be disproportionately responsible for cancer mortality in persons exposed to commercial chrysotile, but to what extent cannot be readily assessed.
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Cohort Mortality Study of Vermiculite Miners Exposed to Fibrous Tremolite: an Update
The Annals of Occupational Hygiene, 2002Co-Authors: J C Mcdonald, Joanne Harris, Ben ArmstrongAbstract:A further follow-up was made of a cohort of 406 American vermiculite mine workers exposed on average to 18 fibres/ml of Tremolite. Total deaths to the end of 1999 were: all causes 285 (SMR 1.27), lung cancer 44 (SMR 2.40), mesothelioma 12 (PMR 4.21%). Lung cancer SMRs increased steeply with cumulative exposure (f/ml.yr). These findings show the potential magnitude of the carcinogenic effects of Tremolite fibres when contaminating commercial chrysotile, and are relevant to risks associated with Tremolite fibres in the general environment.
Shinya Toyokuni - One of the best experts on this subject based on the ideXlab platform.
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Frequent homozygous deletion of Cdkn2a/2b in Tremolite-induced malignant mesothelioma in rats.
Cancer Science, 2020Co-Authors: Yasumasa Okazaki, Norihiko Kohyama, Nobuaki Misawa, Shinya Akatsuka, Yoshitaka Sekido, Takashi Takahashi, Shinya ToyokuniAbstract:The onset of malignant mesothelioma (MM) is linked to exposure to asbestos fibers. Asbestos fibers are classified as serpentine (chrysotile) or amphibole, which includes the crocidolite, amosite, anthophyllite, Tremolite, and actinolite types. Although few studies have been undertaken, anthophyllite has been shown to be associated with mesothelioma, and Tremolite, a contaminant in talc and chrysotile, is a risk factor for carcinogenicity. Here, after characterizing the length and width of these fibers by scanning electron microscopy, we explored the cytotoxicity induced by Tremolite and anthophyllite in cells from an immortalized human mesothelial cell line (MeT5A), murine macrophages (RAW264.7), and in a rat model. Tremolite and short anthophyllite fibers were phagocytosed and localized to vacuoles, whereas the long anthophyllite fibers were caught on the pseudopod of the MeT5A and Raw 264.7 cells, according to transmission electron microscopy. The results from a 2-day time-lapse study revealed that Tremolite was engulfed and damaged the MeT5A and RAW264.7 cells, but anthophyllite was not cytotoxic to these cells. Intraperitoneal injection of Tremolite in rats induced diffuse serosal thickening, whereas anthophyllite formed focal fibrosis and granulomas on peritoneal serosal surfaces. Furthermore, the loss of Cdkn2a/2b, which are the most frequently lost foci in human MM, were observed in 8 cases of rat MM (homozygous deletion [5/8] and loss of heterozygosity [3/8]) by array-based comparative genomic hybridization techniques. These results indicate that Tremolite initiates mesothelial injury and persistently frustrates phagocytes, causing subsequent peritoneal fibrosis and MM. The possible mechanisms of carcinogenicity based on fiber diameter/length are discussed.
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frequent homozygous deletion of cdkn2a 2b in Tremolite induced malignant mesothelioma in rats
Cancer Science, 2020Co-Authors: Yasumasa Okazaki, Norihiko Kohyama, Nobuaki Misawa, Shinya Akatsuka, Yoshitaka Sekido, Takashi Takahashi, Shinya ToyokuniAbstract:The onset of malignant mesothelioma (MM) is linked to exposure to asbestos fibers. Asbestos fibers are classified as serpentine (chrysotile) or amphibole, which includes the crocidolite, amosite, anthophyllite, Tremolite, and actinolite types. Although few studies have been undertaken, anthophyllite has been shown to be associated with mesothelioma, and Tremolite, a contaminant in talc and chrysotile, is a risk factor for carcinogenicity. Here, after characterizing the length and width of these fibers by scanning electron microscopy, we explored the cytotoxicity induced by Tremolite and anthophyllite in cells from an immortalized human mesothelial cell line (MeT5A), murine macrophages (RAW264.7), and in a rat model. Tremolite and short anthophyllite fibers were phagocytosed and localized to vacuoles, whereas the long anthophyllite fibers were caught on the pseudopod of the MeT5A and Raw 264.7 cells, according to transmission electron microscopy. The results from a 2-day time-lapse study revealed that Tremolite was engulfed and damaged the MeT5A and RAW264.7 cells, but anthophyllite was not cytotoxic to these cells. Intraperitoneal injection of Tremolite in rats induced diffuse serosal thickening, whereas anthophyllite formed focal fibrosis and granulomas on peritoneal serosal surfaces. Furthermore, the loss of Cdkn2a/2b, which are the most frequently lost foci in human MM, were observed in 8 cases of rat MM (homozygous deletion [5/8] and loss of heterozygosity [3/8]) by array-based comparative genomic hybridization techniques. These results indicate that Tremolite initiates mesothelial injury and persistently frustrates phagocytes, causing subsequent peritoneal fibrosis and MM. The possible mechanisms of carcinogenicity based on fiber diameter/length are discussed.
