Indirect Band Gap in Scrolled MoS₂ Monolayers

MoS2 nanoscrolls that have inner core radii of similar to 250 nm are generated from MoS2 monolayers, and the optical and transport band gaps of the nanoscrolls are investigated. Photoluminescence spectroscopy reveals that a MoS2 monolayer, originally a direct gap semiconductor (similar to 1.85 eV (optical)), changes into an indirect gap semiconductor (similar to 1.6 eV) upon scrolling. The size of the indirect gap for the MoS2 nanoscroll is larger than that of a MoS2 bilayer (similar to 1.54 eV), implying a weaker interlayer interaction between concentric layers of the MoS2 nanoscroll compared to Bernal-stacked MoS2 few-layers. Transport measurements on MoS2 nanoscrolls incorporated into ambipolar ionic-liquid-gated transistors yielded a band gap of similar to 1.9 eV. The difference between the transport and optical gaps indicates an exciton binding energy of 0.3 eV for the MoS2 nanoscrolls. The rolling up of 2D atomic layers into nanoscrolls introduces a new type of quasi-1D nanostructure and provides another way to modify the band gap of 2D materials.11Nsciescopu

Les déterminants des performances scolaires des élèves marocains

Le Maroc fait partie des pays en développement dont le niveau des acquis des élèves reste relativement faible. En dépit des efforts engagés en vue d’améliorer en partie la qualité des apprentissages, les résultats des enquêtes internationales et nationales révèlent de faibles niveaux des acquis. Dès lors, l’objectif de cet article est de revenir sur les facteurs qui influencent les performances scolaires des élèves. Nous nous intéressons plus spécifiquement aux déterminants microéconomiques de la qualité de l’éducation à travers les performances des élèves. Les études sur les déterminants des performances scolaires sont riches d’enseignement. Les premières contributions se sont focalisées sur le rôle de l’environnement familial dans l’explication de la réussite des élèves (Coleman, 1966, par exemple). D’autres, plus récemment, ont abordé les facteurs liés à l’établissement scolaire. Pour autant, les contributions récentes mettent en avant l’importance à la fois de l’environnement familial et de l’école (Hanushek, 2003). Des travaux plus récents oulignent également l’influence des pairs sur les performances scolaires. Le présent travail s’inscrit dans cette logique. Son originalité se situe à un double niveau. La première réside dans la mise en évidence de l’ensemble des facteurs explicatifs des performances des élèves et des inégalités scolaires. Malgré l’existence d’une littérature abondante sur le sujet, cette question n’a pas été abordée, à notre connaissance, dans le cas marocain. La seconde cherche à corriger les problèmes d’endogénéité dans les modèles multiniveaux. Enfin, La technique d’imputation adoptée permet de traiter de façon pertinente les valeurs manquantes dans les bases de données. Cet article est structuré en trois parties. La première aborde la littérature empirique sur les déterminants de la réussite scolaire des élèves. La deuxième partie examine le modèle utilisé et décrit la base de données du Programme national d’évaluation des acquis (PNEA). Elle examine l’approche et la méthodologie utilisée. Enfin, la troisième partie traite des résultats obtenus et nous permet de formuler les principaux enseignements pouvant être tirés de nos résultats en matière de politiques publiques

