The exactly solvable Kitaev model of two-dimensional honeycomb magnets has a quantum spin liquid phase characterized by the emergence of fractionalized Majorana fermion excitations. In the ...paramagnetic state of α-RuCl3 at high magnetic fields, a half-integer quantization of thermal Hall conductivity has been reported as a signature of edge currents carried by Majorana fermions, but the bulk nature of this state remains unconfirmed. Here, by measuring the heat capacity for different in-plane rotations of an applied magnetic field, we find strongly angle-dependent low-energy excitations in bulk α-RuCl3. The excitation gap has a sextuple node structure, and the gap amplitude increases with the field, as expected for itinerant Majorana fermions in the Kitaev model. Our thermodynamic observations of the opening and closing of the bulk gap according to the magnetic-field direction fully correspond with changes in the edge transport. Moreover, the behaviour at higher magnetic fields where the quantum thermal Hall effect vanishes is consistent with a nematic quantum spin liquid state with two-fold rotational symmetry.α-RuCl has a quantum magnetic phase that may be a spin liquid hosting Majorana fermion excitations. Heat capacity measurements show an anisotropic dependence on magnetic-field direction, consistent with predictions for the putative spin liquid.
The quantum Hall effect in two-dimensional electron gases involves the flow of topologically protected dissipationless charge currents along the edges of a sample. Integer or fractional electrical ...conductance is associated with edge currents of electrons or quasiparticles with fractional charges, respectively. It has been predicted that quantum Hall phenomena can also be created by edge currents with a fundamentally different origin: the fractionalization of quantum spins. However, such quantization has not yet been observed. Here we report the observation of this type of quantization of the Hall effect in an insulating two-dimensional quantum magnet
, α-RuCl
, with a dominant Kitaev interaction (a bond-dependent Ising-type interaction) on a two-dimensional honeycomb lattice
. We find that the application of a magnetic field parallel to the sample destroys long-range magnetic order, leading to a field-induced quantum-spin-liquid ground state with substantial entanglement of local spins
. In the low-temperature regime of this state, the two-dimensional thermal Hall conductance reaches a quantum plateau as a function of the applied magnetic field and has a quantization value that is exactly half of the two-dimensional thermal Hall conductance of the integer quantum Hall effect. This half-integer quantization of the thermal Hall conductance in a bulk material is a signature of topologically protected chiral edge currents of charge-neutral Majorana fermions (particles that are their own antiparticles), which have half the degrees of freedom of conventional fermions
. These results demonstrate the fractionalization of spins into itinerant Majorana fermions and Z
fluxes, which is predicted to occur in Kitaev quantum spin liquids
. Above a critical magnetic field, the quantization disappears and the thermal Hall conductance goes to zero rapidly, indicating a topological quantum phase transition between the states with and without chiral Majorana edge modes. Emergent Majorana fermions in a quantum magnet are expected to have a great impact on strongly correlated quantum matter, opening up the possibility of topological quantum computing at relatively high temperatures.
To determine the effects of continuous aerobic exercise training (CON) vs interval aerobic exercise training (INT) on glycemic control and endothelium‐dependent vasodilatation, 43 participants with ...type 2 diabetes were randomly allocated to the sedentary, CON, and INT groups. The CON and INT exercise training programs were designed to yield the same energy expenditure/exercise session and included walking on treadmill for 30 and 40 min/day, 3 times/week for 12 weeks. Body fatness and heart rate at rest decreased and leg muscle strength increased (all P < 0.05) in both the CON and INT groups. Fasting blood glucose levels decreased (P < 0.05) in both exercise groups but glycosylated hemoglobin levels decreased (P < 0.05) only in the INT group. Maximal aerobic capacity, flow‐mediated dilation, and cutaneous reactive hyperemia increased significantly in both exercise groups; however, the magnitude of improvements was greater in the INT group. Only the INT group experienced reductions in erythrocyte malondialdehyde and serum von Willebrand factor and increases in plasma glutathione peroxidase and nitric oxide (all P < 0.05). We concluded that both continuous and interval training were effective in improving glycemic control, aerobic fitness, and endothelium‐dependent vasodilation, but the interval training program appears to confer greater improvements than the continuous training program.
