The relation between composition in laser absorption region and ambient pressure

In this paper, the compositions in a laser absorption region can be determined from the experiment of laser impulse coupling. When the ambient pressure varies from 9325 to 33325Pa, the compositions are vapour and plasma; while from 35325 to 101325Pa, they are ambient air and plasma. By analysing the relation between the degree of compression and the ambient pressure, the compositions can be determined and the variation of plasma can be explained.     

Is the proton electromagnetic form factor modified in nuclei?

Guided by the recent experimental confirmation of the validity of the Effective Momentum Approximation (EMA) in quasi-elastic scattering off nuclei, we have re-examined the extraction of the Longitudinal and Transverse Response Functions in medium-weight and heavy nuclei. In the EMA we have performed a Rosenbluth separation of the available world data on ⁴⁰Ca, ⁴⁸Ca, ⁵⁶Fe and ²⁰⁸Pb. We find that the Longitudinal Response Function for these nuclei is quenched and that the Coulomb sum is not saturated, at odds with recent claims in the literature.Received: 1 November 2002, Published online: 15 July 2003PACS: 25.30.Fj Inelastic electron scattering to continuum     

A modified Einstein–Nernst relation between mobility and diffusion of charges to evaluate the non-equilibrium, transient processes of ions in electrolytes

Transient correction terms to the nonlinear differential equations, describing the dynamics of migration and diffusion of the ion charges in electrolytes, have been recently defined and numerically evaluated. The system of equations has been modified in accordance with the obtained non-equilibrium corrections and the system variables have been evaluated in the case when the corrections are space-averaged. The purpose of the present work is to obtain a general solution when both the time and space dependencies of the correction terms are preserved i.e. without space-averaging of the corrections. The obtained, under these conditions, set of dynamical equations has been analytically transformed to a simpler form, which is easier to be tackled numerically. The corrected results, in contrast to the results of uncorrected equations, show much faster convergence to equilibrium of the physical system and manifest the presence of characteristic pre-electrode maxima of the transient ion currents.     

The effect of α, β crystalline structure on the mechanical properties of polypropylene

In order to study the effect of the α,β crystalline structure of polypropylene (PP) on its mechanical properties, it is necessary to prepare samples with variable α/β-phase content but with constant crystallinity and constant spherulite size. With this objective, heat treatment was first defined to be applied to an isotactic PP containing a β nucleating agent in order to achieve these conditions. Then study of the effect of the β-phase content on the tensile properties and fracture behaviour has been done at room temperature. The mechanical properties at fracture were assessed by three-point bending tests and were analysed on the basis of the “Essential Work of Fracture” (EWF). The results show that the elongation at fracture under tensile stress and the “near” Plane-Strain Essential Work of Fracture, w _Ie, increase substantially with the β-phase content. Besides, Young's modulus and the yield stress in tensile tests decrease slowly with the β-phase content. Finally, these results are analysed taking account the differences in structure of the α and β spherulites. Received 18 September 2000 and Received in final form 19 December 2000     

Current sheets in the Earth’s magnetosphere and in laboratory experiments: The magnetic field structure and the Hall effect

The main characteristics of current sheets (CSs) formed in laboratory experiments are compared with the results of satellite observations of CSs in the Earth’s magnetotail. We show that many significant features of the magnetic field structure and the distributions of plasma parameters in laboratory and magnetospheric CSs exhibit a qualitative similarity, despite the enormous differences of scales, absolute values of plasma parameters, magnetic fields, and currents. In addition to a qualitative comparison, we give a number of dimensionless parameters that demonstrate the possibility of laboratory modeling of the processes occurring in the magnetosphere.     

