Mössbauer study of mixed valent silicides Eu(Ir1−x Pd x )2Si2

The solid solutions Eu(Ir_1–x Pd _x )₂Si₂, which exist for 0x0.125 and 0.75x1. cristallize with the tetragonal ThCr₂Si₂-type structure. The variation of the europium valence with composition has been thoroughly studied at temperatures 4.2T293 K by¹⁵¹Eu Mössbauer resonance. For 0x0.125 the europium valence at room temperature decreases asx increases. For 0.75x1 the valence transition temperature Eu³⁺Eu²⁺ increases asx increases.     

The crystal structure of a new nonstoichiometric phase Cs1−xLu3F10−x (x ⋍ 0.25)

A high-temperature phase with the formula $\text{Cs}{}_{\mathrm{1?x}}\text{Lu}{}_3\text{F}{}_{\mathrm{10?x}}\text{(x ? 0.25)}$ has been characterized during the investigation of the CsFLuF₃ system. This phase crystallizes in the monoclinic system with unit-cell dimensions a = 13.764(5) Å, b = 7.947(1) Å, c = 4.299(2)Å, β = 90.04(5)° and space group Cm (No. 8), Z = 2. The structure was solved by conventional Patterson and Fourier methods and refined by full-matrix least-squares techniques to a conventional R of 0.053 (R_w = 0.079) for 2038 independent reflections recorded on an automatic four-circle diffractometer. The structure may be regarded as built up of (Lu₃F₁₀)^? layers that may be described as corner- and edge-shared LuF₇ pentagonal bipyramids. These layers run parallel to the (001) plane. The structure extends along the third direction by cornersharing involving axial vertices of the pentagonal bipyramids. This three-dimensional framework delimits tunnels running parallel to the c direction where the Cs⁺ ions lie. The partial occupancies of both the Cs site and one out of the seven independent fluorine sites results in the nonstoichiometry.     

Preparation of new amide-linked pseudodisaccharides by the carboxymethylglycoside lactone (CMGL) strategy

6-Aminodeoxy sugars react with carboxymethyl 3,4,6-tri-O-acetyl-α-d-glucopyranoside 2-O-lactone (α-CMGL) to provide the corresponding new amide-linked glucose/glucose or glucose/galactose pseudodisaccharides in good yields. The strategy is extended to the synthesis of an amide-linked sugar/nucleoside adduct.     

One-step capillary isoelectric focusing for the separation of the recombinant human immunodeficiency virus envelope glycoprotein glycoforms

One-step capillary isoelectric focusing was investigated as a rapid method to resolve the glycoforms of the heterogeneous recombinant human immunodeficiency virus (HIV) envelope glycoprotein (rgp 160sMN/LAI). The separation was performed in a poly(vinyl alcohol) (PVA) coated capillary using a mixture of ampholyte of narrow and wide pH range. A combination of saccaharose and 3-(cyclohexylamino)-1-propanesulfonic acid was shown to be the most efficient additive to avoid protein precipitation which occurs at a pH close to its pI. Although the calibration curve [isoelectric point (pI) vs. migration times] showed a non-linear relationship, an adequate linearity could be yielded for short pI ranges permitting to exhibit the acidic character of the different glycoforms of the rgp 160s MN/LAI (pI from 4.00 to 4.95). Reproducibility evaluated by comparing the performance of a polyacrylamide and a PVA coated capillary showed that low RSD values were obtained for intra-day (0.5 to 1.9%) and inter-day (1.6 to 7.6%) measurements using the PVA capillary. Moreover, the long term stability of the PVA capillary was demonstrated by measuring the variation of migration times of the protein markers for a long period of use. Finally, this method was able to differentiate the glycoform pattern of two close glycoproteins such as the rgp 160 of two sub-populations of the virus HIV-1.     

Commutators and decompositions of orthomodular lattices

We show that in any complete OML (orthomodular lattice) there exists a commutatorc such that [0,c ] is a Boolean algebra. This fact allows us to prove that a complete OML satisfying the relative centre property is isomorphic to a direct product [0,a] × [0,a ] wherea is a join of two commutators, [0,a] is an OML without Boolean quotient and [0,a ] is a Boolean algebra. The proof uses a new characterization of the relative centre property in complete OMLs. In a final section, we specify the previous direct decomposition in the more particular case of locally modular OMLs.     

