86,767 research outputs found
Integrated microalgae biomass production and olive mill wastewater biodegradation: optimization of the wastewater supply strategy
No full textOlive mill wastewater (OMW) was supplied to Scenedesmus sp. cultures to simultaneously achieve biomass production and wastewater biodegradation. Two OMW supply strategies were implemented to prevent the reduced growth performances that are attained, compared to photoautotrophic cultivation, when OMW is supplied at the beginning of cultivation (batch strategy). A fed-batch strategy including the gradual OMW supply yielded a biomass production equal to 0.86 g/L, while 1.4 g/L was attained by a two-stage strategy including OMW addition during nitrogen-starvation. OMW enhanced the carbohydrate accumulation (up to 44%) through the removal of OMW sugars (60–70%). About 55% OMW phenol removal was achieved by the fed-batch strategy when the phenol concentration was lower than 100 mg/L, and by the two-stage strategy when the heterotrophic stage lasted longer than 8–10 days. The illustrated results indicate that the OMW supply strategy can be purposefully tailored to regulate biomass production and OMW biodegradation
Ultrasound-assisted extraction of carbohydrates from microalgae
No full textMicroalgae are a promising new source of carbohydrates usable for several industrial applications in the food and biomaterial sector. Previous works on carbohydrate extraction from microalgae were mainly carried out by using destructive chemical hydrolysis, aiming at the extraction of simple sugars. Here in this work, a physical ultrasonication method was investigated to develop a process to extract microalgal carbohydrates in their polysaccharide form, as starch. To this end, different operative parameters were investigated: biomass concentration (3-6 g L-1), microalgae strain (Tetradesmus obliquus and Chlorella sp.), extraction time, amplitude (21-90 μm) and the configuration of the ultrasonication system (cyclic treatment, pulsed and continuous). The highest extractions were attained with higher amplitude (90 μm). The pulsed ultrasonication (ton/toff = 0.2) worked remarkably better than the continuous one, allowing to attain about 3 folds more carbohydrate extraction yield and consuming 6 folds less kWh per kg of extracted carbohydrates. The higher yield achieved with pulsed ultrasonication was related with a lower drop in the applied power during the ultrasonication treatment, which was -65 % with the continuous system and only -31 % with the pulsed one. The ultrasonication treatment induced a temperature increase up to 70 °C, that caused starch gelatinization and its solubilization in the recovered aqueous solution. Future studies should investigate better the effect of the ton/toff ratio, to limit the dead times (toff) of the process. The specific energy consumption was still too high for many practical applications; however, future optimizations on biomass concentration and operative temperature are expected to reduce remarkably the energy demand of the process
Tra assistenza e solidarietà: la liberazione dal bisogno nel recente dibattito politico parlamentare
No full textIl saggio analizza l'evoluzione della normativa in tema di reddito minimo garantito, illustrando le sperimentazioni che da ormai un ventennio il legislatore ha posto in essere nel nostro ordinamento, fino ad arrivare all'approfondimento delle proposte di legge, presentate nel corso della XVII legislatura in tema di cd. reddito di cittadinanz
Comparative study of technological behavior of German ball clay and Italian kaolinitic clay in unconventional porcelain stoneware body
No full textThis work focused on obtaining a porcelain stoneware body containing only Italian raw materials. The starting mixtures differed in the feldspathic fraction, one pumice-based and one lapillus-based. German ball clay was gradually replaced by Italian kaolinitic clay. The influence of Italian kaolinitic clay on the technical and aesthetic properties of the final product was analyzed by comparing it with the references. The work was carried out in collaboration with a ceramic company which allowed the tile production process to be simulated in the laboratory and fired in an industrial kiln using the production cycle (48 min, 1210 °C). Ceramic bodies were characterized in order to evaluate technological performance by measuring efflux time and density of slip, flexural strength on green, linear shrinkage and water absorption in vacuum on fired samples. Mineralogical, microstructural (ESEM) and colorimetric analyses were also performed on the fired samples. Efflux time and density are processing parameters; these were in line with the reference in the lapillus-based bodies with kaolinitic clay replacement rates of 100%; in the case of the pumice-based bodies, they were considered acceptable only for replacements of 25%. The lapillus-based body showed a microstructure similar to that of porcelain stoneware. Vacuum water absorption values were better in lapillus-based formulations than in pumice-based formulations but showed higher linear shrinkage values for 100% replacements. According to UNI EN 14411 ISO 13006, some of the products obtained can be classified as porcelain stoneware (group BIa)
Nucleation and growth of metal nanoparticles on a planar electrode: A new model based on iso-nucleation-time classes of particles
No full textAn assembly of hemispherical particles continuously nucleating on a planar electrode and growing under mixed kinetic-diffusion control is here considered. A model is derived, from the exact boundary integral formulation of the diffusion equation, to predict the overall current evolution, and the radii distribution of particles nucleating within any prescribed time interval. Iso-nucleation-time classes are introduced in the model, grouping particles (almost) simultaneously nucleating over the underlying substrate. The dynamics of particles belonging to a given iso-nucleation-time class are assumed to be identical. By this approximation, hereby referred to as Averaged Class Approximation (ACA), the computation of the average radius of any iso-nucleation-time class is reduced to the solution of an integro-differential equation, parameterized by the nucleation time. An effective computational method is also presented to solve the model equations, giving predictions that fairly well agree with the results of direct multi-particle numerical simulations
