8,650 research outputs found
Towards predictive modelling of near-edge structures in electron energy loss spectra of AlN based ternary alloys
Although electron energy loss near edge structure analysis provides a tool
for experimentally probing unoccupied density of states, a detailed comparison
with simulations is necessary in order to understand the origin of individual
peaks. This paper presents a density functional theory based technique for
predicting the N K-edge for ternary (quasi-binary) nitrogen alloys by adopting
a core hole approach, a methodology that has been successful for binary nitride
compounds. It is demonstrated that using the spectra of binary compounds for
optimising the core hole charge ( for cubic TiAlN
and for wurtzite AlGaN), the predicted spectra
evolutions of the ternary alloys agree well with the experiments. The spectral
features are subsequently discussed in terms of the electronic structure and
bonding of the alloys.Comment: 11 pages, 9 figures, 1 tabl
A new miniature cryptic species of the seasonal killifish genus Spectrolebias from the Tocantins River basin, central Brazil (Cyprinodontiformes, Aplocheilidae)
The miniature seasonal killifish Spectrolebias costae, first described for the middle Araguaia River basin, has been also recorded from two areas in the middle Tocantins River basin, from where male specimens exhibit some differences in their colour pattern. Analyses directed to species delineation (GMYC and bPTP), using a fragment of the mitochondrial gene COI, strongly support two species, S. costae from the Araguaia River basin and a new species from the Tocantins River basin. Spectrolebias gracilis sp. n. is described on the basis of specimens collected from two localities separated by about 530 km, Canabrava River floodplains near Alvorada do Tocantins and Tocantins River floodplains near Palmeirante. Field inventories were unsuccessful in finding additional populations in the region, which is attributed to the high environmental degradation, including several large dams that have permanently inundated typical killifish habitats. Spectrolebias gracilis is member of a clade also including S. costae, S. inaequipinnatus, and S. semiocellatus, diagnosed by having the dorsal and anal fins in males with iridescent dots restricted to their basal portion, caudal fin in males hyaline, and caudal-fin base with two pairs of neuromasts. Within this clade, a single miniaturisation event is supported for the most recent common ancestor of the subclade comprising S. costae and S. gracilis, which differ from other congeners by reaching only about 20 mm standard length as maximum adult size
Soluble starch and composite starch Bioactive Glass 45S5 particles : synthesis, bioactivity, and interaction with rat bone marrow cells
For many biomedical applications, biodegradable and simultaneously bioactive materials are desired. These materials should at the same
time be able to support cell function and co-exist with the organism without triggering a relevant immune response.
In this work, the synthesis as well as the bioactivity evaluation of newly developed polymer soluble potato starch and composite (with
Bioactive Glass 45S5) micron-size particles are reported. An extremely interesting result is that although with different properties, both
polymer and composite particles were able to form a calcium phosphate layer at their surface, which is a clear indication of their bioactivity.
The cytotoxicity and the ability to support cell attachment and growth of the developed materials were also studied, and both polymer
and composite materials were shown to be non-cytotoxic. Preliminary results show that both types of materials were found to allow rat
bone marrow cells to attach and to proliferate on their surface and to express osteogenic markers, such as alkaline phosphatase and
osteopontin.
