Search results for "CEM"
showing 10 items of 3487 documents
Comparison of magnetic resonance imaging of inhaled SF6 with respiratory gas analysis
2008
Magnetic resonance imaging of inhaled fluorinated inert gases ((19)F-MRI) such as sulfur hexafluoride (SF(6)) allows for analysis of ventilated air spaces. In this study, the possibility of using this technique to image lung function was assessed. For this, (19)F-MRI of inhaled SF(6) was compared with respiratory gas analysis, which is a global but reliable measure of alveolar gas fraction. Five anesthetized pigs underwent multiple-breath wash-in procedures with a gas mixture of 70% SF(6) and 30% oxygen. Two-dimensional (19)F-MRI and end-expiratory gas fraction analysis were performed after 4 to 24 inhaled breaths. Signal intensity of (19)F-MRI and end-expiratory SF(6) fraction were evaluat…
La Strategia del Ventriloquo. Sul Portavoce
2016
This paper examines the activity of the spokesperson by means of an analogy with the art of ventriloquism. It is composed of three parts: in the first one we introduce some definitions of «spokesperson» in order to explain in what consists his activity. The second part is devoted to the analysis of the linguistic aspects of the spokesperson’s activity with particular reference to some language operations: a) self-effacement; b) attribution of agentivity. Finally, in the last part we discuss some questions that remain open in the debate on spokesperson’s activity.
Le competenze statistiche dei laureati italiani alla prova del mercato del lavoro
2019
The statistical skills of Italian graduates in the labor market test · This paper analyses the difference in placement output between graduates in Statistics and others. In particular we focus our attention on the difference in socio-economic and labour market characteristics of graduates having specific skills in method and approach in Statistics, and graduates who during their university courses studied Statistics (almost 10% of hours of their subjects). Data are driven from The AlmaLaurea Graduates’ Employment Status, monitoring of graduates’ access to the labour market within 1 year and 5 years after graduation. It is a very important tool for evaluating the effectiveness of the academi…
Hunting active Brownian particles: Learning optimal behavior
2021
We numerically study active Brownian particles that can respond to environmental cues through a small set of actions (switching their motility and turning left or right with respect to some direction) which are motivated by recent experiments with colloidal self-propelled Janus particles. We employ reinforcement learning to find optimal mappings between the state of particles and these actions. Specifically, we first consider a predator-prey situation in which prey particles try to avoid a predator. Using as reward the squared distance from the predator, we discuss the merits of three state-action sets and show that turning away from the predator is the most successful strategy. We then rem…
Stepping molecular motor amid Lévy white noise
2015
We consider a model of a stepping molecular motor consisting of two connected heads. Directional motion of the stepper takes place along a one-dimensional track. Each head is subject to a periodic potential without spatial reflection symmetry. When the potential for one head is switched on, it is switched off for the other head. Additionally, the system is subject to the influence of symmetric, white Lévy noise that mimics the action of external random forcing. The stepper exhibits motion with a preferred direction which is examined by analyzing the median of the displacement of a midpoint between the positions of the two heads. We study the modified dynamics of the stepper by numerical sim…
Probabilistic response of linear structures equipped with nonlinear damper devices (PIS method)
2008
Passive control introducing energy absorbing devices into the structure has received considerable attention in recent years. Unfortunately the constitutive law of viscous fluid dampers is highly nonlinear, and even supposing that the structure behaves linearly, the whole system has inherent nonlinear properties. Usually the analysis is performed by a stochastic linearization technique (SLT) determining a linear system equivalent to the nonlinear one, in a statistical sense. In this paper the effect of the non-Gaussianity of the response due to the inherent nonlinearity of the damper device will be studied in detail via the Path Integral Solution (PIS) method. A systematic study is conducted…
Triterpene saponins from Billia rosea.
2017
Five previously undescribed triterpene saponins, billiosides A-E, and a known analogue, were isolated from the seeds of Billia rosea (Planch. & Linden) C. Ulloa & P. Jorg. Their structures were elucidated on the basis of extensive 1D and 2D NMR experiments (1H, 13C, DEPT, COSY, TOCSY, NOESY, ROESY, HSQC, and HMBC) and mass spectrometry as (3β,21β,22α)-3-[(2-O-β-D-glucopyranosyl-O-[α-L-arabinopyranosyl-(1 → 4)]-β-D-glucopyranosyl)oxy]-21-[((2E,6S)-2,6-dimethyl-6-hydroxyocta-2,7-dienoyl)oxy]-22-(acetyloxy)-24-hydroxyolean-12-en-28-oic acid, (3β,21β,22α)-3-[(2-O-β-D-galactopyranosyl-β-D-glucopyranosyl)oxy]-21,22-dihydroxyolean-12-en-28-yl O-α-L-arabinopyranosyl-(1 → 4)-β-D-glucopyranoside, (3β…
Cooperative effects on the HS→LS relaxation in the [Fe(ptz)6](BF4)2 spin-crossover system
1992
Abstract The high-spin to low-spin (HS→LS) relaxation in the [Fe(ptz) 6 ](BF 4 ) 2 spin-crossover system deviates strongly from first-order kinetics because of cooperative effects of elastic origin. The shift in horizontal and vertical displacement of the potential wells of the initial and final state relative to each other due to the build-up of an “internal” pressure is estimated from spectroscopic measurements. The HS→LS relaxation as such is described by the theory of nonadiabatic multiphonon relaxation in the strong-coupling limit, with a Huang—Rhys factor S ≈ 45 which is much larger than the reduced energy gap p . The sigmoidal relaxation curves in [Fe(ptz) 6 ](BF 4 ) 2 result when a …
Peptide Metal–Organic Frameworks for Enantioselective Separation of Chiral Drugs
2017
We report the ability of a chiral Cu(II) 3D MOF based on the tripeptide Gly-L-His-Gly (GHG) for the enantioselective separation of metamphetamine and ephedrine. Monte Carlo simulations suggest that chiral recognition is linked to preferential binding of one of the enantiomers as result of either stronger or additional H-bonds with the framework that lead to energetically more stable diastereomeric adducts. Solid phase extraction (SPE) of a racemic mixture by using Cu(GHG) as extractive phase permits isolating more than 50% of the (+)-ephedrine enantiomer as target compound in only four minutes. To the best of our knowledge, this represents the first example of a MOF capable of separating ch…
Two strained hexahelicenophanes
2000
The crystal structures of the [6]helicenes 4,13-(1,10-decamethylenedioxy)hexahelicene, C36H34O2, (I), and 4,13-(1,8-octamethylenedioxy)hexahelicene, C34H30O2, (II), show strong steric interactions between the terminal benzene rings and the polymethylenedioxy chains. The shortest ring A and F distances amount to 2.941 (3) and 2.902 (3) A, respectively. The increased steric energy of the ground state is responsible for a significantly lower racemization barrier of (I) and (II) in comparison to the unsubstituted [6]helicene.