Direct observation of two protons in the decay of 54Zn

The two protons emitted in the decay of 54Zn have been individually observed for the first time in a time projection chamber. The total decay energy and the half-life measured in this work agree with the results obtained in a previous experiment. Angular and energy correlations between the two protons are determined and compared to theoretical distributions of a three-body model. Within the shell model framework, the relative decay probabilities show a strong contribution of the p2 configuration for the two-proton emission. After 45Fe, the present result on 54Zn constitutes only the second case of a direct observation of the ground state two-proton decay of a long-lived isotope.     

Mössbauer study of isothermal crystallization kinetics of the amorphous iron III fluoride FeF3, 0.4HF

The amorphous fluoride FeF₃,xHF (0.4?×?1) synthetized by a soft chemistry reaction, crystallizes to R-FeF₃. Crystallization was followed as a function of time at several constant temperatures by Mössbauer spectroscopy. The evolution of R-FeF₃ rate is in good agreement with a Johnson-Mehl-Avrami transformation equation: The crystallization proceeds like a first-order reaction with an activation energy of ≈2 eV.     

Self‐Assembly of a Giant Tetrahedral 3 d–4 f Single‐Molecule Magnet within a Polyoxometalate System

A giant tetrahedral heterometallic polyoxometalate (POM) [Dy₃₀Co₈Ge₁₂W₁₀₈O₄₀₈(OH)₄₂(OH₂)₃₀]^56?, which shows single‐molecule magnet (SMM) behavior, is described. This hybrid contains the largest number of 4f ions of any polyoxometalate (POM) reported to date and is the first to incorporate two different 3d–4f and 4f coordination cluster assemblies within same POM framework.     

Analysis methodology for 3C-PIV data of rotary wing vortices

3C-PIV data from tip vortices of either fixed-wing or rotating wing experiments are challenging from an analysis point of view. Model motion, vortex wander, spurious vectors, periodic and aperiodic effects, turbulence, and other disturbing effects are all present in the data. In most cases the vortices are not measured perpendicular to their axis as well. Engineers need time-averaged properties from the vortex in the vortex axis system for a proper modelization within simulation codes. This article describes the methods needed to deal with all the mentioned problem areas, including the conditional averaging and rotation into the vortex axis system. The methods are validated by using numerically generated vortex vector fields, and finally applied to experimental data from a hover condition of a model rotor.     

13C-labeled heparan sulfate analogue as a tool to study protein/heparan sulfate interactions by NMR spectroscopy: application to the CXCL12α chemokine

Heparan sulfate (HS), a polysaccharide of the glycosaminoglycan family characterized by a unique level of complexity, has emerged as a key regulator of many fundamental biological processes. Although it has become clear that this class of molecules exert their functions by interacting with proteins, the exact modes of interaction still remain largely unknown. Here we report the engineering of a (13)C-labeled HS-like oligosaccharide with a defined oligosaccharidic sequence that was used to investigate the structural determinants involved in protein/HS recognition by multidimensional NMR spectroscopy. Using the chemokine CXCL12α as a model system, we obtained experimental NMR data on both the oligosaccharide and the chemokine that was used to obtain a structural model of a protein/HS complex. This new approach provides a foundation for further investigations of protein/HS interactions and should find wide application.     

Synthetic methods for polyamine linkers and their application to combinatorial chemistry

Summary Polyamines and polyamine conjugates display a diverse range of important biological functions, ranging from antibiotics to immunosuppressants and glutamate receptor antagonists. For these reasons, polyamines provide an excellent template/scaffold for combinatorial chemistry. In this paper we present methods for the solid-phase immobilisation of polyamines for use in synthetic and combinatorial chemistry and describe how they have been employed in the preparation of a number of important polyamine conjugates and polyamine libraries. Thus, we have designed, synthesised and utilised a number of polyamine linkers for both solution and resin screening combinatorial application.     

Magnetic structure of the canted 1D-antiferromagnet NaBaFe2F9

NaBaFe₂F₉ crystallizes with the Ba₂CoFeF₉ structural type (space group P2₁/n, Z = 4). In this structure, infinite cis double [M₂F₉]^3? chains of corner sharing octahedra are isolated one from each other by sodium and barium ions. At 4.5 K, the cell parameters (Å) are found to be: a = 7.3236(3), b = 17.4525(7), c = 5.4586(2), β = 91.840(3)°. Antiferromagnetic interactions dominate but, below T_N ? 19 K, a parasitic ferromagnetic component appears with σ_r(4.5K) = 0.03(1) μ_B·mole^?.The magnetic structure (C_xF_yC_z mode) was foreseen by the macroscopic theory of Bertaut and established from neutron powder diffraction. Using the Rietveld profile refinement method, the 4.5 K spectrum was analysed at $\text{λ =}\text{1.909}\text{A}\text{?}\text{(R}{}_{\mathrm{<mtext>Profile</mtext>}}\text{=}\text{0.093}\text{, R}{}_{\mathrm{<mtext>Nucl</mtext>}}\text{=}\text{0.053}\text{, R}{}_{\mathrm{<mtext>Mag</mtext>}}\text{=}\text{0.126}\text{)}$ and the 4.5–35K difference spectrum at $\text{λ =}\text{2.518}\text{A}\text{?}\text{(R}{}_{\mathrm{<mtext>Mag</mtext>}}\text{=}\text{0.049}\text{, R}{}_{\mathrm{<mtext>Profile</mtext>}}\text{=}\text{0.092}\text{)}$. The magnetic moments on two Fe³⁺ sites, lie mainly in the (0 1 0) plane, approximately at 45° from the a- and c-axes. They form a pseudo G-type antiferromagnetic arrangement (μ(Fe1) = 3.60(4) μ_B;μ(Fe2) = 3.61(6)μ_B).     

Cutting planes for integer programs with general integer variables

We investigate the use of cutting planes for integer programs with general integer variables. We show how cutting planes arising from knapsack inequalities can be generated and lifted as in the case of 0–1 variables. We also explore the use of Gomory's mixed-integer cuts. We address both theoretical and computational issues and show how to embed these cutting planes in a branch-and-bound framework. We compare results obtained by using our cut generation routines in two existing systems with a commercially available branch-and-bound code on a range of test problems arising from practical applications. © 1998 The Mathematical Programming Society, Inc. Published by Elsevier Science B.V.Corresponding author.This research was partly performed when the author was affiliated with CORE, Université Catholique de Louvain.