Functionalized platinum nanoparticles with surface charge trigged by pH: synthesis, characterization and stability studies

In this work, the synthesis and characterization of functionalized platinum nanoparticles (PtNPs) have been investigated. PtNPs were obtained by a wet redox procedure using 2-diethylaminoethanethiol hydrochloride (DEA) as capping agent. By varying the Pt/thiol molar ratio, monodispersed and stable particles with diameters in the range of 3-40 nm were isolated. The amino functionality allows neutral particles to be obtained in basic water solution and positive charged nanoparticles in neutral or acidic water solution (pH 7-2), as confirmed by DLS and ζ-potential measurements. FTIR spectroscopy, FE-SEM, DLS and ζ-potential measurements confirmed the size and showed long term water stability (up to three months) of the colloidal system

Is the critical Shields stress for incipient sediment motion dependent on channel-bed slope?

Data from laboratory flumes and natural streams show that the critical Shields stress for initial sediment motion increases with channel slope, which indicates that particles of the same size are more stable on steeper slopes. This observation is contrary to standard models that predict reduced stability with increasing slope due to the added downstream gravitational force. Processes that might explain this discrepancy are explored using a simple force-balance model, including increased drag from channel walls and bed morphology, variable friction angles, grain emergence, flow aeration, and changes to the local flow velocity and turbulent fluctuations. Surprisingly, increased drag due to changes in bed morphology does not appear to be the cause of the slope dependency because both the magnitude and trend of the critical Shields stress are similar for flume experiments and natural streams, and significant variations in bed morphology in flumes is unlikely. Instead, grain emergence and changes in local flow velocity and turbulent fluctuations seem to be responsible for the slope dependency due to the coincident increase in the ratio of bed-roughness scale to flow depth (i.e., relative roughness). A model for the local velocity within the grain-roughness layer is proposed based on a 1-D eddy viscosity with wake mixing. In addition, the magnitude of near-bed turbulent fluctuations is shown to depend on the depth-averaged flow velocity and the relative roughness. Extension of the model to mixed grain sizes indicates that the coarser fraction becomes increasingly difficult to transport on steeper slopes

Secondary metabolites with ecologic and medicinal implications in Anthemis cretica subsp. petraea from Majella National Park

Anthemis cretica subsp. petraea (Ten.) Greuter is a plant belonging to the Asteraceae family and endemic of central Italy. In this paper, the first analysisof the ethanolic fraction of samples collected in the Majella National Park is reported. Seven compounds were isolated and identified namely parthenolide (1), 9α-acetoxyparthenolide (2), tamarixetin (3), 7-hydroxycoumarin (4), 4'-hydroxyacetophenone (5), leucanthemitol (conduritol F) (6),and proto-quercitol (7). Isolation of the compounds was achieved by means ofcolumn chromatography (CC), while their identification was achieved through spectroscopic and spectrometric techniques. The presence of these compounds is of great relevance. Compounds 1 and 2 are chemosystematic markers of the family, thus confirming the correct botanical classification of the species. Conversely, compounds 3, 5,and 7 were identified for the first time in the species and, instead, confirm the tendency of endemic entities to develop characteristic metabolite patterns in respect to cosmopolite species. Moreover, the presence of compounds 6 and 7 has ecologic implications and may be linked to this taxon’s adaption to dry environments. The production of these osmolytes may, in fact, represent the reason why this species is able to survive in extreme conditions of aridity. Lastly, from a medicinal standpoint, the isolated compounds are endowed with interesting biological activities and may justify, on a molecular base, the widespread traditional uses of the Anthemis species, as well as a basis for the use ofthe subspecies petraea

Dynamic equilibrium between closed and partially closed states of the bacterial Enzyme I unveiled by solution NMR and X-ray scattering

The bacterial phosphotransferase system couples phosphoryl transfer to sugar transport across the cell membrane. The first protein in the pathway, Enzyme I (EI), undergoes two large rigid body domain reorientations between an autophosphorylation-competent closed state and an open state that allows subsequent phosphoryl transfer to its downstream protein partner. Simultaneous use of solution X-ray scattering and NMR dipolar coupling data to guide simulated annealing refinement reveals the existence of a dynamic equilibrium between closed and partially closed conformations in a complex of a mutant of EI with phosphoenolpyruvate. The partially closed conformation represents an intermediate in the open-to-closed transition

Mitochondrial management of reactive oxygen species

Mitochondria in aerobic eukaryotic cells are both the site of energy production and the formation of harmful species, such as radicals and other reactive oxygen species, known as ROS. They contain an efficient antioxidant system, including low-molecular-mass molecules and enzymes that specialize in removing various types of ROS or repairing the oxidative damage of biological molecules. Under normal conditions, ROS production is low, and mitochondria, which are their primary target, are slightly damaged in a similar way to other cellular compartments, since the ROS released by the mitochondria into the cytosol are negligible. As the mitochondrial generation of ROS increases, they can deactivate components of the respiratory chain and enzymes of the Krebs cycle, and mitochondria release a high amount of ROS that damage cellular structures. More re-cently, the feature of the mitochondrial antioxidant system, which does not specifically deal with intramitochondrial ROS, was discovered. Indeed, the mitochondrial antioxidant system detoxifies exogenous ROS species at the expense of reducing the equivalents generated in mitochondria. Thus, mitochondria are also a sink of ROS. These observations highlight the importance of the mitochon-drial antioxidant system, which should be considered in our understanding of ROS-regulated pro-cesses. These processes include cell signaling and the progression of metabolic and neurodegenera-tive disease

