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Autophagy is an essential recycling mechanism making micronutrients available in vegetative organs for subsequent reallocation to seeds, Micronutrient deficiencies affect a large part of the world’s population. These deficiencies are mostly due to the consumption of grains with insufficient content of iron (Fe) or zinc (Zn). Both de novo uptake by roots and recycling from leaves may provide seeds with nutrients. Autophagy, which is a conserved mechanism for nutrient recycling in eukaryotes, was shown to be involved in nitrogen remobilization to seeds. Here, we have investigated the role of this mechanism in micronutrient translocation to seeds. We found that Arabidopsis thaliana plants impaired in autophagy display defects in nutrient remobilization to seeds. In the atg5-1 mutant, which is completely defective in autophagy, the efficiency of Fe translocation from vegetative organs to seeds was severely decreased even when Fe was provided during seed formation. Combining atg5-1 with the sid2 mutation that counteracts premature senescence associated with autophagy deficiency and using 57Fe pulse labeling, we propose a two-step mechanism in which Fe taken up de novo during seed formation is first accumulated in vegetative organs and subsequently remobilized to seeds. Finally, we show that translocation of Zn and manganese (Mn) to seeds is also dependent on autophagy. Fine-tuning autophagy during seed formation opens up new possibilities to improve micronutrient remobilization to seeds.

The lattice sites, valence states, resulting magnetic behaviour and spin-lattice relaxation of Fe ions in GaN and AIN were investigated by emission Mossbauer spectroscopy following the implantation of radioactive Mn-57(+) ions at ISOLDE/CERN. Angle dependent measurements performed at room temperature on the 14.4 keV gamma-rays from the Fe-57 Mossbauer state (populated from the Mn-57/beta(-) decay) reveal that the majority of the Fe ions are in the 2+ valence state nearly substituting the Ga and Al cations, and/or associated with vacancy type defects. Emission Mossbauer spectroscopy experiments conducted over a temperature range of 100-800 K show the presence of magnetically split sextets in the "wings" of the spectra for both materials. The temperature dependence of the sextets relates these spectral features to paramagnetic Fe3+ with rather slow spin-lattice relaxation rates which follow a T-2 temperature dependence characteristic of a two-phonon Raman process. (C) 2015 Elsevier B.V. All rights reserved.

Multiconfigurational wave functions are calculated for a series of Fe complexes. We find a linear correlation between the experimental Fe-57 Mossbauer isomer shift and the calculated electron density at the Fe nucleus. However, the analysis of the wave function in valence bond terms shows that there is no straightforward relation between the density at the nucleus and the Fe charge. The analysis of the CASSCF wave function expressed in localized orbitals shows that the isomer shift is very sensitive to the weight of charge transfer configurations and hence to the covalency, rather than to the absolute charge. (c) 2008 Elsevier B. V. All rights reserved.

We present the temperature phase diagram of the compound DyFe 4 Ge 2 determined from high-quality powder XRPD for the entire magnetically ordered regime. DyFe 4 Ge 2 undergoes at T N , T c = 55 K a simultaneous structural and magnetic transition of second-order P4 2 /mnm , T N , T c = 55 K → Cmmm , followed by two subsequent isostructural first-order magnetic transitions at T ic 2 = 45 K and T ic 1 = 28 K . The structural transition at T N , T c is characterised by strong changes of the a / b ratio and of the shear strain while the T ic 1 = 28 K transition is related to a lattice expansion along c on cooling. Minor Fe parameter shifts and deformations (torsion angle and out-of plane Fe–Fe distances) of the Fe tetrahedra were found to accompany the two magnetic transitions. Using the XRPD instrumental resolution and modelling the anisotropic micro-strain enabled us to refine the observed anisotropic peak broadening associated with the presence of micro-structure effects. The maximum strain experienced by the crystal lattice during a sequence of subtle magnetic transitions was observed in the intermediate temperature interval T ic 1 = 28 K - T ic 2 = 45 K of incommensurate magnetic phases.

The structure of the UFe 3 B 2 compound has been refined down to R =0.022 and wR 2 =0.052 from single crystal X-ray diffraction data. This uranium boride crystallizes in the CeCo 3 B 2 type-structure ( P 6/ mmm space group no. 191, Z =1, ρ =10.79 g/cm 3 ), with lattice parameters at room temperature a =0.5052(1) nm, c =0.3002(1) nm and V =0.664(1) nm 3 . Magnetization measurements made between 2 K and 800 K suggested that UFe 3 B 2 is an antiferromagnet with a rather high Neel temperature of T N =268±5 K. No other magnetic transitions were observed down to the lowest studied temperature.

We report on the spectroscopic quadrupole moment measurement of the 7/2(1)(-) isomeric state in S-43(16)27 [E* = 320.5(5) keV, T-1/2 = 415(3) ns], using the time dependent perturbed angular distribution technique at the RIKEN RIBF facility. Our value, vertical bar Q(s) vertical bar = 23(3) efm(2), is larger than that expected for a single-particle state. Shell model calculations using the modern SDPF-U interaction for this mass region reproduce remarkably well the measured vertical bar Q(s) vertical bar, and show that non-negligible correlations drive the isomeric state away from a purely spherical shape. ispartof: Physical Review Letters vol:108 issue:16 ispartof: location:United States status: published

We report on the spectroscopic quadrupole moment measurement of the 7/2(1)(-) isomeric state in S-43(16)27 [E* = 320.5(5) keV, T-1/2 = 415(3) ns], using the time dependent perturbed angular distribution technique at the RIKEN RIBF facility. Our value, vertical bar Q(s) vertical bar = 23(3) efm(2), is larger than that expected for a single-particle state. Shell model calculations using the modern SDPF-U interaction for this mass region reproduce remarkably well the measured vertical bar Q(s) vertical bar, and show that non-negligible correlations drive the isomeric state away from a purely spherical shape.

A quantum chemical computational scheme for the calculation of isomer shift in Mossbauer spectroscopy is suggested. Within the described scheme, the isomer shift is treated as a derivative of the total electronic energy with respect to the radius of a finite nucleus. The explicit use of a finite nucleus model in the calculations enables one to incorporate straightforwardly the effects of relativity and electron correlation. The results of benchmark calculations carried out for several iron complexes as well as for a number of atoms and atomic ions are presented and compared with the available experimental and theoretical data. (C) 2007 American Institute of Physics.

This paper demonstrates the feasibility of quadrupole moment measurements on isomeric levels populated in projectile fragmentation reactions. The neutron-rich Fe-61(9/2(+)) [E-*= 861 keV, T-1/2= 239(5) ns] isomer was produced and spin aligned by the intermediate energy fragmentation of a Ni-64 beam and implanted in a Cd single crystal. Its spectroscopic quadrupole moment Q(s)=41(6) e fm(2) agrees with mean-field based calculations using the finite-range Gogny force, suggesting a moderately deformed shape characterized by an intrinsic charge quadrupole moment Q(0)=-85 e fm(2) or Q(0)=+115 e fm(2). The present measurement paves the way for future determinations of isomeric quadrupole moments in more exotic nuclei. ispartof: Physical Review C, Nuclear physics vol:75 issue:5 pages:1-4 status: published