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The band inversion of topological materials in three spatial dimensions is intimately connected to the parity anomaly of 2D massless Dirac fermions, known from quantum field theory. At finite magnetic fields, the parity anomaly reveals itself as a non‐zero spectral asymmetry, i.e., an imbalance between the number of conduction and valence band Landau levels, due to the unpaired zero Landau level. This work reports the realization of this 2D Dirac physics at a single surface of the 3D topological insulator (Hg,Mn)Te. An unconventional re‐entrant sequence of quantized Hall plateaus in the measured Hall resistance can be directly related to the occurrence of spectral asymmetry in a single topological surface state. The effect should be observable in any topological insulator where the transport is dominated by a single Dirac surface state. [ABSTRACT FROM AUTHOR]

The cerebellum is involved in many motor, autonomic and cognitive functions, and new tasks that have a cerebellar contribution are discovered on a regular basis. Simultaneously, our insight into the functional compartmentalization of the cerebellum has markedly improved. Additionally, studies on cerebellar output pathways have seen a renaissance due to the development of viral tracing techniques. To create an overview of the current state of our understanding of cerebellar efferents, we undertook a systematic review of all studies on monosynaptic projections from the cerebellum to the brainstem and the diencephalon in mammals. This revealed that important projections from the cerebellum, to the motor nuclei, cerebral cortex, and basal ganglia, are predominantly di- or polysynaptic, rather than monosynaptic. Strikingly, most target areas receive cerebellar input from all three cerebellar nuclei, showing a convergence of cerebellar information at the output level. Overall, there appeared to be a large level of agreement between studies on different species as well as on the use of different types of neural tracers, making the emerging picture of the cerebellar output areas a solid one. Finally, we discuss how this cerebellar output network is affected by a range of diseases and syndromes, with also non-cerebellar diseases having impact on cerebellar output areas. [ABSTRACT FROM AUTHOR]

This document is a correction notice for an article titled "A Systematic Review of Direct Outputs from the Cerebellum to the Brainstem and Diencephalon in Mammals" published in the journal Cerebellum. The correction states that there was a mistake in the original article, specifically in Table 1 where a reference number was incorrect. The correction provides the correct reference number and mentions that the table has been simplified. The original article has been corrected and the publisher, Springer Nature, remains neutral in terms of jurisdictional claims and affiliations. The authors of the article are Manuele Novello, Laurens W. J. Bosman, and Chris I. De Zeeuw. [Extracted from the article]

The recent advent of topological states of matter spawned many significant discoveries. The quantum anomalous Hall (QAH) effect is a prime example due to its potential for applications in quantum metrology, as well as its influence on fundamental research into the underlying topological and magnetic states and into axion electrodynamics. Here, electronic transport studies on a (V,Bi,Sb)2Te3 ferromagnetic topological insulator nanostructure in the QAH regime are presented. This allows access to the dynamics of an individual ferromagnetic domain. The domain size is estimated to be in the 50–100 nm range. Telegraph noise resulting from the magnetization fluctuations of this domain is observed in the Hall signal. Careful analysis of the influence of temperature and external magnetic field on the domain switching statistics provides evidence for quantum tunneling (QT) of magnetization in a macrospin state. This ferromagnetic macrospin is not only the largest magnetic object in which QT is observed, but also the first observation of the effect in a topological state of matter. [ABSTRACT FROM AUTHOR]

Human androgen receptor contains a large N‐terminal domain (AR‐NTD) that is highly dynamic and this poses a major challenge for experimental and computational analysis to decipher its conformation. Misfolding of the AR‐NTD is implicated in prostate cancer and Kennedy's disease, yet our knowledge of its structure is limited to primary sequence information of the chain and a few functionally important secondary structure motifs. Here, we employed an innovative combination of molecular dynamics simulations and circuit topology (CT) analysis to identify the tertiary structure of AR‐NTD. We found that the AR‐NTD adopts highly dynamic loopy conformations with two identifiable regions with distinct topological make‐up and dynamics. This consists of a N‐terminal region (NR, residues 1–224) and a C‐terminal region (CR, residues 225–538), which carries a dense core. Topological mapping of the dynamics reveals a traceable time‐scale dependent topological evolution. NR adopts different positioning with respect to the CR and forms a cleft that can partly enclose the hormone‐bound ligand‐binding domain (LBD) of the androgen receptor. Furthermore, our data suggest a model in which dynamic NR and CR compete for binding to the DNA‐binding domain of the receptor, thereby regulating the accessibility of its DNA‐binding site. Our approach allowed for the identification of a previously unknown regulatory binding site within the CR core, revealing the structural mechanisms of action of AR inhibitor EPI‐001, and paving the way for other drug discovery applications. [ABSTRACT FROM AUTHOR]

