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At least 505 records · Page 28
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on MgHg3 by Materials Project

MgHg3 is Sodium arsenide structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Mg is bonded to eleven Hg atoms to form a mixture of distorted edge and face-sharing MgHg11 trigonal bipyramids. There are a spread of Mg–Hg bond distances ranging from 2.93–3.34 Å. There are two inequivalent Hg sites. In the first Hg site, Hg is bonded in a distorted single-bond geometry to four equivalent Mg atoms. In the second Hg site, Hg is bonded in a trigonal planar geometry to three equivalent Mg atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LiHg3 by Materials Project

LiHg3 is Uranium Silicide-like structured and crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. Li is bonded to twelve Hg atoms to form a mixture of face and corner-sharing LiHg12 cuboctahedra. There are a spread of Li–Hg bond distances ranging from 3.18–3.20 Å. There are two inequivalent Hg sites. In the first Hg site, Hg is bonded in a distorted see-saw-like geometry to four equivalent Li atoms. In the second Hg site, Hg is bonded in a distorted see-saw-like geometry to four equivalent Li atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on HgTe5H36C12N3(OF5)5 by Materials Project

(N(CH3)4)3HgTe5(OF5)5 crystallizes in the monoclinic Cc space group. The structure is zero-dimensional and consists of twelve tetramethylammonium molecules and four HgTe5(OF5)5 clusters. In each HgTe5(OF5)5 cluster, Hg is bonded to five O atoms to form HgO5 trigonal bipyramids that share corners with five TeOF5 octahedra. The corner-sharing octahedra tilt angles range from 45–61°. There are a spread of Hg–O bond distances ranging from 2.26–2.38 Å. There are five inequivalent Te sites. In the first Te site, Te is bonded to one O and five F atoms to form TeOF5 octahedra that share a cornercorner with one HgO5 trigonal bipyramid. The Te–O bond length is 1.83 Å. There is one shorter (1.90 Å) and four longer (1.91 Å) Te–F bond length. In the second Te site, Te is bonded to one O and five F atoms to form TeOF5 octahedra that share a cornercorner with one HgO5 trigonal bipyramid. The Te–O bond length is 1.83 Å. There are a spread of Te–F bond distances ranging from 1.89–1.92 Å. In the third Te site, Te is bonded to one O and five F atoms to form TeOF5 octahedra that share a cornercorner with one HgO5 trigonal bipyramid. The Te–O bond length is 1.82 Å. There are a spread of Te–F bond distances ranging from 1.90–1.92 Å. In the fourth Te site, Te is bonded to one O and five F atoms to form TeOF5 octahedra that share a cornercorner with one HgO5 trigonal bipyramid. The Te–O bond length is 1.83 Å. There are a spread of Te–F bond distances ranging from 1.89–1.91 Å. In the fifth Te site, Te is bonded to one O and five F atoms to form TeOF5 octahedra that share a cornercorner with one HgO5 trigonal bipyramid. The Te–O bond length is 1.82 Å. There are a spread of Te–F bond distances ranging from 1.90–1.92 Å. There are five inequivalent O sites. In the first O site, O is bonded in a distorted bent 120 degrees geometry to one Hg and one Te atom. In the second O site, O is bonded in a distorted bent 150 degrees geometry to one Hg and one Te atom. In the third O site, O is bonded in a bent 120 degrees geometry to one Hg and one Te atom. In the fourth O site, O is bonded in a distorted bent 120 degrees geometry to one Hg and one Te atom. In the fifth O site, O is bonded in a bent 120 degrees geometry to one Hg and one Te atom. There are twenty-five inequivalent F sites. In the first F site, F is bonded in a single-bond geometry to one Te atom. In the second F site, F is bonded in a single-bond geometry to one Te atom. In the third F site, F is bonded in a single-bond geometry to one Te atom. In the fourth F site, F is bonded in a single-bond geometry to one Te atom. In the fifth F site, F is bonded in a single-bond geometry to one Te atom. In the sixth F site, F is bonded in a single-bond geometry to one Te atom. In the seventh F site, F is bonded in a single-bond geometry to one Te atom. In the eighth F site, F is bonded in a single-bond geometry to one Te atom. In the ninth F site, F is bonded in a single-bond geometry to one Te atom. In the tenth F site, F is bonded in a single-bond geometry to one Te atom. In the eleventh F site, F is bonded in a single-bond geometry to one Te atom. In the twelfth F site, F is bonded in a single-bond geometry to one Te atom. In the thirteenth F site, F is bonded in a single-bond geometry to one Te atom. In the fourteenth F site, F is bonded in a single-bond geometry to one Te atom. In the fifteenth F site, F is bonded in a single-bond geometry to one Te atom. In the sixteenth F site, F is bonded in a single-bond geometry to one Te atom. In the seventeenth F site, F is bonded in a single-bond geometry to one Te atom. In the eighteenth F site, F is bonded in a single-bond geometry to one Te atom. In the nineteenth F site, F is bonded in a single-bond geometry to one Te atom. In the twentieth F site, F is bonded in a single-bond geometry to one Te atom. In the twenty-first F site, F is bonded in a single-bond geometry to one Te atom. In the twenty-second F site, F is bonded in a single-bond geometry to one Te atom. In the twenty-third F site, F is bonded in a single-bond geometry to one Te atom. In the twenty-fourth F site, F is bonded in a single-bond geometry to one Te atom. In the twenty-fifth F site, F is bonded in a single-bond geometry to one Te atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on UHg3 by Materials Project

