Showing papers by "University of Trento published in 1983"
TL;DR: In this article, the structure of the jet final state and its phenomenological consequences are discussed, and a review of QCD results for these quantities and corresponding infrared resummation techniques are presented.
458 citations
TL;DR: In this article, the authors considered a general form of the nonlinear diffusion mechanism and developed a method for establishing the existence and uniqueness of solutions of the resulting equations. And they also described the asymptotic behavior of the solutions when the time variable becomes large, and applied their results to some specific examples.
Abstract: IN THIS paper we study the existence, the uniqueness and the asymptotic behaviour of a class of nonlinear diffusion problems. These problems are motivated by models of age-dependent population dynamics which originate in the article by Gurtin & MacCamy [ll]. Only a few special cases of these models have been analyzed to date, with the most recent published work being that of MacCamy [17], Gurtin & MacCamy [12] and Langlais [15, 161. The cases treated in [12, 171 are restricted to special simple forms of the birth and death moduli that occur in these models and to a specific form of the nonlinear diffusion mechanism. On the other hand, Langlais [16] considers a different nonlinear diffusion mechanism and obtains a type of generalized solution for general forms of the birth and death moduli. In this work, we consider a general form of the nonlinear diffusion mechanism and we develop a method for establishing the existence and uniqueness of solutions of the resulting equations. Our method allows us to obtain classical solutions even with general forms of the birth and death moduli. We also describe the asymptotic behaviour of the solutions when the time variable becomes large, and apply our results to some specific examples. The equations that we study are motivated as follows. Consider a population that can disperse in a spatial domain R. For simplicity we take Q = J, where J is an open interval in R, but it will be clear from the context that more general regions Q of R” can be considered. Let ~(a, t, x) denote the number of individuals, per unit length and unit age, that are of age a at time t and are located at the position x E J. The total population, per unit length, at time t and at position x is given by
82 citations
TL;DR: In this paper, the rotational isovector state couples to the k = 1+ component of the giant quadrupole resonance, and the effect of the coupling on the energy and on the M1 strength of the low-lying state is discussed.
77 citations
TL;DR: In this paper, the evolution of a two-dimensional, incompressible, ideal fluid in a case in which the vorticity is concentrated in small, disjoint regions of the physical space is studied.
Abstract: We study the evolution of a two dimensional, incompressible, ideal fluid in a case in which the vorticity is concentrated in small, disjoint regions of the physical space. We prove, for short times, a connection between this evolution and the vortex model.
69 citations
TL;DR: A model is presented of a disease that can be transmitted directly from parent to offspring as well as through contact with infectives, and a global stability analysis is given for the basic model.
Abstract: A model is presented of a disease that can be transmitted directly from parent to offspring (vertical transmission) as well as through contact with infectives. A global stability analysis is given for the basic model and the epidemiological effects of vertical transmission are discussed. The effects of the addition of maturation and incubation delays as well as spatial diffusion are analyzed in some special cases.
51 citations
TL;DR: In this article, the generalized scaling (GS) and hydrodynamic (HD) models are discussed in detail and their applicability to nuclear giant resonances is explicitly investigated, and the effect of the surface symmetry energy term on isovector excitations can be taken into account by means of a suitable choice of the boundary conditions.
42 citations
TL;DR: In this paper, the role of tensor and short-range correlations in nuclear momentum distribution, electric form factor and two-body density of 4 He is investigated, and the importance of induced tensor correlations in the total photonuclear cross section is reinvestigated.
33 citations
TL;DR: In this paper, a phenomenological explanation for the low frequency Raman spectra was presented, which was interpreted as due to a vibrational density of states mainly due to the silver halide.
26 citations
TL;DR: In this paper, the authors give conditions of a geometric nature sufficient for a dynamical system (antonomous, with finitely many degrees of freedom) which admits two alternative lagrangian descriptions (where the lagrangians are not just trivially related) to be completely integrable, in the sense of having m constants of the motion in involution.
26 citations
TL;DR: In this article, a comparison of the EXAFS structures at the I L 3 edge of the n = 3, x = 0.3 glass and of β-AgI seems to indicate that the Ag-I coordination is substantially unmodified in the glass with respect to that in β -AgI.
24 citations
TL;DR: In this article, the excitonic luminescence spectra of photoexcited GaSe crystals immersed in superfluid He were investigated and the spontaneous and optically amplified luminance due to exciton-electron and direct-direct as well as to direct-indirect excitonexciton scattering were measured.
Abstract: We report on our investigations of the excitonic luminescence spectra of photoexcited GaSe crystals immersed in superfluid He. We measured the spontaneous and optically amplified luminescence due to exciton-electron and to direct-direct as well as to direct-indirect exciton-exciton scattering. The intensity of the exciton-exciton recombination lines is proportional to the squared intensity of the luminescence from simple excitonic recombination. We find good agreement, within experimental uncertainties, between our experimental results and theory. Gain due to exciton scattering processes is weak and difficult to observe in GaSe. From our measurements, we estimate net gain values of up to about 50 ${\mathrm{cm}}^{\ensuremath{-}1}$.