The survival of the quantum spin Hall edge channels in presence of an external magnetic field has been a subject of experimental and theoretical research. The inversion of Landau levels that accommodates the quantum spin Hall effect is destroyed at a critical magnetic field, and a trivial insulating gap appears in the spectrum for stronger fields. In this work, we report the absence of this transport gap in disordered two dimensional topological insulators in perpendicular magnetic fields of up to 16 T. Instead, we observe that a topological edge channel (from band inversion) coexists with a counterpropagating quantum Hall edge channel for magnetic fields at which the transition to the insulating regime is expected. For larger fields, we observe only the quantum Hall edge channel with transverse resistance close to h/e2. By tuning the disorder using different fabrication processes, we find evidence that this unexpected ν = 1 plateau originates from extended quantum Hall edge channels along a continuous network of charge puddles at the edges of the device. The quantum spin Hall effect disappears at high magnetic fields when the band inversion is lifted. The authors demonstrate that in contrast, in disordered samples, counter-propagating topological and quantum Hall edge channels prevent the detection of the trivial gap, explaining a previous observation. [ABSTRACT FROM AUTHOR]

Achieving metrological precision of quantum anomalous Hall resistance quantization at zero magnetic field so far remains limited to temperatures of the order of 20 mK, while the Curie temperature in the involved material is as high as 20 K. The reason for this discrepancy remains one of the biggest open questions surrounding the effect, and is the focus of this article. Here we show, through a careful analysis of the non-local voltages on a multi-terminal Corbino geometry, that the chiral edge channels continue to exist without applied magnetic field up to the Curie temperature of bulk ferromagnetism of the magnetic topological insulator, and that thermally activated bulk conductance is responsible for this quantization breakdown. Our results offer important insights on the nature of the topological protection of these edge channels, provide an encouraging sign for potential applications, and establish the multi-terminal Corbino geometry as a powerful tool for the study of edge channel transport in topological materials. The quantum anomalous Hall effect has so far been limited to temperature of the order of 20 mK. Here, Fijalkowski et al. report the existence of chiral edge channels up to the Curie temperature of bulk ferromagnetism of the magnetic topological insulator with a multi-terminal Corbino geometry. [ABSTRACT FROM AUTHOR]

Purkinje cells are the primary processing units of the cerebellar cortex and display molecular heterogeneity that aligns with differences in physiological properties, projection patterns, and susceptibility to disease. In particular, multiple mouse models that feature Purkinje cell degeneration are characterized by incomplete and patterned Purkinje cell degeneration, suggestive of relative sparing of Purkinje cell subpopulations, such as those expressing Aldolase C/zebrinII (AldoC) or residing in the vestibulo‐cerebellum. Here, we investigated a well‐characterized Purkinje cell‐specific mouse model for spinocerebellar ataxia type 1 (SCA1) that expresses human ATXN1 with a polyQ expansion (82Q). Our pathological analysis confirms previous findings that Purkinje cells of the vestibulo‐cerebellum, i.e., the flocculonodular lobes, and crus I are relatively spared from key pathological hallmarks: somatodendritic atrophy, and the appearance of p62/SQSTM1‐positive inclusions. However, immunohistological analysis of transgene expression revealed that spared Purkinje cells do not express mutant ATXN1 protein, indicating the sparing of Purkinje cells can be explained by an absence of transgene expression. Additionally, we found that Purkinje cells in other cerebellar lobules that typically express AldoC, not only display severe pathology but also show loss of AldoC expression. The relatively preserved flocculonodular lobes and crus I showed a substantial fraction of Purkinje cells that expressed the mutant protein and displayed pathology as well as loss of AldoC expression. Despite considerable pathology in these lobules, behavioral analyses demonstrated a relative sparing of related functions, suggestive of sufficient functional cerebellar reserve. Together, the data indicate that mutant ATXN1 affects both AldoC‐positive and AldoC‐negative Purkinje cells and disrupts normal parasagittal AldoC expression in Purkinje cells. Our results show that, in a mouse model otherwise characterized by widespread Purkinje cell degeneration, sparing of specific subpopulations is sufficient to maintain normal performance of specific behaviors within the context of the functional, modular map of the cerebellum. [ABSTRACT FROM AUTHOR]