We examined the excitations of planetesimals caused by the resonances of a giant planet in a protoplanetary gas disk. The highly excited planetesimals generate bow shocks, the mechanism of which ...results in chondrule formation, crystallization of silicate dust, and evaporation of icy planetesimals. The planetesimals beyond 2:1 resonance migrate owing to the gas drag and obtain the maximum eccentricity around 3:1 resonance, which is located at approximately half the planetary distance. The eccentricity depends on the parameters of the planetesimals and the Jovian planet, such as size and location, and the gas density of the disk. The maximum relative velocity of a 100 km sized planetesimal with respect to the gas disk reaches up to ∼12 km s−1 in the case of Jupiter owing to secular resonance, which occurs because of the disk's gravity. We find that if a Jovian-mass planet is located within 10 au, the planetesimals larger than 100 km gain sufficient velocity to cause the melting of chondrule precursors and crystallization of the silicate. The maximum velocity is higher for large planetesimals and eccentric planets. Planetesimals are trapped temporarily in the resonances and continue to have high speed over 1 Myr after the formation of a Jovian planet. This duration fits into the timescale of chondrule formation suggested by the isotopic data. The evaporation of icy planetesimals occurs when a Jovian planet is located within 15 au. This mechanism can be a new indicator of planet formation in exosystems if some molecules ejected from icy planetesimals are detected.
The thalamus is the hub through which neural signals are transmitted from the basal ganglia and cerebellum to the neocortex. However, thalamocortical axonal activity during motor learning remains ...largely undescribed. We conducted two-photon calcium imaging of thalamocortical axonal activity in the motor cortex of mice learning a self-initiated lever-pull task. Layer 1 (L1) axons came to exhibit activity at lever-pull initiation and termination, while layer 3 (L3) axons did so at lever-pull initiation. L1 population activity had a sequence structure related to both lever-pull duration and reproducibility. Stimulation of the substantia nigra pars reticulata activated more L1 than L3 axons, whereas deep cerebellar nuclei (DCN) stimulation did the opposite. Lesions to either the dorsal striatum or the DCN impaired motor learning and disrupted temporal dynamics in both layers. Thus, layer-specific thalamocortical signals evolve with the progression of learning, which requires both the basal ganglia and cerebellar activities.
•Thalamocortical (TC) axon activity reflects motor representations during learning•TC axon activation induces movement and their inactivation impairs motor learning•TC axons in layers 1 and 3 diverge to show distinct movement-locked activities•Evolving TC axon activity in each layer requires the basal ganglia and cerebellum
Tanaka et al. show that patterns of layer-specific thalamocortical axon activity involving signals from the basal ganglia and cerebellum evolve during learning of a self-initiated motor task. The progression of this activity is impaired by lesions to either region.
Programmable matter by folding Hawkes, E.; An, B.; Benbernou, N. M. ...
Proceedings of the National Academy of Sciences - PNAS,
07/2010, Letnik:
107, Številka:
28
Journal Article
Recenzirano
Odprti dostop
Programmable matter is a material whose properties can be programmed to achieve specific shapes or stiffnesses upon command. This concept requires constituent elements to interact and rear-range ...intelligently in order to meet the goal. This paper considers achieving programmable sheets that can form themselves in different shapes autonomously by folding. Past approaches to creating transforming machines have been limited by the small feature sizes, the large number of components, and the associated complexity of communication among the units. We seek to mitigate these difficulties through the unique concept of self-folding origami with universal crease patterns. This approach exploits a single sheet composed of interconnected triangular sections. The sheet is able to fold into a set of predetermined shapes using embedded actuation. To implement this self-folding origami concept, we have developed a scalable end-to-end planning and fabrication process. Given a set of desired objects, the system computes an optimized design for a single sheet and multiple controllers to achieve each of the desired objects. The material, called programmable matter by folding, is an example of a system capable of achieving multiple shapes for multiple functions.
