Effects of anisotropy of the turbid media on the photon penetration depth

Biomedical applications of near infrared radiation (NIR) techniques (i.e. based on light wavelengths roughly between 400 and 1100?nm) require that a preliminary estimate of the tissue volume being investigated be found. One possible estimate is the depth to which a photon penetrates a tissue before eventually emerging at a separating plane at a given time. A simple model for this problem can be based on a lattice random walk and was initially analyzed when the associated optical coefficients are isotropic with respect to the geometrical configuration. Here we include the effects of anisotropy in the optical coefficients, finding that at long times the statistical properties of the depth of penetration can be accounted for by very simple scaling factors while at short times the anisotropy effects can be quite noticeable.     

Genetic programming with one-point crossover and subtree mutation for effective problem solving and bloat control

Genetic programming (GP) is one of the most widely used paradigms of evolutionary computation due to its ability to automatically synthesize computer programs and mathematical expressions. However, because GP uses a variable length representation, the individuals within the evolving population tend to grow rapidly without a corresponding return in fitness improvement, a phenomenon known as bloat. In this paper, we present a simple bloat control strategy for standard tree-based GP that achieves a one order of magnitude reduction in bloat when compared with standard GP on benchmark tests, and practically eliminates bloat on two real-world problems. Our proposal is to substitute standard subtree crossover with the one-point crossover (OPX) developed by Poli and Langdon (Second online world conference on soft computing in engineering design and manufacturing, Springer, Berlin (1997)), while maintaining all other GP aspects standard, particularly subtree mutation. OPX was proposed for theoretical purposes related to GP schema theorems, however since it curtails exploration during the search it has never achieved widespread use. In our results, on the other hand, we are able to show that OPX can indeed perform an effective search if it is coupled with subtree mutation, thus combining the bloat control capabilities of OPX with the exploration provided by standard mutation.     

Bulk nanocrystalline aluminum 5083 alloy fabricated by a novel technique: Cryomilling and spark plasma sintering

Dense, bulk nanocrystalline aluminum 5083 alloy was fabricatedvia a combined technique: cryomilling (mechanical milling at cryogenic temperature) to achieve the nanocrystalline Al 5083 powder and spark plasma sintering (SPS) to consolidate the cryomilled powder. The results of X-ray diffraction analysis indicate that the average grain size in the SPS consolidated material is 51 nm, one of the smallest grain sizes ever reported in bulk Al alloys produced by powder metallurgy derived methods. In contrast, transmission electron microscopy (TEM) analysis revealed a bimodal grain size distribution, with an average grain size of 47 nm in the fine-grained regions and approximately 300 nm in the coarse-grained regions. Nanoindentation was used to evaluate the mechanical properties and the uniformity of the consolidated nanocrystalline Al 5083. The hardness of the material is greatly improved over that of the conventional equivalent, due to the fine grain size. The mechanisms for spark plasma sintering and the microstructural evolution are discussed on the basis of the experimental findings.     

Seismic Reliability Assessment of Bridges with User-Defined System Failure Events

Bridge-level failure event definitions per limit state have evolved from failure of one key bridge component as representative of the whole bridge system to failure of at least one of multiple components. However, an entire set of bridge failure event possibilities exists between these two extremes in the same limit state, such as failure of any two, any three, or any desired subset of bridge components. This paper proposes a closed-form combinatorial method to evaluate all possible ways in which bridge components can fail within and across limit states. It also highlights bridge component importance measures as key by-products of the closed-form solution. Calculations are illustrated with a particular yet illustrative system failure event, called the augmented event, which incorporates failures of at least one component in a given limit state and joint failures of multiple important components in a previous limit state. Bridges in as-built and retrofitted conditions are used to illustrate the augmentation calculation under seismic loads and the application of the proposed system reliability method. The results reveal an increase in median system fragility at the moderate limit states in the range of 4–20% relative to traditional approaches that neglect augmentation. This methodology to connect bridge components to bridge system reliability can readily support infrastructure stakeholder decision making and risk management through an efficient approach that can adapt to evolving system failure event definitions.     

