Combinatorial laplacians and positivity under partial transpose

Density matrices of graphs are combinatorial laplacians normalized to have trace one (Braunstein \emph{et al.} \emph{Phys. Rev. A,} \textbf{73}:1, 012320 (2006)). If the vertices of a graph are arranged as an array, then its density matrix carries a block structure with respect to which properties such as separability can be considered. We prove that the so-called degree-criterion, which was conjectured to be necessary and sufficient for separability of density matrices of graphs, is equivalent to the PPT-criterion. As such it is not sufficient for testing the separability of density matrices of graphs (we provide an explicit example). Nonetheless, we prove the sufficiency when one of the array dimensions has length two (for an alternative proof see Wu, \emph{Phys. Lett. A}\textbf{351} (2006), no. 1-2, 18--22). Finally we derive a rational upper bound on the concurrence of density matrices of graphs and show that this bound is exact for graphs on four vertices.Comment: 19 pages, 7 eps figures, final version accepted for publication in Math. Struct. in Comp. Sc

Valutazione delle caratteristiche di pre-probioticità di ceppi di Lactobacillus plantarum

Durante tutta la vita l’uomo è in stretto contatto e interagisce con i microrganismi che lo circondano. Molti di questi microrganismi sono ospitati all’interno del nostro stesso corpo e formano la flora microbica. In particolare il nostro tratto gastrointestinale ne è ricco e ospita circa 1012 - 1014 cellule batteriche/g (fino a 10 volte il numero delle cellule che compongono il corpo umano, stimate infatti sull’ordine di 1013 cellule). I fattori ambientali, come l’alimentazione, possono influire in modo considerevole sulla formazione e modulazione della flora microbica. Un’importante aiuto alla salvaguardia della nostra salute viene esplicato da particolari microrganismi detti probiotici. Il termine probiotico venne coniato nel 1965 da Lilly e Stillwell, etimologicamente deriva dall’unione della preposizione latina pro (a favore di) e dell’aggettivo greco βιωτικόϛ (derivante a sua volta dal sostantivo βίος, vita). Quindi un probiotico è un agente che influenza in modo benefico la salute dell’ospite che lo accoglie. Nei vari anni sono state proposte varie definizioni di probiotico, tutte in ogni modo concordano nello specificare che tale agente benefico deve essere vitale, quindi vengono esclusi dalla denominazione di probiotico tutti gli agenti chimici o bioterapeutici che non sono vitali. Secondo la definizione ufficiale del testo unificato FAO/WHO del 2006 i probiotici sono: “organismi vivi che, somministrati in quantità adeguata, apportano un beneficio alla salute dell’ospite” (Guarner e Schaafsma, 1998). Lo scopo di questo elaborato di tesi è quello di valutare ceppi di Lactobacillus plantarum isolati da matrici alimentari di origine animale per le caratteristiche pre-probiotiche e probiotiche. Come già detto probiotico è quel microrganismo che arriva vitale nel tratto intestinale e ivi svolge un’azione positiva nei confronti dell’ospite. Si ritengono quindi molto importanti le caratteristiche di pre-probioticità, ovvero la capacità di arrivare vitale nel tratto intestinale superando le barriere fisiologiche che presenta il nostro organismo. Lo studio di tali caratteristiche è stato preceduto dalla valutazione della sensibilità dei ceppi testati agli antibiotici al fine di verificare la loro sicurezza qualora impiegati come additivi alimentari. Il lavoro di tesi è stato impostato come una selezione che partendo dalla totalità dei ceppi a disposizione, ha previsto l’eliminazione di quelli non rispondenti alle caratteristiche ricercate. Una volta appurata la sensibilità agli antibiotici (sicurezza alimentare), i ceppi oggetto di studio sono stati sottoposti alla valutazione della resistenza al lisozima (cavità orale), resistenza a pH acido (cavità gastrica), resistenza ai sali biliari (passaggio nel duodeno) e possibilità di adesione agli enterociti (permanenza nell’intestino)

Model predictive controllers for reduction of mechanical fatigue in wind farms

We consider the problem of dispatching WindFarm (WF) power demand to individual Wind Turbines (WT) with the goal of minimizing mechanical stresses. We assume wind is strong enough to let each WTs to produce the required power and propose different closed-loop Model Predictive Control (MPC) dispatching algorithms. Similarly to existing approaches based on MPC, our methods do not require changes in WT hardware but only software changes in the SCADA system of the WF. However, differently from previous MPC schemes, we augment the model of a WT with an ARMA predictor of the wind turbulence, which reduces uncertainty in wind predictions over the MPC control horizon. This allows us to develop both stochastic and deterministic MPC algorithms. In order to compare different MPC schemes and demonstrate improvements with respect to classic open-loop schedulers, we performed simulations using the SimWindFarm toolbox for MatLab. We demonstrate that MPC controllers allow to achieve reduction of stresses even in the case of large installations such as the 100-WTs Thanet offshore WF

An integral formulation for wave propagation on weakly non-uniform potential flows