Intersectoral action is advocated as a social practice that can effectively address health inequalities and related social issues. Existing knowledge provides insight into factors that may facilitate or hinder successful intersectoral action, but not much is known about how intersectoral action evolves and becomes embedded in local health policies. This is where this study aims to make its contribution, by adopting the multilevel perspective on transitions, which is increasingly used to study social innovation in sustainability transitions but has not yet been applied to public health and health promotion. Through this perspective, it was unravelled how intersectoral action between youth-care organizations and community sports clubs became embedded in local health policies of Rotterdam, a large city in the Netherlands. A single explorative case study was conducted based on content analysis of policy documents and 15 in-depth interviews with policy officers, managers and field workers operating in the fields of youth and sports in Rotterdam. The findings showed that intersectoral action between community organizations and policymakers evolves through congruent processes at different levels that changed institutional logics. Moreover, it emerged that policymakers and other actors that advocate novel social practices and act as boundary spanners can adopt multiple strategies to embed these practices in local health policy. The multi-level perspective adds value to earlier approaches to research intersectoral collaboration for health promotion as it allows to better capture the politics involved in the social innovation processes. However, further sharpening and more comprehensive application of transition concepts to study transitions in public health and health promotion is needed. [ABSTRACT FROM AUTHOR]

Soon after the discovery of the quantum spin Hall effect, it has been predicted that a magnetic impurity in the presence of strong Coulomb interactions will destroy the quantum spin Hall effect. However, the fate of the quantum spin Hall effect in the presence of magnetic impurities has not yet been experimentally investigated. Here, we report the successful experimental demonstration of a quantized spin Hall resistance in HgTe quantum wells dilutely alloyed with magnetic Mn atoms. These quantum wells exhibit an inverted band structure that is very similar to that of the undoped material. Micron sized devices of (Hg,Mn)Te quantum well (in the topological phase) show a quantized spin Hall resistance of h/2e2 at low temperatures and zero magnetic field. At finite temperatures, we observe signatures of the Kondo effect due to interaction between the helical edge channels and magnetic impurities. Our work lays the foundation for future investigations of magnetically doped quantum spin Hall materials towards the realization of chiral Majorana fermions. The quantum spin Hall effect is expected not to survive the presence of magnetic impurities. Here, authors report full quantization at very low temperatures in HgTe quantum wells alloyed with a few percent of magnetic Mn atoms, due to Kondo screening. [ABSTRACT FROM AUTHOR]

Activity of sensory and motor cortices is essential for sensorimotor integration. In particular, coherence between these areas may indicate binding of critical functions like perception, motor planning, action, or sleep. Evidence is accumulating that cerebellar output modulates cortical activity and coherence, but how, when, and where it does so is unclear. We studied activity in and coherence between S1 and M1 cortices during whisker stimulation in the absence and presence of optogenetic Purkinje cell stimulation in crus 1 and 2 of awake mice, eliciting strong simple spike rate modulation. Without Purkinje cell stimulation, whisker stimulation triggers fast responses in S1 and M1 involving transient coherence in a broad spectrum. Simultaneous stimulation of Purkinje cells and whiskers affects amplitude and kinetics of sensory responses in S1 and M1 and alters the estimated S1-M1 coherence in theta and gamma bands, allowing bidirectional control dependent on behavioral context. These effects are absent when Purkinje cell activation is delayed by 20 ms. Focal stimulation of Purkinje cells revealed site specificity, with cells in medial crus 2 showing the most prominent and selective impact on estimated coherence, i.e., a strong suppression in the gamma but not the theta band. Granger causality analyses and computational modeling of the involved networks suggest that Purkinje cells control S1-M1 phase consistency predominantly via ventrolateral thalamus and M1. Our results indicate that activity of sensorimotor cortices can be dynamically and functionally modulated by specific cerebellar inputs, highlighting a widespread role of the cerebellum in coordinating sensorimotor behavior. [ABSTRACT FROM AUTHOR]

Rodents engage in active touch using their facial whiskers: they explore their environment by making rapid back-and-forth movements. The fast nature of whisker movements, during which whiskers often cross each other, makes it notoriously difficult to track individual whiskers of the intact whisker field. We present here a novel algorithm, WhiskEras, for tracking of whisker movements in high-speed videos of untrimmed mice, without requiring labeled data. WhiskEras consists of a pipeline of image-processing steps: first, the points that form the whisker centerlines are detected with sub-pixel accuracy. Then, these points are clustered in order to distinguish individual whiskers. Subsequently, the whiskers are parameterized so that a single whisker can be described by four parameters. The last step consists of tracking individual whiskers over time. We describe that WhiskEras performs better than other whisker-tracking algorithms on several metrics. On our four video segments, WhiskEras detected more whiskers per frame than the Biotact Whisker Tracking Tool. The signal-to-noise ratio of the output of WhiskEras was higher than that of Janelia Whisk. As a result, the correlation between reflexive whisker movements and cerebellar Purkinje cell activity appeared to be stronger than previously found using other tracking algorithms. We conclude that WhiskEras facilitates the study of sensorimotor integration by markedly improving the accuracy of whisker tracking in untrimmed mice. [ABSTRACT FROM AUTHOR]