The obtained results indicate that the developed carriers might be used as substrates for cell culture in vitro, in order to form constructs
that might be used as a part of a tissue engineering strategy
Acoustic determination of thermophysical properties and critical parameters for R404A and critical line of x CO2+(1− x) R404A
The thermophysical properties and critical parameters for the alternative refrigerant R404A (52 wt % of 1,1,1-
trifluoroethane (R143a) + 44 wt % of pentafluoroethane (R125) + 4 wt % of 1,1,1,2-tetrafluoroethane (R134a))
were investigated using two different acoustic techniques. The critical behavior of the system xCO2 +
(1 - x)R404A was also investigated. Experimental data of speed of sound in liquid R404A from 258 K to
338 K and pressures up to 65 MPa were measured using a pulse-echo method. Derived thermodynamic properties
are calculated, combining our experimental data with density and isobaric heat capacity values published by
other authors. Measurements of the critical temperature Tc and pressure pc on (R404A) and mixtures of xCO2 +
(1 - x)R404A were performed using another simple ultrasonic time-delay technique. The binary critical line was
determined over the whole composition range showing that this system deviates only slightly from ideality since
the critical line is a continuous line. The Peng-Robinson equation of state with conventional mixing and combining
rules was used to correlate the binary experimental data.info:eu-repo/semantics/publishedVersio
Acoustic determination of thermophysical properties and critical parameters for R410A and critical line of x CO2+(1− x) R410A
The thermophysical properties and critical parameters for the alternative refrigerant R410A (a near azeotropic
refrigerant mixture containing difluoromethane (R32) and pentafluoroethane (R125) (50 wt % of each)) were
investigated using two different acoustic techniques. The critical behavior of the system xCO2 + (1 - x)R410A
was also investigated. Experimental data of speed of sound in liquid R410A from (253 to 338) K and pressures
up to 65 MPa were measured using a pulse-echo method. Derived thermodynamic properties were calculated,
combining our experimental data with density and isobaric heat capacity values published by other authors.
Measurements of the critical temperature Tc and pressure pc on (R410A) and mixtures of xCO2 + (1 - x)R410A
were performed using another simple ultrasonic time-delay technique. The binary critical line was determined
over the whole composition range, showing that this system deviates only slightly from ideality since the critical
line is a continuous line. The Peng-Robinson equation of state with conventional mixing and combining rules
was used to correlate the binary experimental data.info:eu-repo/semantics/publishedVersio
Cryptic species diversity in the Hypsolebias magnificus complex, a clade of endangered seasonal killifishes from the São Francisco River basin, Brazilian Caatinga (Cyprinodontiformes, Aplocheilidae)
A great diversity of animal species adapted to life in the semi-arid Caatinga of northeastern Brazil, including seasonal killifishes, has been reported in the last three decades. More recently, field and molecular data have shown a high occurrence of cryptic species. The killifish group herein analysed, the Hypsolebias magnificus species complex, is endemic to the middle and southern portion of the Caatinga, occupying about 120 km along the floodplains of the middle São Francisco River and some adjacent tributaries. Species of this complex are rare and presently considered threatened with extinction, being uniquely found in pools protected by trees and bushes. Single-locus delimitation methods were used to test species limits of populations displaying different colour patterns along the whole distribution of the complex. All analyses consistently supported the three nominal species and two new, herein described: H. gardneri Costa, sp. n., from the floodplains of the middle São Francisco River and H. hamadryades Costa, sp. n., from the Gorotuba River floodplains. The phylogenetic analysis highly supports H. hamadryades as sister to a clade comprising H. gardneri and H. harmonicus. Our field observations suggest that H. hamadryades is a miniature species. This study indicates that the H. magnificus complex comprises cryptic species apparently endemic to small areas and extremely vulnerable to environmental changes, deserving high concern
Bioinspired Synthesis of Reduced Graphene Oxide-Wrapped Geobacter sulfurreducens as a Hybrid Electrocatalyst for Efficient Oxygen Evolution Reaction