UHg3 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. U is bonded to twelve Hg atoms to form a mixture of face and corner-sharing UHg12 cuboctahedra. There are a spread of U–Hg bond distances ranging from 3.20–3.42 Å. There are two inequivalent Hg sites. In the first Hg site, Hg is bonded in a 4-coordinate geometry to four equivalent U atoms. In the second Hg site, Hg is bonded in a 4-coordinate geometry to four equivalent U atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Mercury Exposure is Associated with Urbanization but not Salmonella Status in White Ibis ( Eudocimus albus )

Mercury (Hg) is a ubiquitous contaminant in wetlands that can cause immunosuppression in birds, which may increase susceptibility to colonization with Salmonella spp. Previously, we found that White Ibis (Eudocimus albus), a recently urbanized wading bird, shed Salmonella spp. at a higher prevalence when captured at urban sites, compared with natural sites. In this study, we sought to determine if Hg burdens in ibis are related to Salmonella status or degree of urbanization or both. We analyzed feathers from 94 ibis in Palm Beach County, Florida, USA, along an urbanization gradient (0–68% urbanization) and from individuals with confirmed Salmonella spp. status (shedding or not shedding). We detected Hg in all ibis feathers (0.22–8.47 mg/kg; mean=1.96 mg/kg; SD=1.94). The Hg concentration was not significantly correlated to Salmonella spp. shedding status (Wilcoxon rank sum test, W=1170; P=0.596) but was negatively associated with capture site urbanization level (R 2 =0.327; P=0.026). Our findings may suggest that the immunosuppressive effects of Hg do not affect Salmonella shedding in the ibis or that Hg burdens were too low to affect Salmonella shedding status. Further, ibis that were captured in high urbanization sites appeared to have a lower risk of Hg exposure than ibis that were captured within low urbanization sites.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

Assessing Microbial Communities Related to Mercury Transformations in Contaminated Streambank Soils

