235 research outputs found
Cumulant ratios in fully developed turbulence
In the context of random multiplicative cascade processes, we derive
analytical solutions for one- and two-point cumulants with restored
translational invariance. On taking ratios of cumulants in ln epsilon,
geometrical effects due to spatial averaging cancel out. These ratios can
successfully distinguish between splitting functions while multifractal scaling
exponents and multiplier distributions cannot.Comment: 9th Workshop on Multiparticle Production (Torino), 9 pages latex,
incl 9 figs and espcrc2.st
Translationally invariant cumulants in energy cascade models of turbulence
In the context of random multiplicative energy cascade processes, we derive
analytical expressions for translationally invariant one- and two-point
cumulants in logarithmic field amplitudes. Such cumulants make it possible to
distinguish between hitherto equally successful cascade generator models and
hence supplement lowest-order multifractal scaling exponents and multiplier
distributions.Comment: 11 pages, 3 figs, elsart.cls include
A histological and histomorphometrical evaluation of the application of screw‐designed calciumphosphate (Ca‐P)‐coated implants in the cancellous maxillary bone of the goat
Finite size scaling in the solar wind magnetic field energy density as seen by WIND
Statistical properties of the interplanetary magnetic field fluctuations can provide an important insight into the solar wind turbulent cascade. Recently, analysis of the Probability Density Functions (PDF) of the velocity and magnetic field fluctuations has shown that these exhibit non-Gaussian properties on small time scales while large scale features appear to be uncorrelated. Here we apply the finite size scaling technique to explore the scaling of the magnetic field energy density fluctuations as seen by WIND. We find a single scaling sufficient to collapse the curves over the entire investigated range. The rescaled PDF follow a non Gaussian distribution with asymptotic behavior well described by the Gamma distribution arising from a finite range Lévy walk. Such mono scaling suggests that a Fokker-Planck approach can be applied to study the PDF dynamics. These results strongly suggest the existence of a common, nonlinear process on the time scale up to 26 hours
The effect of Ca-P plasma-sprayed coatings on the initial bone healing of oral implants: An experimental study in the goat
The effect of Ca‐P plasma‐sprayed coatings on the initial bone healing of oral implants: An experimental study in the goat
Reflective multi-immersion microscope objectives inspired by the Schmidt telescope
Imaging large, cleared samples requires microscope objectives that combine a large field of view (FOV) with a long working distance (WD) and a high numerical aperture (NA). Ideally, such objectives should be compatible with a wide range of immersion media, which is challenging to achieve with conventional lens-based objective designs. Here we introduce the multi-immersion 'Schmidt objective' consisting of a spherical mirror and an aspherical correction plate as a solution to this problem. We demonstrate that a multi-photon variant of the Schmidt objective is compatible with all homogeneous immersion media and achieves an NA of 1.08 at a refractive index of 1.56, 1.1-mm FOV and 11-mm WD. We highlight its versatility by imaging cleared samples in various media ranging from air and water to benzyl alcohol/benzyl benzoate, dibenzyl ether and ethyl cinnamate and by imaging of neuronal activity in larval zebrafish in vivo. In principle, the concept can be extended to any imaging modality, including wide-field, confocal and light-sheet microscopy
Entropy production and Lyapunov instability at the onset of turbulent convection
Computer simulations of a compressible fluid, convecting heat in two
dimensions, suggest that, within a range of Rayleigh numbers, two distinctly
different, but stable, time-dependent flow morphologies are possible. The
simpler of the flows has two characteristic frequencies: the rotation frequency
of the convecting rolls, and the vertical oscillation frequency of the rolls.
Observables, such as the heat flux, have a simple-periodic (harmonic) time
dependence. The more complex flow has at least one additional characteristic
frequency -- the horizontal frequency of the cold, downward- and the warm,
upward-flowing plumes. Observables of this latter flow have a broadband
frequency distribution. The two flow morphologies, at the same Rayleigh number,
have different rates of entropy production and different Lyapunov exponents.
The simpler "harmonic" flow transports more heat (produces entropy at a greater
rate), whereas the more complex "chaotic" flow has a larger maximum Lyapunov
exponent (corresponding to a larger rate of phase-space information loss). A
linear combination of these two rates is invariant for the two flow
morphologies over the entire range of Rayleigh numbers for which the flows
coexist, suggesting a relation between the two rates near the onset of
convective turbulence.Comment: 5 pages, 4 figure
Clinical management and microscopic characterisation of fatique-induced failure of a dental implant. Case report
BACKGROUND: Osseointegrated endosseous implants are widely used for the rehabilitation of completely and partially edentulous patients, being the final prosthodontic treatment more predictable and the failures extremely infrequent. A case of fracture of an endosseous dental implant, replacing the maxillary first molar, occurring in a middle-age woman, 5 years after placement is reported. MATERIALS AND METHODS: The difficult management of this rare complication of implant dentistry together with the following rehabilitation is described. Additionally, the authors performed an accurate analysis of the removed fractured implant both by the stereomicroscope and by the confocal laser scanning microscope. RESULTS AND DISCUSSION: The fractured impant showed the typical signs of a fatigue-induced fracture in the coronal portion of the implant together with numerous micro-fractures in the apical one. Three dimensional imaging performed by confocal laser scanning microscope led easily to a diagnosis of "fatigue fracture" of the implant. The biomechanical mechanism of implant fractures when overstress of the implant components due to bending overload is discussed. CONCLUSION: When a fatigue-induced fracture of an dental implant occurs in presence of bending overload, the whole implant suffers a deformation that is confirmed by the alterations (micro-fractures) of the implant observable also in the osseointegrated portion that is easily appraisable by the use of stereomicroscope and confocal laser scanning microscope without preparation of the sample
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