Dilute magnetic semiconductors have proven to be very useful in building an all-semiconductor platform for spintronics--so far they provide the only viable route to establish spin-polarized current injection into a nonmagnetic semiconductor. The reasons for this become apparent from a simple spin-channel model, which predicts that spin injection into a semiconductor can, within linear response, only readily be achieved from a ferromagnetic injector that has: (i) a resistivity that is comparable to the semiconductor and (ii) preferably is 100% spin polarized. Both of these criteria can be met in magnetic semiconductors, but (so far) are hard to achieve using other materials. Experimentally, we demonstrate how dilute magnetic II-VI semiconductors can be used to inject a strongly (up to 90%) spin-polarized current into a light emitting diode. In addition, we discuss the implications of the spin-channel model for the observation of giant magnetoresistance-like effects in th! e magnetoresistance of an all-semiconductor device. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Entropy is a fundamental thermodynamic quantity indicative of the accessible degrees of freedom in a system. While it has been suggested that the entropy of a mesoscopic system can yield nontrivial information on emergence of exotic states, its measurement in such small electron-number system is a daunting task. Here we propose a method to extract the entropy of a Coulomb-blockaded mesoscopic system from transport measurements. We prove analytically and demonstrate numerically the applicability of the method to such a mesoscopic system of arbitrary spectrum and degeneracies. We then apply our procedure to measurements of thermoelectric response of a single quantum dot, and demonstrate how it can be used to deduce the entropy change across Coulomb-blockade valleys, resolving, along the way, a long-standing puzzle of the experimentally observed finite thermoelectric response at the apparent particle-hole symmetric point. Advances in nanotechnology make it possible to probe traditionally macroscopic notions of thermodynamics at the mesoscopic scale. Here the authors propose a method that can determine the entropy of a quantum dot system from transport measurements. [ABSTRACT FROM AUTHOR]

Inferior olivary activity causes both short-term and long-term changes in cerebellar output underlying motor performance and motor learning. Many of its neurons engage in coherent subthreshold oscillations and are extensively coupled via gap junctions. Studies in reduced preparations suggest that these properties promote rhythmic, synchronized output. However, the interaction of these properties with torrential synaptic inputs in awake behaving animals is not well understood. Here we combine electrophysiological recordings in awake mice with a realistic tissue-scale computational model of the inferior olive to study the relative impact of intrinsic and extrinsic mechanisms governing its activity. Our data and model suggest that if subthreshold oscillations are present in the awake state, the period of these oscillations will be transient and variable. Accordingly, by using different temporal patterns of sensory stimulation, we found that complex spike rhythmicity was readily evoked but limited to short intervals of no more than a few hundred milliseconds and that the periodicity of this rhythmic activity was not fixed but dynamically related to the synaptic input to the inferior olive as well as to motor output. In contrast, in the long-term, the average olivary spiking activity was not affected by the strength and duration of the sensory stimulation, while the level of gap junctional coupling determined the stiffness of the rhythmic activity in the olivary network during its dynamic response to sensory modulation. Thus, interactions between intrinsic properties and extrinsic inputs can explain the variations of spiking activity of olivary neurons, providing a temporal framework for the creation of both the short-term and long-term changes in cerebellar output. [ABSTRACT FROM AUTHOR]

Topological superconductors can support localized Majorana states at their boundaries1–5. These quasi-particle excitations obey non-Abelian statistics that can be used to encode and manipulate quantum information in a topologically protected manner6,7. Although signatures of Majorana bound states have been observed in one-dimensional systems, there is an ongoing effort to find alternative platforms that do not require fine-tuning of parameters and can be easily scaled to large numbers of states8–21. Here we present an experimental approach towards a two-dimensional architecture of Majorana bound states. Using a Josephson junction made of a HgTe quantum well coupled to thin-film aluminium, we are able to tune the transition between a trivial and a topological superconducting state by controlling the phase difference across the junction and applying an in-plane magnetic field22. We determine the topological state of the resulting superconductor by measuring the tunnelling conductance at the edge of the junction. At low magnetic fields, we observe a minimum in the tunnelling spectra near zero bias, consistent with a trivial superconductor. However, as the magnetic field increases, the tunnelling conductance develops a zero-bias peak, which persists over a range of phase differences that expands systematically with increasing magnetic field. Our observations are consistent with theoretical predictions for this system and with full quantum mechanical numerical simulations performed on model systems with similar dimensions and parameters. Our work establishes this system as a promising platform for realizing topological superconductivity and for creating and manipulating Majorana modes and probing topological superconducting phases in two-dimensional systems. Majorana bound states are created in a two-dimensional architecture by confining Majorana channels within a planar Josephson junction, using the phase difference across the junction and an in-plane magnetic field. [ABSTRACT FROM AUTHOR]