Enzyme engineering of bovine trypsin

Bovine trypsin is a biocatalyst widely used to cleave recombinant proteins during the downstream processing of therapeutic proteins, and is used particularly for insulin bioprocessing. Evolution has produced a wealth of natural biocatalysts over billions of years, which are generally not optimised for specific industrial applications. Bovine trypsin has a relatively broad specificity towards cleavage at the C-terminal end of arginine or lysine residues. Consequently it has a tendency to cleave alternative sites in the insulin process leading to loss of yield and more complex downstream processing. This project describes efforts to alter the primary specificity of bovine trypsin. Trypsin variants were generated using two traditional random mutagenesis methods tailored to improve the chance of producing a useful mutant. These were focussed error prone PCR (fepPCR) and multiple-site saturation mutagenesis (MSSM). In order to select residues useful for MSSM, a study of the correlation between (1) mutations enhancing specificity or activity and (2) sequence entropy and distance of mutations from the active site was carried out based on past examples of directed and rational evolution. This analysis along with biochemical information for trypsin aided the selection of two specificity "hotspots" for random mutagenesis, each comprising four residues. These hotspots were regions in the trypsin gene close to or directly involved in substrate binding. Depending on the mutagenesis method used, the size of the mutant libraries differed considerably. For example, fepPCR of a 522 bp region of the trypsin gene required approximately 3,000 mutants to encompass all possibilities whereas the library size for MSSM was 160,000 for each of the selected four-residue regions. Two alternative library screening approaches, with different throughput capabilities, were tested to isolate mutants of interest. Automated colony screening was considered suitable for the smaller fepPCR library and consisted of the following steps: (1) transformation of a plasmid library into E. coli BL21-Gold(DE3) cells (2) fermentation of individual colonies in 384 square-well microplates (3) lysis of the cultures and (4) spectrophotometric activity measurement on a variety of substrates. The best mutant had a 2.54-fold improvement in arginine specificity. For the larger MSSM libraries, a nutritional selection method was developed using E. coli arg-auxotrophic strains. An alternative approach to generating trypsin variants was also explored based on the known ability of bovine trypsin to autolyse into "pseudo-trypsins". Since these pseudo-trypsins are variants of the native form of the enzyme, it was anticipated that they would have specificities different to that of the native enzyme. Efforts were made to separate the variants via novel chromatographic techniques and to characterise them with respect to molecular weight and specificity. Finally, the activity profile of bovine trypsin was comprehensively carried out on a range of novel substrates, and a comparison made between commercially available bovine trypsin and Eli Lilly's recombinant trypsin. Similar reaction profiles were returned by both enzymes on all substrates with the previously unreported finding that there was a preference for cleavage at the C-terminal end of two positively charged basic residues (i.e. KR or RR rather than GR)

25th annual computational neuroscience meeting: CNS-2016

The same neuron may play different functional roles in the neural circuits to which it belongs. For example, neurons in the Tritonia pedal ganglia may participate in variable phases of the swim motor rhythms [1]. While such neuronal functional variability is likely to play a major role the delivery of the functionality of neural systems, it is difficult to study it in most nervous systems. We work on the pyloric rhythm network of the crustacean stomatogastric ganglion (STG) [2]. Typically network models of the STG treat neurons of the same functional type as a single model neuron (e.g. PD neurons), assuming the same conductance parameters for these neurons and implying their synchronous firing [3, 4]. However, simultaneous recording of PD neurons shows differences between the timings of spikes of these neurons. This may indicate functional variability of these neurons. Here we modelled separately the two PD neurons of the STG in a multi-neuron model of the pyloric network. Our neuron models comply with known correlations between conductance parameters of ionic currents. Our results reproduce the experimental finding of increasing spike time distance between spikes originating from the two model PD neurons during their synchronised burst phase. The PD neuron with the larger calcium conductance generates its spikes before the other PD neuron. Larger potassium conductance values in the follower neuron imply longer delays between spikes, see Fig. 17.Neuromodulators change the conductance parameters of neurons and maintain the ratios of these parameters [5]. Our results show that such changes may shift the individual contribution of two PD neurons to the PD-phase of the pyloric rhythm altering their functionality within this rhythm. Our work paves the way towards an accessible experimental and computational framework for the analysis of the mechanisms and impact of functional variability of neurons within the neural circuits to which they belong

Modelling human choices: MADeM and decision‑making

Research supported by FAPESP 2015/50122-0 and DFG-GRTK 1740/2. RP and AR are also part of the Research, Innovation and Dissemination Center for Neuromathematics FAPESP grant (2013/07699-0). RP is supported by a FAPESP scholarship (2013/25667-8). ACR is partially supported by a CNPq fellowship (grant 306251/2014-0)

