Search results for "gellan"
showing 10 items of 50 documents
Stable carbon and oxygen isotope fractionation in bivalve (Placopecten magellanicus) larval aragonite
2008
Abstract The relationship between stable isotope composition (δ13C and δ18O) in seawater and in larval shell aragonite of the sea scallop, Placopecten magellanicus, was investigated in a controlled experiment to determine whether isotopes in larval shell aragonite can be used as a reliable proxy for environmental conditions. The linear relationship between δ13CDIC and δ13Caragonite (r2 = 0.97, p δ 13 C DIC = 1.15 ( ± 0.05 ) ∗ δ 13 C aragonite - 0.85 ( ± 0.04 ) The relationship between δ13CDIC and δ13Caragonite described for P. magellanicus resulted in larval shell aragonite that was depleted on average by 1.82‰ (SD = 0.22‰, range = 1.1–2.1‰) from predicted equilibrium values based on the r…
Effect of chelatants on gellan gel rheological properties and setting temperature for immobilization of living bifidobacteria.
1993
The effect of various concentrations of sequestrants (sodium citrate, sodium metaphosphate, and EDTA) was studied on gellan gel (1.5-2.5% (w/v)) setting temperature and rheological properties. Addition of EDTA between 0 and 0.8% (w/v) led to a progressive decrease of setting temperature. Citrate and metaphosphate decreased this parameter when added up to 0.4 or 0.6%, depending on gellan gum concentration, eventually resulting in the absence of gel formation at room temperature for the 1.5% gellan solution containing 0.4% citrate. This effect was accompanied by a significant decrease of gel strength and stiffness and might be attributed to the binding of the divalent cations required for cha…
Bioactive Scaffolds Based on Amine-Functionalized Gellan Gum for the Osteogenic Differentiation of Gingival Mesenchymal Stem Cells
2022
With the aim to produce a cellularized construct for the guided bone regeneration of dento-alveolar defects, here we produce a porous scaffold using an amine derivative of gellan gum to host gingival mesenchymal stem cells (GMSCs) and allow their osteochondral differentiation. Three derivatives were produced by using the same synthetic procedure, and the viscoelastic properties of their aqueous dispersions were investigated and compared to those of the native polysaccharide to choose the derivative with suitable properties for the scaffold production. Freeze-drying was used to obtain a porous sponge that can be rehydrated with the cells’ suspension to produce an implantable cell containing …
Effect of alkyl derivatization of gellan gum during the fabrication of electrospun membranes
2021
Electrospun nanofibers based on polysaccharides represent a consolidated approach in Tissue Engineering and Regenerative Medicine (TERM) and nanomedicine as a drug delivery system (DDS). In this work, two chemical derivatives of a low molecular weight gellan gum (96.7 kDa) with aliphatic pendant tails were processed by electrospinning technique into non-woven nanofibrous mats. In order to generate spinnable blends, it was necessary to associate poly vinyl alcohol (PVA). The relationships between the physicochemical properties and the processability via electrospinning technique of gellan gum alkyl derivatives (GG-C8 and GG-C12 having a degree of alkyl chain derivatization of 17 mol % and 1…
Massive Oe/Be stars at low metallicity: Candidate progenitors of long GRBs?
2010
At low metallicity the B-type stars rotate faster than at higher metallicity, typically in the SMC. As a consequence, it was expected a larger number of fast rotators in the SMC than in the Galaxy, in particular more Be/Oe stars. With the ESO-WFI in its slitless mode, the SMC open clusters were examined and an occurence of Be stars 3 to 5 times larger than in the Galaxy was found. The evolution of the angular rotational velocity seems to be the main key on the understanding of the specific behaviour and of the stellar evolution of such stars at different metallicities. With the results of this WFI study and using observational clues on the SMC WR stars and massive stars, as well as the theo…
Pulsating B and Be stars in the Small Magellanic Cloud
2008
Context: Stellar pulsations in main-sequence B-type stars are driven by the kappa-mechanism due to the Fe-group opacity bump. The current models do not predict the presence of instability strips in the B spectral domain at very low metallicities. As the metallicity of the SMC is lower than Z=0.005, it constitutes a very suitable object to test these predictions. Aims: The main objective is to investigate the existence of B-type pulsators at low metallicities, searching for short-term periodic variability in absorption-line B and Be stars in the SMC. The analysis has been performed in a sample of 313 B and Be stars with fundamental astrophysical parameters accurately determined from high-res…
ALMA spectral survey of Supernova 1987A – molecular inventory, chemistry, dynamics and explosive nucleosynthesis
2017
We report the first molecular line survey of Supernova 1987A in the millimetre wavelength range. In the ALMA 210--300 and 340--360 GHz spectra, we detected cold (20--170 K) CO, 28SiO, HCO+ and SO, with weaker lines of 29SiO from ejecta. This is the first identification of HCO+ and SO in a young supernova remnant. We find a dip in the J=6--5 and 5--4 SiO line profiles, suggesting that the ejecta morphology is likely elongated. The difference of the CO and SiO line profiles is consistent with hydrodynamic simulations, which show that Rayleigh-Taylor instabilities cause mixing of gas, with heavier elements much more disturbed, making more elongated structure. We obtained isotopologue ratios of…
Effects of gellan-based coating application on litchi fruit quality traits
2018
The use of gellan-based coating formulation on litchi (Litchi chinensis Sonn. ‘Wai Chee’) fruit was investigated in order to determine its ability to improve color conservation and to maintain the overall quality. Fruits were treated with gellanbased coating (0.5% w/v) and glycerol (3% w/v) after dipping in ascorbic acid (1.5% w/v) and then stored at 5°C and 90% relative humidity for 15 days. Changes in peel color, soluble solid content, tritatable acidity, weight loss, antioxidant activity and phenolic content, were measured. Formulations containing gellan-based coating exhibited slightly improved water barrier properties and showed their active role in maintaining color characteristics an…
Synthesis, Characterization and Sorption Capacity Examination for a Novel Hydrogel Composite Based on Gellan Gum and Graphene Oxide (GG/GO)
2020
A novel hydrogel composite based on gellan gum and graphene oxide (GG/GO) was synthesized, characterized and tested for sorption capacity in this work. The microstructural, thermogravimetric and spectroscopic analysis confirmed the formation of the GG/GO composite. Comparative batch sorption experiments revealed a sorption capacity of the GG/GO composite for Zn (II) ions of approximately 2.3 higher than that of pure GG. The GG/GO composite exhibits a maximum sorption capacity of 272.57 mg/g at a pH of Zn (II) initial solution of 6. Generally, the sorption capacity of the sorbents is approximately 1.5 higher in slightly acidic conditions (pH 6) comparative with that for strong acidic conditi…
Ciprofloxacin releasing gellan gum/polydopamine based hydrogels with near infrared activated photothermal properties.
2021
Abstract In this work, with the aim to obtain a wound dressing hydrogel, an amine derivative of gellan gum was crosslinked in the presence of 4arm-polyethylenglycole-vinylsulfone. Through this easy and reproducible chemical procedure, a hydrogel with advanced elastic properties and hydrolytic resistance under physiological conditions was obtained. The incorporation of different quantities of polydopamine in the gelling solutions allows to obtain different hydrogels with marked photothermal properties when irradiated with a laser in the near infrared at 810 nm. The organic nanoparticles, reacting with the amino groups of the polysaccharide derivative, contribute to increase the storage modul…