1,721,165 research outputs found
Neurosteroids and neuroactive drugs in mental disorders
No full textClinical and preclinical studies have suggested that fluctuations in the peripheral and brain concentrations of progesterone and deoxycorticosterone and its metabolites 3alpha,5alpha-tetrahydroprogesterone and 3alpha,5alpha-tetrahydrodeoxycorticosterone, respectively, might play an important role in certain pathological conditions characterized by emotional or affective disturbances, including major depression, anxiety disorders, and schizophrenia. Moreover, it has been shown that administration of drugs having clinical relevance in the treatment of these pathologies influence the secretion of these steroids. It remains to be determined, however, whether such changes in the concentrations of neuroactive steroids are a cause of, a risk factor for, or a consequence of mental disorders. The observation that effective pharmacological treatment of some of these pathologies influences the concentrations of neuroactive steroids suggests that these endogenous compounds might themselves prove to be efficacious in the treatment of mental illnes
A novel mathematical model to simulate the size-structured growth of microalgae strains dividing by multiple fission
No full textSeveral microalgae strains are capable to divide by multiple fission, namely they can give rise to variable number of daughter cells after cytokinesis. Such behavior may have implications on the overall growth and productivities of microalgal cultures that are difficult to infer intuitively. Consequently, a novel mathematical model to simulate the dynamics of the size-structured growth of microalgal strains characterized by multiple fission, is proposed in this work. The model relies on the use of population balance equations (PBEs) to describe the evolution of the size distribution of microalgae cells during growth and permits to decouple the single cell growth phase, which is known to take place in the light, from the division one, that on the contrary is assumed to occur under dark conditions according to well corroborated experimental observations. Moreover, the effect of light intensity, photoperiod and nutrients concentration on the continuous growth of the cells, are suitably accounted for by the model. Furthermore, in order to describe the partition of newborn cells after division, a new approach, which relies on suitable experimental observations, is developed to formulate a novel birth term related to PBEs which takes into account the possibility of multiple fission to take place. Model results and literature experimental data pertaining a strain capable to divide by multiple fission, are successfully compared in terms of biomass concentration evolution, thus highlighting a good predictive capability of the model. Subsequently, specific numerical experiments are performed in order to examine the potential improvements arising from this model with respect to the ones currently available in the literature. Finally, suitable simulation based inferences are formulated about the potential implications of multiple fission on photobioreactor's productivity. (C) 2015 Elsevier B.V. All rights reserved
Mechanochemical immobilization of heavy metals in contaminated soils: A novel mathematical modeling of experimental outcomes
No full textMechanochemical processing to immobilize heavy metals in contaminated soils has been proposed few years ago. The corresponding experimental results have shown that, under specific operating conditions, the mechanical energy provided by suitable ball mills, can greatly reduce heavy metals mobility without the addition of any reactant. Such results, together with the extreme simplicity of the proposed technique, are still very promising in view of its industrial transposition. Along these lines, the use of suitable mathematical models might represent a valuable tool which would permit to design and control mechano-chemical reactors for field applications. In this work, a simple albeit exhaustive model is proposed for the first time to quantitatively describe the effects of the dynamics of milling process, such as impact frequency and energy, on the immobilization kinetics. Model results and experimental data obtained so far are successfully compared in terms of leached heavy metals and immobilization efficiency evolution with treatment time. Finally, the potential capability of the model to contribute to the industrial scale transposition of the proposed technique is addressed
A novel simulation model for stem cells differentiation
No full textA novel mathematical model to simulate mesenchymal stem cells differentiation into specialized cells is proposed. The model is based upon material balances for extracellular matrix compounds, growth factors and nutrients coupled with a mass-structured population balance describing cell growth, proliferation and differentiation. The proposed model is written in a general form and it may be used to simulate a generic cell differentiation pathway occurring in vivo or during in vitro cultivation when specific growth factors are used. Literature experimental data concerning the differentiation of mesenchymal stem cells into chondrocytes in terms of total DNA and glycosaminoglycan content are successfully compared with model results, thus demonstrating the validity of the proposed model as well as its predictive capability. A further test of the model capability is performed for the case of in vivo fracture healing during which mesenchymal stem cells differentiate into chondrocytes and osteoblasts. Considerations about the extension of the proposed model to different pathologies beside fracture healing are reported. Finally, sensitivity analysis of model parameters is also performed in order to clarify what mechanisms most strongly influence differentiation and the distribution of cell types. © 2007 Elsevier B.V. All rights reserved
Novel simulation model of the solar collector of BIOCOIL photobioreactors for CO2 sequestration with microalgae
No full textMathematical modelling of chlorella vulgaris growth in semi-batch photobioreactors fed with pure CO2
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Self-propagating reactions for environmental protection: Reactor engineering aspects
No full textThe application of self-propagating reactions for environmental protection is addressed in this work with particular emphasis on certain reactor engineering aspects. Possible reactor configurations are analyzed in view of large-scale applicability of SHS technology for residue recycling and safe waste disposal. A two-dimensional batch SHS reactor model in which heat transfer phenomena are described in detail is presented. The model results are illustrated by considering the treatment of zinc hydrometallurgical wastes as a reference system. The model not only estimates the total cycle time of a potential batch operation but also analyzes the time-space temperature levels of the reactor to guarantee operational safety. Some economical aspects are also addressed by taking advantage of information from SHS processes for materials synthesis
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Trattamento meccanico per l’immobilizzazione di metalli pesanti in suoli contaminati
No full textIn the present work, the use of ball milling for remediation
of heavy metals contaminated soils of sandy, bentonitic and
kaolinitic type is investigated. Immobilization of heavy metals
(Cd(II), Pb(II), Zn(II)) is achieved by mechanically treating the contaminated
soil without additives, thus taking advantage of weak
transformations induced on the soil by mechanical loads occurring
during collisions among the milling spheres. The degree of heavy
metal immobilization is evaluated by analyzing the corresponding
leachable fraction from the treated soil as obtained through the “synthetic
precipitation leaching procedure” SPLP. The reduction of
leachable fraction of heavy metals from the synthetic soils investigated,
was obtained under specific milling regimes. XRD, SEM/EDS
and granulometric analyses do not reveal alterations of the intrinsic
character of sandy and bentonitic soils after milling. The increase of
immobilization efficiency when soils are mechanically treated may
be due to specific phenomena induced during ball milling such as the
formation of new fresh surfaces (through particle breakage) onto
which heavy metals may be irreversibly adsorbed as well as entrapment of heavy metals into aggregates. Also solid diffusion into the
crystalline reticulum of soil particles determined by mechanical
action may contribute to the increase of immobilization capacity
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