Mode I equivalent state of crack-like defects in multiaxial stress fields

The novel concept of equivalent state randomly oriented flaws developed from the generalized fracture toughness theory [1] is presented. Based on this concept, planar defects located in multiaxial stress field regions, characterized by modes I, II, and III stress intensity factor combinations, are distinguished by a mode I equivalent state stress intensity factor % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0dh9WrFfpC0xh9vqqj-hEeeu0xXdbba9frFj0-OqFf% ea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr% 0-vqpWqaaeaabiGaaiaacaqabeaadaqaaqaaaOqaaiqadUeagaqeaa% aa!3846!\[\bar K\]₁ of identical function. Accordingly, the complex mode fracture criterion is exactly replaced by the conventional mode I criterion % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0dh9WrFfpC0xh9vqqj-hEeeu0xXdbba9frFj0-OqFf% ea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr% 0-vqpWqaaeaabiGaaiaacaqabeaadaqaaqaaaOqaaiqadUeagaqeaa% aa!3846!\[\bar K\]₁ K _1C . It is demonstrated that this criterion is mathematically equivalent to other more complex generalized fracture criteria [2,4,5], i.e., it predicts the same critical conditions.Current approximate procedures applied to crack-like defects detected in structural components, based on reorienting or orthogonally projecting the defect over a plane normal to the maximum principal tensile stress, are discussed and applied to two simple structural applications. When the results are compared with those from the proposed equivalent state flaw method, it is concluded that, to a large extent, the procedures are inconsistent and generate significant errors that may lead to incorrect decisions over the remaining service life of the structure.The equivalent state flaw concept is used to establish the equivalent state mode I threshold value % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0dh9WrFfpC0xh9vqqj-hEeeu0xXdbba9frFj0-OqFf% ea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr% 0-vqpWqaaeaabiGaaiaacaqabeaadaqaaqaaaOqaaiqadUeagaqeaa% aa!3846!\[\bar K\]₁ corresponding to complex stress state fatigue loadings.

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Résumé On présente le concept original de défauts équivalents répartis au hasard, développé à partir de la théorie généralisée sur la ténacité à la rupture [Réf. 1]. Sur base de ce concept, des défauts plans situés dans des zones à champs de contrainte multi-axiale, et caractérisés par des facteurs d'intensité de contrainte combinant les modes I, II et III, sont caractérisés par un facteur d'intensité de contrainte équivalent % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0dh9WrFfpC0xh9vqqj-hEeeu0xXdbba9frFj0-OqFf% ea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr% 0-vqpWqaaeaabiGaaiaacaqabeaadaqaaqaaaOqaaiqadUeagaqeaa% aa!3846!\[\bar K\]₁; relatif à un mode I et occupant la même fonction. Dès lors, le critère décrivant la rupture sous un mode complexe est en tous points remplacé par le critère conventionnel % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0dh9WrFfpC0xh9vqqj-hEeeu0xXdbba9frFj0-OqFf% ea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr% 0-vqpWqaaeaabiGaaiaacaqabeaadaqaaqaaaOqaaiqadUeagaqeaa% aa!3846!\[\bar K\]₁ K _1C .Ce critère est mathématiquement equivalent aux autres critères généralisés de rupture, de forme plus complexe [Réf. 2, 4, 5], en ce qu'il prédit les mêmes conditions critiques.On discute, et on applique à deux cas de structures simples, les procédures habituelles d'approximation pour des défauts assimilables à des fissures détectés dans des composants. Ces défauts sont réorientés ou projetés orthogonalement sur un plan normal à la plus grande tension principale.Lorsqu'on compare les résultats de ces procédures d'approximation à ceux que fournit la méthode proposée, on en conclut que ces procédures sont, dans une large mesure, incorrectes, et qu'elles donnent lieu à des erreurs importantes susceptibles de conduire à des décisions erronées sur la vie résiduelle d'une structure.Le concept de défaut équivalent est utilisé pour établir une valeur critique équivalente % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0dh9WrFfpC0xh9vqqj-hEeeu0xXdbba9frFj0-OqFf% ea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr% 0-vqpWqaaeaabiGaaiaacaqabeaadaqaaqaaaOqaaiqadUeagaqeaa% aa!3846!\[\bar K\]₁ en mode I, correspondant à le seuil des sollicitations de fatigue de mode complexe.

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Operated for the U.S. Department of Energy, Contract No. DE-AC12-76-N0052.     