Matthias Gottschalk - One of the best experts on this subject based on the ideXlab platform.
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crystal chemistry of Tremolite tschermakite solid solutions
Pacific Rim Conference on Multimedia, 2003Co-Authors: Jens Najorka, Matthias GottschalkAbstract:Tremolite–tschermakite solid solutions have been synthesized between 700 and 850 °C and 200 and 2000 MPa. The starting materials were oxide–hydroxide mixtures and an additional 0.1–1.8 molal CaBr2 solution. The run products were characterized using SEM, HRTEM, EMP, XRD and FTIR. The synthesized Al Tremolites formed needles and lath-shaped crystals of up to 300 × 20 μm. HRTEM investigations showed that the majority of the amphiboles were well ordered. The EMP analysis revealed that the Al Tremolites were solid solutions in the ternary Tremolite–tschermakite–cummingtonite. The highest observed Al content was close to the composition of magnesiohornblende (Xts=0.54). Different cummingtonite concentrations (Xcum=0.00–0.18) were observed, which generally increased with Al content. Rietveld refinements of the lattice constants showed a linear decrease of the cell parameters a and b with increasing Al content, whereas c and β increased. Small deviations from the linear behaviour were caused by variable amounts of the cummingtonite component. For pure tschermakite lattice parameters of a=9.7438(11) A, b=17.936(14) A, c=5.2995(3) A, β=105.68(9)° and V=891.7 ± 1.4 A3 were extrapolated by least-squares regression. Using the a and β lattice parameters for Tremolite, tschermakite and cummingtonite, it was possible to derive amphibole compositions using powder XRD. IR spectra of the Al Tremolites showed a total of 12 individual bands. The FWHMs of all bands increased with increasing Al content. According to their FWHMs, these bands were grouped into three band systems at 3664–3676 cm−1 (I), 3633–3664 cm−1 (II) and 3526–3633 cm−1 (III). Assuming [6]Al substitution at M2 and/or M3 and [4]Al at T1, three principal different configurational groups could be assigned as local environments for the proton. I: only Si4+ at T1 and one or two Al3+ at M2 and/or M3far, II: one Al3+ at T1 and one to three Al3+ at M2 and/or at M3far, III: either Al3+ on M3near and/or two Al3+ on T1 and additional one to four Al3+ at M2. It is assumed that these three configurational groups correspond to the three groups of observed bands. This was quantitativly supported by Monte-Carlo simulations. A model with random distribution at M2 and M3 including Al avoidance at tetrahedral and octahedral sites yielded the best agreement with the spectroscopical results.
