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Peer Reviewed
See detailSpin structure of Nd-Fe-B-based textured nanocomposites:role of interface chemistry
Titov, Ivan UL; Michels, Andreas UL

Scientific Conference (2017, July 02)

Detailed reference viewed: 77 (4 UL)
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See detailSpin texture of generic helical edge states
Rod, Alexia UL; Schmidt, Thomas UL; Rachel, Stephan

in Physical Review. B (2015), 91

We study the spin texture of a generic helical liquid, the edge modes of a two-dimensional topological insulator with broken axial spin symmetry. By considering honeycomb and square-lattice realizations ... [more ▼]

We study the spin texture of a generic helical liquid, the edge modes of a two-dimensional topological insulator with broken axial spin symmetry. By considering honeycomb and square-lattice realizations of topological insulators, we show that in all cases the generic behavior of a momentum-dependent rotation of the spin quantization axis is realized. Here we establish this mechanism also for disk geometries with continuous rotational symmetry. Finally, we demonstrate that the rotation of spin-quantization axis remains intact for arbitrary geometries, i.e., in the absence of any continuous symmetry. We also calculate the dependence of this rotation on the model and material parameters. Finally, we propose a spectroscopy measurement which should directly reveal the rotation of the spin-quantization axis of the helical edge states. [less ▲]

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See detailSpin texture of two-dimensional topological insulators
Rod, Alexia UL

Doctoral thesis (2017)

Since the discovery of two-dimensional topological insulators a decade ago, their one-dimensional edge states have attracted significant attention due to their unique properties. For example due to time ... [more ▼]

Since the discovery of two-dimensional topological insulators a decade ago, their one-dimensional edge states have attracted significant attention due to their unique properties. For example due to time-reversal symmetry, they are protected against elastic backscattering and they propagate such that electrons with opposite spins move in opposite directions. In fact, the only necessary symmetry to sustain the edge states is time-reversal symmetry. Moreover in experimental setups, the axial spin symmetry seems to be absent. This absence allows new processes to appear such as inelastic backscattering. However, these consequences were neglected in most theoretical works where the spins are considered to be polarized in the z direction. The aim of this thesis is to provide a more realistic model taking into account a broken axial spin symmetry. In this scheme, we show that a rotation of the spin quantization axis as a function of momentum always appears. This observation leads us to develop a deeper understanding of the size of the rotation related to the material parameters and material models, using also realistic values. It also leads us to understand the implications in real space in cases where translation invariance is lost and how to quantify the rotation in such systems. The new processes which arise when the axial spin symmetry is broken have important consequences for transport in real materials. To see this, we consider a Hall bar with a hole in its middle, i.e. an antidot. This enables us to create two tunneling regions in order to probe the effect of this generic model. We also consider the effect of Coulomb interactions around the hole, as they can be important in such geometry. We discover that it is possible to probe directly the absence of axial spin symmetry. As experimental evidence is important to investigate our theoretical findings, we propose spectroscopic means to probe the spin texture. Finally, we also consider one of the experimentally-known candidate materials, namely InAs/GaSb heterostructures. From the k.p Hamiltonian, it is possible to show that their bandstructure shows some anisotropies. The latter is also reflected in the spin texture of their edge states. [less ▲]

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See detailSpin textures and response functions of helical electron systems
Schmidt, Thomas UL

Scientific Conference (2016, July)

Detailed reference viewed: 45 (3 UL)
See detailSpin-charge coupling in correlated one-dimensional quantum systems
Schmidt, Thomas UL

Scientific Conference (2015, August)

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See detailSpin-charge separation in one-dimensional fermion systems beyond Luttinger liquid theory
Schmidt, Thomas UL; Imambekov, Adilet; Glazman, Leonid I.

in Physical Review. B (2010), 82

We develop a nonperturbative zero-temperature theory for the dynamic response functions of interacting one-dimensional spin-1/2 fermions. In contrast to the conventional Luttinger liquid theory, we take ... [more ▼]

