Two modes of motions for a single disk on the vibration stage.

The motion of a single granular particle is important for understanding their collective motions on vibration stage, but it remains poorly studied for simple shaped particles, such as a disk. Here, we systematically measure the motions of a single disk with different vibration amplitudesAat a fixed vibration frequencyfor a fixed accelerationa. The distributions, time-correlations, and power spectra of displacements per step, mean squared displacements and couplings for translational and rotational motions are measured. These analyses reveal that the motions randomly switch between active and inactive modes. Bothaandfare important to particle's motions and the fraction of active mode. The translational and rotational kinetic energy deviates from Boltzmann distribution and violates the equipartition theorem in each mode. We find three types of motion: rolling, lying flat, and fluttering, which give rise to active and inactive modes. The translational and rotational mean squared displacements, autocorrelations, and power spectra at differentacollapse in active modes, because the disk rolls along its rim with a fixed inclination angle though our system is under vibration and confinement. The nonzero cross-correlations between particle's translational and rotational motions indicate that only translational motions are insufficient for understanding dense particle systems.

Experimental investigation of active noise on a rotor in an active granular bath.

In an active bath, besides thermal noise, immersed passive objects also persistently experience collisions from active particles, which are often coarse-grained into a colored active noise with an assumed exponential time correlation. The exponentially correlated active noise extremely simplifies the theoretical description of immersed passive objects but so far lacks direct experimental verification. Here, we experimentally investigate the active noise subjected by a passive rotor confined in an active granular bath. On the basis of Langevin dynamics, we extract the characteristic of the active noise by analyzing the power spectrum of the rotor trajectory. Our experimental results find that the active noise experienced by the granular rotor does show an exponential time correlation to a good extent, even though due to the small experimental system and low collision frequency, the profile of the active noise in our system is non-Gaussian. Our findings give direct experimental evidence, which supports the widely-used active Ornstein-Uhlenbeck particle model in our dry active system.

A unified constitutive model for pressure sensitive shear flow transitions in moderate dense granular materials.

Granular shear flows exhibit complex transitional regimes that are dramatically affected by the pressure level and shear stress state. New advances in granular shear tests at low pressure have enlightened the understanding of the two granular shear flow transitions: between quasi-static and moderate shear flows, and between steady-state and transient shear flows. However, a unified constitutive model to describe these two transitions is yet to develop. In this work, a simplified and unified model is proposed based on innovative triaxial shear flow tests, using two dimensionless physical variables. Model results validated against experimental data suggest that the shear flow transition between a quasi-static to a moderate Isotach type flow state is highly pressure-dependent. At extremely low pressure, the granular viscosity becomes the primary mechanism, suppressing the quasi-static mechanism even under "quasi-static" shear rates. In transient to steady state granular flow transitions, a mobilized shear stress ratio or mobilized friction coefficient between zero and the critical state ratio for consolidated granular packings is taken into consideration. This is coupled with the mechanism of granular viscosity. These findings have not been discussed before and are of great relevance to granular mechanics as well as space and earthquake engineering.

Dynamics of a vibration-driven single disk.

Granular particles exhibit rich collective behaviors on vibration beds, but the motion of an isolated particle is not well understood even for uniform particles with a simple shape such as disks or spheres. Here we measured the motion of a single disk confined to a quasi-two-dimensional horizontal box on a vertically vibrating stage. The translational displacements obey compressed exponential distributions whose exponent [Formula: see text] increases with the frequency, while the rotational displacements exhibit unimodal distributions at low frequencies and bimodal distributions at high frequencies. During short time intervals, the translational displacements are subdiffusive and negatively correlated, while the rotational displacements are superdiffusive and positively correlated. After prolonged periods, the rotational displacements become diffusive and their correlations decay to zero. Both the rotational and the translational displacements exhibit white noise at low frequencies, and blue noise for translational motions and Brownian noise for rotational motions at high frequencies. The translational kinetic energy obeys Boltzmann distribution while the rotational kinetic energy deviates from it. Most energy is distributed in translational motions at low frequencies and in rotational motions at high frequencies, which violates the equipartition theorem. Translational and rotational motions are not correlated. These experimental results show that the random diffusion of such driven particles is distinct from thermal motion in both the translational and rotational degrees of freedom, which poses new challenges to theory. The results cast new light on the motion of individual particles and the collective motion of driven granular particles.

Flow-induced surface crystallization of granular particles in cylindrical confinement.