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Crystal chemistry of Tremolite–tschermakite solid solutions
Physics and Chemistry of Minerals, 2003Co-Authors: Jens Najorka, Matthias GottschalkAbstract:Tremolite–tschermakite solid solutions have been synthesized between 700 and 850 °C and 200 and 2000 MPa. The starting materials were oxide–hydroxide mixtures and an additional 0.1–1.8 molal CaBr2 solution. The run products were characterized using SEM, HRTEM, EMP, XRD and FTIR. The synthesized Al Tremolites formed needles and lath-shaped crystals of up to 300 × 20 μm. HRTEM investigations showed that the majority of the amphiboles were well ordered. The EMP analysis revealed that the Al Tremolites were solid solutions in the ternary Tremolite–tschermakite–cummingtonite. The highest observed Al content was close to the composition of magnesiohornblende (Xts=0.54). Different cummingtonite concentrations (Xcum=0.00–0.18) were observed, which generally increased with Al content. Rietveld refinements of the lattice constants showed a linear decrease of the cell parameters a and b with increasing Al content, whereas c and β increased. Small deviations from the linear behaviour were caused by variable amounts of the cummingtonite component. For pure tschermakite lattice parameters of a=9.7438(11) A, b=17.936(14) A, c=5.2995(3) A, β=105.68(9)° and V=891.7 ± 1.4 A3 were extrapolated by least-squares regression. Using the a and β lattice parameters for Tremolite, tschermakite and cummingtonite, it was possible to derive amphibole compositions using powder XRD. IR spectra of the Al Tremolites showed a total of 12 individual bands. The FWHMs of all bands increased with increasing Al content. According to their FWHMs, these bands were grouped into three band systems at 3664–3676 cm−1 (I), 3633–3664 cm−1 (II) and 3526–3633 cm−1 (III). Assuming [6]Al substitution at M2 and/or M3 and [4]Al at T1, three principal different configurational groups could be assigned as local environments for the proton. I: only Si4+ at T1 and one or two Al3+ at M2 and/or M3far, II: one Al3+ at T1 and one to three Al3+ at M2 and/or at M3far, III: either Al3+ on M3near and/or two Al3+ on T1 and additional one to four Al3+ at M2. It is assumed that these three configurational groups correspond to the three groups of observed bands. This was quantitativly supported by Monte-Carlo simulations. A model with random distribution at M2 and M3 including Al avoidance at tetrahedral and octahedral sites yielded the best agreement with the spectroscopical results.
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Lattice vibrational modes in synthetic Tremolite-Sr-Tremolite and Tremolite-richterite solid solutions
Physics and Chemistry of Minerals, 2000Co-Authors: Michael Andrut, Matthias Gottschalk, S. Melzer, Jens NajorkaAbstract:Powder IR spectra of synthetic richterite-Tremolite and Sr-Tremolite-Tremolite solid solutions were obtained in the spectral range between 1400 and 600 cm−1. Under the consideration of the crystal structure and the Wykoff positions of the atoms in the primitive unit cell, the number, type and symmetry of vibrational modes were deduced. The space group of Tremolite C2h was used as the factor group leading to 16 theoretical stretching vibrations in the IR range caused by the Si4O11∞-ribbon. The energy of the internal vibrations of the Si4O11∞-ribbon is a function of the relative bond strengths and masses of nearby ions. For the amphiboles a one-mode behavior was observed for all the Si-O, Si-O-Si and O-Si-O stretching vibrations, indicating no clustering in the two solid solution series. In both solid solution series the vibrational energy of the stretching vibrations is a linear function of composition. In the system richterite-Tremolite a shift of the stretching frequencies of the Si4O11∞-ribbon over the whole compositional range of up to 30 cm−1 was observed. In contrast, for Sr-Tremolite-Tremolite the maximum shift was only 5 cm−1. These quite small band shifts allow the (Si4O11)∞-ribbon to be treated as an isolated entity for factor group analysis. Nevertheless, by the two exchange mechanisms, Ca(M4) ? Sr(M4) and □(A) Ca(M4) ? Na(A)Na(M4), the FWHHs increased and the amplitudes decreased, indicating a slight distortion of the ribbon. For Sr-Tremolite-Tremolite only a linear expansion of the lattice was observed. In the series richterite-Tremolite individual bond angles of the SiO4 tetrahedra are additionally changed, causing the higher energy shift of the bands. The strongest and sharpest bands were observed for the end member Tremolite. The one-mode behavior of the Si4O11-double chain indicates that there is no short-range order of Na/Ca and Ca/Sr at the M4 sites of these amphiboles.