We develop a nonperturbative zero-temperature theory for the dynamic response functions of interacting one-dimensional spin-1/2 fermions. In contrast to the conventional Luttinger liquid theory, we take into account the nonlinearity of the fermion dispersion exactly. We calculate the power-law singularities of the spectral function and the charge- and spin-density structure factors for arbitrary momenta and interaction strengths. The exponents characterizing the singularities are functions of momenta and differ significantly from the predictions of the linear Luttinger liquid theory. We generalize the notion of the spin-charge separation to the nonlinear spectrum. This generalization leads to phenomenological relations between threshold exponents and the threshold energy. [less ▲]

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See detailSpin-orbit coupling in quasi-one dimensional Wigner crystals
Kornich, Viktoriia UL; Pedder, Christopher UL; Schmidt, Thomas UL

in Physical Review. B, Condensed Matter and Materials Physics (2016)

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See detailSpin-orbit coupling in quasi-one-dimensional Wigner crystals
Kornich, Viktoriia; Pedder, Christopher UL; Schmidt, Thomas UL

in Physical Review. B (2017), 95(4), 045413

We study the effect of Rashba spin-orbit coupling (SOC) on the charge and spin degrees of freedom of a quasi-one-dimensional (quasi-1D) Wigner crystal. As electrons in a quasi-1D Wigner crystal can move ... [more ▼]

We study the effect of Rashba spin-orbit coupling (SOC) on the charge and spin degrees of freedom of a quasi-one-dimensional (quasi-1D) Wigner crystal. As electrons in a quasi-1D Wigner crystal can move in the transverse direction, SOC cannot be gauged away in contrast to the pure 1D case. We show that for weak SOC, a partial gap in the spectrum opens at certain ratios between density of electrons and the inverse Rashba length. We present how the low-energy branch of charge degrees of freedom deviates due to SOC from its usual linear dependence at small wave vectors. In the case of strong SOC, we show that spin sector of a Wigner crystal cannot be described by an isotropic antiferromagnetic Heisenberg Hamiltonian any more, and that instead the ground state of neighboring electrons is mostly a triplet state. We present a new spin sector Hamiltonian and discuss the spectrum of Wigner crystal in this limit. [less ▲]

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See detailSpin-thermoelectric transport induced by interactions and spin-flip processes in two dimensional topological insulators
Ronetti; Vannucci, Luca; Dolcetto, Giacomo UL et al

in Physical Review. B (2016), 93(16), 165414

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See detailSpin-wave dynamics in the helimagnet FeGe studied by small-angle neutron scattering
Siegfried, S.-A.; Sukhanov, A. S.; Altynbaev, E. V. et al

in Physical Review. B (2017), 95(13), 134415

We have studied the spin-wave stiffness of the Dzyaloshinskii-Moriya helimagnet FeGe in a temperature range from 225 K up to TC ≈ 278.7 K by small-angle neutron scattering. The method we have used is ... [more ▼]

We have studied the spin-wave stiffness of the Dzyaloshinskii-Moriya helimagnet FeGe in a temperature range from 225 K up to TC ≈ 278.7 K by small-angle neutron scattering. The method we have used is based on [Grigoriev et al., Phys. Rev. B 92, 220415(R) (2015)] and was extended here for the application in polycrystalline samples. We confirm the validity of the anisotropic spin-wave dispersion for FeGe caused by the Dzyaloshinskii-Moriya interaction. We have shown that the spin-wave stiffness A for the FeGe helimagnet decreases with a temperature as A(T ) = 194[1 − 0.7(T/TC)4.2] meV °A2. The finite value of the spin-wave stiffness A = 58 meV °A2 at TC classifies the order-disorder phase transition in FeGe as being the first-order one. [less ▲]

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See detailSpin-wave stiffness of the Dzyaloshinskii-Moriya helimagnet compounds Fe1−xCoxSi studied by small-angle neutron scattering
Grigoriev; Pschenichnyi; Altynbaev et al

in Physical Review. B, Condensed Matter (2019), 100

The spin wave stiffness was measured by small-angle neutron scattering method in the Dzyaloshinskii-Moriya helimagnet compounds Fe1−xCoxSi with x=0.25,0.30,0.50. It has been shown that the spin wave ... [more ▼]