An interesting phenomenon that a layer of crystallized shell formed at the container wall during an orifice flow in a cylinder is observed experimentally and is investigated in DEM simulation. Different from shear or vibration driven granular crystallization, our simulation shows during the flow the shell layer is formed spontaneously from stagnant zone at the base and grows at a constant rate to the top with no external drive. Roughness of the shell surface is defined as a standard deviation of the surface height and its development is found to disobey existed growth models. The growth rate of the shell is found linearly proportional to the flow rate. This shell is static and served as a rough wall in an orifice flow with frictionless sidewall, which changes the flow profiles and its stress properties, and in turn guarantees a constant flow rate.

Microscopic structure and dynamics study of granular segregation mechanism by cyclic shear.

Granular mixtures with size difference can segregate upon shaking or shear. However, the quantitative study of this process remains difficult because it can be influenced by many mechanisms. Conflicting results on similar experimental systems are frequently obtained when the experimental conditions are not well controlled, which is mainly due to the fact that many mechanisms can be at work simultaneously. Moreover, it is often that macroscopic or empirical measures, which lack microscopic physical bases, are used to explain the experimental findings and therefore cannot provide an accurate and complete depiction of the overall process. Here, we carry out a detailed and systematic microscopic structure and dynamics study of a cyclically sheared granular system with rigorously controlled experimental conditions. We find that both convection and arching effect play important roles in the segregation process in our system, and we can quantitatively identify their respective contributions.

Brassinosteroids synthesised by CYP85A/A1 but not CYP85A2 function via a BRI1-like receptor but not via BRI1 in Picea abies.

Brassinosteroids (BRs) are essential plant hormones. In angiosperms, brassinolide and castasterone, the first and second most active BRs, respectively, are synthesised by CYP85A2 and CYP85A/A1, respectively. BRs in angiosperms function through an essential receptor, BR Insensitive 1 (BRI1). In addition, some angiosperms also have non-essential BRI1-like 1/3 (BRL1/3). In conifers, BRs promote seed germination under drought stress; however, how BRs function in gymnosperms is unknown. In this study, we performed functional complementation of BR biosynthesis and receptor genes from Picea abies with respective Arabidopsis mutants. We found that P. abies possessed functional PaCYP85A and PaBRL1 but not PaCYP85A2 or PaBRI1, and this results in weak BR signaling, and both PaCYP85A and PaBRL1 were abundantly expressed. However, neither BR treatment of P. abies seedlings nor expression of PaBRL1 in the Arabidopsis Atbri1 mutant promoted plant height, despite the fact that BR-responsive genes were activated. Importantly, chimeric AtBRI1 replaced with the BR-binding domain of PaBRL1 complemented the Atbri1 phenotypes. Furthermore, PaBRL1 had less kinase activity than BRI1 in vitro. Overall, P. abies had weak but still active BR signaling, explaining aspects of its slow growth and high stress tolerance. Our study sheds light on the functional and evolutionary significance of distinct BR signaling that is independent of BRI1 and brassinolide.

Clinical research on stereotactic radiosurgery combined with epithermal growth factor tyrosine kinase inhibitors in the treatment of brain metastasis of non-small cell lung cancer.

PURPOSE: To compare the clinical efficacy and safety of stereotactic radiosurgery (SRS) combined with epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) versus whole-brain radiation therapy (WBRT) combined with EGFR-TKIs in the treatment of brain metastasis of non-small cell Lung cancer (NSCLC). METHODS: The clinical data of patients with brain metastatic NSCLC who had EGFR-sensitive mutation and followed between January 2014 and January 2016 was retrospectively analyzed. Patients were divided into two groups according to their treatment types. Fifty seven patients were treated with SRS combined with EGFR-TKIs, while another 57 patients were treated with WBRT combined with EGFR-TKIs. The clinical efficacy, intracranial progression-free survival (iPFS), systemic progression-free survival (sPFS), overall survival (OS,) and adverse reactions were compared between the two groups. Computed tomography (CT) or magnetic resonance imaging (MRI) were used for imaging evaluation in both groups and all patients underwent symptomatic treatment such as dehydration or hormone therapy according to the patient's condition. The efficacy was evaluated using the Response Evaluation Criteria in Solid Tumors (RECIST) (Version 1.1) and adverse reactions were assessed based on the criteria for toxic reaction of anti-cancer drugs of WHO. RESULTS: There were no statistically significant differences in general conditions between the two groups of patients. The median iPFS and median sPFS were similar between the two groups (12.2 months vs. 11.5 months and 10.7 months vs. 9.8 months respectively, p>0.05). The median OS of patients treated with SRS + EGFR-TKIs was significantly longer than in those treated with WBRT + EGFR-TKIs (25.1 months vs. 22.0 months, respectively, p=0.042). No statistically significant differences were found in the objective response rate (ORR), disease control rate (DCR), the incidence rates of cytopenia, gastrointestinal reaction and liver dysfunction between the two groups (p>0.05). There were 8 cases with radiotherapy-associated grade 3 or higher brain damage in SRS + EGFR-TKIs group compared to 19 cases in those treated with WBRT + EGFR-TKIs, suggesting that the incidence rate of radiation-induced brain injuries in SRS + EGFR-TKIs group was remarkably lower than those in WBRT + EGFR-TKIs group (p=0.026). CONCLUSION: The clinical efficacy of SRS combined with EGFR-TKIs is comparable to that of WBRT combined with EGFR-TKIs in the treatment of NSCLC patients with ≤3 brain metastases and EGFR-sensitive mutation and the OS of patients is longer, with lower toxic side effect and higher safety, hence SRS combined with EGFR-TKIs should be used as the preferred therapeutic regimen.