Endothelial to Mesenchymal Transition Represents a Key Link in the Interaction between Inflammation and Endothelial Dysfunction

Endothelial cells that line the inner walls of blood vessels are in direct contact with blood and display remarkable heterogeneity in their response to exogenous stimuli. These ECs have unique location-dependent properties determined by the corresponding vascular beds and play an important role in regulating the homeostasis of the vascular system. Evidence suggests that vascular endothelial cells exposed to various environments undergo dynamic phenotypic switching, a key biological program in the context of endothelial heterogeneity, but that might result in EC dysfunction and, in turn, cause a variety of human diseases. Emerging studies show the importance of endothelial to mesenchymal transition (EndMT) in endothelial dysfunction during inflammation. EndMT is a complex biological process in which ECs lose their endothelial characteristics, acquire mesenchymal phenotypes, and express mesenchymal cell markers, such as alpha smooth muscle actin and fibroblast-specific protein 1. EndMT is induced by inflammatory responses, leading to pathological states, including tissue fibrosis, pulmonary arterial hypertension, and atherosclerosis, via dysfunction of the vascular system. Although the mechanisms associated with inflammation-induced EndMT have been identified, unraveling the specific role of this phenotypic switching in vascular dysfunction remains a challenge. Here, we review the current understanding on the interactions between inflammatory processes, EndMT, and endothelial dysfunction, with a focus on the mechanisms that regulate essential signaling pathways. Identification of such mechanisms will guide future research and could provide novel therapeutic targets for the treatment of vascular diseases

Stability of Composite Cathode Consisting of Doped Bismuth Oxide (Y_(0.25)Bi_(0.75)O_(1.5)) and Conducting Perovskite La_(1-X)Sr_xMeO_(3-δ) (Me=Mn, Cu)

The mixed conducting cathodes for solid oxide fuel cells usually consist of a mixture of oxygen ion conductor and a conducting perovskite oxide. Bismuth oxide based materials are known to exhibit high ionic conductivity. Among them, Y_(0.25)Bi_(0.75)O_(1.5) (25YSB) is a typical example. On the other hand, La_(0.8)Sr_(0.2)MnO_(3-δ) (20LSM) and La_(0.75)Sr_(0.25)CuO_(3-δ) (25LSCu) are well known cathodes for SOFC applications. In this study, the phase stability of composite cathode consisting of 25LSCu or 20LSM and 25YSB mixed powders was examined. No additional phase other than LSM and YSB was observed at temperatures as high as 1000 °C for 8h. However, 25LSCu tends to react with 25YSB and additional phases belonging to La_(0.3)Bi_(0.7)O_(1.5), La)2CuO)4, CuO and Bi)2Sr)2CuO)6 appeared after heat treatment at 800 °C for 20h. The conductivity of 20LSM-25YSB composite electrode increases with increasing volume fraction of 20LSM. The thermal expansion of 20LSM-25YSB composite electrode was also measured as a function of 25YSB content. Based on these results, 20LSM+25YSB is believed to be the desired composite cathode for SOFC application

Differentiation of adult mesenchymal stem cells into chondrogenic cells using small molecules or microRNA: DOI: 10.14800/rd.458

Transplantation of mesenchymal stem cells (MSCs) into osteoarthritis (OA) and rheumatoid arthritis (RA) patients has been studied as a therapeutic tool for regeneration of damaged cartilage. MSCs have several beneficial effects, including immunomodulatory activity, and release various paracrine factors. Despite their abundant beneficial effects, transplantation of naïve MSCs is hampered by heterogeneous populations of differentiated and undifferentiated stem cells. However, transplantation of differentiated MSCs overcomes the problem of transplantation of naïve MSCs. Thus, to repair damaged tissue, a therapeutic strategy based on the use of differentiated MSCs is needed to treat RA or OA patients. Here, we summarize methods that can regulate differentiation of MSCs into chondrocytes by small molecules or miRNAs, and suggest the capacity of patient tissue-derived MSCs as a therapeutic strategy for treatment of OA or RA patients