22 research outputs found
Effect of chemically modified Vulcan XC-72R on the performance of air-breathing cathode in a single-chamber microbial fuel cell
The catalytic activity of modified carbon powder (VulcanXC-72R) for oxygen reduction reaction (ORR) in an air-breathingcathode of amicrobialfuelcell (MFC) has been investigated. Chemical modification was carried out by using various chemicals, namely 5% nitric acid, 0.2 N phosphoric acid, 0.2 N potassium hydroxide and 10% hydrogen peroxide. Electrochemical study was performed for ORR of these modified carbon materials in the buffer solution pH range of 6–7.5 in the anodic compartment. Although, these treatments influenced the surface properties of the carbon material, as evident from the SEM-EDX analysis, treatment with H2PO4, KOH, and H2O2 did not show significant activity during the electrochemical test. The HNO3 treated Vulcan demonstrated significant ORR activity and when used in the single-chamber MFC cathode, current densities (1115 mA/m2, at 5.6 mV) greater than those for a Pt-supported un-treated carbon cathode were achieved. However, the power density for the latter was higher. Such chemicallymodified carbon material can be a cheaper alternative for expensive platinum catalyst used in MFC cathode construction
Nitric acid activation of graphite granules to increase the performance of the non-catalyzed oxygen reduction reaction (ORR) for MFC applications
Nitric acid and thermal activation of graphite granules were explored to increase the electrocatalytic performance of dissolved oxygen reduction at neutral pH for microbial fuel cell (MFC) applications. Electrochemical experiments showed an improvement of +400 mV in open circuit potential for graphite granules when they were activated. The improvement of ORR performance observed with activated granules was correlated to the increase of Brunauer–Emmett–Teller (BET) surface of the activated material and the emergence of nitrogen superficial groups revealed by X-ray photoelectron spectroscopy (XPS) analysis on its surface. The use of activated graphite granules in the cathodic compartment of a dual-chamber MFC led to a high open circuit voltage of 1050 mV, which is among one of the highest reported so far. The stable performance of this cathode material (current density of 96 A m−3 at +200 mV/Ag–AgCl) over a period of 10 days demonstrated its applicability as a cathode material without any costly noble metal
Competition between Allowed and First-Forbidden β Decay: The Case of Hg 208 → Tl 208
6 pags., 4 figs., 1 tab.The β decay of Hg208 into the one-proton hole, one neutron-particle Tl81208127 nucleus was investigated at CERN-ISOLDE. Shell-model calculations describe well the level scheme deduced, validating the proton-neutron interactions used, with implications for the whole of the N>126, Z<82 quadrant of neutron-rich nuclei. While both negative and positive parity states with spin 0 and 1 are expected within the Qβ window, only three negative parity states are populated directly in the β decay. The data provide a unique test of the competition between allowed Gamow-Teller and Fermi, and first-forbidden β decays, essential for the understanding of the nucleosynthesis of heavy nuclei in the rapid neutron capture process. Furthermore, the observation of the parity changing 0+→0-β decay where the daughter state is core excited is unique, and can provide information on mesonic corrections of effective operators.This work was supported by the European Union
under Contracts No. 262010 (ENSAR) and No. 654002
(ENSAR2), the Science and Technology Facilities
Council (UK), the German BMBF under Contract
No. 05P18PKCIA and “Verbundprojekt 05P2018,” the
MINECO Projects No. FPA2015-65035-P, No. RTI2018-
098868-B-I00, No. FPA2015-64969-P, and No. FPA2017-
87568-P (Spain), FWO-Vlaanderen (Belgium), GOA/
2015/010 (BOF KU Leuven), the Excellence of Science
programme (EOS-FWO), the Interuniversity Attraction
Poles Programme initiated by the Belgian Science Policy
Office (BriX network P7/12), the Romanian IFA project
CERN-RO/ISOLDE and the Polish National Science
Centre under Contracts No. UMO-2015/18/M/ST2/00523
and No. UMO-2019/33/N/ST2/03023. P. H. R. and
S. M. J. acknowledge support from the UK Department
for Business, Energy and Industrial Strategy via the
National Measurement Office. Zs. P. acknowledges support
from the ExtreMe Matter Institute EMMI at the GSI
Helmholtzzentrum fr Schwerionenforschung, Darmstadt,
Germa
Investigation of the Δn = 0 selection rule in Gamow-Teller transitions : The β-decay of 207 Hg