Studies on Highly Porous Hybrids Prepared by a Novel Fast Gellation Process Under Ambient Pressure

Supercritical drying of hydrolyzed alkoxysilanes is a typical method for making aerogels that exhibit over 75% porosity. Recent works demonstrated the possibility to prepare, under ambient pressure, aerogel-type of highly porous materials. However, multiple step process is being required for surface modification of pore walls to avoid collapsing effect caused by drying shrinkage. We wish to describe in here a novel fast, single step sol-gel route for the preparation of ultra high porous materials. Commercially available hydrogensilsesquioxane was used as precursor in this approach, leading through a simple, single step process to gels within minutes and thus without any further surface modification needed. Systematic studies of this novel fast gellation process were carried out through careful variation of experimental conditions to gain porosity control and enable improved design of this class of ultra high porous monolithic materials.     

Monolith Passive Adsorbers Prepared with Hydrophobic Porous Silica Rods Coated with Hydrogel

This work focuses on the synthesis and characterization of porous silica monolith-based adsorbent materials. Materials with bimodal porosity (macro and meso) were prepared through a sol–gel process. The capacity of adsorption of organic molecules was ensured by grafting of hydrophobic organic coating on the silica surface. Alkylsilane chains or lauryl acrylate polymer were used for this purpose. The adsorption kinetic behavior of the produced materials was assessed through benzophenone adsorption studies in aqueous media. The results have shown that the macropore size of the monoliths had no effect on the adsorption capacity. The thicker organic layer prepared by polymerization of lauryl acrylate has decreased the adsorption kinetics without affecting the total adsorption capacity. The over-coating with additional external layer of hydrogel further slowed the diffusion of benzophenone thus better matches the passive-sampler requirements.     

A methodology using option pricing to determine a suitable discount rate in environmental management

With the present analysis the authors propose an approach for determining an adequate discount rate in environmental management problems, more specifically radioactive-waste management. It is shown that the classical Black–Scholes pricing formula can be used for determining the adequate present funding to be set-aside for the future. The average funding is equal to the net present value (NPV) of the future costs, including technical-scenario uncertainties. For taking into account the financial uncertainties, the NPV is identified with the strike price of a European put option, and the asset value in the managed fund is identified with the current price. The risk-free rate is the expected return rate of the portfolio. The paper shows that the adequate present funding can be determined for given multi-generational risk levels and an asset allocation by fixing the discount rate and adding a premium to the NPV of future costs.     

A novel epitaxially grown LSO‐based thin‐film scintillator for micro‐imaging using hard synchrotron radiation

The efficiency of high‐resolution pixel detectors for hard X‐rays is nowadays one of the major criteria which drives the feasibility of imaging experiments and in general the performance of an experimental station for synchrotron‐based microtomography and radiography. Here the luminescent screen used for the indirect detection is focused on in order to increase the detective quantum efficiency: a novel scintillator based on doped Lu₂SiO₅ (LSO), epitaxially grown as thin film via the liquid phase epitaxy technique. It is shown that, by using adapted growth and doping parameters as well as a dedicated substrate, the scintillation behaviour of a LSO‐based thin crystal together with the high stopping power of the material allows for high‐performance indirect X‐ray detection. In detail, the conversion efficiency, the radioluminescence spectra, the optical absorption spectra under UV/visible‐light and the afterglow are investigated. A set‐up to study the effect of the thin‐film scintillator's temperature on its conversion efficiency is described as well. It delivers knowledge which is important when working with higher photon flux densities and the corresponding high heat load on the material. Additionally, X‐ray imaging systems based on different diffraction‐limited visible‐light optics and CCD cameras using among others LSO‐based thin film are compared. Finally, the performance of the LSO thin film is illustrated by imaging a honey bee leg, demonstrating the value of efficient high‐resolution computed tomography for life sciences.