Exploring the Physical and Biological Aspects of BNCT with a Carboranylmethylbenzo[b]acridone Compound in U87 Glioblastoma Cells

Boron neutron capture therapy (BNCT) is a re-emerging technique for selectively killing tumor cells. Briefly, the mechanism can be described as follows: after the uptake of boron into cells, the thermal neutrons trigger the fission of the boron atoms, releasing the α-particles and recoiling lithium particles and high-energy photons that damage the cells. We performed a detailed study of the reactor dosimetry, cellular dose assessment, and radiobiological effects induced by BNCT in glioblastoma (GBM) cells. At maximum reactor power, neutron fluence rates were ϕ₀ = 6.6 × 10⁷ cm⁻² s⁻¹ (thermal) and θ = 2.4 × 10⁴ cm⁻² s⁻¹ with a photon dose rate of 150 mGy·h⁻¹. These values agreed with simulations to within 85% (thermal neutrons), 78% (epithermal neutrons), and 95% (photons), thereby validating the MCNPX model. The GEANT4 simulations, based on a realistic cell model and measured boron concentrations, showed that >95% of the dose in cells was due to the BNC reaction. Carboranylmethylbenzo[b]acridone (CMBA) is among the different proposed boron delivery agents that has shown promising properties due to its lower toxicity and important cellular uptake in U87 glioblastoma cells. In particular, the results obtained for CBMA reinforce radiobiological effects demonstrating that damage is mostly induced by the incorporated boron with negligible contribution from the culture medium and adjacent cells, evidencing extranuclear cell radiosensitivity.     

Experimental Variability in Kinetics of Moisture Expansion and Mass Gain in Ceramics

The rehydroxylation dating method of archeological fired‐clay artifacts relies on the reliability of the (time)^1/4 power law model considered for long‐term moisture expansion and mass gain in ceramics. Here, we reanalyze different moisture expansion datasets that were previously used to verify this model. We show that these data obey an accurate (time)^1/N power law, but they reveal a variability in the values of the exponent 1/N between ~1/2 and ~1/4. It is possible that this value is an intrinsic property of ceramics, naturally varying between a behavior governed by a Brownian process (t^1/2 power law) and a behavior controlled by a one‐dimensional diffusion process (t^1/4 power law).     

Defining decision making process performance: Conceptualization and validation of an index

Many studies have demonstrated the impact of information technology (IT) on decision making but few have used decision making process performance (DMPP) as a dependent variable. Our study proposes a rich formative conceptualization of DMPP, a valid and reliable measure for this construct, and studies its influence on the quality of decision making. The results show that DMPP is a formative second-order aggregate construct composed of procedural rationality, exhaustivity of the information analyzed, openness of spirit, and effort. This study illustrates the importance of building proper definitions of constructs and contributes to the development of shared meaning in IS.     

A 2D and 3D X-ray μ-diffraction and μ-fluorescence study of a mixed ionic electronic conductor

Due to the mixed ionic electronic conductive properties of the Lanthanum Strontium Cobalt Ferrite (LSCF) La_0.6Sr_0.4Co_0.2Fe_0.8O_3?δ compound, it is of great scientific and technological interest. Especially in the Solid Oxide Fuel Cell (SOFC) technology, this compound has receiving great attention as a cathode material. However, its chemical reactivity with the Yttria-stabilized Zirconia (YSZ) electrolyte still remains one of the main challenges, which demands a comprehension in the μm and sub-μm range. In order to address the reactivity issues locally in the micrometre scale range, 2D and 3D X-ray μ-diffraction and μ-fluorescence analysis have been performed on a pristine LSCF cathode layer. The cathode was deposited on a dense YSZ electrolyte substrate spaced by a thin Gadolinium doped Ceria Oxide (CGO) barrier layer in between LSCF and YSZ to limit the reactivity. The present approach offers a larger field of view in comparison to electron microscopy techniques. The method can provide a more representative information and may offer some insights on the reactivity distribution along the interfaces. The formation of micro SrZrO₃ inclusions in LSCF layer is then indubitably identified, as well as in the CGO/YSZ interface.     

Quelques mesures-critères de stress et la prédiction de l'état de santé physique. Une étude longitudinale.

