66 research outputs found
A de Haas-van Alphen study of the filled skutterudite compounds PrOsAs and LaOsAs
Comprehensive magnetic-field-orientation dependent studies of the
susceptibility and de Haas-van Alphen effect have been carried out on single
crystals of the filled skutterudites PrOsAs and LaOsAs
using magnetic fields of up to 40~T. Several peaks are observed in the
low-field susceptibility of PrOsAs, corresponding to cascades of
metamagnetic transitions separating the low-field antiferromagnetic and
high-field paramagnetic metal (PMM) phases. The de Haas-van Alphen experiments
show that the Fermi-surface topologies of PrOsAs in its PMM phase
and LaOsAs are very similar. In addition, they are in reasonable
agreement with the predictions of bandstructure calculations for
LaOsAs on the PrOsAs lattice. Both observations suggest
that the Pr 4 electrons contribute little to the number of itinerant
quasiparticles in the PMM phase. However, whilst the properties of
LaOsAs suggest a conventional nonmagnetic Fermi liquid, the effects
of direct exchange and electron correlations are detected in the PMM phase of
PrOsAs. For example, the quasiparticle effective masses in
PrOsAs are found to decrease with increasing field, probably
reflecting the gradual suppression of magnetic fluctuations associated with
proximity to the low-temperature, low-field antiferromagnetic state
SUITABILITY OF SOILS REMETEA MARE, TIMIS COUNTY
Soils studied area formed by the complex interaction of factors of which the mostimportant pedogenetic are: landscape, water, rock parent, climate, vegetation, man. Thus the investigated area are two areas where soils are well differentiated, a result of different pedogenetic conditions.In the high plains and hilly area on the material more or less reddish carbonateformed and evolved preluvisols mollic typical.Mineralization because most parts of the debris that is deposited annually in the topsoil to form a small amount of humus and therefore higher horizon color is brown (Ao), met frequently with preluvisols horizon
International researcher mobility and knowledge transfer in the social sciences and humanities
This article explores knowledge outcomes of international researcher mobility in the social sciences and humanities. Looking in particular at international experiences of longer durations in the careers of European PhD graduates, it proposes a threefold analytical typology for understanding the links between the modes, durations, and outcomes of this mobility in terms of the exchange of codified knowledge; the sharing of more tacit knowledge practices; and the development of a cosmopolitan identity. The findings suggest that, under the right conditions, there can be an important and transformative value to longer stays, which can lead to enduring outcomes in terms of knowledge production and innovation and the spatially distributed networks that sustain it
HPF1-dependent histone ADP-ribosylation triggers chromatin relaxation to promote the recruitment of repair factors at sites of DNA damage
Poly(ADP-ribose) polymerase 1 (PARP1) activity is regulated by its co-factor histone poly(ADP-ribosylation) factor 1 (HPF1). The complex formed by HPF1 and PARP1 catalyzes ADP-ribosylation of serine residues of proteins near DNA breaks, mainly PARP1 and histones. However, the effect of HPF1 on DNA repair regulated by PARP1 remains unclear. Here, we show that HPF1 controls prolonged histone ADP-ribosylation in the vicinity of the DNA breaks by regulating both the number and length of ADP-ribose chains. Furthermore, we demonstrate that HPF1-dependent histone ADP-ribosylation triggers the rapid unfolding of chromatin, facilitating access to DNA at sites of damage. This process promotes the assembly of both the homologous recombination and non-homologous end joining repair machineries. Altogether, our data highlight the key roles played by the PARP1/HPF1 complex in regulating ADP-ribosylation signaling as well as the conformation of damaged chromatin at early stages of the DNA damage response.Smith, Zentout et al. investigate the role of HPF1 in DNA repair using live-cell imaging methods and find that HPF1-dependent histone ADP-ribosylation drives early process in DNA repair, including chromatin relaxation and repair factor recruitment.Genome Instability and Cance
Non-adiabatic small polaron hopping in the n=3 Ruddlesden-Popper compound Ca4Mn3O10
Magnetotransport properties of the compound Ca4Mn3O10 are interpreted in
terms of activated hopping of small magnetic polarons in the non-adiabatic
regime. Polarons are most likely formed around Mn3+ sites created by oxygen
substoichiometry. The application of an external field reduces the size of the
magnetic contribution to the hopping barrier and thus produces an increase in
the conductivity .We argue that the change in the effective activation energy
around TN is due to the crossover to VRH conduction as antiferromagnetic order
sets in.Comment: 29 pages, 7 figure
Systematic functional analysis of Leishmania protein kinases identifies regulators of differentiation or survival
Differentiation between distinct stages is fundamental for the life cycle of intracellular protozoan parasites and for transmission between hosts, requiring stringent spatial and temporal regulation. Here, we apply kinome-wide gene deletion and gene tagging in Leishmania mexicana promastigotes to define protein kinases with life cycle transition roles. Whilst 162 are dispensable, 44 protein kinase genes are refractory to deletion in promastigotes and are likely core genes required for parasite replication. Phenotyping of pooled gene deletion mutants using bar-seq and projection pursuit clustering reveal functional phenotypic groups of protein kinases involved in differentiation from metacyclic promastigote to amastigote, growth and survival in macrophages and mice, colonisation of the sand fly and motility. This unbiased interrogation of protein kinase function in Leishmania allows targeted investigation of organelle-associated signalling pathways required for successful intracellular parasitism
Design of block copolymer micelles via crystallization
This Feature Article provides an overview of the progress made over the last few years in the design of diblock copolymer micelles based on crystallization-driven self-assembly (CDSA) towards the development of novel and fascinating morphologies with crystalline-cores. Here, we describe the different approaches employed in order to engineer a large variety of semicrystalline micellar architectures. We highlight kinetic strategies that have been employed to direct morphological transitions, which can then be further tuned thus increasing the range of possible micellar structures. We then emphasize the development of complex hybrid assemblies generated by taking advantage of the self-assembly process of crystalline-corona di-BCP micelles with colloidal particles. Each section introduces and emphasizes the potential applications of this class of nanomaterials. (C) 2015 Elsevier Ltd. All rights reserved
Nonlinear features of surface-enhanced Raman scattering revealed under non-resonant and resonant optical excitation
International audienceBy performing comparative Raman studies on nanometric thin films (9.5, 39, 88 and 185 nm) of copper phthalocyanine (CuPc) deposited on glass, Au and Ag supports, we demonstrate that the mechanism of the surface-enhanced Raman scattering (SERS) generated on Au and Ag substrates differs in the Stokes and anti-Stokes Raman branches depending on whether non-resonant (515.5 nm) or resonant (647.1 nm) optical excitation is applied. The evaluation of the SERS effect via the I-aS/I-S ratio reveals that this ratio is smaller or larger than that predicted by the Boltzmann law for non-resonant or resonant optical excitation, respectively. In the former case, the enhancement of the Stokes Raman emission is similar to a stimulated Raman process resulting from the plasmon coupling associated with the incident excitation light and spontaneous Stokes Raman emission. For the latter case, the amplification of the anti-Stokes Raman emission results from a wave-mixing process reminiscent of a single-beam CARS effect
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