Dimensional reduction by pressure in the magnetic framework material CuF2_{2}(D2_{2}O)2_{2}pyz: from spin-wave to spinon excitations

Metal organic magnets have enormous potential to host a variety of electronic and magnetic phases that originate from a strong interplay between the spin, orbital and lattice degrees of freedom. We control this interplay in the quantum magnet CuF$_2$(D$_2$O)$_2$pyz by using high pressure to drive the system through a structural and magnetic phase transition. Using neutron scattering, we show that the low pressure state, which hosts a two-dimensional square lattice with spin-wave excitations and a dominant exchange coupling of 0.89 meV, transforms at high pressure into a one-dimensional spin-chain hallmarked by a spinon continuum and a reduced exchange interaction of 0.43 meV. This direct microscopic observation of a magnetic dimensional crossover as a function of pressure opens up new possibilities for studying the evolution of fractionalised excitations in low dimensional quantum magnets and eventually pressure-controlled metal--insulator transitions

Magnetoelastic coupling in triangular lattice antiferromagnet CuCrS2

CuCrS2 is a triangular lattice Heisenberg antiferromagnet with a rhombohedral crystal structure. We report on neutron and synchrotron powder diffraction results which reveal a monoclinic lattice distortion at the magnetic transition and verify a magnetoelastic coupling. CuCrS2 is therefore an interesting material to study the influence of magnetism on the relief of geometrical frustration.Comment: 6 pages, 6 figures, 1 tabl

Neutron scattering study of the field-dependent ground state and the spin dynamics in S=1/2 NH4CuCl3

Elastic and inelastic neutron scattering experiments have been performed on the dimer spin system NH4CuCl3, which shows plateaus in the magnetization curve at m=1/4 and m=3/4 of the saturation value. Two structural phase transitions at T1≈156  K and at T2=70  K lead to a doubling of the crystallographic unit cell along the b direction and as a consequence a segregation into different dimer subsystems. Long-range magnetic ordering is reported below TN=1.3  K. The magnetic field dependence of the excitation spectrum identifies successive quantum phase transitions of the dimer subsystems as the driving mechanism for the unconventional magnetization process in agreement with a recent theoretical model

M\"ossbauer, nuclear inelastic scattering and density functional studies on the second metastable state of Na2[Fe(CN)5NO]⋅\cdot2H2O

The structure of the light-induced metastable state SII of Na2[Fe(CN)5NO]$\cdot$2H2O 14 was investigated by transmission M\"ossbauer spectroscopy (TMS) in the temperature range 15 between 85 and 135 K, nuclear inelastic scattering (NIS) at 98 K using synchrotron 16 radiation and density functional theory (DFT) calculations. The DFT and TMS results 17 strongly support the view that the NO group in SII takes a side-on molecular orientation 18 and, further, is dynamically displaced from one eclipsed, via a staggered, to a second 19 eclipsed orientation. The population conditions for generating SII are optimal for 20 measurements by TMS, yet they are modest for accumulating NIS spectra. Optimization 21 of population conditions for NIS measurements is discussed and new NIS experiments on 22 SII are proposed

Understanding why replacing I3–/I– by cobalt(II)/(III) electrolytes in bis(diimine)copper(I)-based dye-sensitized solar cells improves performance