Coupled Leidenfrost states as a monodisperse granular clock.

Using an event-driven molecular dynamics simulation, we show that simple monodisperse granular beads confined in coupled columns may oscillate as a different type of granular clock. To trigger this oscillation, the system needs to be driven against gravity into a density-inverted state, with a high-density clustering phase supported from below by a gaslike low-density phase (Leidenfrost effect) in each column. Our analysis reveals that the density-inverted structure and the relaxation dynamics between the phases can amplify any small asymmetry between the columns, and lead to a giant oscillation. The oscillation occurs only for an intermediate range of the coupling strength, and the corresponding phase diagram can be universally described with a characteristic height of the density-inverted structure. A minimal two-phase model is proposed and a linear stability analysis shows that the triggering mechanism of the oscillation can be explained as a switchable two-parameter Andronov-Hopf bifurcation. Numerical solutions of the model also reproduce similar oscillatory dynamics to the simulation results.

Phase transition and flow-rate behavior of merging granular flows.

Merging of granular flows is ubiquitous in industrial, mining, and geological processes. However, its behavior remains poorly understood. This paper studies the phase transition and flow-rate behavior of two granular flows merging into one channel. When the main channel is wider than the side channel, the system shows a remarkable two-sudden-drops phenomenon in the outflow rate when gradually increasing the main inflow. When gradually decreasing the main inflow, the system shows obvious hysteresis phenomenon. We study the flow-rate-drop phenomenon by measuring the area fraction and the mean velocity at the merging point. The phase diagram of the system is also presented to understand the occurrence of the phenomenon. We find that the dilute-to-dense transition occurs when the area fraction of particles at the joint point exceeds a critical value ϕ(c)=0.65±0.03.

Construction of microsatellite-based linkage map and mapping of nectarilessness and hairiness genes in Gossypium tomentosum.

Gossypium tomentosum, a wild tetraploid cotton species with AD genomes, possesses genes conferring strong fibers and high heat tolerance. To effectively transfer these genes into Gossypium hirsutum, an entire microsatellite (simple sequence repeat, SSR)-based genetic map was constructed using the interspecific cross of G. hirsutum x G. tomentosum (HT). We detected 1800 loci from 1347 pairs of polymorphic primers. Of these, 1204 loci were grouped into 35 linkage groups at LOD ≥ 4. The map covers 3320.8 cM, with a mean density of 2.76 cM per locus. We detected 420 common loci (186 in the At subgenome and 234 in Dt) between the HT map and the map of TM-1 (G. hirsutum) and Hai 7124 (G. barbadense; HB map). The linkage groups were assigned chromosome numbers based on location of common loci and the HB map as reference. A comparison of common markers revealed that no significant chromosomal rearrangement exist between G. tomentosum and G. barbadense. Interestingly, however, we detected numerous (33.7%) segregation loci deviating from 3:1 ratio (P < 0.05) in HT, mostly clustering on eight chromosomes in the Dt subgenome, with some on three chromosomes in At. Two morphological traits, leaf hairiness and leaf nectarilessness were mapped on chromosomes 6 (A6) and 26 (D12), respectively. The SSR-based map constructed in this study will be useful for further genetic studies on cotton breeding, including mapping loci controlling quantitative traits associated with fiber quality, stress tolerance and developing chromosome segment specific introgression lines from G. tomentosum into G. hirsutum using marker-assisted selection.

Hydrodynamics of granular gases with a two-peak distribution.

Vibrating walls, frequently employed to maintain the temperature (i.e., average velocity) in a granular gas, modify the system strongly, rendering it dissimilar to a molecular one in various aspects. As evidenced by microgravity experiments employing a quasi-two-dimensional (quasi-2D) rectangular box and by 2D simulations, the one-peak velocity distribution is split into two, rendering the stress both nonuniform and anisotropic-without a shear flow and in the absence of gravitation. To account for this, granular hydrodynamics (as first proposed by Haff and later derived employing the kinetic theory) is generalized by introducing two additional variables, with one accounting for the distance between the two peaks and a second for the difference between the average velocities along different directions. The hydrodynamic theory thus generalized relates the velocity distribution to the stress, yielding results that agree with experiments and simulations.

