Biasing a ferronematic-a new way to detect weak magnetic field

The magnetic properties of a ferronematic, i.e., a nematic liquid crystal doped with magnetic nanoparticles in low volume concentration are studied, with the focus on the ac magnetic susceptibility. A weak dc bias magnetic field (a few Oe) applied to the ferronematic in its isotropic phase increases the ac magnetic susceptibility considerably. Passage of the isotropic-to-nematic phase transition resets this enhancement irreversibly (unless the dc bias field is applied again in the isotropic phase). © 2016 The Royal Society of Chemistry

Influence of the anisometry of magnetic particles on the isotropic–nematic phase transition

The influence of the shape anisotropy of magnetic particles on the isotropic-nematic phase transition was studied in ferronematics based on the nematic liquid crystal 4-(trans-4-n-hexylcyclohexyl)-isothiocyanato-benzene (6CHBT). The liquid crystal was doped with spherical or rod-like magnetic particles of different size and volume concentrations. The phase transition from isotropic to nematic phase was observed by polarizing microscope as well as by capacitance measurements. The influence of the concentration and the shape anisotropy of the magnetic particles on the isotropic-nematic phase transition in liquid crystal is demonstrated. The results are in a good agreement with recent theoretical predictions.Comment: 13 pages, 5 figures, to appear in Liq. Crys

The Influence of Magnetic Particles on the Nematic Droplets Formation in Liquid Crystal

In this work the thermotropic nematic liquid crystal 4-trans-4'-n-hexyl-cyclohexyl-isothiocyanato-benzene (6CHBT) was dissolved in phenyl-isothiocyanate and doped with spherical magnetic particles with volume concentration ϕ₁=10¯⁴ and ϕ₂=10¯³. The influence of the volume concentration on the phase transitions from isotropic to nematic phase was studied by three experimental methods: optical microscopy, differential scanning calorimetry, and dielectric measurements. The obtained results confirmed the coexistence of isotropic and nematic phase, i.e. nematic or ferronematic droplets in isotropic phase in a wide temperature range between nematic and isotropic phase

Kinetics of Nematic to Isotropic Phase Transition in Liquid Crystal Doped with Magnetic Nanoparticles

A binary mixture of bent-core and rod-shaped liquid crystals was chosen as a model substance combining the properties of both types of liquid crystals. The mixture was doped with a small amount of spherical and rod-like magnetic nanoparticles. Differential scanning calorimetry experiments were performed for the pure as well as for the doped mixture at different heating rates ranging from 1 to 16°C/min. The addition of the magnetic nanoparticles lowered the phase transition temperature. This effect is more intensive in the case of the rod-like magnetic nanoparticles. The kinetics of the nematic to isotropic phase transition was evaluated in the framework of the differential isoconversional method. The calculated apparent activation energy showed non-monotonic behaviour and a sensitivity on the shape of added magnetic nanoparticles

Low Magnetic Field Response in Ferronematics

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How to Enhance Sensitivity of Liquid Crystals to External Magnetic Field?

Liquid crystals, due to their large dielectric anisotropy, respond very sensitively to application of an external electric field, whereas they are only weakly sensitive to the magnetic field. A possible way of improving that sensitivity is doping liquid crystals with magnetic nanoparticles. As a result, stable colloidal suspensions of liquid crystals with relatively low concentrations of magnetic nanoparticles (called ferronematics, ferrocholesterics, ferrosmectics, etc.) can be produced. We illustrate some examples of the influence of the magnetic field, as well as of a superposition of magnetic and electric fields on the structural transitions (e.g. on the Fréedericksz transition) in ferronematics based on the calamitic liquid crystal 4-(trans-4'-n-hexylcyclohexyl)-isothiocyanatobenzene (6CHBT). It is shown that the samples respond to the applied magnetic field of low strength. The effects of the magnetic particles and magnetic field on the nematic to isotropic phase transition temperature are discussed as well

Interaction of Magnetic Nanoparticles with Lyotropic Liquid Crystal Studied by AFM

In this work the interaction of lysozyme fibrils with magnetic particles has been studied by atomic force microscopy. The experiments were carried out for a better understanding of the binding process of such complex soft matter systems. The obtained results show that interaction between lysozyme fibrils and magnetic particles starts immediately after mixing them together. Moreover, the samples remain stable in duration of several days after preparation

