37 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
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
Good option or only option? Poverty, disability, health and enterprise
Purpose
This paper aims to explore experiences of poverty in the enterprise amongst people with a disability or long-term health challenges. This paper departs somewhat from established wisdom about economic or financial drivers of enterprise by exploring why a disabled individual would start and continue to operate in a business where that business is providing income-poverty. In so doing, it subscribes to the idea that the enterprise involves reflexive engagement of an agent in context where value(s) of the enterprise other than financial may be prioritised.
Design/methodology/approach
The research draws from a larger qualitative study of self-employment and poverty in which half the sample (21 individuals) identified as experiencing disability or poor health. Semi-structured interviews were conducted these participants and a thematic analysis with specific reference to Theory of Venturing, which proposes that the value of enterprise is reflexively and idiosyncratically understood and morphogenetic, was used to explore itinerant issues, experiences and challenges.
Findings
In line with the theory, findings include that disability and poor health are observed to be both prompters and shapers of an enterprise and that the value of enterprise is not always primarily associated with financial wealth for the participants in the sample. Flexibility and autonomy are attractive features of self-employment for some in the face of an inflexible and sometimes hostile labour market.
Originality/value
This paper demonstrates that engaging in enterprise is motivated by an agent's reflexive evaluation of value(s) and how that enables them to navigate their structural condition(s); this contribution enhances theoretical approaches to enterprise and business creation by illuminating some of its diversity. This paper also contributes some much needed data about a group who are under-represented in the enterprise literature despite being over-represented in practice. There are implications and recommendations for policy and practice in the exposure and analysis of the issues emerging
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
Rapid synthesis of colossal magnetoresistance manganites by microwave dielectric heating
Colossal magnetoresistance manganites have been synthesised by the microwave dielectric heating of metal nitrates, which act both as effective microwave susceptors, and a ready source of oxidizing NO2 to induce mixed valency