TL;DR: Dichloroverongiaquinol (1), a 4-hydroxy-4-acetamidocyclohexa-2,5-dienone, which inhibits gram-positive and gram-negative bacteria, has been isolated from the Mediterranean sponge Aplysina (=Verongia) cavernicola, and also obtained by synthesis.
Abstract: Dichloroverongiaquinol (1), a 4-hydroxy-4-acetamidocyclohexa-2,5-dienone, which inhibits gram-positive and gram-negative bacteria, has been isolated from the Mediterranean spongeAplysina (=Verongia) cavernicola, and also obtained by synthesis. It is suggested that1 may be the first chlorine-containing natural product derived from tyrosine that has been isolated.
TL;DR: Penlanfuran (2), a furanoid sesquiterpene with a novel skeleton for sponge products, has been afforded by the marine sponge Dysidea fragilis (Mont.) of Brittany.
TL;DR: In this paper, a ruolo svolto dalla struttura d'ordine dei reali nella teoria dei limiti e dei Γ-limiti.
Abstract: In questo articolo si studia il ruolo svolto dalla struttura d'ordine dei reali nella teoria dei limiti e dei Γ-limiti.
TL;DR: It is found that the magnetic susceptibility of carp carbonmonoxyhemoglobin is sensitive to both inositol hexakisphosphate and chloride ion, which alters the position of the proton resonances in the ring-current-shifted region of the spectrum.
Abstract: We have extended our studies on the magnetic properties of carp carbonmonoxyhemoglobin and the dependence of these properties upon solution variables. Using an improved version of the superconducting magnetometer, we have found that the magnetic susceptibility of carp carbonomonxythemoglobin is sensitive to both inositol hexakisphosphate and chloride ion. The dependence upon chloride ion concentration is complex. At relatively low concentrations this anion reverses the effect of inositol hexakisphosphate, restoring paramagnetism. At higher chloride concentrations the protein is converted to a roughly diamagnetic state in the absence of inositol hexakisphosphate. Along with these suceptibility studies, we have examined the effects of these anions on other properties of carp carbonmonoxyhemoglobin. The positions of the Soret bands of human asd carp methemoglobin derivatives are correlated with spin state; changes in the magnetic suceptibility of carbobmonoxyhemoglobi are similarly associated with alterations in this spectral band. We have also examined the effects of these anions on the proton nuclear magnetic resonance specturm of carp carbonomonoxyhemoglobin. Both chloride and inositol hexakisphosphate alter the position of the position of the proton resonances in the ring-current-shifted region of the spectrum.
TL;DR: In this article, the absence of Gribov copies when non abelian gauge theories are quantized according to a spacelike planar gauge was shown, and it was shown that there are no copies of non-abelian theories when non-Abelian theory is quantized with planar planar girders.
TL;DR: The authors discusses differences in language development between blind and sighted children and adolescents, and provides a review of the literature on the subject, and discusses the differences in the two groups' language development.
Abstract: This article discusses differences in language development between blind and sighted children and adolescents. The first part provides a review of the literature on the subject. The second part des...
TL;DR: The effective magnetic moments were determined in solution at room temperature to confirm the dependence of the spin-state equilibrium of azide methemoglobin on the quarternary state of the hemoglobin and to demonstrate a similar dependence for both human and carp aquomethemoglobin.
Abstract: The effective magnetic moments for a number of human and carp methemoglobin derivatives were determined in solution at room temperature. The data permit us to confirm the dependence of the spin-state equilibrium of azide methemoglobin on the quaternary state of the hemoglobin and to demonstrate a similar dependence for both human and carp aquomethemoglobin.
In addition, the pH dependence of the effective magnetic moment and the Soret spectrum of carp azide-methemoglobin are compared.
TL;DR: In this paper, a new approach for the study of nonlinear age dependent population dynamics is proposed, which consists to transform the hyperbolic PDE into a functional integral equation and investigate it.
Abstract: This paper is devoted to a new approach for the study of nonlinear age dependent population dynamics. It consists to transform the hyperbolic PDE into a functional integral equation and to investigate it. We get global existence, uniqueness, and local stability results. Some applications to the traditional ecological models are made.
TL;DR: In the nonlinear region of Visscher and Evans as mentioned in this paper, Van Kampen's "case against linear response theory" and the numerical experiments on transport properties using perturbation of mechanical trajectories are critically discussed.
Abstract: Computer simulation experiments on transport properties using perturbation of mechanical trajectories are critically discussed in the light of Van Kampen's “case against linear response theory” and of the numerical experiments in the nonlinear region of Visscher, and more recently of Evans.
TL;DR: A tentative model for the gating mechanism is suggested, which associates each conductance level to a configurational state of the channel and considers the transitions between them as a Markow jump process.