Gamow-Teller β decay is forbidden if the number of nodes in the radial wave functions of the initial and final states is different. This Δn=0 requirement plays a major role in the β decay of heavy neutron-rich nuclei, affecting the nucleosynthesis through the increased half-lives of nuclei on the astrophysical r-process pathway below both Z=50 (for N>82) and Z=82 (for N>126). The level of forbiddenness of the Δn=1ν1g 9/2 →π0g 7/2 transition has been investigated from the β − decay of the ground state of 207 Hg into the single-proton-hole nucleus 207 Tl in an experiment at the ISOLDE Decay Station. From statistical observational limits on possible γ-ray transitions depopulating the π0g 7/2 −1 state in 207 Tl, an upper limit of 3.9×10 −3 % was obtained for the probability of this decay, corresponding to logft>8.8 within a 95% confidence limit. This is the most stringent test of the Δn=0 selection rule to date
Maternal α‐linolenic acid availability during gestation and lactation alters the postnatal hippocampal development in the mouse offspring
The availability of ω-3 polyunsaturated fatty acids is essential for perinatal brain development. While the roles of docosahexaenoic acid (the most abundant ω-3 species) were extensively described, less is known about the role of α-linolenic acid (ALA), which is the initial molecular species undergoing elongation and desaturation within the ω-3 pathways. This study describes the association between maternal ALA availability during gestation and lactation, and alterations in hippocampal development (dentate gyrus) in the mouse male offspring, at the end of lactation (postnatal day 19, P19). Postnatal ALA supplementation increased cell proliferation (36% more proliferating cells compared to a control group) and early neuronal differentiation, while postnatal ALA deficiency increased cellular apoptosis within the dentate gyrus of suckling pups (61% more apoptotic cells compared to a control group). However, maternal ALA deficiency during gestation prevented the increased neurogenesis induced by postnatal supplementation. Fatty acid analysis revealed that ALA supplementation increased the concentration of the ω-3 species in the maternal liver and serum, but not in the brain of the offspring, excepting for ALA itself. Interestingly, ALA supplementation also increased the concentration of dihomo γ-linolenic acid (a ω-6 species) in the P19 brains, but not in maternal livers or serum. In conclusion, postnatal ALA supplementation enhances neurogenesis in the dentate gyrus of the offspring at postnatal day 19, but its beneficial effects are offset by maternal ALA deficiency during gestation. These results suggest that ALA is required in both fetal and postnatal stages of brain development
-ray spectroscopy of the neutron-rich nuclei Rb, Y, and Y with multinucleon transfer reactions
The positive-parity yrast states in the ^{89}Rb, ^{92}Y, and ^{93}Y nuclei were studied using -ray spectroscopy with heavy-ion induced reactions. In the multinucleon transfer reactions ^{208}Pb+^{90}Zr (590 MeV) and ^{238}U+^{82}Se (505 MeV), several -ray transitions were identified in these nuclei by means of coincidences between recoiling ions identified with the PRISMA spectrometer and rays detected with the CLARA -ray array in thin target experiments. Level schemes were subsequently determined from triple- coincidences recorded with the GASP array in a thick target experiment, in the reactions produced by a 470 MeV ^{82}Se beam with a ^{192}Os target. The observed level schemes are compared to shell-model calculations
High-resolution spectroscopy of neutron-rich Br isotopes and signatures for a prolate-to-oblate shape transition at N=56
International audienceThe first systematic experimental study of the neutron-rich Br isotopes with two complementary state-of-the-art techniques is presented. These isotopes have been populated in the fission process at two different facilities, GANIL and ILL. New spectroscopic information has been obtained for odd-even Br isotopes and the experimental results have been compared with state-of-the-art Large-Scale Shell-Model and DNO Shell-Model calculations. As a result of such theoretical approaches, a transition from prolate (Br) to oblate (Br) shapes is obtained from the subtle balance between proton and neutron quadrupole deformations, as a clear signature of pseudo-SU3 quadrupole regime
Shape Coexistence at Zero Spin in 64Ni driven by the Monopole Tensor Interaction
info:eu-repo/semantics/publishe
Shape Coexistence at Zero Spin in Driven by the Monopole Tensor Interaction
International audienceThe low-spin structure of the semimagic Ni64 nucleus has been considerably expanded: combining four experiments, several 0+ and 2+ excited states were identified below 4.5 MeV, and their properties established. The Monte Carlo shell model accounts for the results and unveils an unexpectedly complex landscape of coexisting shapes: a prolate 0+ excitation is located at a surprisingly high energy (3463 keV), with a collective 2+ state 286 keV above it, the first such observation in Ni isotopes. The evolution in excitation energy of the prolate minimum across the neutron N=40 subshell gap highlights the impact of the monopole interaction and its variation in strength with N