34 research outputs found
Enhanced Activated Carbon Cathode Performance for Microbial Fuel Cell by Blending Carbon Black
Activated
carbon (AC) is a useful and environmentally sustainable catalyst for
oxygen reduction in air-cathode microbial fuel cells (MFCs), but there
is great interest in improving its performance and longevity. To enhance
the performance of AC cathodes, carbon black (CB) was added into AC
at CB:AC ratios of 0, 2, 5, 10, and 15 wt % to increase electrical
conductivity and facilitate electron transfer. AC cathodes were then
evaluated in both MFCs and electrochemical cells and compared to reactors
with cathodes made with Pt. Maximum power densities of MFCs were increased
by 9–16% with CB compared to the plain AC in the first week.
The optimal CB:AC ratio was 10% based on both MFC polarization tests
and three electrode electrochemical tests. The maximum power density
of the 10% CB cathode was initially 1560 ± 40 mW/m<sup>2</sup> and decreased by only 7% after 5 months of operation compared to
a 61% decrease for the control (Pt catalyst, 570 ± 30 mW/m<sup>2</sup> after 5 months). The catalytic activities of Pt and AC (plain
or with 10% CB) were further examined in rotating disk electrode (RDE)
tests that minimized mass transfer limitations. The RDE tests showed
that the limiting current of the AC with 10% CB was improved by up
to 21% primarily due to a decrease in charge transfer resistance (25%).
These results show that blending CB in AC is a simple and effective
strategy to enhance AC cathode performance in MFCs and that further
improvement in performance could be obtained by reducing mass transfer
limitations
Successional Distance between the Source and Recipient Influence Seed Germination and Seedling Survival during Surface Soil Replacement in SW China
<div><p>Adding propagules (source) to a degraded site (recipient) is a common way of manipulating secondary succession to restore diversity and services formerly provided by forests. However, heretofore no study has considered the effect of “successional distance” between source and recipient site. Four sites in the Shilin karst area of SW China were treated as different states along a secondary successional sere: grass, shrub, young secondary forest, and primary forest. Ten 1 m ×1m soil quadrats in the grass, shrub and young forest sites were replaced with 10 cm deep soil sources from corresponding later successional stage(s) in January 2009. Woody plant seed germination was monitored in the first year and seedling survival was monitored until the end of the second year. At the end of 2010, 2097 seeds of woody plants belonging to 45 taxa had germinated, and 3.9% of the seedlings and 7.8% of the species survived. Germination of most species was sensitive to ambient light (red, far-red, R:FR ratios, photosynthetically active radiation). Soil source and recipient site had a significant effect on the total number of seeds and number of species that germinated, and on the percentage of seedlings that survived through the end of the second year. Closer successional stages between recipient site and soil source had higher seed germination and seedling-survival percentages. However, a transition threshold exists in the young forest state, where seeds can germinate but not survive the second year. Our results, although based on an unreplicated chronosequence, suggest that successional distance between soil sources and recipient sites affect forest recruitment and restoration in degraded karst of SW China.</p> </div
Photosynthetically active radiation (PAR), red radiation (R), far-red radiation (FR), and red/far-red ratio (R:FR) at recipient sites - grass, shrub and young forest - on cloudless days around noon in September 2009, December 2009 and February 2010.
<p>Photosynthetically active radiation (PAR), red radiation (R), far-red radiation (FR), and red/far-red ratio (R:FR) at recipient sites - grass, shrub and young forest - on cloudless days around noon in September 2009, December 2009 and February 2010.</p
Use of Pyrolyzed Iron Ethylenediaminetetraacetic Acid Modified Activated Carbon as Air–Cathode Catalyst in Microbial Fuel Cells
Activated carbon (AC) is a cost-effective
catalyst for the oxygen reduction reaction (ORR) in air-cathode microbial
fuel cells (MFCs). To enhance the catalytic activity of AC cathodes,
AC powders were pyrolyzed with iron ethylenediaminetetraacetic acid
(FeEDTA) at a weight ratio of FeEDTA:AC = 0.2:1. MFCs with FeEDTA
modified AC cathodes and a stainless steel mesh current collector
produced a maximum power density of 1580 ± 80 mW/m<sup>2</sup>, which was 10% higher than that of plain AC cathodes (1440 ±
60 mW/m<sup>2</sup>) and comparable to Pt cathodes (1550 ± 10
mW/m<sup>2</sup>). Further increases in the ratio of FeEDTA:AC resulted
in a decrease in performance. The durability of AC-based cathodes
was much better than Pt-catalyzed cathodes. After 4.5 months of operation,
the maximum power density of Pt cathode MFCs was 50% lower than MFCs
with the AC cathodes. Pyridinic nitrogen, quaternary nitrogen and
iron species likely contributed to the increased activity of FeEDTA
modified AC. These results show that pyrolyzing AC with FeEDTA is
a cost-effective and durable way to increase the catalytic activity
of AC
Oxygen-Reducing Biocathodes Operating with Passive Oxygen Transfer in Microbial Fuel Cells
Oxygen-reducing biocathodes previously developed for
microbial
fuel cells (MFCs) have required energy-intensive aeration of the catholyte.