In nature, the bioaccumulative potent neurotoxin methylmercury (MeHg) is produced from inorganic mercury (Hg) predominantly by anaerobic microorganisms. Hg-contaminated soils are a potential source of MeHg due to microbial activity. We examine streambank soils collected from the contaminated East Fork Poplar Creek (EFPC) in Tennessee, USA, where seasonal variations in MeHg levels have been observed throughout the year, suggesting active microbial Hg methylation. In this study, we characterized the microbial community in contaminated bank soil samples collected from two locations over a period of one year and compared the results to soil samples from an uncontaminated reference site with similar geochemistry (n = 12). Microbial community composition and diversity were assessed by 16S rRNA gene amplicon sequencing. Furthermore, to isolate potential methylators from soils, enrichment cultures were prepared using selective media. A set of three clade-specific primers targeting the gene hgcA were used to detect Hg methylators among the δ-Proteobacteria in EFPC bank soils across all seasons. Two families among the δ-Proteobacteria that have been previously associated with Hg methylation, Geobacteraceae and Syntrophobacteraceae, were found to be predominant with relative abundances of 0.13% and 4.0%, respectively. However, in soil enrichment cultures, Firmicutes were predominant among families associated with Hg methylation. Specifically, Clostridiaceae and Peptococcaceae and their genera Clostridium and Desulfosporosinus were among the ten most abundant genera with relative abundances of 2.6% and 1.7%, respectively. These results offer insights into the role of microbial communities on Hg transformation processes in contaminated bank soils in EFPC. Identifying the biogeochemical drivers of MeHg production is critical for future remediation efforts.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Metabolically diverse microorganisms mediate methylmercury formation under nitrate-reducing conditions in a dynamic hydroelectric reservoir

Brownlee Reservoir is a mercury (Hg)-impaired hydroelectric reservoir that exhibits dynamic hydrological and geochemical conditions and is located within the Hells Canyon Complex in Idaho, USA. Methylmercury (MeHg) contamination in fish is a concern in the reservoir. While MeHg production has historically been attributed to sulfate-reducing bacteria and methanogenic archaea, microorganisms carrying the hgcA gene are taxonomically and metabolically diverse and the major biogeochemical cycles driving mercury (Hg) methylation are not well understood. In this study, Hg speciation and redox-active compounds were measured throughout Brownlee Reservoir across the stratified period in four consecutive years (2016–2019) to identify the location where and redox conditions under which MeHg is produced. Metagenomic sequencing was performed on a subset of samples to characterize the microbial community with hgcA and identify possible links between biogeochemical cycles and MeHg production. Biogeochemical profiles suggested in situ water column Hg methylation was the major source of MeHg. These profiles, combined with genome-resolved metagenomics focused on hgcA-carrying microbes, indicated that MeHg production occurs in this system under nitrate- or manganese-reducing conditions, which were previously thought to preclude Hg-methylation. Using this multidisciplinary approach, we identified the cascading effects of interannual variability in hydrology on the redox status, microbial metabolic strategies, abundance and metabolic diversity of Hg methylators, and ultimately MeHg concentrations throughout the reservoir. This work expands the known conditions conducive to producing MeHg and suggests that the Hg-methylation mitigation efforts by nitrate or manganese amendment may be unsuccessful in some locations.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Incorporating concentration-dependent sediment microbial activity into methylmercury production kinetics modeling

We report in anoxic environments, anaerobic microorganisms carrying the hgcAB gene cluster can mediate the transformation of inorganic mercury (Hg(II)) to monomethylmercury (MMHg). The kinetics of Hg(II) transformation to MMHg in periphyton from East Fork Poplar Creek (EFPC) in Oak Ridge, TN have previously been modeled using a transient availability model (TAM). The TAM for Hg(II) methylation combines methylation/demethylation kinetics with kinetic expressions for processes that decrease Hg(II) and MMHg availability for methylation and demethylation (multisite sorption of Hg(II) and MMHg, Hg(II) reduction/Hg(0) oxidation). In this study, the TAM is used for the first time to describe MMHg production in sediment. We assessed MMHg production in sediment microcosms using two different sediment types from EFPC: a relatively anoxic, carbon-rich sediment with higher microbial activity (higher CO 2 production from sediment) and a relatively oxic, sandy, carbon-poor sediment with lower microbial activity (lower CO 2 production from sediment). Based on 16s rRNA sequencing, the overall microbial community structure in the two sediments was retained during the incubations. However, the hgcA containing methanogenic Euryarchaeota communities differed between sediment types and their growth followed different trajectories over the course of incubations, potentially contributing to the distinct patterns of MMHg production observed. The general TAM paradigm performed well in describing MMHg production in the sediments. However, the MMHg production and ancillary data suggested the need to revise the model structure to incorporate terms for concentration-dependent microbial activity over the course of the incubations. We modified the TAM to include Monod-type kinetics for methylation and demethylation and observed an improved fit for the carbon-rich, microbially active sediment. Overall our work shows that the TAM can be applied to describe Hg(II) methylation in sediments and that including expressions accounting for concentration-dependent microbial activity can improve the accuracy of the model description of the data in some cases.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Pectin methylesterase selectively softens the onion epidermal wall yet reduces acid-induced creep