Diffusivity in water and fluorescence properties of?organic nanoparticles produced in?flames

Rotational and translational diffusion properties in water of nano organic carbon (NOC) particles collected from premixed laminar ethylene/air flames have been investigated using both time resolved fluorescence polarisation anisotropy (TRFPA) and fluorescence correlation spectroscopy (FCS). Insight into the NOC sizes, structures and rigidity has been gained through diffusion properties exploiting their fluorescence in different spectral ranges. The TRFPA measurements revealed the presence of two classes of particles. The first composed of particles with a mean size of 1.5?nm which absorb and fluoresce in the UV, and a second class composed of slightly larger particles, about 2.2?nm, which absorb and fluoresce in the visible and were also detected by FCS. From FCS measurements particle concentration and fluorescence quantum yield have been evaluated.     

The relation between the Good–Walker and triple-regge formalisms for diffractive excitation

In this Letter we analyze the relation between the triple-pomeron and Good–Walker formalisms for diffractive excitation in DIS and hadronic collisions. In both approaches gap events are interpreted as the shadow of absorption into inelastic channels. We here argue that the two formalisms are just different views of the same phenomenon. We first demonstrate how this relation works in a simple toy model, and then show how the relevant features of the toy model are also realized in real perturbative QCD.     

Is the topology of the Internet network really fit to sustain its function?

The Internet is one of the most interesting realizations of a “complex” network. As a non-supervised growing object, it allows the study of the selective pressure which drives the network to assume its current structure. The DIMES and the ROUTEVIEWS projects are ongoing projects aimed at evaluating the topological structure of the Internet (at the Autonomous System or AS grain-level) on the basis of different types of measurements. The topological analysis of the networks produced by the two projects has allowed us to infer a growth mechanism which has been used to build up synthetic networks with similar properties. These networks have been used as test-beds for the implementation of a model of traffic dynamics, with the aim of assessing the ability of the Internet’s topology to support the basic actions for data traffic handling. Results have been compared with those obtained by using a random network of similar size. The effects of some structural perturbations (arcs and nodes’ removal, traffic localization) have been also evaluated in terms of the induced variations of the network’s efficiency. The resulting scenario is consistent with the hypothesis that the structure of the Internet is only partially fit to host communication processes and that the intelligence of the TCP/IP protocol is partly needed to overcome some “structural” deficiencies.     

On the relation between Φ(1,2) and Φ(1,5) perturbed minimal models and unitarity

We consider the RSOS S-matrices of the Φ_(1,5) perturbed minimal models which have recently been found in a companion paper. These S-matrices have some interesting properties, in particular, unitarity may be broken in a stronger sense than seen before, while one of the three classes of Φ_(1,5) perturbations (to be described) shares the same thermodynamic Bethe ansatz as a related Φ_(1,2) perturbation. We test these new S-matrices by the standard Truncated Conformal Space method, and further observe that in some cases the BA equations for two particle energy levels may be continued to complex rapidity to describe (a) single particle excitations and (b) complex eigenvalues of the Hamiltonian corresponding to non-unitary S-matrix elements. We make some comments on identities between characters in the two related models following from the fact that the two perturbed theories share the same breather sector.     

Is the Kramers-Kronig relationship between ultrasonic attenuation and dispersion maintained in the presence of apparent losses due to phase cancellation?

Phase cancellation effects can compromise the integrity of ultrasonic measurements performed with phase sensitive receiving apertures. A lack of spatial coherence of the ultrasonic field incident on a phase sensitive receiving array can produce inaccuracies of the measured attenuation coefficient and phase velocity. The causal (Kramers-Kronig) link between these two quantities in the presence of phase distortion is investigated using two plastic polymer materials, Plexiglas and Lexan, that exhibit attenuation coefficients that increase linearly with frequency, in a fashion analogous to that of soft tissue. Flat and parallel plates were machined to have a step of a thickness corresponding to an integer number of half wavelengths within the bandwidth investigated, 3 to 7 MHz. Insonification of the stepped portion of each plate produces phase cancellation artifacts at the receiving aperture and, therefore, in the measured frequency dependent attenuation coefficient. Dispersion predictions using two different forms of the Kramers-Kronig relations were performed for the flat and the stepped regions of each plastic plate. Despite significant phase distortion and a detection system sensitive to these aberrations, the Kramers-Kronig link between the apparent attenuation coefficient and apparent phase velocity dispersion remains intact.     