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The determination of the cummingtonite content of synthetic Tremolite
European Journal of Mineralogy, 1999Co-Authors: Matthias Gottschalk, Michael Andrut, Stefan MelzerAbstract:Amphiboles of predominantly Tremolite composition have been synthesized at 670-800 degrees C and 200-700 MPa in the system CaO-MgO-SiO 2 -H 2 O. The Tremolite crystals were large enough to be analyzed by electron microprobe. The run products were also studied by scanning electron microscopy, high resolution electron microscopy, X-ray diffraction (Rietveld analysis) and IR spectroscopy. The electron microprobe analyses resulted in average compositions between tr 87 cum 13 and tr 99 cum 1 . The cummingtonite contents determined by electron microprobe varied by up to + or -7 mol% within each run. Investigations using high resolution electron microscopy revealed that the Tremolite-cummingtonite solid solutions were highly ordered and chain multiplicity faults were rare. Although the lattice parameters a, b and beta are expected to be a function of the cummingtonite content, no correlations were observed between the compositions derived by electron microprobe and the lattice parameters. The energy and absorbance of the OH stretching vibration is a function of M4 site occupancy. Therefore, the cummingtonite content was determined precisely by IR spectroscopy. At least 3 different bands at distinct energies were identified: 3674.6 cm (super -1) for the CaCa-CaCa and 3669.3 and 3672.2 cm (super -1) for the MgCa-CaCa and CaCa-MgCa configurations, respectively. The relative integral absorbances showed that all synthesized amphiboles had cummingtonite contents lower than 6 mol%. In some cases nearly pure Tremolite was synthesized (tr 99 cum 1 ). This amount is considerably less than the 10 mol% cummingtonite content (tr 90 cum 10 ) often claimed for synthetic Tremolite. The compositions derived by IR spectroscopy correlate with the lattice parameters. Using these correlations the lattice parameters of pure Tremolite were extrapolated to be a = 9.8354(18) Aa, b = 18.0562(14) Aa, c = 5.2768(6) Aa, beta = 104.74(2) degrees , V = 906.3(2) Aa 3 .
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Structural and compositional characterization of synthetic (Ca,Sr)-Tremolite and (Ca,Sr)-diopside solid solutions
Physics and Chemistry of Minerals, 1998Co-Authors: Matthias Gottschalk, Jens Najorka, M. AndrutAbstract:Tremolite (CaxSr1–x)2Mg5[Si8O22/(OH)2] and diopside (CaxSr1–x)Mg[Si2O6] solid solutions have been synthesized hydrothermally in equilibrium with a 1 molar (Ca,Sr)Cl2 aqueous solution at 750°C and 200 MPa. The solid run products have been investigated by optical, electron scanning and high resolution transmission electron microscopy, electron microprobe, X-ray-powder diffraction and Fourier-transform infrared spectroscopy. The synthesized (Ca,Sr)-Tremolites are up to 2000 µm long and 30 µm wide, the (Ca,Sr)-diopsides are up to 150 µm long and 20 µm wide. In most runs the Tremolites and diopsides are well ordered and chain multiplicity faults are rare. Nearly pure Sr-Tremolite (tr0.02Sr-tr0.98) and Sr-diopside (di0.01Sr-di0.99) have been synthesized. A continuous solid solution series, i.e. complete substitution of Sr2+ for Ca2+ on M4-sites exists for (Ca,Sr)-Tremolite. Total substitution of Sr2+ for Ca2+ on M2-sites can be assumed for (Ca,Sr)-diopsides. For (Ca,Sr)-Tremolites the lattice parameters a, b and β are linear functions of composition and increase with Sr-content whereas c is constant. For the diopside series all 4 lattice parameters are a linear function of composition; a, b, c increase and β decreases with rising Sr-content. The unit cell volume for Tremolite increases 3.47% from 906.68 A3 for Tremolite to 938.21 A3 for Sr-Tremolite. For diopside the unit cell volume increases 4.87 % from 439.91 A3 for diopside to 461.30 A3 for Sr-diopside. The observed splitting of the OH stretching band in Tremolite is caused by different configurations of the next nearest neighbors (multi mode behavior). Resolved single bands can be attributed to the following configurations on the M4-sites: SrSr, SrCa, CaCa and CaMg. The peak positions of these 4 absorption bands are a linear function of composition. They are shifted to lower wavenumbers with increasing Sr-content. No absorption band due to the SrMg configuration on the M4-site is observed. This indicates a very low or negligible cummingtonite component in Sr-rich Tremolites, which is also supported by electron microprobe analysis.
Jens Najorka - One of the best experts on this subject based on the ideXlab platform.