An integral formulation for acoustic radiation in moving flows is presented. It is based on a potential formulation for acoustic radiation on weakly non-uniform subsonic mean flows. This work is motivated by the absence of suitable kernels for wave propagation on non-uniform flow. The integral solution is formulated using a Green's function obtained by combining the Taylor and Lorentz transformations. Although most conventional approaches based on either transform solve the Helmholtz problem in a transformed domain, the current Green's function and associated integral equation are derived in the physical space. A dimensional error analysis is developed to identify the limitations of the current formulation. Numerical applications are performed to assess the accuracy of the integral solution. It is tested as a means of extrapolating a numerical solution available on the outer boundary of a domain to the far field, and as a means of solving scattering problems by rigid surfaces in non-uniform flows. The results show that the error associated with the physical model deteriorates with increasing frequency and mean flow Mach number. However, the error is generated only in the domain where mean flow non-uniformities are significant and is constant in regions where the flow is uniform

HYDRODYNAMIC PERFORMANCES OF SMALL SIZE SWATH CRAFT

The good seakeeping characteristics of SWATH hull form are very interesting for small working craft and pleasure boats. Intrinsic limitations as the low values of weight per inch of immersion and transversal and longitudinal instability, can be acceptable and successfully managed when the mission profile does not ask for significant load variation and shift. The exploitation of SWATH concept is limited by the craft size, but if main dimensions allow enough static stability, this configuration appears very promising. SWATH behaviour in rough sea at zero and low speed have led to consider this hull form within the small craft design research program in progress at University of Naples Federico II. The design of small size SWATH working/pleasure craft has to begin from the consideration of strut waterplane areas that are the key factor to get acceptable static and dynamic stability. Displacement has to be reduced as most as possible to increase static stability, as shown by last design trends. The results of CFD analysis concerning SWATH resistance and propulsion, aspects are presented. A numerical evaluation of the hull-propeller interactions is performed, through simulations of self-propulsion tests with a simplified method (Actuator Disk model) to discretize the propeller effect. The effective wake coefficient, the thrust deduction fraction and hull efficiency are provided. To validate CFD resistance results a comparison with experimental tests performed by Authors is reported. The presented work highlights different hydrodynamic aspects, comments advantages and critical issues of SWATH concept and reports detailed CFD modelling procedure with the aim to provide a reference for SWATH small craft design

Effect of dietary Curcuma longa L. powder on lipid oxidation of frozen pork

Introduction - Modification of the eating habits incremented the consumption of ready-to-eat, ready-to-cook and frozen foods. Meat can be store up as frozen for different time in relation to the animal species, to the cut or to a previous processing. Several researches were conducted to evaluate the use of antioxidant products as dietary supplementation in order to produce modification in chemical composition of meat and lead to a positive influence on the length of shelf life of the products. Aim - The aim of this research was to study the effect of the supplementation with Curcuma longa L. powder in pig diet on the lipid oxidation after common frozen storage (-18 °C) of meat for long time (up to 135 days). Materials and methods - Pigs were fed with two different diets, control and turmeric, for 30 days before been slaughtered. Longissimus lumborum chops were frozen at -18 °C and lipid oxidation was evaluated with the thiobarbituric acid reactive substances (TBARS) method after 45, 60, 75, 90, 105, 120 and 135 days of storage. Results and discussion - The addition of the natural antioxidant did not modify the meat quality of the evaluated samples (P > 0.05). Nor the time of storage increased the TBARS value of the meat (P > 0.05). Our results are in accordance with other similar research studies on antioxidant dietary supplementations. Conclusion - Pigs, as large animal, probably need a bigger amount of antioxidant supplementation in order to modified meat characteristics. Thus, the lack of difference in lipid oxidation of frozen meat showed by Control and Turmeric diets could be associated both to the small dose of dietary turmeric powder and to the length of the diet period

Association between attention and heart rate fluctuations in pathological worriers

Recent data suggests that several psychopathological conditions are associated with alterations in the variability of behavioral and physiological responses. Pathological worry, defined as the cognitive representation of a potential threat, has been associated with reduced variability of heart beat oscillations (i.e., decreased heart rate variability; HRV) and lapses of attention indexed by reaction times (RTs). Clinical populations with attention deficit show RTs oscillation around 0.05 and 0.01 Hz when performing a sustained attention task. We tested the hypothesis that people who are prone to worry do it in a predictable oscillating pattern revealed through recurrent lapses in attention and concomitant oscillating HRV. Sixty healthy young adults (50% women) were recruited: 30 exceeded the clinical cut-off on the Penn State Worry Questionnaire (PSWQ; High-Worry, HW); the remaining 30 constituted the Low-Worry (LW) group. After a diagnostic assessment, participants performed two 15-min sustained attention tasks, interspersed by a standardized worry-induction procedure. RTs, HRV and moods were assessed. The analyses of the frequency spectrum showed that the HW group presents a significant higher and constant peak of RTs oscillation around 0.01 Hz (period 100 s) after the induction of worry, in comparison with their baseline and with the LW group that was not responsive to the induction procedure. Physiologically, the induction significantly reduced high-frequency HRV and such reduction was associated with levels of self-reported worry. Results are coherent with the oscillatory nature of the default mode network (DMN) and further confirm an association between cognitive rigidity and autonomic nervous system inflexibility