Induced Defects in Carbonaceous Materials for Hydrogen Storage

The induced defects in carbonaceous materials for hydrogen storage were studied. The effect of exfoliation was studied and the graphite nanofibers (GNF) diameter before and after exfoliation was quantified. Thermal decomposition of the GNF before and after sulfuric/nitric acid exfoliation indicated a clear loss of thermal stability. GNF exfoliation enhanced the hydrogen uptake by a factor of five compared to the untreated GNF. The amorphous carbon was reactive than GNF, and decomposed before the GNF. The higher pretreatment temperature was intended to preferentially remove amorphous carbon leaving a higher purity of exfoliated GNF

Caspase‐8 variant G regulates rheumatoid arthritis fibroblast‐like synoviocyte aggressive behavior

Objective: Fibroblast-like synoviocytes (FLS) play a pivotal role in rheumatoid arthritis (RA) by contributing to synovial inflammation and progressive joint damage. An imprinted epigenetic state is associated with the FLS aggressive phenotype. We identified CASP8 (encoding for caspase-8) as a differentially marked gene and evaluated its pathogenic role in RA FLSs. Methods: RA FLS lines were obtained from synovial tissues at arthroplasty and used at passage 5-8. Caspase-8 was silenced using small interfering RNA, and its effect was determined in cell adhesion, migration and invasion assays. Quantitative reverse transcription PCR and western blot were used to assess gene and protein expression, respectively. A caspase-8 selective inhibitor was used determine the role of enzymatic activity on FLS migration and invasion. Caspase-8 isoform transcripts and epigenetic marks in FLSs were analyzed in FLS public databases. Crystal structures of caspase-8B and G were determined. Results: Caspase-8 deficiency in RA FLSs reduced cell adhesion, migration, and invasion independent of its catalytic activity. Epigenetic and transcriptomic analyses of RA FLSs revealed that a specific caspase-8 isoform, variant G, is the dominant isoform expressed (~80% of total caspase-8) and induced by PDGF. The crystal structures of caspase-8 variant G and B were identical except for a unique unstructured 59 amino acid N-terminal domain in variant G. Selective knockdown of caspase-8G was solely responsible for the effects of caspase-8 on calpain activity and cell invasion in FLS. Conclusion: Blocking caspase-8 variant G could decrease cell invasion in diseases like RA without the potential deleterious effects of nonspecific caspase-8 inhibition

Delineating the GRIN1 phenotypic spectrum: a distinct genetic NMDA receptor encephalopathy

Objective:To determine the phenotypic spectrum caused by mutations in GRIN1 encoding the NMDA receptor subunit GluN1 and to investigate their underlying functional pathophysiology.Methods:We collected molecular and clinical data from several diagnostic and research cohorts. Functional consequences of GRIN1 mutations were investigated in Xenopus laevis oocytes.Results:We identified heterozygous de novo GRIN1 mutations in 14 individuals and reviewed the phenotypes of all 9 previously reported patients. These 23 individuals presented with a distinct phenotype of profound developmental delay, severe intellectual disability with absent speech, muscular hypotonia, hyperkinetic movement disorder, oculogyric crises, cortical blindness, generalized cerebral atrophy, and epilepsy. Mutations cluster within transmembrane segments and result in loss of channel function of varying severity with a dominant-negative effect. In addition, we describe 2 homozygous GRIN1 mutations (1 missense, 1 truncation), each segregating with severe neurodevelopmental phenotypes in consanguineous families.Conclusions:De novo GRIN1 mutations are associated with severe intellectual disability with cortical visual impairment as well as oculomotor and movement disorders being discriminating phenotypic features. Loss of NMDA receptor function appears to be the underlying disease mechanism. The identification of both heterozygous and homozygous mutations blurs the borders of dominant and recessive inheritance of GRIN1-associated disorders.Johannes R. Lemke (32EP30_136042/1) and Peter De Jonghe (G.A.136.11.N and FWO/ESF-ECRP) received financial support within the EuroEPINOMICS-RES network (www.euroepinomics.org) within the Eurocores framework of the European Science Foundation (ESF). Saskia Biskup and Henrike Heyne received financial support from the German Federal Ministry for Education and Research (BMBF IonNeurONet: 01 GM1105A and FKZ: 01EO1501). Katia Hardies is a PhD fellow of the Institute for Science and Technology (IWT) Flanders. Ingo Helbig was supported by intramural funds of the University of Kiel, by a grant from the German Research Foundation (HE5415/3-1) within the EuroEPINOMICS framework of the European Science Foundation, and additional grants of the German Research Foundation (DFG, HE5415/5-1, HE 5415/6-1), German Ministry for Education and Research (01DH12033, MAR 10/012), and grant by the German chapter of the International League against Epilepsy (DGfE). The project also received infrastructural support through the Institute of Clinical Molecular Biology in Kiel, supported in part by DFG Cluster of Excellence "Inflammation at Interfaces" and "Future Ocean." The project was also supported by the popgen 2.0 network (P2N) through a grant from the German Ministry for Education and Research (01EY1103) and by the International Coordination Action (ICA) grant G0E8614N. Christel Depienne, Caroline Nava, and Delphine Heron received financial support for exome analyses by the Centre National de Genotypage (CNG, Evry, France)