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crystal chemistry of Tremolite tschermakite solid solutions
Pacific Rim Conference on Multimedia, 2003Co-Authors: Jens Najorka, Matthias GottschalkAbstract:Tremolite–tschermakite solid solutions have been synthesized between 700 and 850 °C and 200 and 2000 MPa. The starting materials were oxide–hydroxide mixtures and an additional 0.1–1.8 molal CaBr2 solution. The run products were characterized using SEM, HRTEM, EMP, XRD and FTIR. The synthesized Al Tremolites formed needles and lath-shaped crystals of up to 300 × 20 μm. HRTEM investigations showed that the majority of the amphiboles were well ordered. The EMP analysis revealed that the Al Tremolites were solid solutions in the ternary Tremolite–tschermakite–cummingtonite. The highest observed Al content was close to the composition of magnesiohornblende (Xts=0.54). Different cummingtonite concentrations (Xcum=0.00–0.18) were observed, which generally increased with Al content. Rietveld refinements of the lattice constants showed a linear decrease of the cell parameters a and b with increasing Al content, whereas c and β increased. Small deviations from the linear behaviour were caused by variable amounts of the cummingtonite component. For pure tschermakite lattice parameters of a=9.7438(11) A, b=17.936(14) A, c=5.2995(3) A, β=105.68(9)° and V=891.7 ± 1.4 A3 were extrapolated by least-squares regression. Using the a and β lattice parameters for Tremolite, tschermakite and cummingtonite, it was possible to derive amphibole compositions using powder XRD. IR spectra of the Al Tremolites showed a total of 12 individual bands. The FWHMs of all bands increased with increasing Al content. According to their FWHMs, these bands were grouped into three band systems at 3664–3676 cm−1 (I), 3633–3664 cm−1 (II) and 3526–3633 cm−1 (III). Assuming [6]Al substitution at M2 and/or M3 and [4]Al at T1, three principal different configurational groups could be assigned as local environments for the proton. I: only Si4+ at T1 and one or two Al3+ at M2 and/or M3far, II: one Al3+ at T1 and one to three Al3+ at M2 and/or at M3far, III: either Al3+ on M3near and/or two Al3+ on T1 and additional one to four Al3+ at M2. It is assumed that these three configurational groups correspond to the three groups of observed bands. This was quantitativly supported by Monte-Carlo simulations. A model with random distribution at M2 and M3 including Al avoidance at tetrahedral and octahedral sites yielded the best agreement with the spectroscopical results.
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Crystal chemistry of Tremolite–tschermakite solid solutions
Physics and Chemistry of Minerals, 2003Co-Authors: Jens Najorka, Matthias GottschalkAbstract:Tremolite–tschermakite solid solutions have been synthesized between 700 and 850 °C and 200 and 2000 MPa. The starting materials were oxide–hydroxide mixtures and an additional 0.1–1.8 molal CaBr2 solution. The run products were characterized using SEM, HRTEM, EMP, XRD and FTIR. The synthesized Al Tremolites formed needles and lath-shaped crystals of up to 300 × 20 μm. HRTEM investigations showed that the majority of the amphiboles were well ordered. The EMP analysis revealed that the Al Tremolites were solid solutions in the ternary Tremolite–tschermakite–cummingtonite. The highest observed Al content was close to the composition of magnesiohornblende (Xts=0.54). Different cummingtonite concentrations (Xcum=0.00–0.18) were observed, which generally increased with Al content. Rietveld refinements of the lattice constants showed a linear decrease of the cell parameters a and b with increasing Al content, whereas c and β increased. Small deviations from the linear behaviour were caused by variable amounts of the cummingtonite component. For pure tschermakite lattice parameters of a=9.7438(11) A, b=17.936(14) A, c=5.2995(3) A, β=105.68(9)° and V=891.7 ± 1.4 A3 were extrapolated by least-squares regression. Using the a and β lattice parameters for Tremolite, tschermakite and cummingtonite, it was possible to derive amphibole compositions using powder XRD. IR spectra of the Al Tremolites showed a total of 12 individual bands. The FWHMs of all bands increased with increasing Al content. According to their FWHMs, these bands were grouped into three band systems at 3664–3676 cm−1 (I), 3633–3664 cm−1 (II) and 3526–3633 cm−1 (III). Assuming [6]Al substitution at M2 and/or M3 and [4]Al at T1, three principal different configurational groups could be assigned as local environments for the proton. I: only Si4+ at T1 and one or two Al3+ at M2 and/or M3far, II: one Al3+ at T1 and one to three Al3+ at M2 and/or at M3far, III: either Al3+ on M3near and/or two Al3+ on T1 and additional one to four Al3+ at M2. It is assumed that these three configurational groups correspond to the three groups of observed bands. This was quantitativly supported by Monte-Carlo simulations. A model with random distribution at M2 and M3 including Al avoidance at tetrahedral and octahedral sites yielded the best agreement with the spectroscopical results.
