2,228 research outputs found
Fast microwave-assisted solvothermal synthesis of metal nanoparticles (Pd, Ni, Sn) supported on sulfonated MWCNTs : Pd-based bimetallic catalysts for ethanol oxidation in alkaline medium
The preparation of metal nanoparticles (Pd, Ni, Sn) supported on sulfonated multi-walled carbon
nanotubes (SF-MWCNTs) using a very rapid microwave-assisted solvothermal strategy has been
described. Electrocatalytic behaviour of the SF-MWCNT-Pd and its âmixedâ bimetallic electrocatalysts
(i.e., SF-MWCNT-PdSnmix and SF-MWCNT-PdNimix) towards ethanol oxidation in alkaline medium was
investigated. The result shows that the mixed Pd-based catalysts (obtained by simple ultrasonic-mixing
of the individual MWCNT-metal nanocomposites) gave better electrocatalytic activity than their alloy
nanoparticles (obtained by co-reduction of metal salts) or Pd alone. The SF-MWCNT platform gave better
electrocatalytic performance compared to the unsulfonated and commercial Vulcan carbons. Detailed
electrochemical studies (involving cyclic voltammetry, chronoamperometry, chronopotentiometry, and
impedance spectroscopy) prove that the electrocatalytic oxidation of ethanol at the SF-MWCNT-PdNimix
platform is more stable, occurs at lower potential, gives lower Tafel slopes, with faster charge-transfer
kinetics compared to its SF-MWCNT-PdSnmix counterpart. Also, result revealed that SF-MWCNT-PdNimix
is more tolerant to CO poisoning than the SF-MWCNT-PdSnmix. The results provide some important
insights into the electrochemical response of microwave-synthesised Pd-based bimetallic catalysts for
potential application in direct ethanol alkaline fuel cell technology.The CSIR and NRF.http://www.elsevier.com/locate/electact
Electrocatalytic oxidation of ethylene glycol at palladium-bimetallic nanocatalysts (PdSn and PdNi) supported on sulfonate-functionalised multi-walled carbon nanotubes
Electrocatalytic oxidation of ethylene glycol (EG) in alkaline medium using nano-scaled palladium-based
bimetallic catalysts (PdM, where M = Ni and Sn) supported on sulfonated multi-walled carbon nanotubes
(SF-MWCNTs) is compared. The bimetallic mixture (i.e., SF-MWCNTâPdSnmix and SF-MWCNTâPdNimix)
showed better electrocatalysis towards EG oxidation than the SF-MWCNTâPd. At the SF-MWCNTâ
PdSnmix platform, oxidation of EG occurred at lower onset and peak potentials, higher current density,
and faster kinetics (lower impedance) than at the SF-MWCNTâPdNimix platform. EG oxidation at the
SF-MWCNTâPdNimix is more stable than at the SF-MWCNTâPdSnmix. Indeed, Sn is a more favoured cocatalyst
with Pd in EG electro-oxidation.CSIR and NRFhttp://www.elsevier.com/locate/jelechemhb201
Preparation of carbon nanofibers/tubes using waste tyres pyrolysis oil and coal fly ash derived catalyst
In this study, two waste materials namely; coal ïŹy ash (CFA) and waste tyres pyrolysis oil, were successfuly utilized in the synthesis of carbon nanoïŹbers/tubes (CNF/Ts). In addition, Fe-rich CFA magnetic fraction (Mag-CFA) and ethylene gas were also used for comparison purposes. The carbons obtained from CFA were found to be anchored on the surface of the cenosphere and consisted of both CNTs and CNFs, whereas those obtained from Mag-CFA consisted of only multi-walled carbon nanotubes (MWCNTs). The study further showed that the type of carbon precursor and support material played an important role in determining the nanocarbon growth mechanism. The ïŹndings from this research have demonstrated that it is possible to utilize waste tyres pyrolysis oil vapor as a substitute for some expensive commercial carbonaceous gases.The South African Department of Science and Technology (DST) for the ïŹnancial support towards HySA Infrastructure (Grant No. HTC004X), the Council for ScientiïŹc and Industrial Research (CSIR) for providing facilities and National Research Foundation (NRF) for funding the SA-Poland collaborative project (HTC071X).http://www.tandfonline.com/loi/lesa202019-05-29hj2018Physic
Utilization of waste tyres pyrolysis oil vapour in the synthesis of zeolite templated carbons (ZTCs) for hydrogen storage application
