Membrane‐Free Zn/MnO2 Flow Battery for Large‐Scale Energy Storage

The traditional Zn/MnO₂ battery has attracted great interest due to its low cost, high safety, high output voltage, and environmental friendliness. However, it remains a big challenge to achieve long‐term stability, mainly owing to the poor reversibility of the cathode reaction. Different from previous studies where the cathode redox reaction of MnO₂/MnOOH is in solid state with limited reversibility, here a new aqueous rechargeable Zn/MnO₂ flow battery is constructed with dissolution–precipitation reactions in both cathodes (Mn²⁺/MnO₂) and anodes (Zn²⁺/Zn), which allow mixing of anolyte and catholyte into only one electrolyte and remove the requirement for an ion selective membrane for cost reduction. Impressively, this new battery exhibits a high discharge voltage of ≈1.78 V, good rate capability (10C discharge), and excellent cycling stability (1000 cycles without decay) at the areal capacity ranging from 0.5 to 2 mAh cm^‐2. More importantly, this battery can be readily enlarged to a bench scale flow cell of 1.2 Ah with good capacity retention of 89.7% at the 500th cycle, displaying great potential for large‐scale energy storage.     

Influence of manganese exposure on cognitive function,plasma APP and Aβ levels in older men

BackgroundElevated manganese (Mn) exposure impairs cognition in adults and children, but the association between Mn and cognitive function in elderly people is unclear. Previous studies have linked Mn neurotoxicity in AD to Aβ-dependent mechanisms. However, the association between Mn and plasma APP and Aβ in the general elderly population remains unknown. This study aimed to investigate the association between Mn exposure and cognitive function, plasma APP and plasma Aβ in older adults.MethodsCognitive abilities in 375 men aged 60 and older in Guangxi, China were assessed using the Mini-Mental State Examination (MMSE) and cognitive impairment were identified using education-stratified cut-off points of MMSE scores. Urinary Mn levels and plasma APP, and Aβ levels were measured using ICP-MS and ELISA, respectively.ResultsA total of 109 (29.07 %) older men were identified as having cognitive impairment. The median urinary Mn level was 0.22 μg/g creatinine. Urinary Mn levels were negatively correlated with MMSE scores (β = −1.35, 95 % CI: −2.65 to −0.06; p = 0.041). In addition, higher concentrations of urinary manganese were associated with a greater risk of cognitive impairment (OR = 2.03, 95 % CI: 1.14–3.59; comparing the highest and lowest manganese; p = 0.025). Moreover, plasma APP levels were inversely associated with urinary Mn levels (r = −0.123, p = 0.020), and positively associated with MMSE scores (r = 0.158, p = 0.002). Surprisingly, no correlations were observed between plasma Aβ42, Aβ40, Aβ40/Aβ42, or Aβ42/Aβ40 and urinary Mn levels and MMSE scores.ConclusionThese results suggested that Mn exposure is negatively associated with older men’s cognition and plasma APP levels, but not plasma Aβ levels.     

Canopy throughfall links canopy epiphytes to terrestrial vegetation in pristine conifer forests

To what extent does epiphytic community composition in boreal forests reflect soil nutrient status? To answer this question, we investigated potential links between terrestrial plants and lichen-dominated communities in Picea glauca x engelmannii canopies in south-central British Columbia. We combined original data on vegetational composition in the ground and tree layers with published data on elemental uptake in standardized transplants of the lichen Lobaria pumonaria affixed to the lower branches of studied trees. Procrustean association metrics revealed a significant concordance between community composition among the epiphytic and terrestrial vegetation, which was stronger in Mn-enriched conifer canopy settings, and weaker within the cation-enriched dripzones of adjacent Populus trees. We also found that the NMDS1-gradient for each vegetation layer was strongly correlated with base cations (and inversely with Mn) in canopy throughfall, as well as with soil and bark pH. We conclude that elemental composition in canopy throughfall forms a functional link between terrestrial and epiphytic vegetation.     