Doping/decorating of graphene or reduced graphene oxide (rGO) with heteroatoms provides a promising route for the development of electrocatalysts which will be useful in many technologies, including water splitting. However, current doping approaches are complicated, not eco-friendly, and not cost-effective. Herein, we report the synthesis of doped/decorated rGO for oxygen evolution reaction (OER) using a simple approach that is cost-effective, sustainable, and easy to scale up. The OER catalyst was derived from the reduction of GO by an exo-electron-transferring bacterium, Geobacter sulfurreducens. Various analytical tools indicate that OER active elements such as Fe, Cu, N, P, and S decorate the rGO flakes. The hybrid catalyst (i.e., Geobacter/rGO) produces a geometric current density of 10 mA cm–2 at an overpotential of 270 mV versus the reversible hydrogen electrode with a Tafel slope of 43 mV dec–1 and possesses high durability, as evidenced through 10 h of stability testing. Electrochemical analyses suggest the importance of Fe and its possible role as an active site for OER. Overall, this work represents a simple approach toward the development of an earth-abundant, eco-friendly, and highly active OER electrocatalyst for various applications such as solar fuel production, rechargeable metal–air batteries, and microbial electrosynthesis
Paper-based in-situ gold nanoparticle synthesis for colorimetric, non-enzymatic glucose level determination
ref. 787410
SFRH/BD/115173/2016
SFRH/BD/132057/2017Due to its properties, paper represents an alternative to perform point-of-care tests for colorimetric determination of glucose levels, providing simple, rapid, and inexpensive means of diagnosis. In this work, we report the development of a novel, rapid, disposable, inexpensive, enzyme-free, and colorimetric paper-based assay for glucose level determination. This sensing strategy is based on the synthesis of gold nanoparticles (AuNPs) by reduction of a gold salt precursor, in which glucose acts simultaneously as reducing and capping agent. This leads to a direct measurement of glucose without any enzymes or depending on the detection of intermediate products as in conventional enzymatic colorimetric methods. Firstly, we modelled the synthesis reaction of AuNPs to determine the optical, morphological, and kinetic properties and their manipulation for glucose sensing, by determining the influence of each of the reaction precursors towards the produced AuNPs, providing a guide for the manipulation of nucleation and growth. The adaptation of this synthesis into the developed paper platform was tested and calibrated using different standard solutions with physiological concentrations of glucose. The response of the colorimetric signals obtained with this paper-based platform showed a linear behavior until 20 mM, required for glycemic control in diabetes, using the Red × Value/Grey feature combination as a calibration metric, to describe the variations in color intensity and hue in the spot test zone. The colorimetric sensor revealed a detection limit of 0.65 mM, depending on calibration metric and sensitivity of 0.013 AU/mM for a linear sensitivity range from 1.25 to 20 mM, with high specificity for the determination of glucose in complex standards with other common reducing interferents and human serum.publishersversionpublishe
New 1,3-diarylureas linked by C-C Suzuki coupling to the methyl 3-aminothieno[3,2-b]pyridine-2-carboxylate moiety: synthesis and fluorescence studies in solution and in lipid membranes
New six fluorescent 1,3-diarylureas linked by C-C Suzuki coupling to the 6-position of the methyl 3-aminothieno[3,2-b]pyridine-2-carboxylate moiety were prepared by reaction of the amino groups on the ortho or meta positions relative to the C-C bond of the Suzuki coupling products, with different para-substituted arylisocyanates (H, OMe, CN), in high to excellent yields. The fluorescence properties of the 1,3-diarylureas in solution and in lipid membranes of egg-yolk phosphatidylcholine (Egg-PC), dipalmitoyl phosphatidylcholine (DPPC), dipalmitoyl phosphatidylglycerol (DPPG) or dioctadecyldimethylammonium bromide (DODAB), with or without cholesterol (Ch), were studied. The six 1,3-diarylureas have reasonable fluorescence quantum yields in several solvents (between 0.02 and 0.69) and present a moderately solvent sensitive emission, but are not fluorescent in alcohols and water. The compounds bearing the arylurea moiety in the meta position relative to the C-C bond, especially with the OMe and CN substituents, present the better solvatochromic properties.
Incorporation of the six compounds in lipid membranes indicates that all the compounds are deeply located in the hydrophobic region of the lipid bilayers, feeling the transition between the rigid gel phase and fluid phases.To the Foundation for the Science and Technology (FCT, Portugal) for inancial support to the NMR portuguese network (PTNMR, Bruker Avance III 400-Univ. Minho). To the FCT and FEDER (European Fund for Regional Development)-COMPETE-QREN-EU for financial support to the Research Centres, CQ/UM [PEst-C/QUI/UI0686/2011 (FCOMP-01-0124-FEDER-022716)] and CFUM [PEst-C/FIS/UI0607/2011 (F-COMP-01-0124-FEDER-022711)], and to the research projects PTDC/QUI/81238/2006 (FCOMP-01-0124-FEDER-007467) (photophysical studies) and PTDC/QUI-QUI/111060/2009 (F-COMP-01-0124-FEDER-015603) (organic synthesis)
- …