Abstract: The kinetics of the hemocyanin channel conductance transitions in black lipid membranes have been studied in two different ways In one method, voltagejump current-relaxation experiments were performed with membranes containing many channels (102÷104) The steady-state conductance-voltage curves obtained are S-shaped and the slow kinetic processes (1–100 sec) for the approach to steady-state can be fitted by three exponentials The three time constants were found to depend on the actual applied voltages, but not on the past history (preconditioning voltages) In the other method, membranes with one single channel were used and the spontaneous discrete fluctuations of conductance at constant voltage were analyzed Slow fluctuations occur between four conductance levels with the lower ones preferred at high positive voltages The voltage dependence of the conductance of each level and of the transition rates has been measured A tentative model for the gating mechanism is suggested, which associates each conductance level to a configurational state of the channel and considers the transitions between them as a Markow jump process
TL;DR: In this paper, the conditions for the absence of ghosts and tachyons were given, and the set of the unitary ones of these theories were determined, in particular the conditions of the existence of a scalar field.
Abstract: We consider gravitational theories in which the independent fields are the tetrad vectors, the connection and a scalar field. The actions contain terms quadratic in curvature and torsion and are free of dimensional parameters, a feature that could be interesting in view of their quantum behaviour. We give the conditions for the unitarity of these theories, namely the absence of ghosts and tachyons, and determine the set of the unitary ones. In some cases the introduction of the scalar field allows a larger choice of the terms that contain only curvature and torsion.
TL;DR: In this paper, the surface chemistry changes were monitored using Auger and Mfssbauer spectroscopies and it was found that ion implantation through the film caused Ni to move into the Sn film and Sn to penetrate into the Ni substrate.
Abstract: Nickel substrates were coated with a thin Sn film and implanted with 100 keV Xe+ to fluences between 3 and 7.1015 ions/cm2. Surface chemistry changes were monitored using Auger and Mfssbauer spectroscopies. By comparing between profiles of un-implanted and implanted specimens, it was found that ion implantation through the film caused Ni to move into the Sn film and Sn to penetrate into the Ni substrate. The Mdssbauer analysis disclosed the presence of new surface phases. A substantial increase in the tarnishing resistance of Ni was found by using this treatment.
TL;DR: In this article, a theoretical model calculation for the heating problem during ion implantation was performed, and two situations, good and poor thermal contact between film and substrate, were considered.
TL;DR: X-ray absorption measurements have been performed for the first time at the Ag L 3 edge on glasses Ag 2 O nB 2 O 3 (n=1,2,3,4) and on crystalline Ag 2O. as mentioned in this paper showed that the first coordination shell around the silver ion is substantially insensible to variations in the ag 2 O content of the glass.
01 Sep 1983
TL;DR: Dissociation constants for the binding of Ca2+ and Tb3+ to the M. crenulata haemocyanin channel are calculated and found to be in good agreement with published data on binding of the same cations to other haemOCyanins in physiological conditions.
Abstract: Megathura crenulata haemocyanin can be incorporated in phosphatidylcholine planar bilayers, forming ionic channels. Ca2+ and Tb3+ are known to bind to the protein and to compete for some common sites, here their effects on the electrical properties of the channel have been studied. Both cations have similar characteristics: they diffuse through the channel, linearize and shift its instantaneous current voltage curve and induce inactivation at negative voltages. Two-salt experiments are described in which small amounts of Ca2+ or Tb3+ are added to a KCl solution, allowing titration of these effects on the channel. S-shaped conductance voltage curves and strongly saturating conductance-concentration curves are explained on the basis of a two-state gating mechanism, coupled with the influence of a titratable fixed charge near the pore entrance. The model requires non-specific screening of the negative charge by counter-ions in solution and specific binding to it by divalent and small monovalent cations. Dissociation constants for the binding of Ca2+ and Tb3+ to the M. crenulata haemocyanin channel are calculated and found to be in good agreement with published data on binding of the same cations to other haemocyanins in physiological conditions.
TL;DR: In this article, a comparison between neutron scattering data in single crystals and polycrystals and light scattering data suggest an overall picture of the dynamics of silver and iodine ions, and an interpretation of the Raman spectral shape between 2 and 200 cm−1 is given in terms of transverse and longitudinal acoustic phonons as well as optic phonons.
TL;DR: It was found that hemocyanin is more potent as a channel former if TbCl 3 is added to the bathing solution and the dose response curve indicates that binding of Tb 3+ to the phosphatidylcholine bilayer is involved in creating the effective charge.
01 Jan 1983
TL;DR: In this paper, a new approach for the study of nonlinear age dependent population dynamics is proposed, which consists to transform the hyperbolic PDE into a functional integral equation and investigate it.
Abstract: This paper is devoted to a new approach for the study of nonlinear age dependent population dynamics. It consists to transform the hyperbolic PDE into a functional integral equation and to investigate it. We get global existence, uniqueness, and local stability results. Some applications to the traditional ecological models are made.