379 research outputs found
Ni3TeO6 - a collinear antiferromagnet with ferromagnetic honeycomb planes
We report a comprehensive study of magnetic properties of Ni3TeO6. The system
crystallizes in a noncentrosymmetric rhombohedral lattice, space group R3.
There are three differently coordinated Ni atoms in the unit cell. Two of them
form an almost planar honeycomb lattice, while the third one is placed between
the layers. Magnetization and specific heat measurements revealed a single
magnetic ordering at TN = 52 K. Below TN the susceptibility with the magnetic
field parallel to the c-axis drops towards zero while the perpendicular
susceptibility remains constant, a characteristic of antiferromagnetic
materials. Neutron diffraction confirmed that the system is antiferromagnet
below TN with ferromagnetic ab-planes stacked antiferromagnetically along the
c-axis. All Ni moments are in the S = 1 spin state and point along the c-axis.Comment: accepted for publication in Journal of Physics Condensed Matte
The impact of broadband in schools
The report reviews evidence for the impact of broadband in English schools, exploring; Variations in provision in level of broadband connectivity; Links between the level of broadband activity and nationally accessible performance data; Aspects of broadband connectivity and the school environment that contribute to better outcomes for pupils and teachers; Academic and motivational benefits associated with educational uses of this technology
Magnetic and thermal properties of the S = 1/2 zig-zag spin-chain compound In2VO5
Static magnetic susceptibility \chi, ac susceptibility \chi_{ac} and specific
heat C versus temperature T measurements on polycrystalline samples of In2VO5
and \chi and C versus T measurements on the isostructural, nonmagnetic compound
In2TiO5 are reported. A Curie-Wiess fit to the \chi(T) data above 175 K for
In2VO5 indicates ferromagnetic exchange between V^{4+} (S = 1/2) moments. Below
150 K the \chi(T) data deviate from the Curie-Weiss behavior but there is no
signature of any long range magnetic order down to 1.8 K. There is a cusp at
2.8 K in the zero field cooled (ZFC) \chi(T) data measured in a magnetic field
of 100 Oe and the ZFC and field cooled (FC) data show a bifurcation below this
temperature. The frequency dependence of the \chi_{ac}(T) data indicate that
below 3 K the system is in a spin-glass state. The difference \Delta C between
the heat capacity of In2VO5 and In2TiO5 shows a broad anomaly peaked at 130 K.
The entropy upto 300 K is more than what is expected for S = 1/2 moments. The
anomaly in \Delta C and the extra entropy suggests that there may be a
structural change below 130 K in In2VO5.Comment: 6 pages, 7 figures, 1 tabl
Surface plasmon resonance using the catalytic domain of soluble guanylate cyclase allows the detection of enzyme activators.
Soluble Guanylate Cyclase (sGC) is the receptor for the signalling agent nitric oxide (NO) and catalyses the production of the second messenger cyclic guanosine monophosphate (cGMP) from guanosine triphosphate (GTP). The enzyme is an attractive drug target for small molecules that act in the cardiovascular and pulmonary systems, and has also shown to be a potential target in neurological disorders. We have discovered that 5-(indazol-3-yl)-1,2,4-oxadiazoles activate the enzyme in the absence of added NO and shown they bind to the catalytic domain of the enzyme after development of a surface plasmon resonance assay that allows the biophysical detection of intrinsic binding of ligands to the full length sGC and to a construct of the catalytic domain
A new small molecule inhibitor of soluble guanylate cyclase
Soluble guanylate cyclase (sGC) is a haem containing enzyme that regulates cardiovascular homeostasis and multiple mechanisms in the central and peripheral nervous system. Commonly used inhibitors of sGC activity act through oxidation of the haem moiety, however they also bind haemoglobin and this limits their bioavailability for in vivo studies. We have discovered a new class of small molecule inhibitors of sGC and have characterised a compound designated D12 (compound 10) which binds to the catalytic domain of the enzyme with a KD of 11 μM in a SPR assay
Analysis of and workarounds for element reversal for a finite element-based algorithm for warping triangular and tetrahedral meshes
We consider an algorithm called FEMWARP for warping triangular and
tetrahedral finite element meshes that computes the warping using the finite
element method itself. The algorithm takes as input a two- or three-dimensional
domain defined by a boundary mesh (segments in one dimension or triangles in
two dimensions) that has a volume mesh (triangles in two dimensions or
tetrahedra in three dimensions) in its interior. It also takes as input a
prescribed movement of the boundary mesh. It computes as output updated
positions of the vertices of the volume mesh. The first step of the algorithm
is to determine from the initial mesh a set of local weights for each interior
vertex that describes each interior vertex in terms of the positions of its
neighbors. These weights are computed using a finite element stiffness matrix.