In this study, we investigated the potential for use of waste tyre pyrolysis oil vapour as a carbon precursor in the synthesis of zeolite templated carbons (ZTC). With Zeolite 13X as the template, the ZTCs were synthesised using two methods namely: 1-step process which involved the carbonization of gaseous carbon precursor in the zeolite template (in this case, ethylene and pyrolysis oil vapour) and the 2-step synthesis method involved the impregnation of zeolite pores with furfural alcohol prior to carbonization of the gaseous carbon precursor. The replication of the zeolite 13X structural ordering was successful using both methods. The 2-step synthesized ZTCs were found to possess the highest specific surface area (3341 m2 gâ1) and also had the highest H2 storage capacity (2.5 wt.%). The study therefore confirmed an additional novel strategy for value-addition of waste tyre pyrolysis by-products.The South African Department of Science and Technology (DST) for the ïŹnancial support towards HySA Infrastructure (Grant No. EIMH01X), the Council for Sci-entiïŹc and Industrial Research (CSIR) for providing facilities and National Research Foundation (NRF) for funding the SA-Poland collaborative proj-ect (EIMH04X).http://www.tandfonline.com/loi/lesa202019-05-18hj2018Physic
Case series: convalescent plasma therapy for patients with COVID-19 and primary antibody deficiency
Patients with primary antibody deficiency are at risk for severe and in many cases for prolonged COVID-19. Convalescent plasma treatment of immunocompromised individuals could be an option especially in countries with limited access to monoclonal antibody therapies. While studies in immunocompetent COVID19 patients have demonstrated only a limited benefit, evidence for the safety, timing, and effectiveness of this treatment in antibody-deficient patients is lacking. Here, we describe 16 cases with primary antibody deficiency treated with convalescent plasma in four medical centers. In our cohort, treatment was associated with a reduction in viral load and improvement of clinical symptoms, even when applied over a week after onset of infection. There were no relevant side effects besides a short-term fever reaction in one patient. Longitudinal full-genome sequencing revealed the emergence of mutations in the viral genome, potentially conferring an antibody escape in one patient with persistent viral RNA shedding upon plasma treatment. However, he resolved the infection after a second course of plasma treatment. Thus, our data suggest a therapeutic benefit of convalescent plasma treatment in patients with primary antibody deficiency even months after infection. While it appears to be safe, PCR follow-up for SARS-CoV-2 is advisable and early re-treatment might be considered in patients with persistent viral shedding
Genomic variation in baboons from central Mozambique unveils complex evolutionary relationships with other Papio species
Background: Gorongosa National Park in Mozambique hosts a large population of baboons, numbering over 200 troops. Gorongosa baboons have been tentatively identified as part of Papio ursinus on the basis of previous limited morphological analysis and a handful of mitochondrial DNA sequences. However, a recent morphological and morphometric analysis of Gorongosa baboons pinpointed the occurrence of several traits intermediate between P. ursinus and P. cynocephalus, leaving open the possibility of past and/or ongoing gene flow in the baboon population of Gorongosa National Park. In order to investigate the evolutionary history of baboons in Gorongosa, we generated high and low coverage whole genome sequence data of Gorongosa baboons and compared it to available Papio genomes. Results: We confirmed that P. ursinus is the species closest to Gorongosa baboons. However, the Gorongosa baboon genomes share more derived alleles with P. cynocephalus than P. ursinus does, but no recent gene flow between P. ursinus and P. cynocephalus was detected when available Papio genomes were analyzed. Our results, based on the analysis of autosomal, mitochondrial and Y chromosome data, suggest complex, possibly male-biased, gene flow between Gorongosa baboons and P. cynocephalus, hinting to direct or indirect contributions from baboons belonging to the ânorthernâ Papio clade, and signal the presence of population structure within P. ursinus. Conclusions: The analysis of genome data generated from baboon samples collected in central Mozambique highlighted a complex set of evolutionary relationships with other baboons. Our results provided new insights in the population dynamics that have shaped baboon diversity