Neuroprotective effects of ginkgetin against neuroinjury in Parkinson's disease model induced by MPTP via chelating iron

Abstract

Disruption of neuronal iron homeostasis and oxidative stress are closely related to the pathogenesis of Parkinson's disease (PD). Ginkgetin, a natural biflavonoid isolated from leaves of Ginkgo biloba L, has many known effects, including anti-inflammatory, anti-influenza virus, and anti-fungal activities, but its underlying mechanism of the neuroprotective effects in PD remains unclear. The present study utilized PD models induced by 1-methyl-4-phenylpyridinium (MPP⁺) and 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP) to explore the neuroprotective ability of ginkgetin in vivo and in vitro. Our results showed that ginkgetin could provide significant protection from MPP⁺-induced cell damage in vitro by decreasing the levels of intracellular reactive oxygen species and maintaining mitochondrial membrane potential. Meanwhile, ginkgetin dramatically inhibited cell apoptosis induced by MPP+ through the caspase-3 and Bcl2/Bax pathway. Moreover, ginkgetin significantly improved sensorimotor coordination in a mouse PD model induced by MPTP by dramatically inhibiting the decrease of tyrosine hydroxylase expression in the substantia nigra and superoxide dismutase activity in the striatum. Interestingly, ginkgetin could strongly chelate ferrous ion and thereby inhibit the increase of the intracellular labile iron pool through downregulating L-ferritin and upregulating transferrin receptor 1. These results indicate that the neuroprotective mechanism of ginkgetin against neurological injury induced by MPTP occurs via regulating iron homeostasis. Therefore, ginkgetin may provide neuroprotective therapy for PD and iron metabolism disorder related diseases.     

Bioavailability of metalloporphyrin-based SOD mimics is greatly influenced by a single charge residing on a Mn site

Abstract

In the cell Mn porphyrins (MnPs) likely couple with cellular reductants which results in a drop of total charge from 5+ to 4+ and dramatically increases their lipophilicity by up to three orders of magnitude depending upon the length of alkylpyridyl chains and type of isomer. The effects result from the interplay of solvation, lipophilicit and stericity. Impact of ascorbate on accumulation of MnPs was measured in E. coli and in Balb/C mouse tumours and muscle; for the latter measurements, the LC/ESI-MS/MS method was developed. Accumulation was significantly enhanced when MnPs were co-administered with ascorbate in both prokaryotic and eukaryotic systems. Further, MnTnHex-2-PyP⁵⁺ accumulates 5-fold more in the tumour than in a muscle. Such data increase our understanding of MnPs cellular and sub-cellular accumulation and remarkable in vivo effects. The work is in progress to understand how coupling of MnPs with ascorbate affects their mechanism of action, in particular with respect to cancer therapy.     

Adverse responses of Cabera pusaria caterpillars to high dietary manganese concentration

The adaptation of insects to environmental changes can constitute a crucial factor in their development and activity. The response of Cabera pusaria L. (Lepidoptera: Geometridae) caterpillars to high manganese (Mn) concentrations in the diet was studied. Birch leaves were treated by dipping in MnCl₂·4H₂O solutions, thereby achieving Mn contents of 370 (T0), 695 (T1), 3 198 (T2), and 6 302 mg kg⁻¹ (T3). The reactions were determined by observing caterpillar mortality, development time, food consumption, and pupal weight. Manganese concentrations in larval excrement, pupae, and food were determined. Manganese in the diet at unnaturally increased concentrations caused great stress for caterpillars. All individuals in the treatment with the highest Mn concentration (T3) died during rearing and successful pupation occurred in only four individuals in T2. Even in the case of caterpillars from T1 (twofold higher than T0) a negative reaction (increased food consumption and prolonged development) was recorded. We also determined significantly increased Mn concentration in pupae from T1 (T2 and T3 were not included in this evaluation due to mortality) and excrement (T1‒T3) compared with T0 having a natural Mn concentration. Caterpillars were seen to eliminate negatively acting dietary Mn by its translocation to excrement. However, the highest mortality rate in T2 and T3 and negative reactions of individuals in T1 very likely demonstrate energy insufficiency and the high energy requirements of Mn elimination mechanisms.     

