250 research outputs found
Two regions of Duel STEM EDS EELS data and micrographs for Iron Biomineralization Patterns in a Denitrifying As(III)-Oxidizing Bacterium
No full textRelating to Figure 5 in paper
"Elucidating Heterogeneous Iron Biomineralization Patterns in
a Denitrifying As(III)-Oxidizing Bacterium: Implications for Arsenic
Immobilization" DOI 10.1039/d1en00905b
This is the duel STEM-EDS and EELS of Iron Biomineralization Patterns in a Denitrifying
As(III)-Oxidizing BacteriumShowing both regions of high As and low As
Taken on FEI Titan G2 ChemiSTEM running at 200kV using a 180 pA beam current. This microscope was also fitted with a SuperX EDS detector system and EELS via Gitan GIF Quantum ER EELS spectrometer in which both Duel EELS and EDS data were collected simultaneously using the Gitan Digital Micrograph softwar
NanoSIMS depth profiles of biomineralized cells of Acidovorax sp. ST3 grown under denitrifying and As(III) & Fe(II)-oxidizing conditions, using both the O- & Cs+ beams
No full textData for
Figures 3 and S6 in paper:
"Elucidating
Heterogeneous Iron Biomineralization Patterns in a Denitrifying
As(III)-Oxidizing Bacterium: Implications for Arsenic Immobilization"Single Acidovorax sp. ST3
cells (7 days incubation) were selected for depth profiling. Both Cs+
and O- were used as primary ions and the selected areas were not
implanted prior to starting the analysis (to preserve and keep the biomineral
coating on the cells intact). Image raster sizes were 3-7 µm width. Spatial resolution
was achieved by using D1=4 or 5 (beam size=120-100 nm). Pixel sizes were 128 x 128 or 256 x 256, and
dwell time varied from 5,000-20,000 µs px-1. 50-170 planes were
collected, and the scanning was stopped when the 12C14N or
56Fe+ signal disappeared.
The data was processed using the L’image
software (Larry Nittler, Carnegie Institution of Washington) and the plugin
OpenMIMS for ImageJ (www.nrims.harvard.edu).
3D reconstructions of the depth
profiles were generated using the Thermo Scientific™ Avizo™ Software 9.7.0.
Stack data of the negative secondary ions 12C-, 56Fe16O-
and 75As- , and the positive secondary ions 23Na+,
56Fe+, and 75As+, were first
extracted in ImageJ and saved as “.raw” format files, which were loaded into
Avizo™. The Z depth was compressed to 15-20 %. The 12C-
and 23Na+ signals were smoothed over 2-3 pixels. The
commands “generate surface” and “show surface” were used sequentially, and the
“transparent” display with a transparency of 80 % was selected. 56Fe+
and 56Fe16O- signals were smoothed to 2 pixels
and displayed as “shaded”. The 75As+/- ion counts were
smoothed to 1 pixel.Four depth profile files are presented, including the .im raw nanoSIMS files, extracted 75As+/-, 56Fe16O-/56Fe+, 12C/23Na counts as .raw format (ready to load into AVIZO), and complementary image and videos of the 3D reconstructions for each depth profile (jpg and mpg formats).</p
TEM images of Iron Biomineralization Patterns in a Denitrifying As(III)-Oxidizing Bacterium
No full textRelating to Figure 4 in paper"Elucidating Heterogeneous Iron Biomineralization Patterns in a Denitrifying As(III)-Oxidizing Bacterium: Implications for Arsenic Immobilization" DOI 10.1039/d1en00905bThis is TEM data of Iron Biomineralization Patterns in a Denitrifying As(III)-Oxidizing BacteriumTaken on Jeol F200 using Nanomegas system 200kV 100pATEM micrographs of planktonic ST3 samples at days 1 (A and B), 3 (C and D) and 7 (E and F). Mineralized cells can be observed from day 1, showing a thicker mineralization by day 3 and the appearance of a more crystalline structure by day 7. The red squares in (A)-(C) highlight the cell poles with heavier mineralization than the rest of the cell. (E) is a selected region with “flake-like” biominerals at higher magnification in (F). A, C & E are indicating the nanoparticles aggregated as filaments associated with the cell surface. </div
Scanning electron diffraction data and corresponding TEM data of bio-mineralization Iron Biomineralization Patterns in a Denitrifying As(III)-Oxidizing Bacterium
No full textRelating to Figure 6 in paper
"Elucidating Heterogeneous Iron Biomineralization Patterns in
a Denitrifying As(III)-Oxidizing Bacterium: Implications for Arsenic
Immobilization" DOI 10.1039/d1en00905b
This is the scanning electron diffraction and corresponding TEM data of Iron Biomineralization Patterns in a Denitrifying
As(III)-Oxidizing BacteriumShowing both regions of amorphous and lepidocrocite regions
Taken on Jeol F200 using Nanomegas system 200kV 100p
NanoSIMS files of Acidovorax sp. ST3 biofilm and biominerals obtained under denitrifying and As(III) & Fe(II)-oxidizing conditions, after 7 & 14 days of incubation, using the Cs+ beam
No full textData for Figures 1, 2 and S5 in paper:
"Elucidating
Heterogeneous Iron Biomineralization Patterns in a Denitrifying
As(III)-Oxidizing Bacterium: Implications for Arsenic Immobilization"Sample preparation:Acidovorax sp. strain ST3 cells were grown
anoxically in low phosphate medium with 13C-labelled acetate (10 mM), nitrate (10 mM), arsenite (0.5 mM) and Fe(II) (4 mM) for 7 or
14 days. Si wafers were introduced in the incubation bottles, to support surface colonization and precipitation of