Mechanically Milled Coal and Magnesium Composites for Hydrogen Storage

Anthracite-magnesium composites were prepared via reactive ball milling in cyclohexene, leading to up to ∼0.6% hydrogen evolution at atmospheric pressure and temperatures up to 1273 K. Hydrogen evolution, measured with temperature programmed desorption coupled with mass spectroscopy (TPD-MS), is attributed to dehydrogenation of cyclohexene within the mill. The similarity of the TPD-MS to other reports for carbon-based samples is discussed. No metal hydrides were detected in XRD of the as-milled materials. The hydrogen evolution occurred at lower temperatures (up to 150 K less) than that expected for magnesium or added metals. The intensity and temperature of only one TPD-MS peak (occurring at 780-840 K) was dependent upon Mg addition. Subsequent hydrogen uptake studies after extended degassing of the milled material suggested the hydrogen uptake was reversible and the structures were not fully saturated by milling, with a rapid uptake of 0.3-0.54% at room temperature and atmospheric pressure

Exfoliated Graphite Nanofibers for Hydrogen Storage

Exfoliation of graphite nanofibers (GNF) expands the interplanar spacing of the GNF, which leads to increased hydrogen storage. Hydrogen uptake measurements at 20 bar indicated that the overall hydrogen uptake and operative adsorption temperature are sensitive to the structural variations and graphitic spacing. The increased surface area of the EGNF-1000 led to a 1.2% hydrogen uptake at 77 K and 20 bar, a three-fold increase in hydrogen physisorption of the starting material. These results suggested that selective exfoliation of a nanofiber is a means by which to control the relative binding energy of the hydrogen interaction with the carbon structure and thus vary the operative adsorption temperature. This is an abstract of a paper presented at the ACS Fuel Chemistry Meeting (Washington, DC Fall 2005)

Effect of Expanded Graphite Lattice in Exfoliated Graphite Nanofibers on Hydrogen Storage

A graphite exfoliation technique, using intercalation of a concentrated sulfuric/nitric acid mixture followed by a thermal shock, has successfully exfoliated a herringbone graphite nanofiber (GNF). The exfoliated GNF retains the overall nanosized dimensions of the original GNF, with the exfoliation temperature determining the degree of induced defects, lattice expansion, and resulting microstructure. High-resolution transmission electron microscopy indicated that the fibers treated at an intermediate temperature of 700 °C for 2 min had dislocations in the graphitic structure and a 4% increase in graphitic lattice spacing to 3.5 Å. The fibers treated at 1000 °C for 36 h were expanded along the fiber axis, with regular intervals of graphitic and amorphous regions ranging from 0.5 to \u3e 50 nm in width. The surface area of the starting material was increased from 47 m 2/g to 67 m2/g for the 700-°C treatment and to 555 m 2/g for the 1000-°C treatment. Hydrogen uptake measurements at 20 bar indicate that the overall hydrogen uptake and operative adsorption temperature are sensitive to the structural variations and graphitic spacing. The increased surface area after the 1000-°C treatment led to a 1.2% hydrogen uptake at 77 K and 20 bar, a 3-fold increase in hydrogen physisorption of the starting material. The uptake of the 700-°C-treated material had a 0.29% uptake at 300 K and 20 bar; although low, this was a 14-fold uptake over the starting material and higher than other commonly used pretreatment methods that were tested in parallel. These results suggest that selective exfoliation of a nanofiber is a means by which to control the relative binding energy of the hydrogen interaction with the carbon structure and thus vary the operative adsorption temperature

Exfoliated Graphite Nanofibers: Structure, Adsorption, and Electric Double-layer Capacitance

Herringbone graphite nanofibers (GNF) provide an interesting candidate for carbon exfoliation, with their slit-pore geometry, nano-scale dimensions, high aspect ratio, and graphitic layers that terminate along the fiber axis. Well-established graphite exfoliation techniques of acid intercalation followed by thermal treatment were applied to herringbone GNF, and the resulting fibers were characterized by HRTEM, XRD, EELS, EDS, TPO, gas adsorption, and cyclic voltammetry. Variations in thermal treatment led to drastic variations in the resulting fiber structure: A mild thermal treatment led to dislocations within the graphitic lattice and a 5% lattice expansion, whereas an extended thermal treatment led to an estimated 20-fold expansion and a ten-fold increase in surface area. The latter fiber had a unique structure with repeating interior amorphous carbon mesopores sandwiched between graphitic regions from the original herringbone morphology. The increased surface area of the exfoliated GNF correlated with increased low temperature hydrogen physisorption, whereas the observed dislocations in the graphitic structure correlated with ambient temperature hydrogen adsorption. Mild oxidation of the exfoliated GNF allowed access to the interior mesopores and led to an increased electrical double layer capacitance. These results suggest that selective exfoliation of a nanocarbon is a means to induce interior mesorpores with a controlled pore size distribution which in turn will control the relative adsorption binding energy and the accessibility of mesopores for electrical double layer capacitors. Work to control the interior pore size to provide optimal lattice spacing for a given application will be discussed

The Effect of Calcination on Reactive Milling of Anthracite as Potential Precursor for Graphite Production

The effect of a pretreatment using reactive ball milling and calcination on the graphitizability of an anthracite coal is explored. A thermal anneal of Buck Mountain anthracite at 1400 °C in argon increased the Lc crystallite dimension (from 12 to 20 Å) and led to an increase in the oxidation temperature of the product. Ball milling of the coal reduced particle size with a nominal effect on carbon order and the degree of graphitization after the 1400 °C thermal anneal (Lc from 18 to 29 Å). Ball milling in cyclohexene led to a substantial increase in the graphitizability at 1400 °C (Lc from 12 to 50Å). The enhanced reactivity was due to both carbon structure and introduced metal. The products of the mechano-chemical pretreatment and thermal anneal consisted of nanographene ribbons and multi-walled nanopolyhedral particles. It oxidized at moderate temperatures and had a high (74.3%) degree of graphitization based on X-ray diffraction analysis; the derived material has potential as filler for production of graphite