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12 result(s) for "Mecheri B."
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Platinum Group Metal-Free Catalysts for Oxygen Reduction Reaction: Applications in Microbial Fuel Cells
Scientific and technological innovation is increasingly playing a role for promoting the transition towards a circular economy and sustainable development. Thanks to its dual function of harvesting energy from waste and cleaning up waste from organic pollutants, microbial fuel cells (MFCs) provide a revolutionary answer to the global environmental challenges. Yet, one key factor that limits the implementation of larger scale MFCs is the high cost and low durability of current electrode materials, owing to the use of platinum at the cathode side. To address this issue, the scientific community has devoted its research efforts for identifying innovative and low cost materials and components to assemble lab-scale MFC prototypes, fed with wastewaters of different nature. This review work summarizes the state-of the-art of developing platinum group metal-free (PGM-free) catalysts for applications at the cathode side of MFCs. We address how different catalyst families boost oxygen reduction reaction (ORR) in neutral pH, as result of an interplay between surface chemistry and morphology on the efficiency of ORR active sites. We particularly review the properties, performance, and applicability of metal-free carbon-based materials, molecular catalysts based on metal macrocycles supported on carbon nanostructures, M-N-C catalysts activated via pyrolysis, metal oxide-based catalysts, and enzyme catalysts. We finally discuss recent progress on MFC cathode design, providing a guidance for improving cathode activity and stability under MFC operating conditions.
Electrocatalysts Based on Iron Phthalocyanine and Polyindole Supported on Carbon Nanotubes for Oxygen Reduction in DMFCs
Novel electrocatalysts from iron phthalocyanine (FePc) and polyindole (PID) supported on carbon nanotubes (CNTs) have been synthesized for oxygen reduction reaction (ORR) in Direct Methanol Fuel Cell (DMFC). Two synthetic strategies have been proposed: i) preparation of PID on CNTs (PID/CNTs) through indole polymerization followed by the mechanical mixing of PID/CNTs with FePc (FePc_PID/CNTs); and ii) dispersion of polymerized PID, FePc, and CNTs in methanol and subsequent drying (FePc/PID/CNTs). The morphology of prepared catalysts was examined by SEM, and the electrochemical activity towards ORR was evaluated by cyclic voltammetry. FePc/PID/CNTs catalysts were found to have higher activity than that of FePc_PID/CNTs, due to a better dispersion of PID and FePc on carbon support, as demonstrated by SEM. Furthermore, in comparison with platinum on carbon black the prepared PID-based catalysts exhibited a stable ORR potential in both H2SO4 and H2SO4 + CH3OH solution. These new iron-based catalysts are thus promising to substitute platinum/carbon black at the cathode side of DMFC.
Functional Materials
This textbook is not simply a review of the vast body of literature of the recent years, as it holds the focus upon various aspects of application. Moreover, it selects only a few topics in favor of a solid and thorough treatment of the relevant aspects. This book comes in a good time, when a large body of academic literature has been accumulated and is waiting for a critical inspection in the light of the real demands of application. The chapters cover three important fields in the development of functional materials: energy, environment, and biomedical applications. These topics are explained and discussed from both an experimental and a theoretical perspective. Functional organic and inorganic materials are at the center of most technological breakthroughs. Therefore, the understanding of material properties is fundamental to the development of novel functionalities and applications.
Long-term trajectories of bone metabolism parameters and bone mineral density (BMD) in obese patients treated with metabolic surgery: a real-world, retrospective study
Purpose Potential negative effects of metabolic surgery on skeletal integrity remain a concern, since long-term data of different surgical approaches are poor. This study aimed to describe changes in bone metabolism in subjects with obesity undergoing both Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG). Methods A single center, retrospective, observational clinical study on real-world data was performed enrolling subjects undergoing metabolic surgery. Results 123 subjects were enrolled (males 31: females 92; ages 48.2 ± 7.9 years). All patients were evaluated until 16.9 ± 8.1 months after surgery, while a small group was evaluated up to 4.5 years. All patients were treated after surgery with calcium and vitamin D integration. Both calcium and phosphate serum levels significantly increased after metabolic surgery and remained stable during follow-up. These trends did not differ between RYGB and SG ( p  = 0.245). Ca/P ratio decreased after surgery compared to baseline ( p  < 0.001) and this decrease remained among follow-up visits. While 24-h urinary calcium remained stable across all visits, 24-h urinary phosphate showed lower levels after surgery ( p  = 0.014), also according to surgery technique. Parathyroid hormone decreased ( p  < 0.001) and both vitamin D ( p  < 0.001) and C-terminal telopeptide of type I collagen ( p  = 0.001) increased after surgery. Conclusion We demonstrated that calcium and phosphorous metabolism shows slight modification even after several years since metabolic surgery, irrespective of calcium and vitamin D supplementation. This different set point is characterized by a phosphate serum levels increase, together with a persistent bone loss, suggesting that supplementation alone may not ensure the maintenance of bone health in these patients.
