991 research outputs found
Enzymatic monolith continuous microreactors for the synthesis of xylooligosaccharides by controlled hydrolysis of xylans
No full textImmobilized enzymes are increasingly used in enzymatic microreactors, to encourage applications in different fields: food industry, medical diagnostics, organic synthesis, drug discovery, biosensors. As a matter of facts, microfluidic systems offer many advantages over conventional packed-bed bioreactors, such as higher efficiency, feasibility of multi-enzyme systems, higher mechanical stability, reduced amounts of reagents required [Pirozzi et al., 2016]. In this study β-1,4-xylan obtained from hemicelluloses was used to obtain xylo-oligosaccharides (XOS), the only nutraceutical that can be produced from lignocellulosic biomass. XOS are considered non-digestible food ingredients, and their prebiotic effect of XOS on Bifidobacterium and Lactobacillus species has been recently demonstrated [Aachary et al., 2011; Broekaert et al., 2011; Nacos et al., 2006; Samanta et al, 2015; Vazquez]et al., 2000]. In addition XOS are stable at wide range of pH (2.5–8.0) and temperature (100 °C), they can stimulate the selective growth of the gut microflora, reduce the blood glucose and cholesterol, reduce the pro-carcinogenic enzymes in gastrointestinal tract, and enhance the mineral absorption from large intestine [Aachary et al., 2011; Broekaert et al., 2011; Nacos et al., 2006; Samanta et al, 2015; Vazquez]et al., 2000]. In this view, sol-gel methods were used for the physical entrapment of xylanase from T. lanuginosus. Due to the mild conditions usually adopted for the gel synthesis, enzymes could be added to the initial mixture of precursors and so entrapped within monolithic porous layers in capillary tubes [Pirozzi et al., 2016]. A suitable combination of sol-gel precursors was found for the simultaneous improvement of the monolith adhesion to the tubing internal surfaces and of the catalytic properties of the entrapped enzymes. Specific attention was devoted to the determination of operating conditions suitable to enhance enzyme stability as well as selectivity in terms of XOS produced
Endovascular treatment of non maturing distal arterovenous fistula for haemodialysis associated with forearm artery stenosis
No full textRITARDO DI MATURAZIONE FAV DISTALI NEL PAZIENTE VASCULOPATICO. TRATTAMENTO MEDIANTE PTA DELLE ARTERIE DI AVAMBRACCIO
No full textAsymptotic results for first-passage times of some exponential processes
No full textWe consider the process {V (t) : t ≥ 0} defined by V (t) = v0eX(t) (for all t ≥ 0), where
v0 > 0 and {X(t) : t ≥ 0} is a compound Poisson process with exponentially distributed
jumps and a negative drift. This process can be seen as the neuronal membrane potential in
the stochastic model for the firing activity of a neuronal unit presented in Di Crescenzo and
Martinucci (Math Biosci 209(2):547–563 2007). We also consider the process { ˜ V (t) : t ≥0}, where ˜ V (t) = v0e
˜X(t) (for all t ≥ 0) and { ˜ X(t) : t ≥ 0}
is the Normal approximation (as t →∞) of the process {X(t) : t ≥ 0}. In this paper we are interested in the first-passage
times through a constant firing threshold β (whereβ > v0) for both processes {V (t) : t ≥ 0}
and { ˜ V (t) : t ≥ 0}; our aim is to study their asymptotic behavior as β →∞in the fashion
of large deviations. We also study some statistical applications for both models, with some
numerical evaluations and simulation results
Limit cycles in control system employing smart actuators with hysteresis.
No full textThis paper presents theoretical and experimental results concerning a feedback control system employing a Terfenol-D-based smart actuator. Such magnetostrictive devices exhibit significant hysteresis, which, under some conditions, can generate self-sustained periodic oscillations in the control loop. The paper proposes a general procedure to find these conditions and to compute this periodic solution by exploiting some classical results about describing function analysis and the well-known Preisach operator theory. The theoretical findings are supported by a rigorous mathematical analysis resorting to fixed-point theorems
Asymptotic Results for the Absorption Time of Telegraph Processes with Elastic Boundary at the Origin
No full textWe consider a telegraph process with elastic boundary at the origin studied recently in the
literature (see e.g. Di Crescenzo et al. (Methodol Comput Appl Probab 20:333–352 2018)).
It is a particular random motion with finite velocity which starts at x ≥ 0, and its dynamics
is determined by upward and downward switching rates λ and μ, with λ>μ, and an
absorption probability (at the origin) α ∈ (0, 1]. Our aim is to study the asymptotic behavior
of the absorption time at the origin with respect to two different scalings: x → ∞ in the
first case; μ → ∞, with λ = βμ for some β > 1 and x > 0, in the second case. We prove
several large and moderate deviation results. We also present numerical estimates of β based
on an asymptotic Normality result for the case of the second scaling
Appunti per una riflessione sul diritto alla vita nella Costituzione italiana
No full textIl contributo si propone di indagare il fondamento costituzionale del "diritto alla vita", in una prospettiva critica rispetto alle impostazioni dottrinali e giurisprudenziali che lo qualificano genericamente come diritto implicito o che pervengono alla sua identificazione attraverso l'interpretazione per valori. In particolare, sulla scorta delle disposizioni costituzionali, si perviene a individuare il contenuto specifico di tale diritto nelle sue due declinazioni di "diritto a non essere privato da altri della vita" e di "diritto a ricevere i mezzi economici necessari per vivere". Si giunge, poi, a escludere che dalla Costituzione possa desumersi un dovere di vivere, senza che però se ne possa trarre neppure un diritto costituzionale al suicidio. Quest'ultimo, pertanto, viene inquadrato come comportamento lecito dal punto di vista costituzionale, benché non assistito da specifiche garanzie, con conseguente possibilità per il legislatore di disporre discrezionalmente della sua qualificazione in termini di liceità o illiceità
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