The spin wave stiffness was measured by small-angle neutron scattering method in the Dzyaloshinskii-Moriya helimagnet compounds Fe1−xCoxSi with x=0.25,0.30,0.50. It has been shown that the spin wave dispersion in the fully polarized state is anisotropic due to Dzyaloshinskii-Moriya interaction. It is reflected in the neutron scattering pattern as two circles for neutrons obtaining and losing the magnon energy, respectively. The centers of the circles are shifted by the momentum transfer oriented along the applied magnetic field H and equal to the wave vector of the spiral ±ks. The radius of the circles is directly related to the stiffness of spin waves and depends on the magnetic field. We have found that the spin-wave stiffness A change weakly with temperature for each individual compound. On the other hand, the spin-wave stiffness A increases linearly with x in contrast to the x dependences of the critical temperature Tc and the low-temperature ordered moment. Experimentally obtained values of the stiffness A approve quantitative applicability of the Bak-Jensen model for the compounds under study. [less ▲]

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See detailSpina bifida
Pit-Ten Cate, Ineke UL; Stevenson, Jim

in Ayers, S.; Baum, A.; McManus, C. (Eds.) et al Cambridge Handbook of Psychology, Health, & Medicine (2007)

Detailed reference viewed: 34 (0 UL)
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See detailSpina Bifida
Pit-Ten Cate, Ineke UL

in Llewellyn, C; Ayers, S; McManus, C (Eds.) et al Cambridge Handbook of Psychology, Health, & Medicine (2019)

Detailed reference viewed: 106 (5 UL)
Peer Reviewed
See detailSpinal cord activity during unilateral inflamation of the ankle in the rat: electrophysiological changes and importance of endogenous kappa opioids
Schaible, Hans-Georg; Grubb, Blair; Stiller, Ulrich et al

in Hökfelt, T; Schaible, H-G; Schmidt, RF (Eds.) Neuropeptides, Nociception and Pain (1994)

Detailed reference viewed: 20 (0 UL)
Peer Reviewed
See detailSpinal cord injuries entering the Fas(t) lane.
Letellier, Elisabeth UL; Martin-Villalba, Ana

in Neurosurgery (2007), 6

Detailed reference viewed: 53 (2 UL)
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See detailSpinal lamina I projection neurons in the rat: collateral innervation of parabrachial area and thalamus
Hylden, Janice LK; Anton, Fernand UL; Nahin, Richard L

in Neuroscience (1989), 28(1), 27-37

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See detailSpinal motor neurons are regenerated after mechanical lesion and genetic ablation in larval zebrafish
Ohnmacht, Jochen UL; Yang, Yujie; Maurer, Giana et al

in Development (2016), 143(9), 1464-1474

In adult zebrafish, relatively quiescent progenitor cells show lesion-induced generation of motor neurons. Developmental motor neuron generation from the spinal motor neuron progenitor domain (pMN ... [more ▼]

In adult zebrafish, relatively quiescent progenitor cells show lesion-induced generation of motor neurons. Developmental motor neuron generation from the spinal motor neuron progenitor domain (pMN) sharply declines at 48 hours post-fertilisation (hpf). After that, mostly oligodendrocytes are generated from the same domain. We demonstrate here that within 48 h of a spinal lesion or specific genetic ablation of motor neurons at 72 hpf, the pMN domain reverts to motor neuron generation at the expense of oligodendrogenesis. By contrast, generation of dorsal Pax2-positive interneurons was not altered. Larval motor neuron regeneration can be boosted by dopaminergic drugs, similar to adult regeneration. We use larval lesions to show that pharmacological suppression of the cellular response of the innate immune system inhibits motor neuron regeneration. Hence, we have established a rapid larval regeneration paradigm. Either mechanical lesions or motor neuron ablation is sufficient to reveal a high degree of developmental flexibility of pMN progenitor cells. In addition, we show an important influence of the immune system on motor neuron regeneration from these progenitor cells. [less ▲]

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See detailSpinning Functional Fibers: An Interplay of Rheology, Miscibility & Crosslinking
Vats, Shameek UL