biominerals. The samples were fixed with glutaraldehyde and dehydrated with
ethanol solutions, air-dried and Pt coated (10 nm). NanoSIMS analysis details:NanoSIMS analysis was
performed in a NanoSIMS 50L ion microprobe (CAMECA) using a Cs+ primary
ion beam at 16 keV. The beam current was between 0.131-1.435 pA with a spatial
resolution from 150-300 nm (D1 aperture= 4-2). The negative secondary ions detected simultaneously were: 12C, 13C, 12C14N, 28Si, 56Fe12C, 56Fe16O
and 75As. An ion-induced SE image was also obtained. The
regions of analysis (ROIs) were implanted with Cs+ ions to a
dose of 1x1017 ions cm-2 to remove the Pt
coating and reach steady state. The dwell time for image collection was between 2000-5000
µs px-1. The CAMECA mass resolving power (MRP) was >7000 using
ES=3 and AS=2. The image pixel sizes were 128 x 128 or 256 x 256. The field
of view of these nanoSIMS ions images was 30-60 µm. The data was processed using the L’image
software (Larry Nittler, Carnegie Institution of Washington) and the plugin
OpenMIMS for ImageJ (www.nrims.harvard.edu).
About the files: Three and nine nanoSIMS files are presented for days 7 and 14 of incubation, respectively. Files are presented in the .im raw nanoSIMS file format with additional complementary png images showing all the masses for each area of interest (AOI). All normalised counts and AOI details are compiled in the Excel spreadsheet.</p
NanoSIMS imaging of extracellular electron transport processes during microbial iron(III) reduction
No full textA framework for the analysis of mineral tax policy in sub-Saharan Africa
No full textGiven the dual role played by the Government as resource owner and tax collector in many sub - Saharan economies, it is important to separate"resource factor payments"from taxes through the use of different instruments. The instruments to be considered are: (1) a factor payment system that includes"ad rem"or"ad valorem"royalties. Production sharing, resource rent schemes, and fixed fees could also be used, but some form of unit payment is necessary and justified, because natural resources in the ground are inputs into the production process; (2) a cash flow and withholding tax system initially for the mineral sectors and eventually for other sectors of the economy. The cash flow tax would capture a share of the"economic rent"from each sector and be neutral across sectors; and (3) a depletion account to preserve the nations capital stock. Natural resources are part of an economy's capital stock, which will fall unless"replacement investment"is made as the resource is depleted.Economic Theory&Research,Environmental Economics&Policies,Banks&Banking Reform,Public Sector Economics&Finance,Health Economics&Finance
Dissimilatory Fe(III) reduction controls on arsenic mobilisation: a combined biogeochemical and NanoSIMS imaging approach
No full textMicrobial metabolism plays a key role in controlling the fate of toxic groundwater contaminants such as arsenic. Dissimilatory metal reduction catalysed by subsurface bacteria can facilitate the mobilisation of arsenic via the reductive dissolution of As(V)-bearing Fe(III) mineral assemblages. The mobility of liberated As(V) can then be amplified via reduction to the more soluble As(III) by As(V)-respiring bacteria. This investigation focused on the reductive dissolution of As(V) sorbed onto Fe(III)-(oxyhydr)oxide by model Fe(III)- and As(V)-reducing bacteria, to elucidate the mechanisms underpinning these processes at the single cell scale. Axenic cultures of Shewanella sp. ANA-3 wild-type cells (able to respire both Fe(III) and As(V)) were grown using 13C-labelled lactate on an arsenical Fe(III)-(oxyhydr)oxide thin film, and after colonisation, the distribution of Fe and As in the solid phase was assessed using nanoscale secondary ion mass spectrometry (NanoSIMS), complemented with aqueous geochemistry analyses. Parallel experiments were conducted using an arrA mutant, able to respire Fe(III) but not As(V). NanoSIMS imaging showed that most metabolically active cells were not in direct contact with the Fe(III) mineral. Flavins were released by both strains, suggesting that these cell-secreted electron shuttles mediated extracellular Fe(III)-(oxyhydr)oxide reduction, but did not facilitate extracellular As(V) reduction, demonstrated by the presence of flavins yet lack of As(III) in the supernatants of the arrA deletion mutant strain. 3D reconstructions of NanoSIMS depth-profiled single cells revealed that As and Fe were associated with the cell surface in the wild-type cells, whereas for the arrA mutant only Fe was associated with the biomass. These data were consistent with Shewanella sp. ANA-3 respiring As(V) in a multistep process; first the reductive dissolution of the Fe(III) mineral released As(V), and once in solution, As(V) was respired by the cells to As(III). As well as highlighting Fe(III) reduction as the primary release mechanism for arsenic, our data also identified unexpected cellular As(III) retention mechanisms that require further investigation
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