After a boundary transformation is applied, a linear system of equations based
upon the weights is solved to determine the final positions of the interior
vertices. The FEMWARP algorithm has been considered in the previous literature
(e.g., in a 2001 paper by Baker). FEMWARP has been succesful in computing
deformed meshes for certain applications. However, sometimes FEMWARP reverses
elements; this is our main concern in this paper. We analyze the causes for
this undesirable behavior and propose several techniques to make the method
more robust against reversals. The most successful of the proposed methods
includes combining FEMWARP with an optimization-based untangler.Comment: Revision of earlier version of paper. Submitted for publication in
BIT Numerical Mathematics on 27 April 2010. Accepted for publication on 7
September 2010. Published online on 9 October 2010. The final publication is
available at http://www.springerlink.co
Helicoidal magnetic order in a clean copper oxide spin chain compound
We report susceptibility, specific heat, and neutron diffraction measurements
on NaCuO, a spin-1/2 chain compound isostructural to LiCuO,
which has been extensively investigated. Below 13 K, we find a long-range
ordered, incommensurate magnetic helix state with a propagation vector similar
to that of LiCuO. In contrast to the Li analogue, substitutional
disorder is negligible in NaCuO. We can thus rule out that the helix is
induced by impurities, as was claimed on the basis of prior work on
LiCuO. A spin Hamiltonian with frustrated longer-range exchange
interactions provides a good description of both the ordered state and the
paramagnetic susceptibility.Comment: 4 pages, 4 figures Improved Fig.1 and 4. Minor rephrasing. Reference
adde
Recommended from our members
Tablet PCs in schools: Case study report: A report for Becta by the Open University
The publication provides an analysis of twelve case studies involving schools in England that were using Tablet PCs. The analysis is complemented by brief individual reports describing aspects of how each of these schools was using Tablet PCs
Emerging small-molecule treatments for multiple sclerosis: focus on B cells
Multiple sclerosis (MS) is a major cause of disability in young adults. Following an unknown trigger (or triggers), the immune system attacks the myelin sheath surrounding axons, leading to progressive nerve cell death. Antibodies and small-molecule drugs directed against B cells have demonstrated good efficacy in slowing progression of the disease. This review focusses on small-molecule drugs that can affect B-cell biology and may have utility in disease management. The risk genes for MS are examined from the drug target perspective. Existing small-molecule therapies for MS with B-cell actions together with new drugs in development are described. The potential for experimental molecules with B-cell effects is also considered. Small molecules can have diverse actions on B cells and be cytotoxic, anti-inflammatory and anti-viral. The current B cell-directed therapies often kill B-cell subsets, which can be effective but lead to side effects and toxicity. A deeper understanding of B-cell biology and the effect on MS disease should lead to new drugs with better selectivity, efficacy, and an improved safety profile. Small-molecule drugs, once the patent term has expired, provide a uniquely sustainable form of healthcare
Hepatitis C virus exploits cyclophilin A to evade PKR
Counteracting innate immunity is essential for successful viral replication. Host cyclophilins (Cyps) have been implicated in viral evasion of host antiviral responses, although the mechanisms are still unclear. Here, we show that hepatitis C virus (HCV) co-opts the host protein CypA to aid evasion of antiviral responses dependent on the effector protein kinase R (PKR). Pharmacological inhibition of CypA rescues PKR from antagonism by HCV NS5A, leading to activation of an interferon regulatory factor-1 (IRF1)-driven cell intrinsic antiviral program that inhibits viral replication. These findings further the understanding of the complexity of Cyp-virus interactions, provide mechanistic insight into the remarkably broad antiviral spectrum of Cyp inhibitors, and uncover novel aspects of PKR activity and regulation. Collectively, our study identifies a novel antiviral mechanism that harnesses cellular antiviral immunity to suppress viral replication
- …