Acetylene reduction and hydrogen metabolism by a cyanobacterial/sulfate‐reducing bacterial mat ecosystem

We report a study of nitrogenase activity (acetylene reduction) and hydrogen gas metabolism in intact smooth cyanobacterial mats from Hamelin Pool, Shark Bay, Western Australia. The predominant cyanobacterial population in these mats is Microcoleus chthonoplastes. The mats had a significant capacity for nitrogen fixation, predominantly attributable to the photosyn‐thetic component. By physical and chemical perturbation we revealed an active hydrogen metabolism within the mats. Most of the H₂ formation was attributed to fermentative processes, whereas hydrogen was consumed in light‐dependent, together with oxygen‐ and sulfate‐dependent respiratory processes. It was concluded that H₂ formed by fermentative bacteria in the dark drives a significant proportion of sulfate reduction in the mats, but there was little H₂ transfer from the cyanobacteria to the sulfate‐reducing bacteria. Thus photosynthetically produced H₂ gas is unlikely to significantly alter the previously measured carbon: sulfur ratio relating photosynthesis to sulfate reduction.     

FTIR Spectroscopic Study of Biogenic Mn-Oxide Formation by Pseudomonas putida GB-1

Biomineralization in heterogeneous aqueous systems results from a complex association between pre-existing surfaces, bacterial cells, extracellular biomacromolecules, and neoformed precipitates. Fourier transform infrared (FTIR) spectroscopy was used in several complementary sample introduction modes (attenuated total reflectance [ATR], diffuse reflectance [DRIFT], and transmission) to investigate the processes of cell adhesion, biofilm growth, and biological Mn-oxidation by Pseudomonas putida strain GB-1. Distinct differences in the adhesive properties of GB-1 were observed upon Mn oxidation. No adhesion to the ZnSe crystal surface was observed for planktonic GB-1 cells coated with biogenic MnO _x , whereas cell adhesion was extensive and a GB-1 biofilm was readily grown on ZnSe, CdTe, and Ge crystals prior to Mn-oxidation. IR peak intensity ratios reveal changes in biomolecular (carbohydrate, phosphate, and protein) composition during biologically catalyzed Mn-oxidation. In situ monitoring via ATR-FTIR of an active GB-1 biofilm and DRIFT data revealed an increase in extracellular protein (amide I and II) during Mn(II) oxidation, whereas transmission mode measurements suggest an overall increase in carbohydrate and phosphate moieties. The FTIR spectrum of biogenic Mn oxide comprises Mn-O stretching vibrations characteristic of various known Mn oxides (e.g., “acid” birnessite, romanechite, todorokite), but it is not identical to known synthetic solids, possibly because of solid-phase incorporation of biomolecular constituents. The results suggest that, when biogenic MnO _x accumulates on the surfaces of planktonic cells, adhesion of the bacteria to other negatively charged surfaces is hindered via blocking of surficial proteins.     

Reassessment of the Microbial Role in Mn-Fe Nodule Genesis in Andean Paleosols

The presence of Mn-Fe nodules in the epipedons (surface horizons) of paleosols of presumed Upper Neogene age in the northwestern Venezuelan Andes have been interpreted as products of inorganic oxidation and reduction processes operating over the full range of glacial and interglacial cycles that affected paleosol morphogenesis. New microscopic/chemical data from combined SEM-EDS-FIB analyses of representative Mn-Fe nodules indicate microbes play an important role in Mn/Fe precipitation leading to their genesis in alpine Mollisols (Argiustolls). Although the prevailing new data are based mainly on fossil forms of filamentous bacteria and fungi and other biogenic pseudomorphs that may represent the former resident bacteria, the presence of extant microbes must await field experiments/collection, followed by a molecular microbiology approach to determine the biological drivers of metal precipitation. As in other terrestrial niche environments, microbes are seen here to play a role, perhaps a key one, in the morphogenesis of paleosols of importance in upper Neogene paleoenvironmental reconstruction.