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Sample records for jam da uhhab

  1. Network analyzer for nonstatic jamming

    NASA Astrophysics Data System (ADS)

    Cheng, Unjeng

    1989-06-01

    The survivability of a packet radio network (PRNET) under jamming attack is an important issue. The goal of this research is to develop the analytical methods for understanding as well as predicting the behavior of PRNETs under various jamming conditions. Jamming can be stationary or nonstationary. For the stationary jamming, the jamming strategy is fixed, but it can be described stochastically. For instance, we may say that a node is jammed with probability 0.5 in each slot. Therefore, although the jamming strategy is fixed, the actual jamming pattern changes from slot to slot. A subclass of the stationary jamming is the static jamming, where the jamming pattern is fixed. For the nonstationary jamming, the jamming strategy changes from time to time. A subclass of the nonstationary jamming is the nonstatic jamming, where a fixed jamming pattern is applied in each block of time, but the jamming pattern changes from block to block. We analyzed the behavior of PRNETs under static jamming attack in our previous report. In this report, we introduce a method of analyzing the PRNET behavior under the nonstatic jamming attack. The analytical results for the static jamming attack scenario were presented in our previous report for both the transmitter-based code and the receiver-based code networks. The numerical results were given only for the receiver-based code case. Simulations were performed to verify the accuracy of the analytical approach.

  2. Jamming in Vertical Channels

    NASA Astrophysics Data System (ADS)

    Baxter, G. William; Steel, Fiona

    2011-03-01

    We study jamming of low aspect-ratio cylindrical Delrin grains in a vertical channel. Grain heights are less than their diameter so the grains resemble antacid tablets, coins, or poker chips. These grains are allowed to fall through a vertical channel with a square cross section where the channel width is greater than the diameter of a grain and constant throughout the length of the channel with no obstructions or constrictions. Grains are sometimes observed to form jams, stable structures supported by the channel walls with no support beneath them. The probability of jam occurrence and the strength or robustness of a jam is effected by grain and channel sizes. We will present experimental measurements of the jamming probability and jam strength in this system and discuss the relationship of these results to other experiments and theories. Supported by an Undergraduate Research Grant from Penn State Erie, The Behrend College.

  3. Jamming in Vertical Channels

    NASA Astrophysics Data System (ADS)

    Baxter, G. William; McCausland, Jeffrey; Steel, Fiona

    2010-03-01

    We experimentally study jamming of cylindrical grains in a vertical channel. The grains have a low aspect-ratio (height/diameter < 1) so their shape is like antacid tablets or poker chips. They are allowed to fall through a vertical channel with a square cross section. The channel width is greater than the diameter of a grain and constant throughout the length of the channel with no obstructions or constrictions. It is observed that grains sometimes jam in this apparatus. In a jam, grains form a stable structure from one side of the channel to the other with nothing beneath them. Jams may be strong enough to support additional grains above. The probability of a jam occurring is a function of the grain height and diameter. We will present experimental measurements of the jamming probability in this system and discuss the relationship of these results to other experiments and theories.

  4. Jamitons: Phantom Traffic Jams

    ERIC Educational Resources Information Center

    Kowszun, Jorj

    2013-01-01

    Traffic on motorways can slow down for no apparent reason. Sudden changes in speed by one or two drivers can create a chain reaction that causes a traffic jam for the vehicles that are following. This kind of phantom traffic jam is called a "jamiton" and the article discusses some of the ways in which traffic engineers produce…

  5. JAM-A is present in Mammalian Spermatozoa where it is Essential for Normal Motility

    PubMed Central

    Shao, Minghai; Ghosh, Ananya; Cooke, Vesselina G.; Naik, Ulhas P.; Martin-DeLeon, Patricia A.