De-esterification of homogalacturonan (HG) is thought to stiffen pectin gels and primary cell walls by increasing calcium cross-linking between HG chains. Contrary to this idea, recent studies found that HG de-esterification correlated with reduced stiffness of living tissues, measured by surface indentation. The physical basis of such apparent wall softening is unclear, but possibly involves complex biological responses to HG modification. To assess the direct physical consequences of HG de-esterification on wall mechanics without such complications, we treated isolated onion (Allium cepa) epidermal walls with pectin methylesterase (PME) and assessed wall biomechanics with indentation and tensile tests. In nanoindentation assays, PME action softened the wall (reduced the indentation modulus). In tensile force/extension assays, PME increased plasticity, but not elasticity. These softening effects are attributed, at least in part, to increased electrostatic repulsion and swelling of the wall after PME treatment. Despite softening and swelling upon HG de-esterification, PME treatment alone failed to induce cell wall creep. Instead, acid-induced creep, mediated by endogenous α-expansin, was reduced. We conclude that HG de-esterification physically softens the onion wall, yet reduces expansin-mediated wall extensibility.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1975

Water and soil biotic relations in Mercury distribution

The distribution of Hg is considered both in terms of its availability in soil fractions and the relationship between Hg in plant samples and Hg in ambient soils or other supportive media. The plants were grouped by habitat into epipedic-epiphytic (mosses, lichens) and endopedic-aquatic-marine (Basidiomycetes and algae) samples; nonvascular and vascular forms were also distinguished. Sources included Alaska, Hawaii, New England and Iceland. Brief consideration was also given to Hg distribution in a plant-animal-soil community. Data were expressed in terms of plant Hg content and plant substratum concentration ratio. Average Hg contents and concentration ratios, and modal ranges for the ratios were determined. The results showed similar average Hg contents in all groups (126 to 199 ppb) but a low value (84 ppb) in the lichens; terrestrial forms had ratios of 3.5 to 7.6 whereas the marine algae yielded a figure of 78.7. A secondary mode in the range 0 to 0.1 appeared only in the Alaska-New England Group, over 500 km distant from active thermal sites. Evidence for both exclusion and concentration behavior was obtained.

Siegel, S. M.↗
NASA NTRS1984

Hypergravity effects on litter size, nursing activity, prolactin, TSH, T3, and T4 in the rat

In a recent study of the effects of hypergravity (HG) on the reproductive system of the rat, it was found that the estrous cycle is perturbed in a pseudopregnancy-like pattern upon first exposure of animals to HG. This can be prevented by previous exposure to HG or by administration of bromergo cryptin. Adapted rats can mate and deliver in HG. However, little is known of the condition of the individual pregnant rat, fetuses, and newborn pups in this environment. There are also questions regarding the effects of HG on the number of fetuses, the mortality rate in different HG levels, and the effects on production and secretion of PRL and TSH. The present investigation is concerned with such questions, taking into account possible approaches to avoid or minimize the lethal effects of HG. The obtained results suggest that peripartum plasma PRL levels and thyroid hormone levels are critical for the survival of the litter.

Megory, E.↗
NASA NTRS2002

Neither Milk Production, Milk Transfer Nor Pup Growth Hormone Account for Reduced Body Weights of Rat Pups Reared In Hypergravity