Gluing bifurcation and noise-induced hopping in the oscillatory phenomena of compartmentalized bidisperse granular gases.

Oscillatory phenomena of compartmentalized bidisperse granular gases are studied through experiments, molecular dynamics simulations, and a flux model [Mikkelsen et al., Phys. Rev. E 70, 061307 (2004)]. The degenerate oscillatory state (d-OSC), which has been predicted in our previous simulations [Liu et al., Phys. Rev. E 79, 052301 (2009)], is experimentally observed and well described by the flux model. From the d-OSC state, the system takes a transition to a complete oscillatory state (OSC) through a homoclinic gluing bifurcation. Around the bifurcation point, noise-induced periodic irregularity is observed, and it can be perfectly reproduced by simulations and the flux model with additional random flux terms. The numerical results show a low-frequency divergence characteristic of the irregular oscillation, which is clearly caused by noise-induced hopping between OSC and d-OSC states.

Elastic waves in the presence of a granular shear band formed by direct shear.

The propagation of elastic waves in a box under direct shear, filled with glass beads and being sheared at constant rates, is studied experimentally and theoretically. The respective velocities are shown to be essentially unchanged from that in a static granular system under the same pressure and shear stress but without a shear band. Influence of shear band on sound behaviors are also briefly discussed.

Traveling shock front in quasi-two-dimensional granular flows.

While the density profile of a granular shock front can be obtained by the conventional treatment of supersonic fluids, its temperature profile is very different from that in ordinary shocks. We study the density and temperature profiles of a traveling granular shock generated by piling up metal spheres in a closed bottom quasi-two-dimensional channel. We successfully account for the temperature profile in the granular shock using a simple kinetic theory in terms of energy transfer from the mean flow direction to the transverse direction. Contrary to ordinary fluids and previous granular shock experiments, the granular shock width is found to increase with the inflow rate.

Depth dependence of vertical plunging force in granular medium.

Depth dependence of vertical plunging force in granular medium is studied experimentally by measuring the slow-pushing force of different size and shape objects intruding vertically into a granular bed. It is found that all of the force curves of fully immersed intruders have concave-to-convex transition. The depth dependence of the force turns from supralinear to sublinear. By studying the properties of the inflection point of the concave-convex transition, we find that the plunging force at inflection point is proportional to intruder's volume, and the inflection point occurs when the intruder is fully buried to a level around twice its diameter. Testing by plunging a long cylinder, which is always partially immersed, we find no inflection point in this case, which verifies that the inflection of the plunging force is related to the filled-in loose granules on top of the intruder. The slowdown of the increasing rate of the force is, therefore, not a result of sidewall support proposed by previous researchers.

Oscillatory phenomena of compartmentalized bidisperse granular gases.

Compartmentalized bidisperse granular gases are numerically studied. Molecular-dynamics simulations studying granular clock phenomenon in three dimensions are presented, which complement previously reported two-dimensional simulation results. A flux model for binary mixtures is found to give qualitative descriptions for the oscillations, with no undetermined parameters or functions. Two different states, a degenerate oscillatory state and a state with large particles segregated and small particles homogeneously distributed, are found in our simulations. These features reveal a much more complex phase diagram for the system, which challenges the existing theoretical models.

Temperature oscillations in a compartmentalized bidisperse granular gas.

A granular clock is observed in a vertically vibrated compartmentalized granular gas composed of two types of grains with the same size. The dynamics of the clock is studied in terms of an unstable evaporation or condensation model for the granular gas. In this model, the temperatures of the two types of grains are considered to be different, and they are functions of the composition of the gas. Oscillations in the system are driven by the asymmetric collisions properties between the two types of grains. Both our experiments and model show that the transition of the system from a homogeneous state to an oscillatory state is via a Hopf bifurcation.

van der Waals-like phase-separation instability of a driven granular gas in three dimensions.

We show that the van der Waals-like phase-separation instability of a driven granular gas at zero gravity, previously investigated in two-dimensional settings, persists in three dimensions. We consider a monodisperse granular gas driven by a thermal wall of a three-dimensional rectangular container at zero gravity. The basic steady state of this system, as described by granular hydrodynamic equations, involves a denser and colder layer of granulate located at the wall opposite to the driving wall. When the inelastic energy loss is sufficiently high, the driven granular gas exhibits, in some range of average densities, negative compressibility in the directions parallel to the driving wall. When the lateral dimensions of the container are sufficiently large, the negative compressibility causes spontaneous symmetry breaking of the basic steady state and a phase separation instability. Event-driven molecular dynamics simulations confirm and complement our theoretical predictions.