    2008-01-01

    Junctional Adhesion Molecules (JAMs) that are expressed in endothelial and epithelial cells and function in tight junction assembly, also perform important roles in testis where the closely-related JAM-A, JAM-B, and JAM-C are found. Disruption of murine Jam-B and Jam-C has varying effects on sperm development and function, however deletion of Jam-A has not yet been studied. Here we show for the first time that in addition to expression in the Sertoli-Sertoli tight junctions in the seminiferous tubules, the ∼32 kDa murine JAM-A is present in elongated spermatids and in the plasma membrane of the head and flagellum of sperm. Deletion of Jam-A, using the gene trap technology, results in flagellar defects at the ultrastructural level. In Jam-A-deficient mice, which have reduced litter size, both progressive and hyperactived motility are significantly affected (P<0.0001) before and, more severely, after capacitation. The findings show that JAM-A is involved in sperm tail formation and is essential for normal motility, which may occur via its signal transduction and protein phosphorylation properties. Detection of JAM-A in human sperm protein indicates that its role may be conserved in sperm motility and that JAM-A may be a candidate gene for the analysis of idiopathic sperm motility defects resulting in male subfertility in the human population. PMID:18022613

  6. Fragile granular jamming

    SciTech Connect

    Rivera, Michael K; Ecke, Robert E; Bandi, Mahesh M; Kzakala, Florent

    2009-01-01

    We demonstrate experimentally that the route to a jammed state for a set of bi-dispersed frictional disks, subjected to uni-axial compression from a random initial unjammed state, consists of a consolidation state, a fragile jammed state, and finally a rigid jammed state. In the consolidation regime, the pressure on the sides increases very slowly with the packing fraction {phi} and there are no detectable stress chains. In the fragile jammed state, stress chains are visible, the pressure increases exponentially with {phi}, and the fraction of moving disks drops exponentially. Eventually, a final regime where particle displacements are below our resolution and the pressure varies approximately linearly with {phi} is reached. We argue that this scenario is generic for ather mal frictional compressed particles.

  7. Shocks near Jamming

    NASA Astrophysics Data System (ADS)

    Gómez, Leopoldo R.; Turner, Ari M.; van Hecke, Martin; Vitelli, Vincenzo

    2012-02-01

    Nonlinear sound is an extreme phenomenon typically observed in solids after violent explosions. But granular media are different. Right when they jam, these fragile and disordered solids exhibit a vanishing rigidity and sound speed, so that even tiny mechanical perturbations form supersonic shocks. Here, we perform simulations in which two-dimensional jammed granular packings are dynamically compressed and demonstrate that the elementary excitations are strongly nonlinear shocks, rather than ordinary phonons. We capture the full dependence of the shock speed on pressure and impact intensity by a surprisingly simple analytical model.

  8. Myelin Avoids the JAM.

    PubMed

    Follis, Rose M; Carter, Bruce D

    2016-08-17

    In this issue of Neuron, Redmond et al. (2016) identify junction adhesion molecule 2 (JAM2) as an inhibitor of somatodendritic myelination in spinal cord neurons, thereby elucidating how myelin forms on axons but avoids dendrites and cell bodies. PMID:27537479

  9. The Classroom Traffic Jam

    ERIC Educational Resources Information Center

    Edwards, Arthur W.

    1977-01-01

    The importance of energy conservation is developed in this simulation. Children draw an automobile and then are asked to drive it through the classroom roadways. When a traffic jam results, students offer ways to eliminate it. The importance of mass transportation and car pools is stressed by the teacher. (MA)

  10. Jamming in hierarchical networks

    NASA Astrophysics Data System (ADS)

    Cheng, Xiang; Boettcher, Stefan

    2015-11-01

    We study the Biroli-Mezard model for lattice glasses on a number of hierarchical networks. These networks combine certain lattice-like features with a recursive structure that makes them suitable for exact renormalization group studies and provide an alternative to the mean-field approach. In our numerical simulations here, we first explore their equilibrium properties with the Wang-Landau algorithm. Then, we investigate their dynamical behavior using a grand-canonical annealing algorithm. We find that the dynamics readily falls out of equilibrium and jams in many of our networks with certain constraints on the neighborhood occupation imposed by the Biroli-Mezard model, even in cases where exact results indicate that no ideal glass transition exists. But while we find that time-scales for the jams diverge, our simulations cannot ascertain such a divergence for a packing fraction distinctly above random close packing. In cases where we allow hopping in our dynamical simulations, the jams on these networks generally disappear.

  11. Jam-resistant speech encoding

    NASA Astrophysics Data System (ADS)

    Poole, M. A.; Rifkin, R.