Production of microalgae biomass in a two-stage continuous bioreactor. Control of microalgae-bacteria competition by spatial uncoupling of nitrogen and organic carbon feeding
No full textThe spatial uncoupling of nitrogen and organic carbon is proposed to control the competition between microalgae and bacteria in continuous bioreactors. A series of two continuous stirred bioreactors with recycle is considered where the upstream and the downstream reactor are fed with only the nitrogen and only the organic carbon source, respectively. A Droop-like model and a multiplicative Monod model are used to describe microalgae and bacteria growth kinetics, respectively. The stability regions of steady state solutions corresponding to pure microalgae cultures, pure bacteria cultures, and microalgae-bacteria consortia are identified by bifurcation analysis of the mass balance equations governing reactor dynamics. By capitalizing the competitive advantage of microalgae to uncouple nitrogen and carbon uptake, the proposed configuration allows attaining global stability of the microalgae and the microalgae-bacteria solution. Analytical approximations are derived for stability boundaries of steady states, providing guidelines for the design and control
Characterization of Volcano-Sedimentary Rocks and Related Scraps for Design of Sustainable Materials
No full textThis work started as a joint academia and company research project with the aim of finding
new applications for domestically sourced volcanic products and related waste (pumice, lapillus,
zeolitic tuff and volcanic debris from Tessennano and Arlena quarry) by creating a database of
secondary volcanic raw materials and their intrinsic characteristics to help industry replace virgin
materials and enhance circularity. In this context, accurate chemical, mineralogical, morphological,
granulometric and thermal characterizations were performed. Based on the results presented, it can
be concluded that due to their lightness, these materials can be used in the design and preparation of
lightweight aggregates for agronomic purposes or in the construction field. Furthermore, due to their
aluminosilicate nature and amorphous fraction, pumice and lapillus can play the role of precursor or
activator for geopolymer preparation. With its porous nature, zeolitic tuff can be exploited for flue
gas treatment. Due to the presence of feldspathic phase (sanidine), these materials can be used in
tile production as a fluxing component, and with their pozzolanic activity and calcium content, they
have application in the binder field as supplementary cementitious material or as aggregates
Alcune curiosità linguistiche nell’Emira di Francesco Antonio Santori
No full textL’Emira di Antonio Francesco Santori (1819-1894) è un testo importante sia sotto il profilo linguistico - siamo in presenza di una testimonianza di ben oltre un secolo fa - sia sotto quello letterario, in quanto primo dramma scritto nella variante linguistica arbëreshe, la lingua degli albanesi della diaspora in Italia, formatasi a partire dalla metà del XV secolo.
Il testo analizzato presenta molte particolarità nel sistema fonologico, morfologico, lessicale (nel sistema verbale, in quello nominale, pronominale e aggettivale) e sintattico (nelle strutture modali, causative, riflessive, passive, nella posizione dell’aggettivo all’interno del sintagma nominale).
Accanto a tratti arcaici, che riflettono fenomeni condivisi da altre varietà arbëreshe della Calabria settentrionale, troviamo le molte sperimentazioni dell’autore. La combinazione di tutti questi fattori regala al lettore un testo molto singolare, realizzato con una lingua composita e ricchissima di forme
Investigation on the effect of inorganic acid attack on composite prepared with MK-based geopolymer and waste cork dust
No full textThe chemical, microstructural and mechanical characterization of novel lightweight composites produced by
adding waste cork dust to a metakaolin-based geopolymeric matrix prepared by alkaline activation is presented.
The alkaline activator solutions used for the reticulation of the 3D aluminosilicate network at room temperature
are composed of NaOH and sodium silicate to maintain a low cost of the final composite. In this line, the research
of the highest addition of waste, e.g. cork dust, is pursued starting from 1 and reaching a maximum content of 10
wt% over metakaolin. The chemical stability is evaluated in water as well as in HNO3 or in H2SO4 0.5 and 2.5 N
solutions. The addition of cork does not affect the reticulation of the geopolymeric binder used as matrix, as is
demonstrated by FT-IR and XRD analyses. The modification of the dense geopolymeric microstructure with the
introduction of cork dust weakens the hardened composites that become more permeable to water and acid
solutions increasing the weight loss after immersion and decreasing the mechanical resistance to compression.
The mechanical performance of the hardened composite with 10 wt% of cork dust still seems to be sufficient for
application as self-supporting thermal insulation panels
Electrodeposition of cobalt nanoparticles: an analysis of the mechanisms behind the deviation from three-dimensional diffusion-control
No full textElectrochemical nucleation and growth of cobalt nanoparticles on aluminium was investigated by potentiostatic electrodeposition from cobalt sulphate solutions buffered with boric acid. At sufficiently low overpotential, the experimental current transients could be fairly reproduced by a mathematical model describing nucleation and growth under mixed kinetic-diffusion control, yielding an estimated number of particles per surface area in agreement with the SEM analysis of the deposits. However, the model gave estimates for the charge-transfer kinetic constant several orders of magnitude lower as compared to the Tafel analysis of cobalt electrodeposition on a previously electrodeposited cobalt film. This deviation can be explained by the inhibition of the direct attachment of metal ions, which can be induced by the adsorption of hydrogen onto cobalt particles and/or the formation of stable nanocluster aggregates. The implemented model failed to reproduce the current transients generated at larger overpotential values. A revision of the implemented mathematical model overcoming this limitation is proposed
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