We investigate the crystal properties of CdTe nanowires overgrown with HgTe. Scanning electron microscopy and scanning transmission electron microscopy confirm that the growth results in a high ensemble uniformity and that the individual heterostructures are single-crystalline, respectively. We use high-resolution X-ray diffraction to investigate strain, caused by the small lattice mismatch between the two materials. We find that both CdTe and HgTe show changes in the lattice constant compared to the respective bulk lattice constants. The measurements reveal a complex strain pattern with signatures of both uniaxial and shear strains present in the overgrown nanowires. [ABSTRACT FROM AUTHOR]

Picosecond photon echo experiments on pentacene in polymethylmethacrylate (PMMA) show that the homogeneous width exhibits a T1.3 temperature dependence. This behavior is ascribed to coupling of the pentacene transition to randomly distributed low-frequency excitations in the amorphous host. A calculation of the resulting homogeneous width is presented which uses optical Redfield theory as a starting point. From the results of this calculation we conclude that the coupling between the pentacene molecule and the host low frequency excitations is of static dipolar nature and that the density of states of these excitations varies as ω0.3. Results of nonphotochemical hole-burning experiments on the same system are also reported. Comparison of these results with the ones obtained by the photon echo method indicates, that in the hole-burning experiments, the hole width and its temperature-induced broadening are dominated by spectral diffusion. [ABSTRACT FROM AUTHOR]

Objectives: To evaluate aortic velocity, wall shear stress (WSS) and viscous energy loss (EL) of stented and stentless bioprostheses using 4D flow MRI 1 year after surgical aortic valve replacement.Methods: For this cross-sectional study 28 patients with stented (n = 14) or stentless (n = 14) bioprosthesis underwent non-contrast-enhanced 4D-flow MRI at 1.5 T. Analyses included a comparison of velocity, WSS and EL in the ascending aorta during peak systole for both spatially averaged values and a comparison of local differences using per-voxel analysis.Results: No significant differences were found in peak and mean velocity (stented vs. stentless: 2.45 m/s vs. 2.11 m/s; p = 0.09 and 0.60 m/s vs. 0.62 m/s; p = 0.89), WSS (0.60 Pa vs. 0.59 Pa; p = 0.55) and EL (10.17 mW vs. 7.82 mW; p = 0.10). Per-voxel analysis revealed significantly higher central lumen velocity, and lower outer lumen velocity, WSS and EL for stentless versus stented prostheses.Conclusion: One year after aortic valve implantation with stented and stentless bioprostheses, velocity, WSS and EL were comparable when assessed for averaged values in the ascending aorta. However, the flow profile described with local analysis for stentless prosthesis is potentially favourable with a significantly higher central velocity profile and lower values for outer lumen velocity, WSS and EL.Key Points: • Stentless bioprostheses can be implanted instead of stented aortic valve bioprostheses. • Haemodynamic performance of valve prosthesis can be assessed using 4D flow MRI. • Averaged ascending aorta PSV, WSS and EL are comparable 1 year post-implantation. • Centreline velocity is highest, WSS and EL is lowest for stentless prosthesis. [ABSTRACT FROM AUTHOR]

B Macroscopic Quantum Tunneling b The profound question of how the laws of quantum mechanics merge into those governing classical physics at macroscopic sizes remains largely unexplored. In article number 2303165 by Kajetan M. Fijalkowski, Charles Gould, Laurens W. Molenkamp, and co-workers, quantum tunneling of the magnetization, a phenomenon quantum by nature, is studied in a magnetic object that is, without any doubt, macroscopic. [Extracted from the article]

Absence epilepsy is characterized by the occurrence of generalized spike and wave discharges (GSWDs) in electrocorticographical (ECoG) recordings representing oscillatory activity in thalamocortical networks. The oscillatory nature of GSWDs has been shown to be reflected in the simple spike activity of cerebellar Purkinje cells and in the activity of their target neurons in the cerebellar nuclei, but it is unclear to what extent complex spike activity is implicated in generalized epilepsy. Purkinje cell complex spike firing is elicited by climbing fiber activation and reflects action potential firing in the inferior olive. Here, we investigated to what extent modulation of complex spike firing is reflected in the temporal patterns of seizures. Extracellular single-unit recordings in awake, headrestrained homozygous tottering mice, which suffer from a mutation in the voltage-gated CaV2.1 calcium channel, revealed that a substantial proportion of Purkinje cells (26%) showed increased complex spike activity and rhythmicity during GSWDs. Moreover, Purkinje cells, recorded either electrophysiologically or by using Ca2+-imaging, showed a significant increase in complex spike synchronicity for both adjacent and remote Purkinje cells during ictal events. These seizure-related changes in firing frequency, rhythmicity and synchronicity were most prominent in the lateral cerebellum, a region known to receive cerebral input via the inferior olive. These data indicate profound and widespread changes in olivary firing that are most likely induced by seizure-related activity changes in the thalamocortical network, thereby highlighting the possibility that olivary neurons can compensate for pathological brain-state changes by dampening oscillations. [ABSTRACT FROM AUTHOR]