Chlorella sorokiniana dietary supplementation increases antioxidant capacities and reduces ros release in mitochondria of hyperthyroid rat liver

The ability of aerobic organisms to cope with the attack of radicals and other reactive oxygen species improves by feeding on foods containing antioxidants. Microalgae contain many molecules showing in vitro antioxidant capacity, and their food consumption can protect cells from oxidative insults. We evaluated the capacity of dietary supplementation with 1% dried Chlorella sorokiniana strain 211/8k, an alga rich in glutathione, α-tocopherol, and carotenoids, to counteract an oxidative attack in vivo. We used the hyperthyroid rat as a model of oxidative stress, in which the increase in metabolic capacities is associated with an increase in the release of mitochondrial reactive oxygen species (ROS) and the susceptibility to oxidative insult. Chlorella sorokiniana supplementation prevents the increases in oxidative stress markers and basal oxygen consumption in hyperthyroid rat livers. It also mitigates the thyroid hormone-induced increase in maximal aerobic capacities, the mitochondrial ROS release, and the susceptibility to oxidative stress. Finally, alga influences the thyroid hormone-induced changes in the factors involved in mitochondrial biogenesis peroxisomal proliferator-activated receptor-γ coactivator (PGC1-1) and nuclear respiratory factor 2 (NRF-2). Our results suggest that Chlorella sorokiniana dietary supplementation has beneficial effects in counteracting oxidative stress and that it works primarily by preserving mitochondrial function. Thus, it can be useful in preventing dysfunctions in which mitochondrial oxidative damage and ROS production play a putative role

Programmed schedule holds for improving launch vehicle holds

Baseline definition and system optimization are used for the analysis of programmed holds developed through prelaunch system analysis. Identification of design specifications for ground support equipment and maintenance concepts, and design specifications are used to describe the functional utilization of the overall flow process

The grain size gap and abrupt gravel-sand transitions in rivers due to suspension fallout

Median grain sizes on riverbeds range from boulders in uplands to silt in lowlands; however, rivers with ~1–5 mm diameter bed sediment are rare. This grain size gap also marks an abrupt transition between gravel- and sand-bedded reaches that is unlike any other part of the fluvial network. Abrupt gravel-sand transitions have been attributed to rapid breakdown or rapid transport of fine gravel, or a bimodal sediment supply, but supporting evidence is lacking. Here we demonstrate that rivers dramatically lose the ability to transport sand as wash load where bed shear velocity drops below ~0.1 m/s, forcing an abrupt transition in bed-material grain size. Using thresholds for wash load and initial motion, we show that the gap emerges only for median bed-material grain sizes of ~1–5 mm due to Reynolds number dependencies in suspension transport. The grain size gap, therefore, is sensitive to material properties and gravity, with coarser gaps predicted on Mars and Titan

Isoflavones and other compounds from the roots of Iris marsica I. Ricci E Colas. Collected from Majella National Park, Italy

In this study, a phytochemical analysis was performed, for the first time, on Iris marsica I. Ricci e Colas. In particular, the attention was focused on the constituents of the roots. Twenty-one compounds were isolated by column chromatography and were analyzed/identified by NMR spectroscopy and mass spectrometry. They all own chemotaxonomic, ethno-pharmacological and nutraceutical relevance which allowed us to provide a phytochemical rationale, for the correct botanical classification of this species, for the employment of its roots in folk medicine like for all the other species belonging to the Iris genus and, lastly, for their further uses as food with important healthy benefits. All of these parts were broadly discussed about within the text

Modeling Sediment Transport in Ice-Walled Subglacial Channels and Its Implications for Esker Formation and Proglacial Sediment Yields

Sediment yields from glacierized basins are used to quantify erosion rates on seasonal to decadal timescales as well as conditions at the glacier bed, and eskers hold valuable information about past subglacial hydraulic conditions in their spatial organization, geometry, and sedimentary structures. Ultimately, eskers are a record of past glacio‐fluvial sediment transport, but there is currently no physical model for this process. We develop a 1‐D model of morphodynamics in semicircular bedrock‐floored subglacial channels. We adapt a sediment conservation law developed for mixed alluvial‐bedrock conditions to subglacial channels. Channel evolution is a function of melt opening by viscous heat dissipation from flowing water and creep closure of the overlying ice, to which we add the closure or enlargement due to sediment deposition or removal, respectively. We apply the model to an idealized land‐terminating glacier and find that temporary sediment accumulation in the vicinity of the terminus, or the formation of an incipient esker, is inherent to the dynamics of the channelized water flow. The alluviation of the bed combined with the pressurized channel flow produces unexpected patterns of sediment evacuation: We show that the direction of hysteresis between sediment and water discharge is not necessarily linked to a supply‐ or transport‐limited system, as has been hypothesized for proglacial sediment yields. We also find that the deposition of an incipient esker is a function of a compromise between water discharge and sediment supply, but perhaps more importantly, ice‐surface slope and the temporal pattern of water delivery to the bed