Studies spanning the gravity continuum from 0 to 2-g are revealing new insights into how mammalian reproduction and development may proceed in the microgravity of space. Rat pups reared from either conception or midgestation in hypergravity (hg) weigh 6-15% less than 1-g controls. In the present study we analyzed maternal and pup factors that may account for reduced body weight of hg reared pups. Beginning on Gestational day (G)11 of the rats' 22 day pregnancy, rat dams and their litters were continuously exposed to either 1.5-g, 1.75-g or 2.0-g. Prolaction (Prl) and oxytocin (OT) were measured in hg-exposed dams during either pregnancy (G20) or lactation (Postnatal day [P] 10). Gravity related differences in Prl were not observed whereas OT was depressed during lactation in hg dams relative to controls (p less than 0.05). Milk transfer measured during a discrete suckling episode was actually increased in hg-reared litters and comparable numbers of milk-letdowns were observed in the two conditions. Recent reports using dwarfing phenotypes in mouse mutants have provided evidence for postnatal dependence on growth hormone (GH) and insulin-like growth factors (IGFs). Plasma GH measured in P10 pups using enzyme immunoassay (EIA) was significantly elevated in hg pups relative to 1-g controls (mean +/- sd., ng/ml: 2.0-g, 10.6 [3.0], 1.5-g 8.9 [4.0], 1.0-g, 7.95 [3.1]). Together, these findings suggest that neither milk production, milk transfer nor pup GH play significant roles in reduced body weights of hg-reared pups. Studies underway are focused on insulin-like growth factors.

Bear, L. A.↗
NASA NTRS2003

Baroreflex-mediated heart rate and vascular resistance responses 24 h after maximal exercise

INTRODUCTION: Plasma volume, heart rate (HR) variability, and stimulus-response relationships for baroreflex control of forearm vascular resistance (FVR) and HR were studied in eight healthy men after and without performing a bout of maximal exercise to test the hypotheses that acute expansion of plasma volume is associated with 1) reduction in baroreflex-mediated HR response, and 2) altered operational range for central venous pressure (CVP). METHODS: The relationship between stimulus (DeltaCVP) and vasoconstrictive reflex response (DeltaFVR) during unloading of cardiopulmonary baroreceptors was assessed with lower-body negative pressure (LBNP, 0, -5, -10, -15, -20 mm Hg). The relationship between stimulus (Deltamean arterial pressure (MAP)) and cardiac reflex response (DeltaHR) during loading of arterial baroreceptors was assessed with steady-state infusion of phenylephrine (PE) designed to increase MAP by 15 mm Hg alone and during application of LBNP (PE+LBNP) and neck pressure (PE+LBNP+NP). Measurements of vascular volume and autonomic baroreflex responses were conducted on two different test days, each separated by at least 1 wk. On one day, baroreflex response was tested 24 h after graded cycle exercise to volitional exhaustion. On another day, measurement of baroreflex response was repeated with no exercise (control). The order of exercise and control treatments was counterbalanced. RESULTS: Baseline CVP was elevated (P = 0.04) from a control value of 10.5 +/- 0.4 to 12.3 +/- 0.4 mm Hg 24 h after exercise. Average DeltaFVR/DeltaCVP during LBNP was not different (P = 0.942) between the exercise (-1.35 +/- 0.32 pru x mm Hg-1) and control (-1.32 +/- 0.36 pru x mm Hg-1) conditions. However, maximal exercise caused a shift along the reflex response relationship to a higher CVP and lower FVR. HR baroreflex response (DeltaHR/DeltaMAP) to PE+LBNP+NP was lower (P = 0.015) after maximal exercise (-0.43 +/- 0.15 beats x min-1 x mm Hg-1) compared with the control condition (-0.83 +/- 0.14 beats x min-1 x mm Hg-1). CONCLUSION: Expansion of vascular volume after acute exercise is associated with altered operational range for CVP and reduced HR response to arterial baroreceptor stimulation.

Non-NASA Center↗
NASA NTRS2004

Evaluation of a Multi-Parameter Sensor for Automated, Continuous Cell Culture Monitoring in Bioreactors