    1983-06-01

    This report describes techniques that provide increased jam resistance for digitized speech. Methods for increasing the jam resistance of pulse code modulated data are analyzed and evaluated in listener tests. Special emphasis is placed on new voice encoding approaches that take advantage of a spread spectrum system with a variable (or multiple)-data-rate/variable (or multiple)-AJ capability. Methods for matching a source to a channel in a jamming environment are investigated. Several techniques that provide about a 4 dB increase in jam resistance have been identified.

  12. Nonconvex optimization and jamming

    NASA Astrophysics Data System (ADS)

    Kallus, Yoav

    Recent work on the jamming transition of particles with short-range interactions has drawn connections with models based on minimization problems with linear inequality constraints and a concave objective. These properties reduce the continuous optimization problem to a discrete search among the corners of the feasible polytope. I will discuss results from simulations of models with and without quenched disorder, exhibiting critical power laws, scaling collapse, and protocol dependence. These models are also well-suited for study using tools of algebraic topology, which I will discuss briefly. Supported by an Omidyar Fellowship at the Santa Fe Institute.

  13. Shear jamming in granular materials

    NASA Astrophysics Data System (ADS)

    Zhang, Jie

    2013-11-01

    For frictionless particles with purely repulsive interactions, there is a critical packing fraction ϕJ below which no jammed states exist. Recent experiments have shown that applying shear to a stress-free initial state can generate states which are either fragile or shear jammed depending on the way the force-network is percolated (Bi et al. Nature 2011). The nature of the jamming transition however is obscured because the existence of friction between the system and the third dimension. A new apparatus at SJTU has been designed to completely eliminate this friction by letting the particles float on the surface of a shallow water layer, which allows a study of the more detailed nature of the shear-jammed states and the transition from an unjammed state to a shear-jammed state. In this study, we also use high-precision force sensors to monitor the dynamical changes near the jamming transition. We further combine numerical simulations with the experiments to diagnose the nature of this jamming transition and its possible dependence on certain particle properties. The work at SJTU is in collaboration with Ling Zhang and Jie Zheng. The numerical simulations are in collaboration with Maobin Hu at Univ. of Sci. & Tech. of China.

  14. Jamming vs Caging in Three Dimensional Jamming Percolation

    NASA Astrophysics Data System (ADS)

    Shokef, Yair; Segall, Nimrod; Teomy, Eial

    We study a three-dimensional kinetically-constrained lattice-gas model, in which the ability of a particle to move depends on the occupation of neighboring sites in an orientational manner. The kinetic rules are constructed such that chains of permanently-frozen particles reach an infinite length at the critical density of directed percolation. Thus at this critical density the system undergoes a jamming transition, above which there is a finite fraction of jammed particles. We demonstrate that the three-dimensional mesh-like structure of the one-dimensional jammed chains enables the free particles to propagate through the holes in this mesh. This diffusive motion is terminated at a second critical density above which all particles are caged. The largest and second largest clusters of dynamically-connected sites exhibit singularities at both densities. Thus our model assists in separating between the two distinct phenomena of jamming and caging.

  15. The simplest model of jamming

    NASA Astrophysics Data System (ADS)

    Franz, Silvio; Parisi, Giorgio

    2016-04-01

    We study a well known neural network model—the perceptron—as a simple statistical physics model of jamming of hard objects. We exhibit two regimes: (1) a convex optimization regime where jamming is hypostatic and non-critical; (2) a non-convex optimization regime where jamming is isostatic and critical. We characterize the critical jamming phase through exponents describing the distribution laws of forces and gaps. Surprisingly we find that these exponents coincide with the corresponding ones recently computed in high dimensional hard spheres. In addition, modifying the perceptron to a random linear programming problem, we show that isostaticity is not a sufficient condition for singular force and gap distributions. For that, fragmentation of the space of solutions (replica symmetry breaking) appears to be a crucial ingredient. We hypothesize universality for a large class of non-convex constrained satisfaction problems with continuous variables.

  16. Biophysics: Life in a jam

    NASA Astrophysics Data System (ADS)

    Gokhale, Shreyas; Gore, Jeff

    2016-08-01

    Jammed states in growing yeast populations share intriguing similarities with amorphous solids, despite being generated through self-replication. The impact this behaviour has on cell division highlights one way that physical forces regulate biological function.