Total ankle arthroplasty is a treatment option for end-stage osteoarthritis of the ankle, as is ankle arthrodesis. Many variables, including patient characteristics, are thought to influence clinical outcome and survival. As with any surgery, but especially with total ankle replacement (TAR), patient selection is considered critical for good (long-term) outcome. In this review, we summarize the available scientific evidence regarding patient characteristics and its influence on the results of TAR. [ABSTRACT FROM AUTHOR]

Topological insulators are a new class of materials with an insulating bulk and topologically protected metallic surface states. Although it is widely assumed that these surface states display a Dirac-type dispersion that is symmetric above and below the Dirac point, this exact equivalence across the Fermi level has yet to be established experimentally. Here, we present a detailed transport study of the 3D topological insulator-strained HgTe that strongly challenges this prevailing viewpoint. First, we establish the existence of exclusively surface-dominated transport via the observation of an ambipolar surface quantum Hall effect and quantum oscillations in the Seebeck and Nernst effect. Second, we show that, whereas the thermopower is diffusion driven for surface electrons, both diffusion and phonon drag contributions are essential for the hole surface carriers. This distinct behavior in the thermoelectric response is explained by a strong deviation from the linear dispersion relation for the surface states, with a much flatter dispersion for holes compared with electrons. These findings show that the metallic surface states in topological insulators can exhibit both strong electron–hole asymmetry and a strong deviation from a linear dispersion but remain topologically protected. [ABSTRACT FROM AUTHOR]

This article reviews recent thermoelectric experiments on quantum dot (QD) systems. The experiments focus on two types of inter-dot coupling: tunnel coupling and Coulomb coupling. Tunnel-coupled QDs allow particles to be exchanged between the attached reservoirs via the QD system. Hence, an applied temperature bias results in a thermovoltage. When being investigated as a function of QD energies, this leads to the thermopower stability diagram. Here, largest thermovoltage is observed in the regions of the triple points. In a QD system which exhibits only capacitive inter-dot coupling, electron transfer is suppressed. Such a device is studied in a three-terminal geometry: while one QD connects to the heat reservoir, the other one can exchange electrons with two reservoirs at a lower temperature. When the symmetry of the tunneling coefficients in the cold system is broken, the device becomes an energy harvester: thermal energy is extracted from the heat reservoir and is converted into a directed charge current between the two cold reservoirs. This review illustrates the large potential of multi-QD devices for thermoelectrics and thermal management at the nanometer-scale. [ABSTRACT FROM AUTHOR]

Rectification of thermal fluctuations in mesoscopic conductors is the key idea behind recent attempts to build nanoscale thermoelectric energy harvesters to convert heat into useful electric power. So far, most concepts have made use of the Seebeck effect in a two-terminal geometry, where heat and charge are both carried by the same particles. Here, we experimentally demonstrate the working principle of a new kind of energy harvester, proposed recently, using two capacitively coupled quantum dots. We show that, due to the novel three-terminal design of our device, which spatially separates the heat reservoir from the conductor circuit, the directions of charge and heat flow become decoupled. This enables us to manipulate the direction of the generated charge current by means of external gate voltages while leaving the direction of heat flow unaffected. Our results pave the way for a new generation of multi-terminal nanoscale heat engines. [ABSTRACT FROM AUTHOR]

We review on time and spatially resolved two-color pump-probe magneto-optical Kerr effect (MOKE) microscopy studies of electron spins in bulk n-GaAs and GaAs (110) quantum wells (QWs) at low lattice temperatures. The influence of photocarrier heating by above-bandgap optical spin excitation on the spatially resolved magneto-optical spin detection is considered in detail. We demonstrate that a continuous-wave (cw) measurement of the local Kerr rotation at a fixed arbitrary probe wavelength in general does not correctly reveal the local spin polarization when hot electrons are present. For bulk GaAs we determine the true lateral electron spin polarization profile from cw measurements of the spatial dependence of the full excitonic Kerr rotation spectrum. For the (110) QWs, we directly obtain the electron spin diffusion coefficient from picosecond real space imaging of the time evolution of an optically excited electron spin packet, which we observe with a spectrally broad probe pulse. [ABSTRACT FROM AUTHOR]