GTV<Emphasis Type="SmallCaps">cut</Emphasis> for neuro-radiosurgery treatment planning: an MRI brain cancer seeded image segmentation method based on a cellular automata model

Despite of the development of advanced segmentation techniques, achieving accurate and reproducible gross tumor volume (GTV) segmentation results is still an important challenge in neuro-radiosurgery. Nowadays, magnetic resonance imaging (MRI) is the most prominent modality in radiation therapy for soft-tissue anatomical districts. Gamma Knife stereotactic neuro-radiosurgery is a minimally invasive technology for dealing with inaccessible or insufficiently treated tumors with traditional surgery or radiotherapy. During a treatment planning phase, the GTV is generally contoured by experienced neurosurgeons and radiation oncologists using fully manual segmentation procedures on MR images. Unfortunately, this operative methodology is definitely time-expensive and operator-dependent. Delineation result repeatability, in terms of both intra- and inter-operator reliability, can be achieved only by using computer-assisted approaches. In this paper a novel semi-automatic seeded image segmentation method, based on a cellular automata model, for MRI brain cancer detection and delineation is proposed. This approach, called GTVcut, employs an adaptive seed selection strategy and helps to segment the GTV, by identifying the target volume to be treated using the Gamma Knife device. The accuracy of GTVcut was evaluated on a dataset composed of 32 brain cancers, using both spatial overlap-based and distance-based metrics. The achieved experimental results are very reproducible, showing the effectiveness and the clinical feasibility of the proposed approach.     

Assessing cellular toxicities in fibroblasts upon exposure to lipid-based nanoparticles: a high content analysis approach

Lipid-based nanoparticles (LNPs) are widely used for the delivery of drugs and nucleic acids. Although most of them are considered safe, there is confusing evidence in the literature regarding their potential cellular toxicities. Moreover, little is known about the recovery process cells undergo after a cytotoxic insult. We have previously studied the systemic effects of common LNPs with different surface charge (cationic, anionic, neutral) and revealed that positively charged LNPs ((+)LNPs) activate pro-inflammatory cytokines and induce interferon response by acting as an agonist of Toll-like receptor 4 on immune cells. In this study, we focused on the response of human fibroblasts exposed to LNPs and their cellular recovery process. To this end, we used image-based high content analysis (HCA). Using this strategy, we were able to show simultaneously, in several intracellular parameters, that fibroblasts can recover from the cytotoxic effects of (+)LNPs. The use of HCA opens new avenues in understanding cellular response and nanotoxicity and may become a valuable tool for screening safe materials for drug delivery and tissue engineering.     

Self-organized TiO2 nanotube arrays: synthesis by anodization in an ionic liquid and assessment of photocatalytic properties

Self-organized TiO(2) nanotube (NT) arrays were produced by anodization in ethylene glycol (EG) electrolytes containing 1-n-butyl-3-methyl-imidazolium tetrafluoroborate (BMI.BF(4)) ionic liquid and water. The morphology of the as-formed NTs was considerably affected by changing the anodization time, voltage, and water and ionic liquid electrolyte concentrations. In general, a nanoporous layer was formed on the top surface of the TiO(2) NTs, except for anodization at 100 V with 1 vol % of BMI.BF(4), where the NT's mouth was revealed. The length and bottom diameter of the NTs as well as the pore diameter of the top layer showed a linear relationship with increased anodization voltage. These TiO(2) NTs were tested as photocatalysts for methyl orange photodegradation and hydrogen evolution from water/methanol solutions by UV light irradiation. The results show that the TiO(2) NTs obtained by anodization in EG/H(2)O/BMI.BF(4) electrolytes are active and efficient for both applications.     

High-throughput assay of oleopentanedialdheydes in extra virgin olive oil by the UHPLC-ESI-MS/MS and isotope dilution methods

The quality of extra virgin olive oil is associated with the presence of microcomponents whose healing effects have been proved in some special cases. The enzymatic hydrolysis of oleuropein and ligstroside, and of their demethylated analogues, affords four different pentanedialdehydes, and for one of which, 2-(4-hydroxyphenyl)ethyl (3S,4E)-4-formyl-3-(2-oxoethyl)hex-4-enoate, also known as oleocanthal, an anti-inflammatory effect was quite recently carefully assessed. Extra virgin olive oil is now worldwide considered as a functional food whose daily intake, as for the Mediterranean diet, helps consumers in keeping a constant level of nonsteroidal anti-inflammatory drug (NSAID) in the blood. The presence of these active principles provides, therefore, olive oil with an important added value. In the framework of the actions of the recently funded Agrifood Regional Center, which should coordinate the scientific research and production worlds, an absolute analytical method was developed for the mass spectrometric detection of the two most abundant NSAIDs, Tyr-OLPD and HTyr-OLPD (oleopentanedialdehydes (OLPDs) conjugated to p-hydroxyphenylethanol and 3,4-dihydroxyphenylethanol, respectively), by UHPLC-ESI-MS/MS.