1,355,326 research outputs found
Abilità di definire parole e comprendere teti nei bambini con DSA: strumenti e indici di valutazine a confronto
No full textLa comprensione di testi comporta l’integrazione di abilità cognitive e linguistiche. La competenza lessicale svolge un ruolo centrale, non solo come padronanza del lessico (comprensione/produzione di parole a scopo pragmatico-comunicativo) e delle strutture morfo-sintattiche (organizzazione del discorso narrativo), ma anche come consapevole riflessione, analisi ed esplicitazione dei significati (definizione metalinguistica). Finora gli studi si sono prevalentemenete occupati dei primi due tipi di competenze, trascurando gli aspetti metalinguistici e metarappresentazionali, anche per la carenza di strumenti specifici. Ad esempio, il sub-test di Vocabolario della WISC, impropriamente considerato una prova di definizione, non considera la formulazione formale delle risposte, che sola consente l’accesso alle rappresentazioni semantiche (Belacchi, Benelli, 2007). Questo contributo, prosieguo di riceche precedenti (Bellelli e Belacchi, 2013; 2014) si propone di approfondire il rapporto tra abilità linguistiche e comprensione di testi, confrontando gli indici di valutazione del sub-test di Vocabolario e la Scala di competenza definitoria, in bambini con DSA
Cyanide dissociation from the hemoglobin of Parascaris equorum.
No full textThe reduction of cyanomethemoglobin by dithionite leads to the appearance of an intermediate, the complex of cyanide with ferrous hemoglobin, whose dissociation is easily followed in a stopped flow apparatus. This reaction was studied in the hemoglobin from the parasitic nematode Parascaris equorum, whose extremely high oxygen affinity is due to a very low dissociation rate. The rate of cyanide dissociation from ferrous Parascaris hemoglobin is not so dramatically different from that of other hemoglobins and myoglobins. Other features of the reaction are: (i) the rate constant of cyanide release is pH independent, an observation which is agreement with the possible absence of the distal histidine, given the mechanism suggested in a previous study (Bellelli, A., Antonini, G., Brunori, M, Springer, B.A. and Sligar, S.G. (1990) J. Biol. Chem. 265, 18898-18901), and (ii) the time-course shows no kinetic cooperativity. The structural basis of the extremely high oxygen affinity of Parascaris hemoglobin cannot be explained on the basis of the results here reported. This study also confirms that, even though cyanide binding to ferrous hemoglobins is controlled by distal interactions, the functional behaviour of this ligand is characteristic and differs from the behaviour of oxygen
Magnetorheological elastomers characterization under shear loading up to failure: A magneto-mechanical multivariate analysis
No full textThis work analyses the shear behavior of magnetorheological elastomers (MRE), a class of smart materials which presents interesting magneto-mechanical properties. In order to determine the effect of several variables at a time, a design of experiment approach is adopted. A set of several samples of MRE was manufactured, by varying the weight fraction of ferromagnetic material inside the viscoelastic matrix and the isotropicity of the material, by adding an external magnetic field while the elastomeric matrix was still liquid. The mechanical behavior of each sample was analyzed by conducting cyclic tests at several shear rates, both with and without an external magnetic field. Moreover, in order to estimate the maximum shear stress, the specimens were loaded monotonically up to failure. Shear stiffness, maximum shear stress and specific dissipated energy were calculated on the basis of the experimental data. The results were analyzed using an Analysis of Variance (ANOVA) to assess the statistical influence of each variable. The experimental results highlighted a strong correlation between the weight fraction of ferromagnetic material in each sample and its mechanical behavior. Moreover, the dissipated energy of the MRE drops down when the magnetic field stiffens the behavior or the shear rate increases. The ultimate failure shear stress is strongly affected by the external magnetic field, increasing it by nearly 50%. The ANOVA on the results provides a simple phenomenological model is built for each output variable and it is compared with the experimental tests. These models produce a fast and fairly accurate prediction of each analyzed response of the MRE under various shear rates and applied magnetic fields
Remontajes aplicados a la interpretación de la tecnología lítica: las primeras ocupaciones de Campo Moncada 2 (Pcia. del Chubut).