Topological insulators are a newly discovered phase of matter characterized by gapped bulk states surrounded by conducting boundary states. Since their theoretical discovery, these materials have encouraged intense efforts to study their properties and capabilities. Among the most striking results of this activity are proposals to engineer a new variety of superconductor at the surfaces of topological insulators. These topological superconductors would be capable of supporting localized Majorana fermions, particles whose braiding properties have been proposed as the basis of a fault-tolerant quantum computer. Despite the clear theoretical motivation, a conclusive realization of topological superconductivity remains an outstanding experimental goal. Here we present measurements of superconductivity induced in two-dimensional HgTe/HgCdTe quantum wells, a material that becomes a quantum spin Hall insulator when the well width exceeds dC = 6.3 nm (ref. ). In wells that are 7.5 nm wide, we find that supercurrents are confined to the one-dimensional sample edges as the bulk density is depleted. However, when the well width is decreased to 4.5 nm the edge supercurrents cannot be distinguished from those in the bulk. Our results provide evidence for supercurrents induced in the helical edges of the quantum spin Hall effect, establishing this system as a promising avenue towards topological superconductivity. In addition to directly confirming the existence of the topological edge channels, our results also provide a measurement of their widths, which range from 180 nm to 408 nm. [ABSTRACT FROM AUTHOR]

ABSTRACT In this review, we discuss the current surgical treatment for aortic valve stenosis. Surgical strategy for treatment of aortic valve stenosis is based on the risk profile of the patient. We reviewed the existing literature and present the current state of the art of these various approaches, taking into account clinical outcomes, quality of life, costs, and learning curve. doi: 10.1111/jocs.12384 (J Card Surg 2014;29:630-637) [ABSTRACT FROM AUTHOR]

Whisker-based object localization requires activation and plasticity of somatosensory and motor cortex. These parts of the cerebral cortex receive strong projections from the cerebellum via the thalamus, but it is unclear whether and to what extent cerebellar processing may contribute to such a sensorimotor task. Here, we subjected knock-out mice, which suffer from impaired intrinsic plasticity in their Purkinje cells and long-term potentiation at their parallel fiber-to-Purkinje cell synapses (L7-PP2B), to an object localization task with a time response window (RW). Water-deprived animals had to learn to localize an object with their whiskers, and based upon this location they were trained to lick within a particular period ("go" trial) or refrain from licking ("no-go" trial). L7-PP2B mice were not ataxic and showed proper basic motor performance during whisking and licking, but were severely impaired in learning this task compared with wild-type littermates. Significantly fewer L7-PP2B mice were able to learn the task at long RWs. Those L7-PP2B mice that eventually learned the task made unstable progress, were significantly slower in learning, and showed deficiencies in temporal tuning. These differences became greater as the RW became narrower. Trained wild-type mice, but not L7-PP2B mice, showed a net increase in simple spikes and complex spikes of their Purkinje cells during the task. We conclude that cerebellar processing, and potentiation in particular, can contribute to learning a whisker-based object localization task when timing is relevant. This study points toward a relevant role of cerebellum- cerebrum interaction in a sophisticated cognitive task requiring strict temporal processing. [ABSTRACT FROM AUTHOR]

The quantum spin Hall (QSH) state is a state of matter characterized by a non-trivial topology of its band structure, and associated conducting edge channels. The QSH state was predicted and experimentally demonstrated to be realized in HgTe quantum wells. The existence of the edge channels has been inferred from local and non-local transport measurements in sufficiently small devices. Here we directly confirm the existence of the edge channels by imaging the magnetic fields produced by current flowing in large Hall bars made from HgTe quantum wells. These images distinguish between current that passes through each edge and the bulk. On tuning the bulk conductivity by gating or raising the temperature, we observe a regime in which the edge channels clearly coexist with the conducting bulk, providing input to the question of how ballistic transport may be limited in the edge channels. Our results represent a versatile method for characterization of new QSH materials systems. [ABSTRACT FROM AUTHOR]

The prediction and experimental verification of the quantum spin Hall state marked the discovery of a new state of matter now known as topological insulators. Two-dimensional topological insulators exhibit the quantum spin-Hall effect, characterized by gapless spin-polarized counter-propagating edge channels. Whereas the helical character of these edge channels is now well established, experimental confirmation that the transport in the edge channels is spin polarized is still outstanding. We report experiments on nanostructures fabricated from HgTe quantum wells with an inverted band structure, in which a split gate technique allows us to combine both quantum spin Hall and metallic spin Hall transport in a single device. In these devices, the quantum spin Hall effect can be used as a spin current injector and detector for the metallic spin Hall effect, and vice versa, allowing for an all-electrical detection of spin polarization. [ABSTRACT FROM AUTHOR]

