Anomalous Nernst effect in the topological and magnetic material MnBi₄Te₇

The recently discovered magnetic topological insulators (MnBi2Te4)(Bi2Te3)n, n = 0–4, are an ideal playground to study the influence of magnetic properties on band topology, giving access to diverse quantum states in a single compound. In the low temperature-antiferromagnetic state and vanishing magnetic field, the n = 1 system is a topological insulator protected by a combination of time reversal and a translation symmetries. It has been argued that, when the antiferromagnetic phase is forced to a the fully spin polarized state by the application of an external magnetic field, this system develops Weyl cones in the conduction band, which become accessible in presence of an intrinsic electronic doping. In this work, we experimentally prove the raising of field-induced Weyl state through the detection of an intrinsic anomalous Nernst effect in a bulk single crystal of MnBi4Te7.</p

Field-effect transistors assembled from functionalized carbon nanotubes

We have fabricated field effect transistors from carbon nanotubes using a novel selective placement scheme. We use carbon nanotubes that are covalently bound to molecules containing hydroxamic acid functionality. The functionalized nanotubes bind strongly to basic metal oxide surfaces, but not to silicon dioxide. Upon annealing, the functionalization is removed, restoring the electronic properties of the nanotubes. The devices we have fabricated show excellent electrical characteristics.Comment: 5 pages, 6 figure

Stimulation der TSH-Sekretion durch TRF-Belastung bei hypothalamischen und hypophysären Krankheitsbildern

1. Die Antworten der Serum-TSH-Spiegel (Thyreoidea-stimulierendes Hormon) auf TRF-Injektion (Thyrotropin Releasing Factor) bei 8 Normalpersonen und 37 z. T. zweimal untersuchten Patienten mit hypophysärer oder hypothalamischer Erkrankung werden mitgeteilt. 2. Hypophysektomierte Patienten mit intrasellären Tumoren (N=12) zeigten keine oder nur subnormale Anstiege der TSH-Spiegel. 3. Von 9 präoperativ untersuchten Patienten mit intrasellärem HVL-Adenom hatten 3 eine sekundäre Hypothyreose. Diese 3 reagierten dennoch mit einem normalen Anstieg der TSH-Spiegel. Dieser Befund schränkt die diagnostische Wertigkeit der TRF-Belastung zur Differenzierung hypophysärer und hypothalamischer sekundärer Hypothyreosen ein. Die 6 euthyreoten Patienten dieser Gruppe zeigten erwartungsgemäß einen normalen TSH-Anstieg. 4. Bei den Patienten mit sekundärer Hypothyreose bei suprasellärem Tumor oder hypothalamischer Erkrankung (N=7) fand sich mit einer Ausnahme ein normaler oder ein erhöhter TSH-Anstieg. Die Bedeutung des Ausschlusses einer primären Hypothyreose wurde dargestellt, da diese Erkrankung ebenfalls durch erhöhte TSH-Anstiege bei TRF-Belastung charakterisiert ist. 5. Je ein Patient aus der Gruppe der aktiven (N=7) und der behandelten (N=6) Akromegalie zeigten einen nicht auf eine primäre Hypothyreose zurückführbaren erhöhen TSH-Anstieg, dessen Rolle für das gehäufte Auftreten einer Struma bei Akromegalie zu diskutieren ist.1. The response of the serum TSH levels after i.v. administration of 500 µg TRF have been determined in normal controls (n=8) and in 37 patients with pituitary tumour or hypothalamic disease. 2. Following hypophysectomy in patients with intrasellar tumours (n=12), the increment in TSH levels after TRF was absent or diminished. 3. Secondary hypothyroidism was found pre-operatively in 3 of 9 patients with intrasellar pituitary adenoma. In these 3 patients, however, a normal TSH response to TRF was found. This result diminishes the diagnostic value of the TRF test regarding the distinction of pituitary and hypothalamic secondary hypothyroidism. A normal TSH response was found, as expected, in the 6 euthyroid patients of this group. 4. The TSH response was found to be normal or elevated in all but one of 7 patients with secondary hypothyroidism due to suprasellar tumour or hypothalamic disease. Primary hypothyroidism is also characterized by an increased TSH response and has to be excluded. 5. Among the patients with active (n=7) or treated (n=6) acromegaly, increased TSH response was found twice, i.e. in one patient of each of the two groups. In both patients, primary hypothyroidism could be excluded. The relevance of this increased TSH response for goitrogenesis in acromegaly is discussed

Two-dimensional ferromagnetic extension of a topological insulator

Inducing a magnetic gap at the Dirac point of the topological surface state (TSS) in a three-dimensional (3D) topological insulator (TI) is a route to dissipationless charge and spin currents. Ideally, magnetic order is present only at the surface, as through proximity of a ferromagnetic (FM) layer. However, experimental evidence of such a proximity-induced Dirac mass gap is missing, likely due to an insufficient overlap of TSS and the FM subsystem. Here, we take a different approach, namely ferromagnetic extension (FME), using a thin film of the 3D TI Bi2Te3, interfaced with a monolayer of the lattice-matched van der Waals ferromagnet MnBi2Te4. Robust 2D ferromagnetism with out-of-plane anisotropy and a critical temperature of Tc≈15 K is demonstrated by x-ray magnetic dichroism and electrical transport measurements. Using angle-resolved photoelectron spectroscopy, we observe the opening of a sizable magnetic gap in the 2D FM phase, while the surface remains gapless in the paramagnetic phase above Tc. Ferromagnetic extension paves the way to explore the interplay of strictly 2D magnetism and topological surface states, providing perspectives for realizing robust quantum anomalous Hall and chiral Majorana states

