Particle Penetration through Inclined and L-Shaped Cracks

This paper presents a particle penetration model predicting particle penetration coefficient (Pp) through a narrow crack of arbitrary incline angles (θ). The objective was to simulate Pp for outdoor-to-indoor particle penetration for residential infiltration conditions. This model assumes laminar infiltration flow and considers particle deposition from both gravitational sedimentation and Brownian diffusion. For micron-sized particles, modeling results indicate that gravitational sedimentation is the major deposition mechanism. Pp increases monotonically with ∣θ∣ because effective particle sedimentation velocity (vs?cos?θ) decreases monotonically with ∣θ∣. For submicron-sized particles (0.1?μm), Brownian diffusion is the major particle deposition mechanism. Because Brownian diffusion is a nondirectional deposition mechanism, crack inclination did not affect Pp. This study applied this model to estimate Pp for L-shaped cracks, and validated modeling results with experiments. Experimental results indicated that inertial impaction and crack entrance cutoff effects were not significant particle deposition mechanisms for the test micron-sized particles. Gravitational sedimentation was the major deposition mechanism. An L-shaped crack can be simulated as the combination of horizontal and vertical sections. This model agreed reasonably with experimental results.     

Two-Dimensional Physical and Numerical Modeling of a Pile-Supported Earth Platform over Soft Soil

This paper focuses on the mechanisms occurring in a granular earth platform over soft ground improved by rigid piles. Two-dimensional physical model experiments were performed using the Schneebeli’s analogical soil to investigate the load transfer mechanisms by arching and the settlement reduction and homogenization. Experimental outputs are compared to results obtained on a numerical model using a plane strain continuum approach. The impact of the constitutive model complexity to simulate the platform material behavior was first assessed, but no large difference was recorded. As far as the proposed model, which takes the main features of the observed behavior satisfactorily into account, the numerical procedure could be validated and the parametric studies extended numerically. Both approaches of this study underlined the main geometrical and geotechnical parameters which should inevitably be taken into account in a simplified design method, namely the capping ratio, the platform height, and the platform material shear strength.     

Polynomial-Space Decidable Membership Problems for Recurrent Systems over Sets of Natural Numbers

A finite recurrent system over sets of natural numbers of dimension n is a pair composed of n n-ary functions over sets of natural numbers and an n-tuple of singleton sets of natural numbers. Every function is applied to the entries of the tuple and computes a set of natural numbers, that may also be empty. The results are composed into another tuple, and the process is started anew. Thus, a finite recurrent system defines an infinite sequence of n-tuples containing sets of natural numbers. The last entry of a generated n-tuple is called the output of a step, and the union of the output sets of all steps is the set defined by the finite recurrent system. Membership problems ask whether a given number is in a specified output set or in some output set. We study membership problems for special finite recurrent systems, whose functions are built from the set operations union, intersection and complementation and the arithmetical operations addition and multiplication. Sum and product of two sets of natural numbers are defined elementwise. We restrict the set of operations from which functions are built and determine the impact on the complexity of the membership problems. We focus on PSPACE-decidable membership problems and show completeness results for the complexity classes NL, NP and PSPACE.     

Hearing the horror: A comment on the final report of the APA Task Force on the Victims of Crime and Violence.

Comments that a critical element in the final report of the American Psychological Association (APA) Task Force on the Victims of Crime and Violence may be lost simply because of the enormity and complexity of the issues involved. The real nature of the victim's emotional experience is often not directly addressed by researchers or service providers in the mental health community. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Some electron microscope observations of longitudinal splitting from surface flaws in Kevlar 29

Journal of Materials Science Letters -     

Periodontal management of gingival overgrowth in the heart transplant patient: a case report

Heart transplant patients take several medications that could affect their periodontal health. Gingival overgrowth associated with cyclosporin (immunosuppressant agent) and nifedipine (calcium channel blocker) is well documented. Candidal infections often develop because of immune suppression. This report describes the clinical and histopathological changes in the gingival tissues of a heart transplant patient and their management. The gingival tissues exhibited pronounced enlargement. The gingivae were lobulated, and the surface of the lobulations was pebbly and granular. Biopsies showed lobules of fibrous connective tissue covered by stratified squamous epithelium. The outer surfaces were dotted with numerous smaller papillations. Candidal hyphae were present in the superficial layers of the epithelium. The extensive papillary lesions appear to be related to candidiasis and constitute a condition which is best designated as papillary stomatitis. Hyperplastic gingival tissues were excised, and the patient was placed on periodic maintenance. One-year postoperative follow-up showed minor gingival growth.     

Pulmonary Wegener''s disease mimicking tuberculosis]

We report a case of early Wegener's disease mimicking tuberculosis in a 36 year old man. Lungs are solely affected for 6 months. Unusual appearance of radiographic features with large apical excavations explain the delai for the diagnosis. We discuss morphological features in the lungs and kidney.     

Reactivity of steam in exhaust gas catalysis III. Steam and oxygen/steam conversions of propane on a Pd/Al2O3 catalyst

A 1% Pd catalyst (38% dispersion) was prepared by impregnating a γ-alumina with palladium acetylacetonate dissolved in acetone. The behaviour of this catalyst in oxidation and steam reforming (SR) of propane was investigated. Temperature-programmed reactions of C₃H₈ with O₂ or with O₂ + H₂O were carried out with different stoichiometric ratios S(S =[O₂]/5[C₃H₈]). The conversion profiles of C₃H₈ for the reaction carried out in substoichiometry of O₂ (S < 1) showed two discrete domains of conversion: oxidation at temperatures below 350°C and SR at temperatures above 350°C. The presence of steam in the inlet gases is not necessary for SR to occur: there is sufficient water produced in the oxidation to form H₂ and carbon oxides by this reaction. Contrary to what was observed with Pt, an apparent deactivation between 310 and 385°C could be observed with Pd in oxidation. This is due to a reduction of PdO_x into Pd⁰, which is much less active than the oxide in propane oxidation. Steam added to the reactants inhibits oxidation while it prevents the reduction of PdO_x into Pd⁰. Compared to Pt and to Rh, Pd has a higher thermal resistance: no deactivation occurred after treatment up to 700°C and limited deactivation after treatment up to 900°C, provided that the catalyst is maintained in an oxygen-rich atmosphere during the cooling.     

Effect of the pressure drop rate on cell nucleation in continuous processing of microcellular polymers

Microllular plastics are cellular polymers characterized by cell densities greater than 10⁹ cells/cm³ and cells smaller than 10 μm. One of the critical steps in the continuous production of microcellular plastics is the promotion of high cell nucleation rates in a flowing polymer matrix. These high nucleation rates can be achieved by first forming a polymer/gas solution followed by rapidly decreasing the solubility of gas in the polymer. Since, in the processing range of interest, the gas solubility in the polymer decreases as the pressure decreases, a rapid pressure drop element, consisting of a nozzle, has been employed as a continuous microcellular nucleation device. In this paper, the effects of the pressure drop rate on the nucleation of cells and the cell density are discussed. The experimental results indicate that both the magnitude and the cell density are discussed. The experimental results indicate that both the magnitude and the rate of pressure drop play a strong role in microcellular processing. The pressure phenomenon affects the thermodynamic instability induced in the polymer/gas solution and the competition between cell nucleation and growth.