No full text27 ref.Fil: Bellelli, Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina.Fil: Carballido, Mariana. Instituto Nacional de Antropología y Pensamiento Latinoamericano; Argentina.Fil: Bellelli, Cristina. Instituto Nacional de Antropología y Pensamiento Latinoamericano; Argentina.27 ref
Remontajes aplicados a la interpretación de la tecnología lítica: las primeras ocupaciones de Campo Moncada 2 (Pcia. del Chubut).
No full text27 ref.Fil: Bellelli, Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina.Fil: Carballido, Mariana. Instituto Nacional de Antropología y Pensamiento Latinoamericano; Argentina.Fil: Bellelli, Cristina. Instituto Nacional de Antropología y Pensamiento Latinoamericano; Argentina.27 ref
Magneto-mechanical characterization of magnetorheological elastomers
No full textThis work analyses the properties and the magneto-mechanical characteristics of magnetorheological elastomers, a class of smart materials not yet broadly investigated. First, set of several samples of this material was manufactured, each one characterized by a different percentage of ferromagnetic material inside the viscoelastic matrix. The specimens were manufactured in order to create isotropic and anisotropic configurations, respectively, with randomly dispersed ferromagnetic particles or with an aligned distribution, obtained through and external magnetic field. Then, the mechanical behaviour of each sample was analysed by conducting a compression test, both with and without an external magnetic field. Moreover, a three-point bending test was also performed on the same specimens. Stiffness, deformation at maximum stress and specific energy dissipated were calculated based on the experimental data. The results were analysed considering the mechanical responses, and an analysis of variance was carried out in order to assess the statistical influence of each variable. The experimental results highlighted a strong correlation between the percentage of ferromagnetic material in each sample and its mechanical behaviour. The anisotropicity of the material, aligned in columnar structures, also affects the stiffness measured in the compression test, while the external magnetic field’s main contribution is to reduce the samples’ maximum deformation. Using analysis of variance results as guidelines, we built a simple phenomenological model which produces quite reliable predictions regarding the mechanical response of the magnetorheological elastomers under compressive stress
Control of oxygen affinity in mammalian hemoglobins: Implications for a system biology description of the respiratory properties of the red blood cell
No full textL'emoglobina e la mioglobin sono state considerate i modelli paradigmatici della funzione delle proteine, al punto da essere stati definiti "gli atomi di idrogeno della biologia" [Frauenfelder et al. Proc. Natl. Acad. Sci. USA, 2003; 100, 8615-8617]. Data questa posizione privilegiata e l'enorme mole di informazione disponibile su queste proteine, il globulo rosso potrebbe apparire come il modello e "l'atomo di idrogeno" della biologia dei sistemi cellulari. Infatti, essendo il trasporto dell'O2 la principale funzione del globulo rosso, la distanza che separa la proteina (emoglobina) e la cellula potrebbe apparire modesta. Ciononostante una grande quantità di informazione biochimica è necessaria per modellizzare le proprietà respiratorie dell'eritrocita. Questo problema è aumentato se la modellizzazione si prefigge lo scopo di scoprire o spiegare proprietà dell'emoglobine selezionate dall'evoluzione. La difficoltà principale risiede nel fatto che emoglobine dotate di proprietà funzionali e storie evoluzionistiche diverse potrebbero comportarsi in modo simile nel complesso ambiente del sangue, mentre emoglobine simili che condividono una sostanziale omologia di sequenza possono presentare importanti differenze funzionali a causa della mutazione di pochi residui critici. Quindi, la proprietà funzionali dell'emoglobina e del sangue possono riflettere più strettamente adattamenti ambientali recenti piuttosto che la storia evoluzionistica dell'animale. In questa review noi analizziamo il caso delle emoglobine di mammiferi in un tentativo di fornire un sommario della loro complessità che, noi speriamo, possa essere di aiuto per gli scienziati interessati alla esplorazione quantitativa dell'evoluzione della funzione respiratoria. Alla base di ogni modellizzazione di successo deve infatti trovarsi un grande corpus di informazione raccolta in faticose e spesso dimenticati studi sulle proprietà biochimiche dell'emoglobina condotti in un intervallo di tempo di oltre cento anni.Hemoglobin and myoglobin have been considered for a long time the