Regulatory CD4+Foxp3+ T Cells Control the Severity of Anaphylaxis
Anaphylaxis is a life-threatening outcome of immediate-type hypersensitivity to allergen, consecutive to mast cell degranulation by allergen-specific IgE. Regulatory T cells (Treg) can control allergic sensitization and mast cell degranulation, yet their clinical benefit on anaphylactic symptoms is poorly documented. Here we investigated whether Treg action during the effector arm of the allergic response alleviates anaphylaxis. We used a validated model of IgE-mediated passive systemic anaphylaxis, induced by intravenous challenge with DNP-HSA in mice passively sensitized with DNP-specific IgE. Anaphylaxis was monitored by the drop in body temperature as well as plasma histamine and serum mMCP1 levels. The role of Treg was analyzed using MHC class II-deficient (Aβ(°/°)) mice, treatment with anti-CD25 or anti-CD4 mAbs and conditional ablation of Foxp3(+) Treg in DEREG mice. Therapeutic efficacy of Treg was also evaluated by transfer experiments using FoxP3-eGFP knock-in mice. Anaphylaxis did not occur in mast cell-deficient W/W(v) mutant mice and was only moderate and transient in mice deficient for histamine receptor-1. Defects in constitutive Treg, either genetic or induced by antibody or toxin treatment resulted in a more severe and/or sustained hypothermia, associated with a rise in serum mMCP1, but not histamine. Adoptive transfer of Foxp3(+) Treg from either naïve or DNP-sensitized donors similarly alleviated body temperature loss in Treg-deficient DEREG mice. Constitutive Foxp3(+) Treg can control the symptomatic phase of mast cell and IgE-dependent anaphylaxis in mice. This might open up new therapeutic avenues using constitutive rather than Ag-specific Treg for inducing tolerance in allergic patients.
The Genetic Architecture of Parkinson's Disease in the AfrAbia Population: Current State and Future Perspectives
Over 80% of genetic studies in the Parkinson’s disease (PD) field have been conducted on individuals of European descent. There is a social and scientific imperative to understand the genetic basis of PD across global populations for therapeutic development and deployment. PD etiology is impacted by genetic and environmental factors that are variable by ancestry and region, emphasising the need for worldwide programs to gather large numbers of patients to identify novel candidate genes and risk loci involved in disease. Only a handful of documented genetic assessments have investigated families with PD in AfrAbia, which comprises the member nations of the Arab League and the African Union, with very limited cohort and case-control studies reported. This review article summarises prior research on PD genetics in AfrAbia, highlighting gaps and challenges. We discuss the etiological risk spectrum in the context of historical interactions, highlighting allele frequencies, penetrance, and the clinical manifestations of known genetic variants in the AfrAbian PD patient community.
Plasmodium falciparum PfSET7: enzymatic characterization and cellular localization of a novel protein methyltransferase in sporozoite, liver and erythrocytic stage parasites
Epigenetic control via reversible histone methylation regulates transcriptional activation throughout the malaria parasite genome, controls the repression of multi-copy virulence gene families and determines sexual stage commitment. Plasmodium falciparum encodes ten predicted SET domain-containing protein methyltransferases, six of which have been shown to be refractory to knock-out in blood stage parasites. We have expressed and purified the first recombinant malaria methyltransferase in sufficient quantities to perform a full enzymatic characterization and reveal the ill-defined PfSET7 is an AdoMet-dependent histone H3 lysine methyltransferase with highest activity towards lysines 4 and 9. Steady-state kinetics of the PfSET7 enzyme are similar to previously characterized histone methyltransferase enzymes from other organisms, however, PfSET7 displays specific protein substrate preference towards nucleosomes with pre-existing histone H3 lysine 14 acetylation. Interestingly, PfSET7 localizes to distinct cytoplasmic foci adjacent to the nucleus in erythrocytic and liver stage parasites and throughout the cytoplasm in salivary gland sporozoites. Characterized recombinant PfSET7 now allows for target based inhibitor discovery. Specific PfSET7 inhibitors can aid in further investigating the biological role of this specific methyltransferase in transmission, hepatic and blood stage parasites and may ultimately lead to the development of suitable antimalarial drug candidates against this novel class of essential parasite enzymes.