Abstract
We study scattered-light properties of protoplanetary discs at near-infrared wavelengths for various dust size and structure by performing radiative transfer simulations. We show that ...different dust structures might be probed by measuring disc polarization fraction as long as the dust radius is larger than the wavelength. When the radius is larger than observing wavelength, disc scattered light will be highly polarized for highly porous dust aggregates, whereas more compact dust structure tends to show low polarization fraction. Next, roles of monomer radius and fractal dimension for scattered-light colours are studied. We find that, outside the Rayleigh regime, as fractal dimension or monomer radius increases, colours of the effective albedo at near-infrared wavelengths vary from blue to red. Our results imply that discs showing grey or slightly blue colours and high polarization fraction in near-infrared wavelengths might be explained by the presence of large porous aggregates containing sub-micron-sized monomers.
•Fly ash containing large amounts of unburned carbon was sintered by applying separated electrical field of microwaves.•The fly ash exhibited anomalous heating behavior at 450 °C.•At 900–1200 °C, the ...amount of chlorine and carbon in the fly ash decreased as the temperature increased.•The chlorine concentration in the sample decreased as a result of the heating, leading to the addition of carbon.
Recently, the application of microwave heating to high-temperature processing has received increased attention. In this study, fly ash containing large amounts of unburnt carbon and sodium chloride was sintered by applying microwaves as part of an investigation of the application of microwave heating to high-temperature processes. Microwave fields were separated by cavities, and pure electrical fields were employed as a heat source. The heating rate and maximum temperature increased with the microwave power, while the fly ash exhibited anomalous heating behavior at 450 °C. In this case, unburnt carbon in the fly ash plays an important role in the microwave absorption properties. At 900–1200 °C, no change was observed in the hardness or composition even when the heating duration was increased. In addition, it was found that the amount of chlorine and carbon in the fly ash decreased as the temperature increased. The chlorine concentration in the sample decreased due to the addition of carbon.
Abstract
A key feature of quantum spin liquids is the predicted formation of fractionalized excitations. They are expected to produce changes in the physical response, providing a way to observe the ...quantum spin liquid state
1
. In the honeycomb magnet α-RuCl
3
, a quantum spin liquid has been proposed to explain the behaviour observed on applying an in-plane magnetic field
H
||
. Previous work reported that the thermal Hall conductivity took on a half-integer quantized value and suggested this as a signature of a fractionalized Majorana edge mode predicted to exist in Kitaev quantum spin liquids
2
. However, the temperature and magnetic-field range of the half-quantized signal
2–4
and its association with Majorana edge modes are still under debate
5,6
. Here we present a comprehensive study of the thermal Hall conductivity in α-RuCl
3
showing that approximately half-integer quantization exists in an extended region of the phase diagram, particularly across a plateau-like parameter regime for
H
||
exceeding 10 T and temperature below 6.5 K. At lower fields, the thermal Hall conductivity exhibits correlations with complex anomalies in the longitudinal thermal conductivity and magnetization, and is suppressed by cooling to low temperatures. Our results can be explained by the existence of a topological state in magnetic fields above 10 T.
Background
Peritoneal metastasis is a frequent cause of death in patients with gastric cancer. The aim of this study was to identify molecules responsible for mediating peritoneal metastasis of ...gastric cancer.
Methods
Transcriptome and bioinformatics analyses were conducted to identify molecules associated with peritoneal metastasis. The therapeutic effects of intraperitoneally administered small interfering (si) RNA were evaluated using mouse xenograft models. Expression of mRNA and protein was determined in gastric tissues from patients with gastric cancer.
Results
Synaptotagmin XIII (SYT13) was expressed at significantly higher levels in patients with peritoneal recurrence, but not in those with hepatic or distant lymph node recurrence. Inhibition of SYT13 expression in a gastric cancer cell line transfected with SYT13‐specific siRNA (siSYT13) was associated with decreased invasion and migration ability of the cells, but not with proliferation and apoptosis. Intraperitoneal administration of siSYT13 significantly inhibited the growth of peritoneal nodules and prolonged survival in mice. In an analysis of 200 patients with gastric cancer, SYT13 expression in primary gastric cancer tissues was significantly greater in patients with peritoneal recurrence or metastasis. A high level of SYT13 expression in primary gastric cancer tissues was an independent risk factor for peritoneal recurrence.
Conclusion
SYT13 expression in gastric cancer is associated with perioneal metatases and is a potential target for treatment.
Potential target for therapy
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