  17. Protocol dependence of the jamming transition

    NASA Astrophysics Data System (ADS)

    Bertrand, Thibault; Behringer, Robert P.; Chakraborty, Bulbul; O'Hern, Corey S.; Shattuck, Mark D.

    2016-01-01

    We propose a theoretical framework for predicting the protocol dependence of the jamming transition for frictionless spherical particles that interact via repulsive contact forces. We study isostatic jammed disk packings obtained via two protocols: isotropic compression and simple shear. We show that for frictionless systems, all jammed packings can be obtained via either protocol. However, the probability to obtain a particular jammed packing depends on the packing-generation protocol. We predict the average shear strain required to jam initially unjammed isotropically compressed packings from the density of jammed packings, shape of their basins of attraction, and path traversed in configuration space. We compare our predictions to simulations of shear strain-induced jamming and find quantitative agreement. We also show that the packing fraction range, over which shear strain-induced jamming occurs, tends to zero in the large system limit for frictionless packings with overdamped dynamics.

  18. Traffic jam at adjustable tollgates controlled by line length

    NASA Astrophysics Data System (ADS)

    Nagatani, Takashi

    2016-01-01

    We present the stochastic model for the jam formation at the tollgates of which the number is adjusted by synchronizing with the jam's length. We study the jam formation and its fluctuation in front of the adjustable tollgates on a highway. Controlling the number of tollgates has an important effect on the jam formation. The jams are classified into three kinds: (a) localized jam, (b) synchronized jam, and (c) growing jam. The jamming transitions from the localized jam, through the synchronized jam, to the growing jam occur with increasing inflow probability. At an intermediate inflow, the jam fluctuates largely by synchronizing with the number of tollgates. When the inflow probability is higher than the sum of outflow probabilities at tollgates, the jam continues to grow and diverge with time. The dependence of the fluctuating jam on the inflow probability is clarified.

  19. Hidden geometry of traffic jamming.

    PubMed

    Andjelković, Miroslav; Gupte, Neelima; Tadić, Bosiljka

    2015-05-01

    We introduce an approach based on algebraic topological methods that allow an accurate characterization of jamming in dynamical systems with queues. As a prototype system, we analyze the traffic of information packets with navigation and queuing at nodes on a network substrate in distinct dynamical regimes. A temporal sequence of traffic density fluctuations is mapped onto a mathematical graph in which each vertex denotes one dynamical state of the system. The coupling complexity between these states is revealed by classifying agglomerates of high-dimensional cliques that are intermingled at different topological levels and quantified by a set of geometrical and entropy measures. The free-flow, jamming, and congested traffic regimes result in graphs of different structure, while the largest geometrical complexity and minimum entropy mark the edge of the jamming region. PMID:26066222

  20. Magnetorheological Shear Flow Near Jamming

    NASA Astrophysics Data System (ADS)

    Vågberg, Daniel; Tighe, Brian

    2015-03-01

    Flow in magnetorheological (MR) fluids and systems near jamming both display hallmarks of complex fluid rheology, including yield stresses and shear thinning viscosities. They are also tunable, which means that both phenomena can be used as a switching mechanism in ``smart'' fluids, i.e. fluids where properties can be tuned rapidly and reversibly by changing external parameters. We use numerical simulations to investigate the rheological properties of MR fluids close to the jamming transition as a function of the applied field and volume fraction. We are especially interested in the crossover region where both phenomena are needed to describe the observed dynamics. Funded by the Dutch Organization for Scientific Research (NWO).

  1. Ice jam flooding: a location prediction model

    NASA Astrophysics Data System (ADS)

    Collins, H. A.

