597 research outputs found
Magnetic Fluctuations, Precursor Phenomena and Phase Transition in MnSi under Magnetic Field
The reference chiral helimagnet MnSi is the first system where skyrmion
lattice correlations have been reported. At zero magnetic field the transition
at to the helimagnetic state is of first order. Above , in a region
dominated by precursor phenomena, neutron scattering shows the build up of
strong chiral fluctuating correlations over the surface of a sphere with radius
, where is the pitch of the helix. It has been suggested that
these fluctuating correlations drive the helical transition to first order
following a scenario proposed by Brazovskii for liquid crystals. We present a
comprehensive neutron scattering study under magnetic fields, which provides
evidence that this is not the case. The sharp first order transition persists
for magnetic fields up to 0.4 T whereas the fluctuating correlations weaken and
start to concentrate along the field direction already above 0.2 T. Our results
thus disconnect the first order nature of the transition from the precursor
fluctuating correlations. They also show no indication for a tricritical point,
where the first order transition crosses over to second order with increasing
magnetic field. In this light, the nature of the first order helical transition
and the precursor phenomena above , both of general relevance to chiral
magnetism, remain an open question
Universality of the helimagnetic transition in cubic chiral magnets: Small angle neutron scattering and neutron spin echo spectroscopy studies of FeCoSi
We present a comprehensive Small Angle Neutron Scattering (SANS) and Neutron
Spin Echo Spectroscopy (NSE) study of the structural and dynamical aspects of
the helimagnetic transition in FeCoSi with = 0.30. In contrast
to the sharp transition observed in the archetype chiral magnet MnSi, the
transition in FeCoSi is gradual and long-range helimagnetic
ordering coexists with short-range correlations over a wide temperature range.
The dynamics are more complex than in MnSi and involve long relaxation times
with a stretched exponential relaxation which persists even under magnetic
field. These results in conjunction with an analysis of the hierarchy of the
relevant length scales show that the helimagnetic transition in
FeCoSi differs substantially from the transition in MnSi and
question the validity of a universal approach to the helimagnetic transition in
chiral magnets
Epithelial specific splicing regulator proteins as emerging oncogenes in aggressive prostate cancer
Skyrmions and spirals in MnSi under hydrostatic pressure
The archetype cubic chiral magnet MnSi is home to some of the most
fascinating states in condensed matter such as skyrmions and a non-Fermi liquid
behavior in conjunction with a topological Hall effect under hydrostatic
pressure. Using small angle neutron scattering, we study the evolution of the
helimagnetic, conical and skyrmionic correlations with increasing hydrostatic
pressure. We show that the helical propagation vector smoothly reorients from
to at intermediate pressures. At
higher pressures, above the critical pressure, the long-range helimagnetic
order disappears at zero magnetic field. Nevertheless, skyrmion lattices and
conical spirals form under magnetic fields, in a part of the phase diagram
where a topological Hall effect and a non-Fermi liquid behavior have been
reported. These unexpected results shed light on the puzzling behavior of MnSi
at high pressures and the mechanisms that destabilize the helimagnetic
long-range order at the critical pressure
Furnace for in situ and simultaneous studies of nano-precipitates and phase transformations in steels by SANS and neutron diffraction
Interphase precipitation occurring during solid-state phase transformations in micro-alloyed steels is generally studied through transmission electron microscopy, atom probe tomography, and ex situ measurements of Small-Angle Neutron Scattering (SANS). The advantage of SANS over the other two characterization techniques is that SANS allows for the quantitative determination of size distribution, volume fraction, and number density of a statistically significant number of precipitates within the resulting matrix at room temperature. However, the performance of ex situ SANS measurements alone does not provide information regarding the probable correlation between interphase precipitation and phase transformations. This limitation makes it necessary to perform in situ and simultaneous studies on precipitation and phase transformations in order to gain an in-depth understanding of the nucleation and growth of precipitates in relation to the evolution of austenite decomposition at high temperatures. A furnace is, thus, designed and developed for such in situ studies in which SANS measurements can be simultaneously performed with neutron diffraction measurements during the application of high-temperature thermal treatments. The furnace is capable of carrying out thermal treatments involving fast heating and cooling as well as high operation temperatures (up to 1200 °C) for a long period of time with accurate temperature control in a protective atmosphere and in a magnetic field of up to 1.5 T. The characteristics of this furnace give the possibility of developing new research studies for better insight of the relationship between phase transformations and precipitation kinetics in steels and also in other types of materials containing nano-scale microstructural features.This work was financially supported equally by the Technology Foundation TTW, as part of the Netherlands Organization for Scientific Research (NWO), and Tata Steel Europe through the Grant No. 14307 under the Project No. S41.5.14548 in the framework of the Materials Innovation Institute (M2i) Partnership Program. The experiments performed at ISIS Neutron and Muon Source were supported by beam-time allocation from the Netherlands Organization for Scientific Research (NWO) through Project No. 721.012.102 (LARMOR) with Experiment No. RB1869024
Consistency-based detection of potential tumor-specific deletions in matched normal/tumor genomes
Wittler R, Chauve C. Consistency-based detection of potential tumor-specific deletions in matched normal/tumor genomes. BMC Bioinformatics. 2011;12(Suppl. 9):S21
Androgen-regulated transcription of ESRP2 drives alternative splicing patterns in prostate cancer
Prostate is the most frequent cancer in men. Prostate cancer progression is driven by androgen steroid hormones, and delayed by androgen deprivation therapy (ADT). Androgens control transcription by stimulating androgen receptor (AR) activity, yet also control pre-mRNA splicing through less clear mechanisms. Here we find androgens regulate splicing through AR-mediated transcriptional control of the epithelial-specific splicing regulator ESRP2. Both ESRP2 and its close paralog ESRP1 are highly expressed in primary prostate cancer. Androgen stimulation induces splicing switches in many endogenous ESRP2-controlled mRNA isoforms, including splicing switches correlating with disease progression. ESRP2 expression in clinical prostate cancer is repressed by ADT, which may thus inadvertently dampen epithelial splice programmes. Supporting this, treatment with the AR antagonist bicalutamide (Casodex) induced mesenchymal splicing patterns of genes including FLNB and CTNND1. Our data reveals a new mechanism of splicing control in prostate cancer with important implications for disease progression.This article is freely available via Open Access. Click on the Publisher URL to access the full-text via the publisher's site
Universality of the helimagnetic transition in cubic chiral magnets: Small angle neutron scattering and neutron spin echo spectroscopy studies of FeCoSi
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