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Lattice vibrational modes in synthetic Tremolite-Sr-Tremolite and Tremolite-richterite solid solutions
Physics and Chemistry of Minerals, 2000Co-Authors: Michael Andrut, Matthias Gottschalk, S. Melzer, Jens NajorkaAbstract:Powder IR spectra of synthetic richterite-Tremolite and Sr-Tremolite-Tremolite solid solutions were obtained in the spectral range between 1400 and 600 cm−1. Under the consideration of the crystal structure and the Wykoff positions of the atoms in the primitive unit cell, the number, type and symmetry of vibrational modes were deduced. The space group of Tremolite C2h was used as the factor group leading to 16 theoretical stretching vibrations in the IR range caused by the Si4O11∞-ribbon. The energy of the internal vibrations of the Si4O11∞-ribbon is a function of the relative bond strengths and masses of nearby ions. For the amphiboles a one-mode behavior was observed for all the Si-O, Si-O-Si and O-Si-O stretching vibrations, indicating no clustering in the two solid solution series. In both solid solution series the vibrational energy of the stretching vibrations is a linear function of composition. In the system richterite-Tremolite a shift of the stretching frequencies of the Si4O11∞-ribbon over the whole compositional range of up to 30 cm−1 was observed. In contrast, for Sr-Tremolite-Tremolite the maximum shift was only 5 cm−1. These quite small band shifts allow the (Si4O11)∞-ribbon to be treated as an isolated entity for factor group analysis. Nevertheless, by the two exchange mechanisms, Ca(M4) ? Sr(M4) and □(A) Ca(M4) ? Na(A)Na(M4), the FWHHs increased and the amplitudes decreased, indicating a slight distortion of the ribbon. For Sr-Tremolite-Tremolite only a linear expansion of the lattice was observed. In the series richterite-Tremolite individual bond angles of the SiO4 tetrahedra are additionally changed, causing the higher energy shift of the bands. The strongest and sharpest bands were observed for the end member Tremolite. The one-mode behavior of the Si4O11-double chain indicates that there is no short-range order of Na/Ca and Ca/Sr at the M4 sites of these amphiboles.
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Structural and compositional characterization of synthetic (Ca,Sr)-Tremolite and (Ca,Sr)-diopside solid solutions
Physics and Chemistry of Minerals, 1998Co-Authors: Matthias Gottschalk, Jens Najorka, M. AndrutAbstract:Tremolite (CaxSr1–x)2Mg5[Si8O22/(OH)2] and diopside (CaxSr1–x)Mg[Si2O6] solid solutions have been synthesized hydrothermally in equilibrium with a 1 molar (Ca,Sr)Cl2 aqueous solution at 750°C and 200 MPa. The solid run products have been investigated by optical, electron scanning and high resolution transmission electron microscopy, electron microprobe, X-ray-powder diffraction and Fourier-transform infrared spectroscopy. The synthesized (Ca,Sr)-Tremolites are up to 2000 µm long and 30 µm wide, the (Ca,Sr)-diopsides are up to 150 µm long and 20 µm wide. In most runs the Tremolites and diopsides are well ordered and chain multiplicity faults are rare. Nearly pure Sr-Tremolite (tr0.02Sr-tr0.98) and Sr-diopside (di0.01Sr-di0.99) have been synthesized. A continuous solid solution series, i.e. complete substitution of Sr2+ for Ca2+ on M4-sites exists for (Ca,Sr)-Tremolite. Total substitution of Sr2+ for Ca2+ on M2-sites can be assumed for (Ca,Sr)-diopsides. For (Ca,Sr)-Tremolites the lattice parameters a, b and β are linear functions of composition and increase with Sr-content whereas c is constant. For the diopside series all 4 lattice parameters are a linear function of composition; a, b, c increase and β decreases with rising Sr-content. The unit cell volume for Tremolite increases 3.47% from 906.68 A3 for Tremolite to 938.21 A3 for Sr-Tremolite. For diopside the unit cell volume increases 4.87 % from 439.91 A3 for diopside to 461.30 A3 for Sr-diopside. The observed splitting of the OH stretching band in Tremolite is caused by different configurations of the next nearest neighbors (multi mode behavior). Resolved single bands can be attributed to the following configurations on the M4-sites: SrSr, SrCa, CaCa and CaMg. The peak positions of these 4 absorption bands are a linear function of composition. They are shifted to lower wavenumbers with increasing Sr-content. No absorption band due to the SrMg configuration on the M4-site is observed. This indicates a very low or negligible cummingtonite component in Sr-rich Tremolites, which is also supported by electron microprobe analysis.
