77 research outputs found
Effects of thermal- and spin- fluctuations on the band structure of purple bronze LiMoO
The band structures of ordered and thermally disordered
LiMoO are calculated by use of ab-initio DFT-LMTO method. The
unusual, very 1-dimensional band dispersion obtained in previous band
calculations is confirmed for the ordered structure, and the overall band
structure agrees reasonably with existing photoemission data. Dispersion and
bandstructure perpendicular to the main dispersive direction is obtained. A
temperature dependent band broadening is calculated from configurations with
thermal disorder of the atomic positions within the unit cell. This leads a
band broadening of the two bands at the Fermi energy which can become
comparable to their energy separation. The bands are particularly sensitive to
in-plane movements of Mo sites far from the Li-sites, where the
density-of-states is highest. The latter fact makes the effect of Li vacancies
on the two bands relatively small. Spin-polarized band results for the ordered
structure show a surprisingly large exchange enhancement on the high DOS Mo
sites. Consequences for spin fluctuations associated with a cell doubling along
the conducting direction are discussed
Accelerator system for the PRISM based muon to electron conversion experiment
The next generation of lepton flavor violation experiments need high
intensity and high quality muon beams. Production of such beams requires
sending a short, high intensity proton pulse to the pion production target,
capturing pions and collecting the resulting muons in the large acceptance
transport system. The substantial increase of beam quality can be obtained by
applying the RF phase rotation on the muon beam in the dedicated FFAG ring,
which was proposed for the PRISM project.This allows to reduce the momentum
spread of the beam and to purify from the unwanted components like pions or
secondary protons. A PRISM Task Force is addressing the accelerator and
detector issues that need to be solved in order to realize the PRISM
experiment. The parameters of the required proton beam, the principles of the
PRISM experiment and the baseline FFAG design are introduced. The spectrum of
alternative designs for the PRISM FFAG ring are shown. Progress on ring main
systems like injection and RF are presented. The current status of the study
and its future directions are discussed.Comment: Studies performed within the PRISM Task Force initiativ
Orbital current patterns in doped two-leg Cu-O Hubbard ladders
In the weak coupling limit, we investigate two-leg ladders with a unit cell
containing both Cu and O atoms, as a function of doping. For purely repulsive
interactions, using bosonization, we find significant differences with the
single orbital case: a completely massless quantum critical regime is obtained
for a finite range of carrier concentration. In a broad region of the phase
diagram the ground state consists of a pattern of orbital currents plus a
density wave. NMR properties of the Cu and O nuclei are presented for the
various phases
Metal Hydrides Form Halogen Bonds: Measurement of Energetics of Binding
The formation of halogen bonds from iodopentafluorobenzene and 1-iodoperfluorohexane to a series of bis(η5-cyclopentadienyl)metal hydrides (Cp2TaH3, 1; Cp2MH2, M = Mo, 2, M = W, 3; Cp2ReH, 4; Cp2Ta(H)CO, 5; Cp = η5-cyclopentadienyl) is demonstrated by 1H NMR spectroscopy. Interaction enthalpies and entropies for complex 1 with C6F5I and C6F13I are reported (ÎH° = â10.9 ± 0.4 and â11.8 ± 0.3 kJ/mol; ÎS° = â38 ± 2 and â34 ± 2 J/(mol·K), respectively) and found to be stronger than those for 1 with the hydrogen-bond donor indole (ÎH° = â7.3 ± 0.1 kJ/mol, ÎS° = â24 ± 1 J/(mol·K)). For the more reactive complexes 2â5, measurements are limited to determination of their low-temperature (212 K) association constants with C6F5I as 2.9 ± 0.2, 2.5 ± 0.1, <1.5, and 12.5 ± 0.3 Mâ1, respectively
Stress-induced lipocalin-2 controls dendritic spine formation and neuronal activity in the amygdala.
This is a freely-available open access publication. Please cite the published version which is available via the DOI link in this record.Behavioural adaptation to psychological stress is dependent on neuronal plasticity and dysfunction at this cellular level may underlie the pathogenesis of affective disorders such as depression and post-traumatic stress disorder. Taking advantage of genome-wide microarray assay, we performed detailed studies of stress-affected transcripts in the amygdala - an area which forms part of the innate fear circuit in mammals. Having previously demonstrated the role of lipocalin-2 (Lcn-2) in promoting stress-induced changes in dendritic spine morphology/function and neuronal excitability in the mouse hippocampus, we show here that the Lcn-2 gene is one of the most highly upregulated transcripts detected by microarray analysis in the amygdala after acute restraint-induced psychological stress. This is associated with increased Lcn-2 protein synthesis, which is found on immunohistochemistry to be predominantly localised to neurons. Stress-naĂŻve Lcn-2(-/-) mice show a higher spine density in the basolateral amygdala and a 2-fold higher rate of neuronal firing rate compared to wild-type mice. Unlike their wild-type counterparts, Lcn-2(-/-) mice did not show an increase in dendritic spine density in response to stress but did show a distinct pattern of spine morphology. Thus, amygdala-specific neuronal responses to Lcn-2 may represent a mechanism for behavioural adaptation to psychological stress.Marie Curie Excellence Grant from the European Commission.Medical Research Council Project GrantCOST Action ECMNe
Effects of Charge and Substituent on the SâââN Chalcogen Bond
Neutral complexes containing a S···N chalcogen bond are compared with similar systems in which a positive charge has been added to the S-containing electron acceptor, using high-level ab initio calculations. The effects on both XS···N and XS+···N bonds are evaluated for a range of different substituents X = CH3, CF3, NH2, NO2, OH, Cl, and F, using NH3 as the common electron donor. The binding energy of XMeS···NH3 varies between 2.3 and 4.3 kcal/mol, with the strongest interaction occurring for X = F. The binding is strengthened by a factor of 2â10 in charged XH2S+···NH3 complexes, reaching a maximum of 37 kcal/mol for X = F. The binding is weakened to some degree when the H atoms are replaced by methyl groups in XMe2S+···NH3. The source of the interaction in the charged systems, like their neutral counterparts, is derived from a charge transfer from the N lone pair into the Ï*(SX) antibonding orbital, supplemented by a strong electrostatic and smaller dispersion component. The binding is also derived from small contributions from a CH···N H-bond involving the methyl groups, which is most notable in the weaker complexes
Open Bis(triazolium) Structural Motifs as a Benchmark To Study Combined Hydrogen- and Halogen-Bonding Interactions in Oxoanion Recognition Processes
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