paradigmatic model systems for protein function, to the point of being defined the “hydrogen atom[s] of biology” [Frauenfelder et al. Proc. Natl. Acad. Sci. USA, 2003; 100, 8615-8617]. Given this privileged position and the huge amount of quantitative information available on these proteins, the red blood cell might appear as the model system and“hydrogen atom” of system biology. Indeed, since the red cell's main function is O2 transport by hemoglobin, the gap between the protein and the cell may appear quite small. Yet, a surprisingly large amount of detailed biochemical information is required for the modelization of the respiratory properties of the erythrocyte. This problem is compounded if modelization aims at uncovering or explaining evolutionarily selected functional properties of hemoglobin. The foremost difficulty lies in the fact that hemoglobins having different intrinsic properties and relatively ancient evolutionary divergence may behave similarly in the complex milieu of blood, whereas very similar hemoglobins sharing a substantial sequence similarity may present important functional differences because of the mutation of a few key residues. Thus, the functional properties of hemoglobin and blood may reflect more closely the recent environmental challenges than the remote evolutionary history of the animal. We summarize in this review the case of hemoglobins from mammals, in an attempt to provide a reasoned summary of their complexity that, we hope, may be of help to scientists interested in the quantitative exploration of the evolutionary physiology of respiration. Indeed the basis of a meaningful modelization of the red cell requires a large amount of information collected in painstaking and often forgotten studies of the biochemical properties of hemoglobin carried out over more than a century
Shear behaviour of magnetorheological elastomers: Viscoelastic and magnetorheological properties
No full textLogica e Fatti nelle Teorie Freudiane
No full textL'opera freudiana è difficile da valutare, perché affronta argomenti assai disparati, dallo studio e dalla terapia di singoli casi clinici alle ipotesi sulle cause delle malattie mentali, allo sviluppo psichico del bambino, alle teorie antropologiche, al commento di opere d'arte. Il volume presenta una rassegna storica dello sviluppo della psicoanalisi e delle critiche che le sono state mosse. Le teorie freudiane vengono analizzate attraverso più chiavi di lettura: distinguendo le interpretazioni cllniche da quelle scientifiche e, su un piano diverso, gli approcci empirico-deduttivi da quelli ermeneutici. Con un atteggiamento improntato a libertà di pensiero, curiosità intellettuale e grande rispetto verso la materia trattata, l'autore prende in considerazione la possibilità che la psicoanalisi non sia affatto una "scienza", ma piuttosto una disciplina affine all'ermeneutica
Design and characterization of a magnetorheological elastomer linear actuator for low-frequency applications
No full textThis work presents the design and characterization of an innovative linear actuator for low-frequency applications based on a magnetorheological elastomer (MRE) disc coupled to an electromagnet. MREs are a class of smart materials in which micrometre-sized magnetic particles are suspended in an elastomeric matrix. Most research works study their applicability as semi-active systems, but less effort is devoted to their applicability in actuators, but their applicability in the field is possible and could lead to potential advantages in terms of integration of the system especially for microactuation. The proposed MRE device relies on a commercial electromagnet which provides linear motion of the MRE element. The stiffness of the elastomeric matrix is exploited to bring the system back to its initial position, so that the system is monostable. The magneto-mechanical behaviour is modelled both analytically and by means of finite element magneto-mechanical simulations, and the models are compared with the experimental tests. Two membrane thicknesses and two different gaps between the membrane and the electromagnetic actuator were manufactured and characterized. The results show the effect of the design variable on the actuator behaviour and confirm that the analytical model provided can predict the actuator's behaviour with a good approximation in all the configuration analysed. The dynamic range of the proposed system, regardless of the configuration selected, demonstrates that the magnetic contribution is always able to increase the actuator force by 50% and that the provided model can easily be used as a reliable design tool for this kind of smart system
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