Magnetic systems at criticality: different signatures of scaling

Different aspects of critical behaviour of magnetic materials are presented and discussed. The scaling ideas are shown to arise in the context of purely magnetic properties as well as in that of thermal properties as demonstrated by magnetocaloric effect or combined scaling of excess entropy and order parameter. Two non-standard approaches to scaling phenomena are described. The presented concepts are exemplified by experimental data gathered on four representatives of molecular magnets.Comment: 33 pages, 16 figure

Quantum phase transitions in alternating spin-(1/2, 5/2) Heisenberg chains

The ground state spin-wave excitations and thermodynamic properties of two types of ferrimagnetic chains are investigated: the alternating spin-1/2 spin-5/2 chain and a similar chain with a spin-1/2 pendant attached to the spin-5/2 site. Results for magnetic susceptibility, magnetization and specific heat are obtained through the finite-temperature Lanczos method with the aim in describing available experimental data, as well as comparison with theoretical results from the semiclassical approximation and the low-temperature susceptibility expansion derived from Takahashi's modified spin-wave theory. In particular, we study in detail the temperature vs. magnetic field phase diagram of the spin-1/2 spin-5/2 chain, in which several low-temperature quantum phases are identified: the Luttinger Liquid phase, the ferrimagnetic plateau and the fully polarized one, and the respective quantum critical points and crossover lines

Observation of inhibited electron-ion coupling in strongly heated graphite

Creating non-equilibrium states of matter with highly unequal electron and lattice temperatures (Tele≠Tion) allows unsurpassed insight into the dynamic coupling between electrons and ions through time-resolved energy relaxation measurements. Recent studies on low-temperature laser-heated graphite suggest a complex energy exchange when compared to other materials. To avoid problems related to surface preparation, crystal quality and poor understanding of the energy deposition and transport mechanisms, we apply a different energy deposition mechanism, via laser-accelerated protons, to isochorically and non-radiatively heat macroscopic graphite samples up to temperatures close to the melting threshold. Using time-resolved x ray diffraction, we show clear evidence of a very small electron-ion energy transfer, yielding approximately three times longer relaxation times than previously reported. This is indicative of the existence of an energy transfer bottleneck in non-equilibrium warm dense matter

TIME EVOLUTION of KELVIN-HELMHOLTZ VORTICES ASSOCIATED with COLLISIONLESS SHOCKS in LASER-PRODUCED PLASMAS

We report experimental results on Kelvin-Helmholtz (KH) instability and resultant vortices in laser-produced plasmas. By irradiating a double plane target with a laser beam, asymmetric counterstreaming plasmas are created. The interaction of the plasmas with different velocities and densities results in the formation of asymmetric shocks, where the shear flow exists along the contact surface and the KH instability is excited. We observe the spatial and temporal evolution of plasmas and shocks with time-resolved diagnostics over several shots. Our results clearly show the evolution of transverse fluctuations, wavelike structures, and circular features, which are interpreted as the KH instability and resultant vortices. The relevant numerical simulations demonstrate the time evolution of KH vortices and show qualitative agreement with experimental results. Shocks, and thus the contact surfaces, are ubiquitous in the universe; our experimental results show general consequences where two plasmas interact

Urinary 1-Hydroxypyrene as a Biomarker of PAH Exposure in 3-Year-Old Ukrainian Children

Urinary 1-hydroxypyrene (1-OHP) is a biomarker of polycyclic aromatic hydrocarbon (PAH) exposure. We measured urinary 1-OHP in 48 children 3 years of age in Mariupol, Ukraine, who lived near a steel mill and coking facility and compared these with 1-OHP concentrations measured in 42 children of the same age living in the capital city of Kiev, Ukraine. Children living in Mariupol had significantly higher urinary 1-OHP and creatinine-adjusted urinary 1-OHP than did children living in Kiev (adjusted: 0.69 vs. 0.34 μmol/mol creatinine, p < 0.001; unadjusted: 0.42 vs. 0.30 ng/mL, p = 0.002). Combined, children in both cities exposed to environmental tobacco smoke in their homes had higher 1-OHP than did children not exposed (0.61 vs. 0.42 μmol/mol creatinine; p = 0.04; p = 0.07 after adjusting for city). In addition, no significant differences were seen with sex of the children. Our sample of children in Mariupol has the highest reported mean urinary 1-OHP concentrations in children studied to date, most likely due to their proximity to a large industrial point source of PAHs

Transcriptional control by adenovirus E1A conserved region 3 via p300/CBP

The human adenovirus type 5 (HAdV-5) E1A 13S oncoprotein is a potent regulator of gene expression and is used extensively as a model for transcriptional activation. It possesses two independent transcriptional activation domains located in the N-terminus/conserved region (CR) 1 and CR3. The protein acetyltransferase p300 was previously identified by its association with the N-terminus/CR1 portion of E1A and this association is required for oncogenic transformation by E1A. We report here that transcriptional activation by 13S E1A is inhibited by co-expression of sub-stoichiometric amounts of the smaller 12S E1A isoform, which lacks CR3. Transcriptional inhibition by E1A 12S maps to the N-terminus and correlates with the ability to bind p300/CBP, suggesting that E1A 12S is sequestering this limiting factor from 13S E1A. This is supported by the observation that the repressive effect of E1A 12S is reversed by expression of exogenous p300 or CBP, but not by a CBP mutant lacking actyltransferase activity. Furthermore, we show that transcriptional activation by 13S E1A is greatly reduced by siRNA knockdown of p300 and that CR3 binds p300 independently of the well-characterized N-terminal/CR1-binding site. Importantly, CR3 is also required to recruit p300 to the adenovirus E4 promoter during infection. These results identify a new functionally significant interaction between E1A CR3 and the p300/CBP acetyltransferases, expanding our understanding of the mechanism by which this potent transcriptional activator functions

Nanometer-scale characterization of laser-driven compression, shocks, and phase transitions, by x-ray scattering using free electron lasers

We study the feasibility of using small angle X-ray scattering (SAXS) as a new experimental diagnostic for intense laser-solid interactions. By using X-ray pulses from a hard X-ray free electron laser, we can simultaneously achieve nanometer and femtosecond resolution of laser-driven samples. This is an important new capability for the Helmholtz international beamline for extreme fields at the high energy density endstation currently built at the European X-ray free electron laser. We review the relevant SAXS theory and its application to transient processes in solid density plasmas and report on first experimental results that confirm the feasibility of the method. We present results of two test experiments where the first experiment employs ultra-short laser pulses for studying relativistic laser plasma interactions, and the second one focuses on shock compression studies with a nanosecond laser system

Thomson scattering measurement of a collimated plasma jet generated by a high-power laser system

One of the important and interesting problems in astrophysics and plasma physics is collimation of plasma jets. The collimation mechanism, which causes a plasma flow to propagate a long distance, has not been understood in detail. We have been investigating a model experiment to simulate astrophysical plasma jets with an external magnetic field [Nishio et al., EPJ. Web of Conferences 59, 15005 (2013)]. The experiment was performed by using Gekko XII HIPER laser system at Institute of Laser Engineering, Osaka University. We shot CH plane targets (3 mm × 3 mm × 10 μm) and observed rear-side plasma flows. A collimated plasma flow or plasma jet was generated by separating focal spots of laser beams. In this report, we measured plasma jet structure without an external magnetic field with shadowgraphy, and simultaneously measured the local parameters of the plasma jet, i.e., electron density, electron and ion temperatures, charge state, and drift velocity, with collective Thomson scattering