Studied the relation of stress to physical and psychological states of health. Human subjects: 91 Canadian female adults (mean age 30.3 yrs). Ss' stress levels and physical and psychological status were evaluated via administration of a questionnaire 3 times during an 8-mo period, and sequential effects were evaluated. Tests used: The "Mesure de Stress Psychologique" (Measure of Psychological Stress), the Depression Inventory by A. T. Beck et al (1961), the General Health Questionnaire by D. P. Goldberg (1978), and a physical state questionnaire derived from the "Santé Canada" (Health Canada) instrument. An analysis of variance (ANOVA) and other statistical tests were used. (English abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Non-exclusion effects in g.p.c.: a review

Steric exclusion is generally the predominant separation mechanism in gel chromatography. However, adsorption on the gel and dissolution inside the gel also occur, greatly disturbing solute retention and especially hindering universal calibration for polymers. Some typical examples of such effects are given. The corresponding mechanisms are discussed and the bases of methods to present non-exclusion effects are given.     

Hybrid parallelization of molecular dynamics simulations to reduce load imbalance

The most widely used technique to allow for parallel simulations in molecular dynamics is spatial domain decomposition, where the physical geometry is divided into boxes, one per processor. This technique can inherently produce computational load imbalance when either the spatial distribution of particles or the computational cost per particle is not uniform. This paper shows the benefits of using a hybrid MPI+OpenMP model to deal with this load imbalance. We consider LAMMPS (Large-scale Atomic/Molecular Massively Parallel Simulator), a prototypical molecular dynamics simulator that provides its own balancing mechanism and an OpenMP implementation for many of its modules, allowing for a hybrid setup. In this work, we extend the current OpenMP implementation of LAMMPS and optimize it and evaluate three different setups: MPI-only, MPI with the LAMMPS balance mechanism, and hybrid setup using our improved OpenMP version. This comparison is made using the five standard benchmarks included in the LAMMPS distribution plus two additional test cases. Results show that the hybrid approach can deal with load balancing problems better and more effectively (50% improvement versus MPI-only for a highly imbalanced test case) than the LAMMPS balance mechanism (only 43% improvement) and improve simulations with issues other than load imbalance.

     

Influence of the load modelling during gait on the stress distribution in a femoral implant

Introduction

When designing and installing implants, stress analyses should be performed in conditions close to those of everyday use. Specifically, for femoral implants, cyclic loading during gait has been demonstrated to produce fatigue failure. However, there is still no consensus in the literature regarding which modelling procedure is the most appropriate to simulate implant working conditions. This work proposes a method for realistic load modelling of the human body during gait based on flexible multibody dynamics.

Method

The proposed dynamic method was applied to a case study of a lower limb implant that failed by fatigue. The computed stresses were compared to the stresses obtained using the other three methods found in the literature, which are principally based on static or quasi-static load modelling.

Results

For all compared methods, the maximum computed stress was located in the same region of the implant. The maximum stress provided using flexible multibody dynamics was equal to 346 MPa, which was 355% greater than the maximum value given by the static method and 18% greater than the value given by the quasi-static method.

Discussion and conclusion

The proposed dynamic method was in agreement with the conclusions of the previous failure analysis performed on the broken implant. Conversely, the static and quasi-static methods were not representative of the real loading conditions induced by gait. Moreover, the dynamic method emphasizes the pertinence of evaluating the fluctuations in the critical stress during the gait cycle, which is mandatory when studying fatigue failures.

     

Topology optimization for microstructural design under stress constraints

This work aims at introducing stress responses within a topology optimization framework applied to the design of periodic microstructures. The emergence of novel additive manufacturing techniques fosters research towards new approaches to tailor materials properties. This paper derives a formulation to prevent the occurrence of high stress concentrations, often present in optimized microstructures. Applying macroscopic test strain fields to the material, microstructural layouts, reducing the stress level while exhibiting the best overall stiffness properties, are sought for. Equivalent stiffness properties of the designed material are predicted by numerical homogenization and considering a metallic base material for the microstructure, it is assumed that the classical Von Mises stress criterion remains valid to predict the material elastic allowable stress at the microscale. Stress constraints with arbitrary bounds are considered, assuming that a sizing optimization step could be applied to match the actual stress limits under realistic service loads. Density–based topology optimization, relying on the SIMP model, is used and the qp–approach is exploited to overcome the singularity phenomenon arising from the introduction of stress constraints with vanishing material. Optimization problems are solved using mathematical programming schemes, in particular MMA, so that a sensitivity analysis of stress responses at the microstructural level is required and performed considering the adjoint approach. Finally, the developed method is first validated with classical academic benchmarks and then illustrated with an original application: tailoring metamaterials for a museum anti–seismic stand.