Thermal properties of fluorinated graphene

Large scale atomistic simulations using the reactive force field approach (ReaxFF) are implemented to investigate the thermomechanical properties of fluorinated graphene (FG). A new set of parameters for the reactive force field potential (ReaxFF) optimized to reproduce key quantum mechanical properties of relevant carbon-fluor cluster systems are presented. Molecular dynamics (MD) simulations are used to investigate the thermal rippling behavior of FG and its mechanical properties and compare them with graphene (GE), graphane (GA) and a sheet of BN. The mean square value of the height fluctuations $$ and the height-height correlation function $H(q)$ for different system sizes and temperatures show that FG is an un-rippled system in contrast to the thermal rippling behavior of graphene (GE). The effective Young's modulus of a flake of fluorinated graphene is obtained to be 273 N/m and 250 N/m for a flake of FG under uniaxial strain along arm-chair and zig-zag direction, respectively.Comment: To appear in Phys. Rev.

On the origin of the quantum-critical transition in the bilayer Heisenberg model

The bilayer Heisenberg antiferromagnet is known to exhibit a quantum-critical transition at a particular value of the inter-layer coupling. Using a new type of coherent state, appropriate to the special order parameter structure of the bilayer, we map the problem onto the quantum non-linear sigma model. It is found that the bare coupling constant diverges at the classical transition of Chubukov and Morr, so that in any finite dimension the actual transition occurs inside the ordered phase of the classical theory.Comment: 9 pages Revtex, no figures, submitted to Phys. Rev. Let

Pop-off mechanisms in fetal megacystis: extravasation, umbilical cord cyst, ureterocele and mega-ureter

UCC was associated with early-onset megacystis, normal AFI, other congenital anomalies and the highest prevalences of IUFD, while the occurrence of urinary extravasation was associated with an antenatal clinical picture characterised by severe megacystis, abnormal AFI and other congenital anomalies and associated with high rates of pregnancy termination and neonatal death. A mega-ureter/ureterocele mainly occurred in late-onset and isolated megacystis showing a thickened bladder wall, low prevalences of other congenital anomalies and highest survival rates

Molecular Dynamics Simulations of the Interactions between Platinum Clusters and Carbon Platelets

Molecular dynamics simulations have been performed with two reactive force fields to investigate the structure of a Pt_(100) cluster adsorbed on the three distinct sides of a carbon platelet. A revised Reax force field for the carbon−platinum system is presented. In the simulations, carbon platelet edges both with and without hydrogen termination have been studied. It is found that the initial mismatch between the atomic structure of the platelet egde and the adsorbed face of the Pt_(100) cluster leads to a desorption of a few platinum atoms from the cluster and the subsequent restructuring of the cluster. Consequently, the average Pt−Pt bond length is enlarged in agreement with experimental results. This change in the bond length is supposed to play an important role in the enhancement of the catalytic activity, which is demonstrated by studying the changes in the bond order of the platinum atoms. We found an overall shift to lower values as well as a loss of the well-defined peak structure in the bond-order distribution

Melting of Partially Fluorinated Graphene: From Detachment of Fluorine Atoms to Large Defects and Random Coils

The melting of fluorographene is very unusual and depends strongly on the degree of fluorination. For temperatures below 1000 K, fully fluorinated graphene (FFG) is thermo-mechanically more stable than graphene but at T$_m\approx$2800 K FFG transits to random coils which is almost twice lower than the melting temperature of graphene, i.e. 5300 K. For fluorinated graphene (PFG) up to 30 % ripples causes detachment of individual F-atoms around 2000 K while for 40-60 % fluorination, large defects are formed beyond 1500 K and beyond 60% of fluorination F-atoms remain bonded to graphene until melting. The results agree with recent experiments on the dependence of the reversibility of the fluorination process on the percentage of fluorination.Comment: 16 pages, 6 figure

Junior doctors' experiences with interprofessional collaboration:Wandering the landscape

Context The transition from medical student to junior doctor is challenging. Junior doctors need to become part of the physician community of practice (CoP), while dealing with new responsibilities, tasks and expectations. At the same time, they need to learn how to navigate the frontiers and intersections with the other communities of practice that form the Landscape of Practice (LoP). This study aims to understand how junior doctors experience interprofessional collaboration (IPC) and what elements shape these experiences considering their transition to clinical practice. Methods In this multicentre qualitative study, 13 junior doctors individually drew two rich pictures of IPC experiences, one positive and one negative. A rich picture is a visual representation, a drawing of a particular situation intended to capture the complex and non-verbal elements of an experience. We used semi-structured interviews to deepen the understanding of junior doctors' depicted IPC experiences. We analysed both visual materials and interview transcripts iteratively, for which we adopted an inductive constructivist thematic analysis. Results While transitioning into a doctor, junior doctors become foremost members of the physician CoP and shape their professional identity based on perceived values in their physician community. Interprofessional learning occurs implicitly, without input from the interprofessional team. As a result, junior doctors struggle to bridge the gap between themselves and the interprofessional team, preventing IPC learning from developing into an integrative process. This professional isolation leaves junior doctors wandering the landscape of practice without understanding roles, attitudes and expectations of others. Conclusions Learning IPC needs to become a collective endeavour and an explicit learning goal, based on multisource feedback to take advantage of the expertise already present in the LoP. Furthermore, junior doctors need a safe environment to embrace and reflect on the emotions aroused by interprofessional interactions, under the guidance of experienced facilitators

Superconductivity and Quantum Spin Disorder in Cuprates

A fundamental connection between superconductivity and quantum spin fluctuations in underdoped cuprates, is revealed. A variational calculation shows that {\em Cooper pair hopping} strongly reduces the local magnetization $m_0$. This effect pertains to recent neutron scattering and muon spin rotation measurements in which $m_0$ varies weakly with hole doping in the poorly conducting regime, but drops precipitously above the onset of superconductivity

Suppression of Antiferromagnetic Order by Light Hole Doping in La_2Cu_{1-x}Li_xO_4: A ^{139}La NQR Study

^{139}La nuclear quadrupole resonance measurements in lightly doped La_2Cu_{1-x}Li_xO_4 have been performed to reveal the dependence of the magnetic properties of the antiferromagnetic CuO_2 planes on the character of the doped holes and their interactions with the dopant. A detailed study shows that the magnetic properties are remarkably insensitive to the character of the dopant impurity. This indicates that the added holes form previously unrecognized collective structures.Comment: 4 pages, 3 figures. Slightly modified version, as accepted for publication in Physical Review Letter