Two-dimensional ferromagnetic extension of a topological insulator

Inducing a magnetic gap at the Dirac point of the topological surface state (TSS) in a 3D topological insulator (TI) is a route to dissipationless charge and spin currents. Ideally, magnetic order is present only at the surface and not in the bulk, e.g. through proximity of a ferromagnetic (FM) layer. However, such a proximity-induced Dirac mass gap has not been observed, likely due to insufficient overlap of TSS and the FM subsystem. Here, we take a different approach, namely FM extension, using a thin film of the 3D TI Bi$_2$Te$_3$, interfaced with a monolayer of the lattice-matched van der Waals ferromagnet MnBi$_2$Te$_4$. Robust 2D ferromagnetism with out-of-plane anisotropy and a critical temperature of $\text{T}_\text{c}\approx$~15 K is demonstrated by X-ray magnetic dichroism and electrical transport measurements. Using angle-resolved photoelectron spectroscopy, we observe the opening of a sizable magnetic gap in the 2D FM phase, while the surface remains gapless in the paramagnetic phase above T$_c$. This sizable gap indicates a relocation of the TSS to the FM ordered Mn moments near the surface, which leads to a large mutual overlap.Comment: 6 pages, 3 figure

The Radish Gene Reveals a Memory Component with Variable Temporal Properties

Memory phases, dependent on different neural and molecular mechanisms, strongly influence memory performance. Our understanding, however, of how memory phases interact is far from complete. In Drosophila, aversive olfactory learning is thought to progress from short-term through long-term memory phases. Another memory phase termed anesthesia resistant memory, dependent on the radish gene, influences memory hours after aversive olfactory learning. How does the radish-dependent phase influence memory performance in different tasks? It is found that the radish memory component does not scale with the stability of several memory traces, indicating a specific recruitment of this component to influence different memories, even within minutes of learning

Studies on the genetic and non-genetic (physiological) variation of human erythrocyte glutamic oxaloacetic transaminase

The thermostability profile of seven different electrophoretic variants of human erythrocyte GOT found in 13 different, unrelated families from a racially heterogeneous population was examined. The five different slow-variant and the two different fast-variant classes could be grouped into four different thermostability classes which were termed unstable, less stable, normal and more stable than normal. The thermostability differences among and within the electrophoretic variant classes permitted differentiation of the 13 individusals possessing an electrophoretic variant phenotype into a total of ten different variants.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66025/1/j.1469-1809.1982.tb00711.x.pd

Intermixing-Driven Surface and Bulk Ferromagnetism in the Quantum Anomalous Hall Candidate MnBi6Te10

The recent realizations of the quantum anomalous Hall effect (QAHE) in MnBi2Te4 and MnBi4Te7 benchmark the (MnBi2Te4)(Bi2Te3)n family as a promising hotbed for further QAHE improvements. The family owes its potential to its ferromagnetically (FM) ordered MnBi2Te4 septuple layers (SLs). However, the QAHE realization is complicated in MnBi2Te4 and MnBi4Te7 due to the substantial antiferromagnetic (AFM) coupling between the SLs. An FM state, advantageous for the QAHE, can be stabilized by interlacing the SLs with an increasing number n of Bi2Te3 quintuple layers (QLs). However, the mechanisms driving the FM state and the number of necessary QLs are not understood, and the surface magnetism remains obscure. Here, robust FM properties in MnBi6Te10 (n = 2) with Tc ≈ 12 K are demonstrated and their origin is established in the Mn/Bi intermixing phenomenon by a combined experimental and theoretical study. The measurements reveal a magnetically intact surface with a large magnetic moment, and with FM properties similar to the bulk. This investigation thus consolidates the MnBi6Te10 system as perspective for the QAHE at elevated temperatures

Consumption of pasteurized human lysozyme transgenic goats’ milk alters serum metabolite profile in young pigs

Nutrition, bacterial composition of the gastrointestinal tract, and general health status can all influence the metabolic profile of an organism. We previously demonstrated that feeding pasteurized transgenic goats’ milk expressing human lysozyme (hLZ) can positively impact intestinal morphology and modulate intestinal microbiota composition in young pigs. The objective of this study was to further examine the effect of consuming hLZ-containing milk on young pigs by profiling serum metabolites. Pigs were placed into two groups and fed a diet of solid food and either control (non-transgenic) goats’ milk or milk from hLZ-transgenic goats for 6 weeks. Serum samples were collected at the end of the feeding period and global metabolite profiling was performed. For a total of 225 metabolites (160 known, 65 unknown) semi-quantitative data was obtained. Levels of 18 known and 4 unknown metabolites differed significantly between the two groups with the direction of change in 13 of the 18 known metabolites being almost entirely congruent with improved health status, particularly in terms of the gastrointestinal tract health and immune response, with the effects of the other five being neutral or unknown. These results further support our hypothesis that consumption of hLZ-containing milk is beneficial to health