DFT Calculations as a Tool to Analyse Quadrupole Splittings of Spin Crossover Fe(II) complexes

Density functional methods have been applied to calculate the quadrupole splitting of a series of iron(II) spin crossover complexes. Experimental and calculated values are in reasonable agreement. In one case spin-orbit coupling is necessary to explain the very small quadrupole splitting value of 0.77 mm/s at 293 K for a high-spin isomer

Development of Collembolans after coversion towards organic farming

In Northern Germany, a diverse and complex experimental farm of the Federal Agricultural Research Centre (FAL) was set-up in 2001 covering all main aspects of organic farming. Previously, the 600 ha farm had been managed conventionally. Adjacent conventional farms were used as reference. The aim of this project was to study collembolans, microbial biomass and soil organic carbon in six organically farmed fields managed as a crop rotation of six different crops compared with an adjacent conventionally managed field. We hypothesised that the specific management in organic farming promotes soil biota. Soil samples were taken during the growing season in 2004. Collembolan abundances and microbial biomass were lower under organic management, but, generally, collembolan diversity was higher in organically farmed fields combined with a shifting in the dominance structure of the species. This result reveals that, even after three years, the soil biota is still changing with management conversion

An automated and versatile ultra-low temperature SQUID magnetometer

We present the design and construction of a SQUID-based magnetometer for operation down to temperatures T = 10 mK, while retaining the compatibility with the sample holders typically used in commercial SQUID magnetometers. The system is based on a dc-SQUID coupled to a second-order gradiometer. The sample is placed inside the plastic mixing chamber of a dilution refrigerator and is thermalized directly by the 3He flow. The movement though the pickup coils is obtained by lifting the whole dilution refrigerator insert. A home-developed software provides full automation and an easy user interface.Comment: RevTex, 10 pages, 10 eps figures. High-resolution figures available upon reques

Pressure-induced changes of the vibrational modes of spin-crossover complexes studied by nuclear resonance scattering of synchrotron radiation

Nuclear inelastic scattering (NIS) spectra were recorded for the spin-crossover complexes STP and ETP (STP = [Fe(1,1,1-trisf[N-(2-pyridylmethyl)-N-methylamino]methylg- ethane)](ClO4)2 and ETP = [Fe(1,1,1-trisf[N-(2-pyridylmethyl)-N-methylamino]methylg-butane)](ClO4)2) at 30 K and at room temperature and also at ambient pressure and applied pressure (up to 2.6 GPa). Spin transition from the high-spin (HS) to the low-spin (LS) state was observed by lowering temperature and also by applying pressure at room temperature and has been assigned to the hardening of iron-bond stretching modes due to the smaller volume in the LS isomer

Dynamics of Metal Centers Monitored by Nuclear Inelastic Scattering

Nuclear inelastic scattering of synchrotron radiation has been used now since 10 years as a tool for vibrational spectroscopy. This method has turned out especially useful in case of large molecules that contain a M\"ossbauer active metal center. Recent applications to iron-sulfur proteins, to iron(II) spin crossover complexes and to tin-DNA complexes are discussed. Special emphasis is given to the combination of nuclear inelastic scattering and density functional calculations

Superconducting phase diagram of the filled skuterrudite PrOs4Sb12

We present new measurements of the specific heat of the heavy fermion superconductor PrOs4Sb12, on a sample which exhibits two sharp distinct anomalies at Tc1= 1.89K and Tc2= 1.72K. They are used to draw a precise magnetic field-temperature superconducting phase diagram of PrOs4Sb12 down to 350 mK. We discuss the superconducting phase diagram of PrOs4Sb12 and its possible relation with an unconventional superconducting order parameter. We give a detailed analysis of Hc2(T), which shows paramagnetic limitation (a support for even parity pairing) and multiband effects

Density functional theory calculations and vibrational spectroscopy on iron spin-crossover compounds

Iron complexes with a suitable ligand field undergo spin-crossover (SCO), which can be induced reversibly by temperature, pressure or even light. Therefore, these compounds are highly interesting candidates for optical information storage, for display devices and pressure sensors. The SCO phenomenon can be conveniently studied by spectroscopic techniques like Raman and infrared spectroscopy as well as nuclear inelastic scattering, a technique which makes use of the M\"ossbauer effect. This review covers new developments which have evolved during the last years like, e.g. picosecond infrared spectroscopy and thin film studies but also gives an overviewon newtechniques for the theoretical calculation of spin transition phenomena and vibrational spectroscopic data of SCO complexes

Delta-like and gtl2 are reciprocally expressed, differentially methylated linked imprinted genes on mouse chromosome 12

AbstractThe distal portion of mouse chromosome 12 is imprinted. To date, however, Gtl2 is the only imprinted gene identified on chromosome 12. Gtl2 encodes multiple alternatively spliced transcripts with no apparent open reading frame. Using conceptuses with maternal or paternal uniparental disomy for chromosome 12 (UPD12), we found that Gtl2 is expressed from the maternal allele and methylated at the 5′ end of the silent paternal allele. A reciprocally imprinted gene, Delta-like (Dlk), with homology to genes involved in the Notch signalling pathway was identified 80kb upstream of Gtl2. Dlk was expressed exclusively from the paternal allele in both the embryo and placenta, but the CpG-island promoter of Dlk was completely unmethylated on both parental alleles. Rather, a paternally methylated region was identified in the last exon of the active Dlk allele. The proximity, reciprocal imprinting and methylation in this domain are reminiscent of the co-ordinately regulated Igf2–H19 imprinted domain on mouse chromosome 7. Like H19 and Igf2, Gtl2 and Dlk were found to be co-expressed in the same tissues throughout development, though not after birth. These results have implications for the regulation, function and evolution of imprinted domains

Pressure Evolution of the Magnetic Field induced Ferromagnetic Fluctuation through the Pseudo-Metamagnetism of CeRu2Si2

Resistivity measurements performed under pressure in the paramagnetic ground state of CeRu2Si2 are reported. They demonstrate that the relative change of effective mass through the pseudo metamagnetic transition is invariant under pressure. The results are compared with the first order metamagnetic transition due to the antiferromagnetism of Ce0.9La0.1Ru2Si2 which corresponds to the "negative" pressure of CeRu2Si2 by volume expansion. Finally, we describe the link between the spin-depairing of quasiparticles on CeRu2Si2 and that of Cooper pairs on the unconventional heavy fermion superconductor CeCoIn5.Comment: 5 pages, 6 figures, accepted for publication in J. Phys. Soc. Jp

M\"ossbauer, nuclear inelastic scattering and density functional studies on the second metastable state of Na2[Fe(CN)5NO]⋅\cdot2H2O

The structure of the light-induced metastable state SII of Na2[Fe(CN)5NO]$\cdot$2H2O 14 was investigated by transmission M\"ossbauer spectroscopy (TMS) in the temperature range 15 between 85 and 135 K, nuclear inelastic scattering (NIS) at 98 K using synchrotron 16 radiation and density functional theory (DFT) calculations. The DFT and TMS results 17 strongly support the view that the NO group in SII takes a side-on molecular orientation 18 and, further, is dynamically displaced from one eclipsed, via a staggered, to a second 19 eclipsed orientation. The population conditions for generating SII are optimal for 20 measurements by TMS, yet they are modest for accumulating NIS spectra. Optimization 21 of population conditions for NIS measurements is discussed and new NIS experiments on 22 SII are proposed