The performances of dye-sensitized solar cells (DSCs) comprising heteroleptic bis(diimine)copper( I ) based dyes combined with either [Co(bpy) 3 ] 2+/3+ , [Co(phen) 3 ] 2+/3+ or I 3 /I redox mediators (bpy 1/4 2,2 0 - bipyridine, phen 1/4 1,10-phenanthroline) have been evaluated. The copper( I ) dyes contain the anchoring ligand ((6,6 0 -dimethyl-[2,2 0 -bipyridine]-4,4 0 -diyl)bis(4,1-phenylene))bis(phosphonic acid), 1, and an ancillary ligand (2, 3 or 4) with a 2,9-dimethyl-1,10-phenanthroline metal-binding domain. Ligands 2 and 3 include imidazole 2 0 -functionalities with 4-(diphenylamino)phenyl (2) or 4-(bis(4-n-butoxy) phenylamino)phenyl (3) domains; in 4, the phen unit is substituted in the 4,7-positions with holetransporting 4-(diphenylamino)phenyl groups. The photoconversion efficiency, h, of each of [Cu(1)(2)] + , [Cu(1)(3)] + and [Cu(1)(4)] + considerably improves by replacing the I 3 /I electrolyte by [Co(bpy) 3 ] 2+/3+ or [Co(phen) 3 ] 2+/3+ , and after a change of electrolyte solvent (MeCN to 3-methoxypropionitrile). Due to the faster charge transfer kinetics and more positive redox potential, the cobalt-based electrolytes are superior to the I 3 /I electrolyte in terms of open-circuit voltage (V OC ), short-circuit current (J SC ) and h; values of V OC 1/4 594 mV, J SC 1/4 9.58 mA cm 2 and h 1/4 3.69% (relative to h 1/4 7.12% for N719) are achieved for the best performing DSC which contains [Cu(1)(4)] + and [Co(bpy) 3 ] 2+/3+ . Corresponding values for [Cu(1)(4)] + and I 3 /I DSCs are 570–580 mV, 5.98–6.37 mA cm 2 and 2.43–2.62%. Electrochemical impedance spectroscopy (EIS) has been used to study DSCs with [Cu(1)(4)] + and the three electrolytes. EIS shows that the DSC with I 3 /I has the highest recombination resistance, whereas the [Co(phen) 3 ] 2+/3+ electrolyte gives the highest chemical capacitance and V OC and, between [Co(bpy) 3 ] 2+/3+ and [Co(phen) 3 ] 2+/3+ , the higher recombination resistance. The [Co(phen) 3 ] 2+/3+ electrolyte exhibits the highest mass transport restrictions which result in a lower J SC and DSC efficiency compared to the [Co(bpy) 3 ] 2+/3+ electrolyte

Behind the stiff upper lip: war narratives of older men with dementia.

The concept of the stiff upper lip stands as a cultural metaphor for the repression and figurative ¿biting back¿ of traumatic experience, particularly in military contexts. For men born in the first half of the 20th century, maintaining a stiff upper lip involved the ability to exert high levels of cognitive control over the subjective, visceral and emotional domains of experience. In the most common forms of dementia, which affect at least one in five men now in their 80s and 90s, this cognitive control is increasingly lost. One result is that, with the onset of dementia, men who have in the intervening years maintained a relative silence about their wartime experiences begin to disclose detailed memories of such events, in some cases for the first time. This article draws on narrative biographical data from three men with late-onset dementia who make extensive reference to their experience of war. The narratives of Sid, Leonard and Nelson are used to explore aspects of collective memory of the two World Wars, and the socially constructed masculinities imposed on men who grew up and came of age during those decades. The findings show that in spite of their difficulties with short term memory, people with dementia can contribute rich data to cultural studies research. Some aspects of the narratives discussed here may also be considered to work along the line of the counter-hegemonic, offering insights into lived experiences of war that have been elided in popular culture in the post-War years

Effect of noise on coupled chaotic systems

Effect of noise in inducing order on various chaotically evolving systems is reviewed, with special emphasis on systems consisting of coupled chaotic elements. In many situations it is observed that the uncoupled elements when driven by identical noise, show synchronization phenomena where chaotic trajectories exponentially converge towards a single noisy trajectory, independent of the initial conditions. In a random neural network, with infinite range coupling, chaos is suppressed due to noise and the system evolves towards a fixed point. Spatiotemporal stochastic resonance phenomenon has been observed in a square array of coupled threshold devices where a temporal characteristic of the system resonates at a given noise strength. In a chaotically evolving coupled map lattice with logistic map as local dynamics and driven by identical noise at each site, we report that the number of structures (a structure is a group of neighbouring lattice sites for whom values of the variable follow certain predefined pattern) follow a power-law decay with the length of the structure. An interesting phenomenon, which we call stochastic coherence, is also reported in which the abundance and lifetimes of these structures show characteristic peaks at some intermediate noise strength.Comment: 21 page LaTeX file for text, 5 Postscript files for figure

Reviews of

Antibiotic Switch therapy is defined by the switch of intravenous antibiotic therapy to oral form. This research aimed to learn about the relationship of switch therapy toward the value of wound healing, lenght of stay and the antibiotic expenditure. The data of this cross sectional study was collected from medical record and by direct investigation to patients for their macroscopis the wound healings value. T-test was used to compared the relationship of the patient wound healings value, lenght of stay and the antibiotic expenditure between the those with and accurate switch therapy and those without it. The result showed that there was no different of wound healing value between those groups of patients (P>0,1). On the other hand, lenght of stay and antibiotic expenditure of the patient with the accurate switch therapy was cuted on the patient with the accurate switch therapy. These indicated that accuracy of switch therapy will proceed a benefit outcome to the patient with appendicitis, especially to there lenght of stay and antibiotic expenditure as well