4f-spin dynamics in La(2-x-y)Sr(x)Nd(y)CuO(4)

We have performed inelastic magnetic neutron scattering experiments on La(2-x-y)Sr(x)Nd(y)CuO(4) in order to study the Nd 4f-spin dynamics at low energies. In all samples we find at high temperatures a quasielastic line (Lorentzian) with a line width which decreases on lowering the temperature. The temperature dependence of the quasielastic line width Gamma/2(T) can be explained with an Orbach-process, i.e. a relaxation via the coupling between crystal field excitations and phonons. At low temperatures the Nd-4f magnetic response S(Q,omega) correlates with the electronic properties of the CuO(2)-layers. In the insulator La(2-y)Nd(y)CuO(4) the quasielastic line vanishes below 80 K and an inelastic excitation occurs. This directly indicates the splitting of the Nd3+ ground state Kramers doublet due to the static antiferromagnetic order of the Cu moments. In La(1.7-x)Sr(x)Nd(0.3)CuO(4) with x = 0.12, 0.15 and La(1.4-x)Sr(x)Nd(0.6)CuO(4) with x = 0.1, 0.12, 0.15, 0.18 superconductivity is strongly suppressed. In these compounds we observe a temperature independent broad quasielastic line of Gaussian shape below T about 30 K. This suggests a distribution of various internal fields on different Nd sites and is interpreted in the frame of the stripe model. In La(1.8-y)Sr(0.2)Nd(y)CuO(4) (y = 0.3, 0.6) such a quasielastic broadening is not observed even at lowest temperature.Comment: 8 pages, 10 figures included, to appear in Phys. Rev.

Ion mobility action spectroscopy of flavin dianions reveals deprotomer-dependent photochemistry

The intrinsic optical properties and photochemistry of flavin adenine dinucleotide (FAD) dianions are investigated using a combination of tandem ion mobility spectrometry and action spectroscopy. Two principal isomers are observed, the more stable form being deprotonated on the isoalloxazine group and a phosphate (N-3,PO4 deprotomer), and the other on the two phosphates (PO4,PO4 deprotomer). Ion mobility data and electronic action spectra suggest that photo-induced proton transfer occurs from the isoalloxazine group to a phosphate group, converting the PO4,PO4 deprotomer to the N-3,PO4 deprotomer. Comparisons of the isomer selective action spectra of FAD dianions and flavin monoanions with solution spectra and gas-phase photodissociation action spectra suggests that solvation shifts the electronic absorption of the deprotonated isoalloxazine group to higher energy. This is interpreted as evidence for significant charge transfer in the lowest optical transition of deprotonated isoalloxazine. Overall, this work demonstrates that the site of deprotonation of flavin anions strongly affects their electronic absorptions and photochemistry

Heat stress assessments in dairy cattle based on milk MIR spectral data

peer reviewedThe effect of heat stress (HS) on milk production traits is well documented. However, HS effect on the detailed milk composition has been much less studied. First findings in different environments (e.g. Belgium, Tunisia) reported responses in MIR spectra to HS in dairy cows. This study investigated the effect of HS on milk production traits and MIR spectrum which reflects the detailed composition of milk samples in the German federal state of BadenWürttemberg (BW). Milk test-day records for the period 2012 to 2019 were merged with temperature and humidity data provided by public weather stations in BW. Values for the daily average temperature-humidity index (THI) were calculated. Statistical analysis was made in R using ‘glmnet’ and spectral data was first standardized, then pre-processed by first derivative. Models relying in THI index were used to compare between HS effect on milk traits (milk yield, fat, protein contents and fatty acids) and 212 points of standardized spectra. Fixed effects were breeds, parity, milking moment, DIM classes, age at calving. The average 3-day lag average THI value was used as a covariate. In this study, the monthly average THI values ranged between 36±7.3 and 65±5.2 from January until August, respectively. The average daily THI was 50±8.6, 49±8.1, 64±5.4, and 37±7.5 during the autumn, spring, summer and winter periods, respectively. The average THI values indicated that dairy cows are exposed to HS during the summer period in BW. The results showed that there are differences in MIR spectra recorded during HS and thermoneutral conditions; specific wavenumbers of the MIR spectrum were reacting differently. Further analyses will be required to identify potential MIR milk-based phenotypes that could be used in this context for herd management and breeding for resilience to HS

Positive biodiversity–productivity relationships in forests: climate matters

International audienceWhile it is widely acknowledged that forest biodiversity contributes to climate change mitigation through improved carbon sequestration, conversely how climate affects tree species diversity–forest productivity relationships is still poorly understood. We combined the results of long-term experiments where forest mixtures and corresponding monocultures were compared on the same site to estimate the yield of mixed-species stands at a global scale, and its response to climatic factors. We found positive mixture effects on productivity using a meta-analysis of 126 case studies established at 60 sites spread across five continents. Overall, the productivity of mixed-species forests was 15% greater than the average of their component monocultures, and not statistically lower than the productivity of the best component monoculture. Productivity gains in mixed-species stands were not affected by tree age or stand species composition but significantly increased with local precipitation. The results should guide better use of tree species combinations in managed forests and suggest that increased drought severity under climate change might reduce the atmospheric carbon sequestration capacity of natural forests

Models comparison from Positive biodiversity–productivity relationships in forests: climate matters

Table S2. Outcomes of models comparison for the test of moderators effects on overyielding (OY) and transgressive overyielding (TOY) in young and old forests, respectively