754 research outputs found
Non-collinear long-range magnetic ordering in HgCr2S4
The low-temperature magnetic structure of \HG has been studied by
high-resolution powder neutron diffraction. Long-range incommensurate magnetic
order sets in at T22K with propagation vector
\textbf{k}=(0,0,0.18). On cooling below T, the propagation vector
increases and saturates at the commensurate value \textbf{k}=(0,0,0.25). The
magnetic structure below T consists of ferromagnetic layers in the
\textit{ab}-plane stacked in a spiral arrangement along the \textit{c}-axis.
Symmetry analysis using corepresentations theory reveals a point group symmetry
in the ordered magnetic phase of 422 (D), which is incompatible with
macroscopic ferroelectricity. This finding indicates that the spontaneous
electric polarization observed experimentally cannot be coupled to the magnetic
order parameter
Hydrogeological controls on microbial activity and habitability in the Precambrian continental crust
The potential of magnetic hyperthermia for triggering the differentiation of cancer cells
Magnetic hyperthermia is a potential technique for cancer therapy that exploits heat generated by magnetic nanoparticles to kill cancerous cells. Many studies have shown that magnetic hyperthermia is effective at killing cancer cells both in vitro and in vivo, however little attention has been paid to the cellular functioning of the surviving cells. We report here new evidence demonstrating the onset of thermally triggered differentiation in osteosarcoma cancer cells that survive magnetic hyperthermia treatment. This raises the possibility that in addition to causing cell death, magnetic hyperthermia could induce surviving cancer cells to form more mature cell types and thereby inhibit their capacity to self-renew. Such processes could prove to be as important as cell death when considering magnetic hyperthermia for treating cancer
Excitations of quantum Ising chain CoNb2O6 in low transverse field: quantitative description of bound states stabilized by off-diagonal exchange and applied field
We present experimental and theoretical evidence of novel bound state
formation in the low transverse field ordered phase of the
quasi-one-dimensional Ising-like material CoNbO. High resolution single
crystal inelastic neutron scattering measurements observe that small transverse
fields lead to a breakup of the spectrum into three parts, each evolving very
differently upon increasing field. We show that this can be naturally
understood starting from the excitations of the ordered phase of the transverse
field Ising model, domain wall quasiparticles (solitons). The transverse field
and a staggered off-diagonal exchange create one-soliton hopping terms with
opposite signs. This leads to a rich spectrum and a special field, when the
strengths of the off-diagonal exchange and transverse field match, at which
solitons become localized; the highest field investigated is very close to this
special regime. We solve this case analytically and find three two-soliton
continua, along with three novel bound states. We also present calculations
using exact diagonalization of a recently refined Hamiltonian model for
CoNbO and using diagonalization of the two-soliton subspace, both of
which provide a quantitative agreement with the observed spectrum. The
theoretical two-soliton model qualitatively and quantitatively captures a
variety of non-trivial features in the observed spectrum, providing insight
into the underlying physics of bound state formation.Comment: 17 pages, 5 figure
Inelastic neutron scattering studies of the quantum frustrated magnet clinoatacamite, -Cu2(OD)3Cl, a proposed valence bond solid (VBS)
The frustrated magnet clinoatacamite, -Cu(OH)Cl, is
attracting a lot of interest after suggestions that at low temperature it forms
an exotic quantum state termed a Valence Bond Solid (VBS) made from dimerised
Cu () spins.\cite{Lee_clinoatacamite} Key to the arguments
surrounding this proposal were suggestions that the kagom\'e planes in the
magnetic pyrochlore lattice of clinoatacamite are only weakly coupled, causing
the system to behave as a quasi-2-dimensional magnet. This was reasoned from
the near 95 angles made at the bridging oxygens that mediate exchange
between the Cu ions that link the kagom\'e planes.
Recent work pointed out that this exchange model is inappropriate for
-Cu(OH)Cl, where the oxygen is present as a
-OH.\cite{Wills_JPC} Further, it used symmetry calculations and neutron
powder diffraction to show that the low temperature magnetic structure (
K) was canted and involved significant spin ordering on all the Cu
spins, which is incompatible with the interpretation of simultaneous VBS and
N\'eel ordering. Correspondingly, clinoatacamite is best considered a distorted
pyrochlore magnet. In this report we show detailed inelastic neutron scattering
spectra and revisit the responses of this frustrated quantum magnet.Comment: Proceedings of The International Conference on Highly Frustrated
Magnetism 2008 (HFM2008
Thin slice sampling of video footage for mother/child interaction: application to single cases
The purpose was to test the reliability of short samples of parent/child interaction for use in single-subject research. Four variable pairs of mother/child behaviour were coded for seven mother/child play sessions. Each session lasted 20 min and 18 min of the session was behaviourally coded using frame-by-frame analysis. The co-occurrence of the mother/child behaviours within a given time window was computed and an odds ratio was calculated for the co-occurrence of the targeted behaviours. The play session was divided into shorter segments (3, 6 and 9 min) and odds ratios of the variable pairs from the shorter segments were compared to the odds ratios from the entire session. Segments of 3 and 6 min did not yield the same pattern of results as the entire session. In single-subject research, evidence of the reliability of the time segment for behavioural coding should be reported in the methods section of original research manuscripts
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