The Adam–Gibbs relation and the TIP4P/2005 model of water

ABSTRACT

We report a numerical test of the Adam–Gibbs relation for the TIP4P/2005 model of water. The configurational entropy is here evaluated as the logarithm of the number of different basins in the potential energy landscape sampled in equilibrium conditions. Despite the non-monotonic behaviour which characterise the density dependence of the diffusion coefficient, the Adam–Gibbs relation is satisfied within the numerical precision in a wide range of densities and temperatures. We also show that expressions based on the excess entropy (the logarithm of the number of sampled microstates in phase space) fail in the region of densities where a tetrahedral hydrogen bond network develops.     

The effect of ultraviolet radiation on water vapour absorption between 5 and 50cm−1

Both field measurements and laboratory experiments suggested that absorption of UV radiation affected the near-millimetre wave absorption by water vapour. Experiments with different flux values and at different temperatures have confirmed this and pumping by UV radiation has been shown to give near-millimetre wave emission.     

Is there a universality of the helix-coil transition in protein models?

The similarity in the thermodynamic properties of two completely different theoretical models for the helix-coil transition is examined critically. The first model is an all-atomic representation for a poly-alanine chain, while the second model is a minimal helix-forming model that contains no system specifics. Key characteristics of the helix-coil transition, in particular, the effective critical exponents of these two models agree with each other, within a finite-size scaling analysis. Received 8 December 1999     

The effect of adding aluminum and iron to Tb–Dy–Ho–Co multicomponent alloys on their structure and magnetic and magnetocaloric properties

A comprehensive analysis of the structure, phase composition, surface topology features, and magnetic and magnetocaloric properties of Tb_0.3Dy_0.35Ho_0.35Co_1.75 T _0.25 (T = Al, Fe) multicomponent alloys has been performed. The specifics of variations in the structure and functional properties induced by the partial substitution of cobalt atoms in the 3d sublattice of RCo₂ with aluminum or iron atoms have been determined.     

Can Competition between the crystal field and the Kondo effect cause non-Fermi-liquid-like behavior?

The recently reported unusual behavior of the static and dynamical magnetic susceptibility as well as the specific heat in Ce(1-x)La(x)Ni9Ge4 has raised the question of a possible non-Fermi-liquid ground state in this material. We argue that for a consistent physical picture the crystal-field splitting of two low-lying magnetic doublets of the Ce 4f-shell must be taken into account. Furthermore, we show that for a splitting of the order of the low temperature scale T* of the system a crossover behavior between an SU(4) and an SU(2) Kondo effect is found. The screening of the two doublets occurs on different temperature scales leading to a different behavior of the magnetic susceptibility and the specific heat at low temperatures. The experimentally accessible temperature regime down to 50 mK still lies in the extended crossover regime into a strong-coupling Fermi-liquid fixed point.     

Is it possible to intervene in the EPRB correlations?

The effect of a quasi-periodic shutter inserted between the source and one of the detectors in a correlated-photon type EPRB experiment is studied. It is shown that the time and polarization correlations are expected to disappear because an intermediate quantized field system is introduced by the shutter between the source field and the detector.     

About the luminescence properties of YAG∶Nd,Ce and YAG∶Nd single crystals and their relation to laser properties

Laser excited luminescence studies of various YAGNd, Ce and YAG:Nd (with an excess of yttrium) single crystals together with a testing of laser properties of rods made from the same crystals have been investigated in this paper. It was observed that laser pulse energies increase with increasing halfwidths of the luminescence spectral bands. This dependence and other observations indicate that local structure changes or Nd³⁺ nonequivalent centres are present in the studied crystals. Various mechanisms leading to the formation of Nd³⁺ nonequivalent centres are discussed and it seems that the more probable mechanism is oxygen segregation and diffusion.