Compact and automated sensors are desired for assessing the health of cell cultures in biotechnology experiments in microgravity. Measurement of cell culture medium allows for the optirn.jzation of culture conditions on orbit to maximize cell growth and minimize unnecessary exchange of medium. While several discrete sensors exist to measure culture health, a multi-parameter sensor would simplify the experimental apparatus. One such sensor, the Paratrend 7, consists of three optical fibers for measuring pH, dissolved oxygen (p02), dissolved carbon dioxide (pC02) , and a thermocouple to measure temperature. The sensor bundle was designed for intra-arterial placement in clinical patients, and potentially can be used in NASA's Space Shuttle and International Space Station biotechnology program bioreactors. Methods: A Paratrend 7 sensor was placed at the outlet of a rotating-wall perfused vessel bioreactor system inoculated with BHK-21 (baby hamster kidney) cells. Cell culture medium (GTSF-2, composed of 40% minimum essential medium, 60% L-15 Leibovitz medium) was manually measured using a bench top blood gas analyzer (BGA, Ciba-Corning). Results: A Paratrend 7 sensor was used over a long-term (>120 day) cell culture experiment. The sensor was able to track changes in cell medium pH, p02, and pC02 due to the consumption of nutrients by the BHK-21. When compared to manually obtained BGA measurements, the sensor had good agreement for pH, p02, and pC02 with bias [and precision] of 0.02 [0.15], 1 mm Hg [18 mm Hg], and -4.0 mm Hg [8.0 mm Hg] respectively. The Paratrend oxygen sensor was recalibrated (offset) periodically due to drift. The bias for the raw (no offset or recalibration) oxygen measurements was 42 mm Hg [38 mm Hg]. The measured response (rise) time of the sensor was 20 +/- 4s for pH, 81 +/- 53s for pC02, 51 +/- 20s for p02. For long-term cell culture measurements, these response times are more than adequate. Based on these findings , the Paratrend sensor could offer automated, continuous monitoring of cell cultures with a temporal resolution of 1 minute, which is not attainable by sampling via handheld blood analyzer (i-STAT). Conclusion: The resulting bias and precision found in these cell culture-based studies is comparable to Paratrend sensor clinical results. Although the large error in p02 measurements (+/-18 mm Hg) may be acceptable for clinical applications, where Paratrend values are periodically adjusted to a BGA measurement, the O2 sensor in this bundle may not be reliable enough for the single-calibration requirement of sensors used in NASA's bioreactors. The pH and pC02 sensors in the bundle are reliable and stable over the measurement period, and can be used without recalibration to measure cell cultures in rn.jcrogravity biotechnology experiments. Future work will test additional Paratrend sensors to provide statistical assessment of sensor performance.

Pappas, D.↗
DOE OSTI2020

Materials Data on BaHg2 by Materials Project

BaHg2 is hexagonal omega structure structured and crystallizes in the orthorhombic Imma space group. The structure is three-dimensional. Ba is bonded to twelve equivalent Hg atoms to form a mixture of edge and face-sharing BaHg12 cuboctahedra. There are a spread of Ba–Hg bond distances ranging from 3.71–3.73 Å. Hg is bonded in a 9-coordinate geometry to six equivalent Ba and three equivalent Hg atoms. All Hg–Hg bond lengths are 3.02 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CaHg2 by Materials Project

CaHg2 crystallizes in the hexagonal P6/mmm space group. The structure is three-dimensional. Ca is bonded to twelve equivalent Hg atoms to form a mixture of edge and face-sharing CaHg12 cuboctahedra. All Ca–Hg bond lengths are 3.42 Å. Hg is bonded in a 9-coordinate geometry to six equivalent Ca and three equivalent Hg atoms. All Hg–Hg bond lengths are 2.90 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on DyHg2 by Materials Project

DyHg2 crystallizes in the hexagonal P6/mmm space group. The structure is three-dimensional. Dy is bonded to twelve equivalent Hg atoms to form a mixture of distorted edge and face-sharing DyHg12 cuboctahedra. All Dy–Hg bond lengths are 3.34 Å. Hg is bonded in a 9-coordinate geometry to six equivalent Dy and three equivalent Hg atoms. All Hg–Hg bond lengths are 2.86 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on ErHg2 by Materials Project

ErHg2 crystallizes in the hexagonal P6/mmm space group. The structure is three-dimensional. Er is bonded to twelve equivalent Hg atoms to form a mixture of distorted edge and face-sharing ErHg12 cuboctahedra. All Er–Hg bond lengths are 3.33 Å. Hg is bonded in a 9-coordinate geometry to six equivalent Er and three equivalent Hg atoms. All Hg–Hg bond lengths are 2.85 Å.

36 MATERIALS SCIENCE↗