Differential branching fraction and angular analysis of the decay B0âKâ0ÎŒ+ÎŒâ
The angular distribution and differential branching fraction of the decay B 0â K â0 ÎŒ + ÎŒ â are studied using a data sample, collected by the LHCb experiment in pp collisions at sâ=7 TeV, corresponding to an integrated luminosity of 1.0 fbâ1. Several angular observables are measured in bins of the dimuon invariant mass squared, q 2. A first measurement of the zero-crossing point of the forward-backward asymmetry of the dimuon system is also presented. The zero-crossing point is measured to be q20=4.9±0.9GeV2/c4 , where the uncertainty is the sum of statistical and systematic uncertainties. The results are consistent with the Standard Model predictions
Carbon, nitrogen, and oxygen stable isotopes in modern tooth enamel: A case study from Gorongosa National Park, central Mozambique
The analyses of the stable isotope ratios of carbon (delta C-13), nitrogen (delta N-15), and oxygen (delta O-18) in animal tissues are powerful tools for reconstructing the feeding behavior of individual animals and characterizing trophic interactions in food webs. Of these biomaterials, tooth enamel is the hardest, most mineralized vertebrate tissue and therefore least likely to be affected by chemical alteration (i.e., its isotopic composition can be preserved over millions of years), making it an important and widely available archive for biologists and paleontologists. Here, we present the first combined measurements of delta C-13, delta N-15, and delta O-18 in enamel from the teeth of modern fauna (herbivores, carnivores, and omnivores) from the well-studied ecosystem of Gorongosa National Park (GNP) in central Mozambique. We use two novel methods to produce high-precision stable isotope enamel data: (i) the "oxidation-denitrification method," which permits the measurement of mineral-bound organic nitrogen in tooth enamel (delta N-15(enamel)), which until now, has not been possible due to enamel's low organic content, and (ii) the "cold trap method," which greatly reduces the sample size required for traditional measurements of inorganic delta C-13(enamel) and delta O-18(enamel) (from >= 0.5 to <= 0.1 mg), permitting analysis of small or valuable teeth and high-resolution serial sampling of enamel. The stable isotope results for GNP fauna reveal important ecological information about the trophic level, dietary niche, and resource consumption. delta N-15(enamel) values clearly differentiate trophic level (i.e., carnivore delta N-15(enamel) values are 4.0 parts per thousand higher, on average, than herbivores), delta C-13(enamel) values distinguish C-3 and/or C-4 biomass consumption, and delta O-18(enamel) values reflect local meteoric water (delta O-18(water)) in the park. Analysis of combined carbon, nitrogen, and oxygen stable isotope data permits geochemical separation of grazers, browsers, omnivores, and carnivores according to their isotopic niche, while mixed-feeding herbivores cannot be clearly distinguished from other dietary groups. These results confirm that combined C, N, and O isotope analyses of a single aliquot of tooth enamel can be used to reconstruct diet and trophic niches. Given its resistance to chemical alteration, the analysis of these three isotopes in tooth enamel has a high potential to open new avenues of research in (paleo)ecology and paleontology.info:eu-repo/semantics/publishedVersio
Observation of excited Lambda_b0 baryons
Using pp collision data corresponding to 1.0 fb-1 integrated luminosity
collected by the LHCb detector, two narrow states are observed in the
Lambda_b0pi+pi- spectrum with masses 5911.97 +- 0.12(stat) +- 0.02(syst) +-
0.66(Lambda_b0 mass) MeV/c^2 and 5919.77 +- 0.08(stat) +- 0.02(syst) +-
0.66(Lambda_b0 mass) MeV/c^2. The significances of the observations are 5.2 and
10.2 standard deviations, respectively. These states are interpreted as the
orbitally-excited Lambda_b0 baryons, Lambda_b*0(5912) and Lambda_b*0(5920).Comment: Replaced by version published in Phys. Rev. Lett, modified fit with
better mass resolution treatmen
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