Reliability of Digital Dental Cast Measures as Compared to Cone-Beam Computed Tomography for Analyzing the Transverse Dimension

The purpose of this study was to assess the consistency in diagnosing the transverse dimension on cone-beam computed tomography (CBCT) images as compared to digital dental models. The study consisted of 11 patients with posterior crossbite at the level of the first molar and 17 patients with no crossbite at the level of the first molar. 13 patients were male and 15 patients were female with an overall mean age of 13.6 years. Eight linear measurements and two angular measurements were made on CBCT images of the patients and six linear measurements were made on the corresponding digital dental casts. CBCT and model measurements were compared using One-Way Analysis of Variance (ANOVA) and Pearson correlation tests were used to seek relationships between the dental and skeletal measurements on CBCT. All ratios between maxillary and corresponding mandibular measurements were larger in non-crossbite patients than in crossbite patients. The central fossa (CF) was found to be the most representative and reliable tooth measurement in judging dental and skeletal transverse dimensions. A normative CF-CF ratio was determined to be equal to or greater than 1.10 for non-crossbite patients. High correlations were found between dental and skeletal measurements for non-crossbite patients with a CF-CF ratio equal to or greater than 1.10, but were not found for crossbite patients with a CF-CF ratio less than 1.10. In conclusion, CBCT scans may not provide additional diagnostic information as compared to dental models for non-crossbite patients. However, CBCT scans may be diagnostically beneficial for crossbite patients. Further studies with a larger sample size are needed to determine the validity of this study

Small deviations for beta ensembles

We establish various small deviation inequalities for the extremal (soft edge) eigenvalues in the beta-Hermite and beta-Laguerre ensembles. In both settings, upper bounds on the variance of the largest eigenvalue of the anticipated order follow immediately

Biofilms in porous media: development of macroscopic transport equations via volume averaging with closure for local mass equilibrium conditions

In this work, we upscale a pore-scale description of mass transport in a porous medium containing biofilm to develop the relevant Darcy-scale equations. We begin with the pore-scale descriptions of mass transport, interphase mass transfer, and biologically-mediated reactions; these processes are then upscaled using the method of volume averaging to obtain the macroscale mass balance equations. We focus on the case of local mass equilibrium conditions where the averaged concentrations in the fluid and biological phases can be assumed to be proportional and for which a one-equation macroscopic model may be developed. We predict the effective dispersion tensor by a closure scheme that is solved for the cases of both simple and complex unit cells. The domain of validity of the approach is clearly identified, both theoretically and numerically, and unitless groupings indicating the domain of validity are reported

Modeling non-equilibrium mass transport in biologically reactive porous media.

We develop a one-equation non-equilibrium model to describe the Darcy-scale transport of a solute undergoing biodegradation in porous media. Most of the mathematical models that describe the macroscale transport in such systems have been developed intuitively on the basis of simple conceptual schemes. There are two problems with such a heuristic analysis. First, it is unclear how much information these models are able to capture; that is, it is not clear what the model's domain of validity is. Second, there is no obvious connection between the macroscale effective parameters and the microscopic processes and parameters. As an alternative, a number of upscaling techniques have been developed to derive the appropriate macroscale equations that are used to describe mass transport and reactions in multiphase media. These approaches have been adapted to the problem of biodegradation in porous media with biofilms, but most of the work has focused on systems that are restricted to small concentration gradients at the microscale. This assumption, referred to as the local mass equilibrium approximation, generally has constraints that are overly restrictive. In this article, we devise a model that does not require the assumption of local mass equilibrium to be valid. In this approach, one instead requires only that, at sufficiently long times, anomalous behaviors of the third and higher spatial moments can be neglected; this, in turn, implies that the macroscopic model is well represented by a convection–dispersion–reaction type equation. This strategy is very much in the spirit of the developments for Taylor dispersion presented by Aris (1956). On the basis of our numerical results, we carefully describe the domain of validity of the model and show that the time-asymptotic constraint may be adhered to even for systems that are not at local mass equilibrium

LiBeB Production by Nuclei and Neutrinos

The production of LiBeB isotopes by nuclear and neutrino spallation are compared in the framework of galactic evolutionary models. As motivated by $\gamma$-ray observations of Orion, different possible sources of low-energy C and O nuclei are considered, such as supernovae of various masses and WC stars. We confirm that the low energy nuclei (LEN), injected in molecular clouds by stellar winds and type II supernovae originating from the most massive progenitors, can very naturally reproduce the observed Be and B evolution in the early galaxy (halo phase). Assuming the global importance of the LEN component, we compute upper and lower bounds to the neutrino process contribution corresponding to limiting cases of LEN particle spectra. A consistent solution is found with a spectrum of the kind proposed by Ramaty \etal (1995a,b), e.g. flat up to $E_c=30$ MeV/n and decreasing abruptly above. This solution fulfills the challenge of explaining at the same time the general Be and B evolution, and their solar system abundances without overproducing \li7 at very low metallicities, and the meteoritic \b11/\b10 ratio. In this case, neutrino spallation is constrained to play a limited role in the genesis of the solar system \b11. Galactic cosmic rays (GCR) become operative late in the evolution of the disk ([Fe/H]$>$-1), but their contribution to the solar abundances of \be9, \b10 and \b11 is not dominant (35\%, 30\% and 20\% respectively). Thus, with this LEN spectrum, GCR are {\it not}\ the main source of \be9 and B in the Galaxy. The most favorable case for neutrinos, (adopting the same kind of spectrum) has $E_c=20$ MeV/n. Even in this case, the neutrino yields of Woosley and Weaver (1995) must to be reduced by a factor of 5 to avoid \b11 overproduction. Furthermore, this solution leads to a high B/BeComment: 19 pages, 5 postscript figures, uses plain LaTeX, also available at http://www.nd.edu/~bfields/vcfo.htm

Controllable emission of a dipolar source coupled with a magneto-dielectric resonant subwavelength scatterer

We demonstrate experimentally and theoretically that a local excitation of a single scatterer of relative dielectric permittivity {\epsilon} = 6 permits to excite broad dipolar and quadrupolar electric and magnetic resonances that shape the emission pattern in an un- precedented way. By suitably positioning the feed with respect to the sphere at a ?=3 distance, this compact antenna is able to spectrally sort the electromagnetic emission ei- ther in the forward or in the backward direction, together with a high gain in directivity. Materials with {\epsilon} = 6 can be found in the whole spectrum of frequencies promising Mie antennas to become an enabling technology in numbers of applications, ranging from quantum single photon sources to telecommunications

Solidification macroprocesses - Thermal-mechanical Modeling of Stress, Distortion and Hot Tearing)

http://www.crcpress.com/product/isbn/9780849332166International audienceThe application of numerical methods to the mechanical modeling in solidification analysis has received a continuously growing interest over the last twenty years. After having concentrated their efforts on the thermal and microstructural predictions, research teams have been more and more interested in the coupled thermomechanical analysis. These developments have been motivated by the efforts done by the casting industry to increase the quality of final products while lowering the costs. Manufacturers are then interested in the development of new numerical tools able to model the thermomechanical response of castings during the processes. Accurate calculation of stress and distortions during casting is just the first step, however, as engineers are more interested in their practical consequences. These include residual stress and distortion, and defects such as segregation and the formation of cracks such as hot tears. As computing power and software tools advance, it is becoming increasingly possible to perform useful mechanical analysis of castings and these important related behaviors