To avoid the need for aeration, the ability of biocathodes to function
with passive oxygen transfer was examined here using air cathode MFCs.
Two-chamber, air cathode MFCs with biocathodes produced a maximum
power density of 554 ± 0 mW/m<sup>2</sup>, which was comparable
to that obtained with a Pt cathode (576 ± 16 mW/m<sup>2</sup>), and 38 times higher than that produced without a catalyst (14
± 3 mW/m<sup>2</sup>). The maximum current density with biocathodes
in this air-cathode MFC was 1.0 A/m<sup>2</sup>, compared to 0.49
A/m<sup>2</sup> originally produced in a two-chamber MFC with an aqueous
cathode (with cathode chamber aeration). Single-chamber, air-cathode
MFCs with the same biocathodes initially produced higher voltages
than those with Pt cathodes, but after several cycles the catalytic
activity of the biocathodes was lost. This change in cathode performance
resulted from direct exposure of the cathodes to solutions containing
high concentrations of organic matter in the single-chamber configuration.
Biocathode performance was not impaired in two-chamber designs where
the cathode was kept separated from the anode solution. These results
demonstrate that direct-air biocathodes can work very well, but only
under conditions that minimize heterotrophic growth of microorganisms
on the cathodes
Image_5_A splicing site change between exon 5 and 6 of the nuclear-encoded chloroplast-localized HvYGL8 gene results in reduced chlorophyll content and plant height in barley.jpeg
The chloroplast is an important cellular organelle and metabolic hub, which is not only responsible for plant photosynthesis but is also involved in the de novo biosynthesis of pigments, fatty acids, and hormone metabolisms. Several genes that are responsible for rice leaf color variations have been reported to be directly or indirectly involved in chlorophyll biosynthesis and chloroplast development, whereas a few genes have been functionally confirmed to be responsible for leaf color changes in barley at the molecular level. In this study, we obtained a yellow leaf and dwarf ygl8 mutant from the progeny of Morex (a variety of barley) seeds treated with EMS. We performed bulked-segregant analysis (BSA) and RNA-seq analysis and targeted a UMP kinase encoding gene, YGL8, which generated a splicing site change between exon 5 and 6 of YGL8 due to a G to A single-nucleotide transition in the 5th exon/intron junction in the ygl8 mutant. The splicing site change between exon 5 and 6 of YGL8 had no effects on chloroplast subcellular localization but resulted in an additional loop in the UMP kinase domain, which might disturb the access of the substrates. On one hand, the splicing site change between exon 5 and 6 of YGL8 downregulated the transcriptional expression of chloroplast-encoded genes and chlorophyll-biosynthesis-related genes in a temperature-dependent manner in the ygl8 mutant. On the other hand, the downregulation of bioactive GA-biosynthesis-related GA20ox genes and cell-wall-cellulose-biosynthesis-related CesA genes was also observed in the ygl8 mutant, which led to a reduction in plant height. Our study will facilitate the understanding of the regulation of leaf color and plant height in barley.</p
Image_4_A splicing site change between exon 5 and 6 of the nuclear-encoded chloroplast-localized HvYGL8 gene results in reduced chlorophyll content and plant height in barley.jpeg
The chloroplast is an important cellular organelle and metabolic hub, which is not only responsible for plant photosynthesis but is also involved in the de novo biosynthesis of pigments, fatty acids, and hormone metabolisms. Several genes that are responsible for rice leaf color variations have been reported to be directly or indirectly involved in chlorophyll biosynthesis and chloroplast development, whereas a few genes have been functionally confirmed to be responsible for leaf color changes in barley at the molecular level. In this study, we obtained a yellow leaf and dwarf ygl8 mutant from the progeny of Morex (a variety of barley) seeds treated with EMS. We performed bulked-segregant analysis (BSA) and RNA-seq analysis and targeted a UMP kinase encoding gene, YGL8, which generated a splicing site change between exon 5 and 6 of YGL8 due to a G to A single-nucleotide transition in the 5th exon/intron junction in the ygl8 mutant. The splicing site change between exon 5 and 6 of YGL8 had no effects on chloroplast subcellular localization but resulted in an additional loop in the UMP kinase domain, which might disturb the access of the substrates. On one hand, the splicing site change between exon 5 and 6 of YGL8 downregulated the transcriptional expression of chloroplast-encoded genes and chlorophyll-biosynthesis-related genes in a temperature-dependent manner in the ygl8 mutant. On the other hand, the downregulation of bioactive GA-biosynthesis-related GA20ox genes and cell-wall-cellulose-biosynthesis-related CesA genes was also observed in the ygl8 mutant, which led to a reduction in plant height. Our study will facilitate the understanding of the regulation of leaf color and plant height in barley.</p