Safety and outcomes of intravenous thrombolysis in posterior versus anterior circulation stroke

Background and Purpose— Posterior circulation stroke (PCS) accounts for 5% to 19% of patients with acute stroke receiving intravenous thrombolysis. We aimed to compare safety and outcomes following intravenous thrombolysis between patients with PCS and anterior circulation stroke (ACS) and incorporate the results in a meta-analysis. Methods— We included patients in the Safe Implementation of Treatments in Stroke Thrombolysis Registry 2013 to 2017 with computed tomography/magnetic resonance angiographic occlusion data. Outcomes were parenchymal hematoma, symptomatic intracerebral hemorrhage (SICH) per SITS-MOST (Safe Implementation of Thrombolysis in Stroke Monitoring Study), ECASS II (Second European Co-operative Stroke Study) and NINDS (Neurological Disorders and Stroke definition), 3-month modified Rankin Scale score, and death. Adjustment for SICH risk factors (age, sex, National Institutes of Health Stroke Scale, blood pressure, glucose, and atrial fibrillation) and center was done using inverse probability treatment weighting, after which an average treatment effect (ATE) was calculated. Meta-analysis of 13 studies comparing outcomes in PCS versus ACS after intravenous thrombolysis was conducted. Results— Of 5146 patients, 753 had PCS (14.6%). Patients with PCS had lower median National Institutes of Health Stroke Scale: 7 (interquartile range, 4–13) versus 13 (7–18), P<0.001 and fewer cerebrovascular risk factors. In patients with PCS versus ACS, parenchymal hematoma occurred in 3.2% versus 7.9%, ATE (95% CI): −4.7% (−6.3% to 3.0%); SICH SITS-MOST in 0.6% versus 1.9%, ATE: −1.4% (−2.2% to −0.7%); SICH NINDS in 3.1% versus 7.8%, ATE: −3.0% (−6.3% to 0.3%); SICH ECASS II in 1.8% versus 5.4%, ATE: −2.3% (−5.3% to 0.7%). In PCS versus ACS, 3-month outcomes (70% data availability) were death 18.5% versus 20.5%, ATE: 6.0% (0.7%–11.4%); modified Rankin Scale score 0–1, 45.2% versus 37.5%, ATE: 1.7% (−6.6% to 3.2%); modified Rankin Scale score 0–2, 61.3% versus 49.4%, ATE: 2.4% (3.1%–7.9%). Meta-analysis showed relative risk for SICH in PCS versus ACS being 0.49 (95% CI, 0.32–0.75). Conclusions— The risk of bleeding complications after intravenous thrombolysis in PCS was half that of ACS, with similar functional outcomes and higher risk of death, acknowledging limitations of the National Institutes of Health Stroke Scale for stroke severity or infarct size adjustment

Recessive null-allele variants in MAG associated with spastic ataxia, nystagmus, neuropathy, and dystonia.

Introduction:The gene encoding myelin-associated glycoprotein (MAG) has been implicated in autosomal-recessive spastic paraplegia type 75. To date, only four families with biallelic missense variants in MAG have been reported. The genotypic and phenotypic spectrum of MAG-associated disease awaits further elucidation.Methods: Four unrelated patients with complex neurologic conditions underwent whole-exome sequencing within research or diagnostic settings. Following determination of the underlying genetic defects, in-depth phenotyping and literature review were performed.Results: In all case subjects, we detected ultra-rare homozygous or compound heterozygous variants in MAG. The observed nonsense (c.693C > A [p.Tyr231*], c.980G > A [p.Trp327*], c.1126C > T [p.Gln376*], and 1522C > T [p.Arg508*]) and frameshift (c.517_521dupAGCTG [p.Trp174*]) alleles were predicted to result in premature termination of protein translation. Affected patients presented with variable combinations of psychomotor delay, ataxia, eye movement abnormalities, spasticity, dystonia, and neuropathic symptoms. Cerebellar signs, nystagmus, and pyramidal tract dysfunction emerged as unifying features in the majority of MAG-mutated individuals identified to date.Conclusions: Our study is the first to describe biallelic null variants in MAG, confirming that loss of myelin associated glycoprotein causes severe infancy-onset disease with central and peripheral nervous system involvement