Neurons are generally considered to communicate information by increasing or decreasing their firing rate. However, in principle, they could in addition convey messages by using specific spatiotemporal patterns of spiking activities and silent intervals. Here, we review expanding lines of evidence that such spatiotemporal coding occurs in the cerebellum, and that the olivocerebellar system is optimally designed to generate and employ precise patterns of complex spikes and simple spikes during the acquisition and consolidation of motor skills. These spatiotemporal patterns may complement rate coding, thus enabling precise control of motor and cognitive processing at a high spatiotemporal resolution by fine-tuning sensorimotor integration and coordination. [ABSTRACT FROM AUTHOR]

In a vortex-state magnetic nanodisc, the static magnetization curls in the plane, except in the core region, where it points out of plane, either up or down, leading to two possible stable states of opposite core polarity p. Dynamical reversal of p by large-amplitude motion of the vortex core has recently been demonstrated experimentally, raising the prospect of practical applications, in particular in magnetic-storage devices. Here we demonstrate coherent control of p by single- and double-microwave-pulse sequences, taking advantage of the resonant vortex dynamics in a perpendicular-bias magnetic field. Experimental optimization of the microwave-pulse duration required for switching p also yields information about the characteristic decay time of the vortex core in the large-oscillation regime. This time is found to be less than half the length seen in the small-oscillation regime, suggesting a nonlinear behaviour of magnetic dissipation. [ABSTRACT FROM AUTHOR]

The cerebellar cortex is crucial for sensorimotor integration. Sensorimotor inputs converge on cerebellar Purkinje cells via two afferent pathways: the climbing fibre pathway triggering complex spikes, and the mossy fibre-parallel fibre pathway, modulating the simple spike activities of Purkinje cells. We used, for the first time, the mouse whisker system as a model system to study the encoding of somatosensory input by Purkinje cells. We show that most Purkinje cells in ipsilateral crus 1 and crus 2 of awake mice respond to whisker stimulation with complex spike and/or simple spike responses. Single-whisker stimulation in anaesthetised mice revealed that the receptive fields of complex spike and simple spike responses were strikingly different. Complex spike responses, which proved to be sensitive to the amplitude, speed and direction of whisker movement, were evoked by only one or a few whiskers. Simple spike responses, which were not affected by the direction of movement, could be evoked by many individual whiskers. The receptive fields of Purkinje cells were largely intermingled, and we suggest that this facilitates the rapid integration of sensory inputs from different sources. Furthermore, we describe that individual Purkinje cells, at least under anaesthesia, may be bound in two functional ensembles based on the receptive fields and the synchrony of the complex spike and simple spike responses. The 'complex spike ensembles' were oriented in the sagittal plane, following the anatomical organization of the climbing fibres, while the 'simple spike ensembles' were oriented in the transversal plane, as are the beams of parallel fibres. [ABSTRACT FROM AUTHOR]

The organic semiconductor dibenzotetrathiafulvalene (DB-TTF) presents, at ambient conditions, four polymorphic modifications. In addition to the already known monoclinic structure (α) with Z= 2, we have resolved by single crystal X-ray diffraction (XRD) a second crystal structure (β), also monoclinic but with Z= 4. Two other polymorphic modifications (γ and δ) have been found by means of lattice phonon confocal Raman microscopy and XRD. In this paper we present a series of growth experiments, from vapour or from solution, in films and in the bulk phase, describing the variety of transformations which occur among the different phases and their mixing, also at a micrometric scale. Quasi harmonic lattice dynamics calculations satisfactorily reproduce the structures of the α and the β polymorphs and help the phonon assignment of polarized Raman spectra in single crystals. [ABSTRACT FROM AUTHOR]

During the developmental formation of neuronal circuits, redundant synapses are eliminated and persisting synapses strengthened. In the immature cerebellum, climbing fiber-Purkinje cell synapses undergo a pronounced synaptic rewiring, from a multiple innervation around birth to a mono-innervation in adults. An early stage of this process consists in the differentiation of initially equally strong synapses into one "large" and several "small" synaptic inputs. By performing whole-cell recordings in Purkinje cells of rat cerebellar slices, we found that the coincident activation of a Purkinje cell and one of its afferent climbing fibers induces homosynaptic long-term synaptic potentiation (LTP). This LTP requires postsynaptic Ca2+ signaling and involves an increase in the single channel conductance of the postsynaptic AMPA receptors. Interestingly, LTP occurs exclusively at large synaptic inputs. It is not observed at small inputs that are eventually eliminated. Thus, we identified a new form of LTP that is expressed uniquely and just for a restricted period of early development in the large climbing fiber inputs. Our results suggest that this LTP mediates the activity-dependent maturation of the "winner" climbing fiber. [ABSTRACT FROM AUTHOR]