Image_3_A splicing site change between exon 5 and 6 of the nuclear-encoded chloroplast-localized HvYGL8 gene results in reduced chlorophyll content and plant height in barley.jpeg
The chloroplast is an important cellular organelle and metabolic hub, which is not only responsible for plant photosynthesis but is also involved in the de novo biosynthesis of pigments, fatty acids, and hormone metabolisms. Several genes that are responsible for rice leaf color variations have been reported to be directly or indirectly involved in chlorophyll biosynthesis and chloroplast development, whereas a few genes have been functionally confirmed to be responsible for leaf color changes in barley at the molecular level. In this study, we obtained a yellow leaf and dwarf ygl8 mutant from the progeny of Morex (a variety of barley) seeds treated with EMS. We performed bulked-segregant analysis (BSA) and RNA-seq analysis and targeted a UMP kinase encoding gene, YGL8, which generated a splicing site change between exon 5 and 6 of YGL8 due to a G to A single-nucleotide transition in the 5th exon/intron junction in the ygl8 mutant. The splicing site change between exon 5 and 6 of YGL8 had no effects on chloroplast subcellular localization but resulted in an additional loop in the UMP kinase domain, which might disturb the access of the substrates. On one hand, the splicing site change between exon 5 and 6 of YGL8 downregulated the transcriptional expression of chloroplast-encoded genes and chlorophyll-biosynthesis-related genes in a temperature-dependent manner in the ygl8 mutant. On the other hand, the downregulation of bioactive GA-biosynthesis-related GA20ox genes and cell-wall-cellulose-biosynthesis-related CesA genes was also observed in the ygl8 mutant, which led to a reduction in plant height. Our study will facilitate the understanding of the regulation of leaf color and plant height in barley.</p
Image_2_A splicing site change between exon 5 and 6 of the nuclear-encoded chloroplast-localized HvYGL8 gene results in reduced chlorophyll content and plant height in barley.jpeg
The chloroplast is an important cellular organelle and metabolic hub, which is not only responsible for plant photosynthesis but is also involved in the de novo biosynthesis of pigments, fatty acids, and hormone metabolisms. Several genes that are responsible for rice leaf color variations have been reported to be directly or indirectly involved in chlorophyll biosynthesis and chloroplast development, whereas a few genes have been functionally confirmed to be responsible for leaf color changes in barley at the molecular level. In this study, we obtained a yellow leaf and dwarf ygl8 mutant from the progeny of Morex (a variety of barley) seeds treated with EMS. We performed bulked-segregant analysis (BSA) and RNA-seq analysis and targeted a UMP kinase encoding gene, YGL8, which generated a splicing site change between exon 5 and 6 of YGL8 due to a G to A single-nucleotide transition in the 5th exon/intron junction in the ygl8 mutant. The splicing site change between exon 5 and 6 of YGL8 had no effects on chloroplast subcellular localization but resulted in an additional loop in the UMP kinase domain, which might disturb the access of the substrates. On one hand, the splicing site change between exon 5 and 6 of YGL8 downregulated the transcriptional expression of chloroplast-encoded genes and chlorophyll-biosynthesis-related genes in a temperature-dependent manner in the ygl8 mutant. On the other hand, the downregulation of bioactive GA-biosynthesis-related GA20ox genes and cell-wall-cellulose-biosynthesis-related CesA genes was also observed in the ygl8 mutant, which led to a reduction in plant height. Our study will facilitate the understanding of the regulation of leaf color and plant height in barley.</p
(a) Cumulative number of species (mean ± SE) per m<sup>2</sup> and (b) number of seeds (mean ± SE) per m<sup>2</sup> germinated from different recipient sites, and (c) cumulative number of species (mean ± SE) per m<sup>2</sup> and (d) number of seeds (mean ± SE) per m<sup>2</sup> germinated from different soil sources at different months after soil (10 cm depth of 1 m ×1m sample) of earlier successional stages were replaced by soil from later successional stages.
<p>Grass, shrub, secondary forest and primary forest were treated as different states along a successional sere.</p