Search results for "character"
showing 10 items of 2956 documents
Relativistic perfect fluids in local thermal equilibrium
2017
Every evolution of a fluid is uniquely described by an energy tensor. But the converse is not true: an energy tensor may describe the evolution of different fluids. The problem of determining them is called here the {\em inverse problem}. This problem may admit unphysical or non-deterministic solutions. This paper is devoted to solve the inverse problem for perfect energy tensors in the class of perfect fluids evolving in local thermal equilibrium (l.t.e.). The starting point is a previous result (Coll and Ferrando in J Math Phys 30: 2918-2922, 1989) showing that thermodynamic fluids evolving in l.t.e. admit a purely hydrodynamic characterization. This characterization allows solving this i…
Theoretical and experimental behaviour of the muscle viscosity coefficient during maximal concentric actions
1994
The aim of this study was to calculate the theoretical variation of the nonlinear damping factor (B) as a function of the muscle shortening velocity, and then to compare the theoretical values with the experimental data obtained on both the elbow flexor and the ankle extensor muscles. The theoretical variation of the B factor was determined from a muscle model consisting of a contractile component in parallel with a viscous damper both in series with an elastic component, and by using, the characteristic equation of the force velocity curve. In this muscle model, the viscous element modelled the inability of the muscle to generate as big a contracting force (while shortening) as possible un…
Covariant determination of the Weyl tensor geometry
2001
We give a covariant and deductive algorithm to determine, for every Petrov type, the geometric elements associated with the Weyl tensor: principal and other characteristic 2-forms, Debever null directions and canonical frames. We show the usefulness of these results by applying them in giving the explicit characterization of two families of metrics: static type I spacetimes and type III metrics with a hypersurface-orthogonal Killing vector. PACS numbers: 0240M, 0420C
Probing the creatable character of some significant universe models
2008
An unambiguous physical definition of creatable universes was recently proposed. According to it, flat and closed Friedmann-Robertson-Walker (FRW) backgrounds can be created as quantum vacuum fluctuations, whereas open backgrounds are not creatable. Here, physically motivated perturbations of closed and flat backgrounds are analyzed. Various creatable perturbed FRW universes are thus found. Some of them involve scalar and tensor perturbations with appropriate spectra, whereas other ones are Bianchi models.
High performance 3D CZT spectro-imager for BNCT-SPECT: preliminary characterization
2018
The National Institute of Nuclear Physics (INFN) is supporting the 3CaTS project with the aim of developing a new Single Photon Emission Computed Tomography (SPECT) system for real time 10 B therapeutic dose monitoring in the binary experimental hadron therapy called Boron Neutron Capture Therapy (BNCT). BNCT is a highly selective tumour treatment based on the neutron capture reaction 10 B(n,α) 7 Li. The secondary particles have a high LET with ranges in tissues of the order of 10 μm (thus less than the mean cell diameter of few tens μm). Targeting the 10 B delivery towards cancer, the released energy lethally damages only the malignant cells sparing the normal tissues, thus enabling a cell…
One-particle Green's function
2013
In this chapter we get acquainted with the one-particle Green's function G , or simply the Green's function. The chapter is divided in three parts. In the first part (Section 6.1) we illustrate what kind of physical information can be extracted from the different Keldysh components of G . The aim of this first part is to introduce some general concepts without being too formal. In the second part (Section 6.2) we calculate the noninteracting Green's function. Finally in the third part (Sections 6.3 and 6.4) we consider the interacting Green's function and derive several exact properties. We also discuss other physical (and measurable) quantities that can be calculated from G and that are re…
Periodic orbits of a neuron model with periodic internal decay rate
2015
In this paper we will study a non-autonomous piecewise linear difference equation which describes a discrete version of a single neuron model with a periodic internal decay rate. We will investigate the periodic behavior of solutions relative to the periodic internal decay rate. Furthermore, we will show that only periodic orbits of even periods can exist and show their stability character.
Identification of plant cells in black pigments of prehistoric Spanish Levantine rock art by means of a multi-analytical approach. A new method for s…
2017
We present a new multi-analytical approach to the characterization of black pigments in Spanish Levantine rock art. This new protocol seeks to identify the raw materials that were used, as well as reconstruct the different technical gestures and decision-making processes involved in the obtaining of these black pigments. For the first of these goals, the pictorial mat- ter of the black figurative motifs documented at the Les Dogues rock art shelter (Ares del Maestre, Castello ́ n, Spain) was characterized through the combination of physicochemical and archeobotanical analyses. During the first stage of our research protocol, in situ and non- destructive analyses were carried out by means of…
Effect of rootstock on growth, yield and fruit characteristics in cv 'Bianca' pistachio (Pistacia vera L.) trees
2005
This paper, following preliminary field evaluation trials started in 1993, reports a study on the effect of eight different in vitro-propagated clonal rootstocks (P. atlantica and P. integerrima) and one seedling rootstock (P. terebinthus) on the vegetative and productive behaviour of pistachio cultivar 'Bianca'. The trees, budded in 1991, were grown using standard cultural practices for dry-land farming in a sandy clay loam soil, located inland in Sicily. On average, clones of P. integerrima (I-6 and I-2) were the most vigorous rootstocks. Clones of P. atlantica had intermediate vigour. Rootstock significantly affect yield but not fruit weight, kernel to nut ratio, splitting and blanking p…
Preparation and Characterization of Polyolefin-Based Nanocomposite Blown Films for Agricultural Applications
2009
These kinds of filmshave,asaprimaryaim,tocreateafavorablemicro-climateto accelerate the plant growth.Thematerialsfortheseapplicationsmustpossessseveralspecificandpeculiarcharacteristics,suchastheabilitytobeshaped into films (even with wide dimensions and largethickness ranges), good deformability and tear resistancetogetherwithasufficientrigidity,transparencyforUVandIR radiation in particular regions of the spectrum, a goodresistance to photo-oxidative phenomena and for someapplications to provide a barrier for certain gases.Moreover, an important property requested for thematerials used for greenhouse covering is the capabilityto diffuse the light. In fact, according to some studies,diffused l…