Doctoral thesis (2021)

Wearable technology in general has increasingly gained interest in the last few decades and textile with incorporated functional component constitute one form of it. There are multiple ways to produce ... [more ▼]

Wearable technology in general has increasingly gained interest in the last few decades and textile with incorporated functional component constitute one form of it. There are multiple ways to produce polymer fibers on both laboratory and industrial scales, and one of them is core–sheath electrospinning, which is a powerful method for producing advanced composite fibers. Liquid crystals (LCs), are materials that readily exhibit optical response to fluctua- tions and change in their immediate environment. By incorporating LC within polymer fibers through electrospinning, it is possible to create responsive LC-polymer fiber mats. However, incorporating a functional core has proven challenging for certain combinations of materials. This thesis explores and addresses some of the concerns involved in the coaxial electrospinning of fibers incorporating LCs from several standpoints. Firstly, the effect of solvents on the electrospinning process was systematically studied. Fol- lowing this, an optimum viscosity with pure and mixed solvents for successful electrospinning was identified and uniform fibers with different solvent combinations was produced. Using the knowledge gained, core-sheath electrospinning with LC as the core was carried out. One of the key findings of this work, the identification of a suitable means to reduce the interfacial tension between the core and sheath fluid to prevent break up of the jet and produce uniformly filled fibers, while at the same time avoiding complete mixing between core and sheath. These findings can be applied to any combination of core and sheath materials and should appeal to a large community of researchers. Eventually, to achieve the durability of the LC-functionalized electrospun fiber mats for use in wearable technology, the sheath polymer of the fiber were crosslinked after spinning. The resultant crosslinked fibers were easily manipulated by hand and even fully immersed in water without dissolving and without losing their functional LC core. [less ▲]

Detailed reference viewed: 100 (9 UL)
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See detailSpinocerebellar ataxia type 6: genotype and phenotype in German kindreds.
Schols, L.; Krüger, Rejko UL; Amoiridis, G. et al

in Journal of neurology, neurosurgery, and psychiatry (1998), 64(1), 67-73

OBJECTIVE: Spinocerebellar ataxia type 6 (SCA6) is an autosomal dominant cerebellar ataxia (ADCA) of which the mutation causing the disease has recently been characterised as an expanded CAG trinucleotide ... [more ▼]

OBJECTIVE: Spinocerebellar ataxia type 6 (SCA6) is an autosomal dominant cerebellar ataxia (ADCA) of which the mutation causing the disease has recently been characterised as an expanded CAG trinucleotide repeat in the gene coding for the alpha1A-subunit of the voltage dependent calcium channel. The aim was to further characterise the SCA6 phenotype METHODS: The SCA6 mutation was investigated in 69 German families with ADCA and 61 patients with idiopathic sporadic cerebellar ataxia and the CAG repeat length of the expanded allele was correlated with the disease phenotype. RESULTS: Expanded alleles were found in nine of 69 families as well as in four patients with sporadic disease. Disease onset ranged from 30 to 71 years of age and was significantly later than in other forms of ADCA. Age at onset correlated inversely with repeat length. The SCA6 phenotype comprises predominantly cerebellar signs in concordance with isolated cerebellar atrophy on MRI. Non-cerebellar systems were only mildly affected with external ophthalmoplegia, spasticity, peripheral neuropathy, and parkinsonism. Neither these clinical signs nor progression rate correlated with CAG repeat length. CONCLUSIONS: This study provides the first detailed characterisation of the SCA6 phenotype. Clinical features apart from cerebellar signs were highly variable in patients with SCA6. By comparison with SCA1, SCA2, and SCA3 no clinical or electrophysiological finding was specific for SCA6. Therefore, the molecular defect cannot be predicted from clinical investigations. In Germany, SCA6 accounts for about 13% of families with ADCA. However, up to 30% of SCA6 kindreds may be misdiagnosed clinically as sporadic disease due to late manifestation in apparently healthy parents. Genetic testing is therefore recommended for the SCA6 mutation also in patients with putative sporadic ataxia. [less ▲]

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