Search results for " Chemical Engineering"
showing 10 items of 2965 documents
Optimization of the biocide properties of chitosan for its application in the design of active films of interest in the food area
2009
The influence on biocide performance of some unprecedented physicochemical features of chitosan cast films such as film thickness, pH of the nutrient broth, film neutralization, film autoclave sterilization and temperature exposure were analyzed against Staphylococcus aureus and in some experiments also against Salmonella spp. The work demonstrates for the first time the influence of the release or positive migration of protonated glucosamine fractions from the biopolymer into the microbial culture as the responsible event for the antimicrobial performance of the biopolymer under the studied conditions. From the results, a reliable and reproducible method for the determination of the bacter…
Biogenic Selenium Nanoparticles: A Fine Characterization to Unveil Their Thermodynamic Stability
2021
Among the plethora of available metal(loid) nanomaterials (NMs), those containing selenium are interesting from an applicative perspective, due to their high biocompatibility. Microorganisms capable of coping with toxic Se-oxyanions generate mostly Se nanoparticles (SeNPs), representing an ideal and green alternative over the chemogenic synthesis to obtain thermodynamically stable NMs. However, their structural characterization, in terms of biomolecules and interactions stabilizing the biogenic colloidal solution, is still a black hole that impairs the exploitation of biogenic SeNP full potential. Here, spherical and thermodynamically stable SeNPs were produced by a metal(loid) tolerant Mic…
A thermo-alkaline lipase from a new thermophileGeobacillus thermodenitrificansAV-5 with potential application in biodiesel production
2015
BACKGROUND A thermophilic lipase-producing Geobacillus thermodenitrificans strain AV-5 was isolated from the Mushroom Spring of Yellowstone National Park in WY, USA and studied as a source of lipase for transesterification of vegetable oils to biodiesel. RESULTS A maximum activity of 330 U mL−1 was produced on 2% (v/v) waste cooking oil at 50 °C, pH 8, aeration rate of 1 vvm and agitation speed of 400 rpm. However, the higher lipase productivity (14.04 U mL−1 h−1) was found at a volumetric oxygen transfer coefficient (kLa) value of 18.48 h−1. The partially purified lipase had a molecular weight, temperature and pH optimum of 50 kDa, 65 °C and pH 9, respectively, and was thermo-alkali stable…
Gasification of pelletized renewable fuel for clean energy production
2011
Abstract The main aim of the study was to develop and investigate a small-scale experimental gasification technique for the effective thermal decomposition of pelletized renewable fuels (wood sawdust, wheat straw). The technical solution of the biomass gasifier for gasification of renewable fuels presents a downdraft gasifier with controllable additional heat energy supply to the biomass using the radial propane flame injection into the bottom part of the biomass layer. From the kinetic study of the mass conversion rate of pelletized biomass and variations of the composition of produced gas it is concluded that the process of biomass gasification is strongly influenced by the amount of addi…
Interfacial shear strength of flax fibers in thermoset resins evaluated via tensile tests of UD composites
2012
Abstract A method of interfacial shear strength evaluation, based on the length distribution of fibers pulled out from the tensile fracture surface of an oriented flax-reinforced composite, is applied to composites with vinyl ester and acrylated epoxidized soy oil resin matrices. Two approaches for characterizing the strength of fibers with modified Weibull distribution, fiber fragmentation tests and fiber tension tests, are compared in the analysis of pull-out data. Interfacial shear strength is found to increase by a few percent when loading rate is increased from 1.33% to 8%/min.
Performance of polyester-based electrospun scaffolds under in vitro hydrolytic conditions: From short-term to long-term applications
2019
The evaluation of the performance of polyesters under in vitro physiologic conditions is essential to design scaffolds with an adequate lifespan for a given application. In this line, the degradation-durability patterns of poly(lactide-co-glycolide) (PLGA), polydioxanone (PDO), polycaprolactone (PCL) and polyhydroxybutyrate (PHB) scaffolds were monitored and compared giving, as a result, a basis for the specific design of scaffolds from short-term to long-term applications. For this purpose, they were immersed in ultra-pure water and phosphate buffer solution (PBS) at 37 °
Biphenyl derivatives containing trimethylsilyl benzyl ether or oxime groups as probes for NO2 detection
2016
[EN] Four probes based in the use of a biphenyl moiety and functionalized with trimethylsilyl benzyl ether (P1 and P3) and oxime (P2 and P4) groups have been prepared and tested as optical probes for the detection of NO2. Reaction of NO2 with acetonitrile solutions of P2-P4 resulted in the formation of aldehydes 7 and 8 with a concomitant redshift of the absorption bands. Probe P2 displayed a bathochromic shift of 45 nm upon reaction with NO2 and was able to detect this poisonous gas at concentrations as low as 0.02 ppm. P2 was highly selective against NO2 and other gases (i.e. NO, CO2, H2S, SO2) and vapours of organic solvents (i.e. acetone, hexane, chloroform, acetonitrile or toluene) had…
Magnetoelectrochemistry of 4,4′-bis(dimethylamino)biphenyl and 4,4′-dinitrobiphenyl azacrown macrocyclic lactams
2005
Abstract The voltammetric behaviour at carbon fibre microelectrodes under the application of static magnetic fields of two series of macrolactams containing in their structure 4,4′-bis(dimethylamino)biphenyl or 4,4′-dinitrobiphenyl groups in MeCN solution is described. The response of 4,4′-dinitrobiphenyl receptors is dominated by two successive one-electron reduction processes at −0.9 and −1.6 V versus AgCl/Ag. 4,4′-bis(dimethylamino)biphenyl-containing receptors display two one-electron oxidations above +0.8 and +1.0 V. In both cases, a dihedral/planar interconversion precedes the second electron transfer step. Upon application of moderate (0.05–0.2 T) static magnetic fields to the electr…
Design and synthesis of biobased epoxy thermosets from biorenewable resources
2017
International audience; Biobased diepoxy synthons derived from isoeugenol, eugenol or resorcinol (DGE-isoEu, DGE-Eu and DGER, respectively) have been used as epoxy monomers in replacement of the diglycidyl ether of bisphenol A (DGEBA). Their curing with six different biobased anhydride hardeners leads to fully biobased epoxy thermosets. These materials exhibit interesting thermal and mechanical properties comparable to those obtained with conventional petrosourced DGEBA-based epoxy resins cured in similar conditions. In particular, a high Tg in the range of 90–130 °C and instantaneous moduli higher than 4.3 GPa have been recorded. These good performances are very encouraging, making these n…
Identification and quantitation of trace amounts of barbiturates with glass capillary gas chromatography
1979
Pre-chromatographic reactions are no longer a necessary evil. Equipment such as the microrefluxer now allows reproducible 7-μl-reactions to be carried out in a short time. Thus multiple derivatisations can be used together with glass capillary GC for routine identifications. The method has been succesfully applied to barbiturates. Retention data of their methyl-, allyl- and benzyl-derivatives are given. Quantitative blood level determinations are briefly discussed.