    2009-12-01

    Flooding created by ice jamming is a climatically dependent natural hazard frequently affecting cold regions with disastrous results. Basic known physical characteristics which combine in the landscape to create an ice jam flood are modeled on the Cattaraugus Creek Watershed, located in Western New York State. Terrain analysis of topographic features, and the built environment features is conducted using Geographic Information Systems in order to predict the location of ice jam flooding events. The purpose of this modeling is to establish a broadly applicable Watershed scale model for predicting the probable locations of ice jam flooding.location of historic ice jam flooding events

  2. Shear jamming in granular materials

    NASA Astrophysics Data System (ADS)

    Zhang, Jie

    2013-03-01

    For frictionless particles with purely repulsive interactions, there is a critical packing fraction ϕJ below which no jammed states exist. Frictional granular particles in the regime of ϕ <ϕJ act differently under shear: early experiments by Zhang & Behringer at Duke University show jammed states can be created by the application of shear stress. Compared to the states above ϕJ, the shear-jammed states (SJS) are mechanically more fragile, but they can resist shear. Formation of these states requires the anisotropic contact network as a backbone and these new states must be incorporated into a more general jamming picture (Bi et al Nature 2011). If time permits, I will present some new results from recent experiments at SJTU aimed towards understanding the more detailed nature of SJS and the transition from unjammed states to SJS. This work is in collaboration with Bob Behringer at Duke University, Dapeng Bi (now at Syracuse) and Bulbul Chakraborty at Brandeis University. The work at SJTU is in collaboration with Ling Zhang and several undergrads in the physics department.

  3. Microscopic features of moving traffic jams

    NASA Astrophysics Data System (ADS)

    Kerner, Boris S.; Klenov, Sergey L.; Hiller, Andreas; Rehborn, Hubert

    2006-04-01

    Empirical and numerical microscopic features of moving traffic jams are presented. Based on a single vehicle data analysis, it is found that within wide moving jams, i.e., between the upstream and downstream jam fronts there is a complex microscopic spatiotemporal structure. This jam structure consists of alternations of regions in which traffic flow is interrupted and flow states of low speeds associated with “moving blanks” within the jam. Moving blanks within a wide moving jam resemble electron holes in the valence band of semiconductors: As the moving blanks that propagate upstream appear due to downstream vehicle motion within the jam, so appearance of electron holes moving with the electric field results from electron motion against the electric field in the valence band of semiconductors. Empirical features of moving blanks are found. Based on microscopic models in the context of the Kerner’s three-phase traffic theory, physical reasons for moving blanks emergence within wide moving jams are disclosed. Microscopic nonlinear effects of moving jam emergence, propagation, and dissolution as well as a diverse variety of hysteresis effects in freeway traffic associated with phase transitions and congested traffic propagation are numerically investigated. Microscopic structure of moving jam fronts is numerically studied and compared with empirical results.

  4. Array radars solve communication jams

    NASA Astrophysics Data System (ADS)

    Lewis, H. D.

    1982-04-01

    The possibilities of incorporating mobile radar units as slave stations in communications relay applications during times of disrupted communications is examined. The limitations on uses of search, tracking, and multifunction radars are examined, noting that employment of the mobile system entails some tracking by the master phased-arrays to keep the mobile units in focus. The tracking patterns and dwell times are outlined, and the possibility of 700-1000 dwell times of 1220 microsec duration/sec is mentioned as opening the opportunity for high quality data transmissions. Signal-to-noise ratios are formulated for jamming situations, with offsetting tactical features for the jamming including the directivity and gain of the master antenna, the master station's power aperture product, on-axis to off-axis gain ratio, and antenna positioning ability. A slave station must be equipped with a transponder for communications, which are best achieved with pseudo-random coded waveforms.

  5. Penrose Tilings as Jammed Solids

    NASA Astrophysics Data System (ADS)

    Stenull, Olaf; Lubensky, T. C.

    2014-10-01

    Penrose tilings form lattices, exhibiting fivefold symmetry and isotropic elasticity, with inhomogeneous coordination much like that of the force networks in jammed systems. Under periodic boundary conditions, their average coordination is exactly four. We study the elastic and vibrational properties of rational approximants to these lattices as a function of unit-cell size NS and find that they have of order √NS zero modes and states of self-stress and yet all their elastic moduli vanish. In their generic form, obtained by randomizing site positions, their elastic and vibrational properties are similar to those of particulate systems at jamming with a nonzero bulk modulus, vanishing shear modulus, and a flat density of states.

  6. Statistical Mechanics of Jammed Matter

    NASA Astrophysics Data System (ADS)

    Behringer, Bob

    2009-03-01

    Jammed systems consist of large numbers of macroscopic particles. As such, they are inherently statistical in nature. However, in general, key assumptions of ordinary statistical mechanics need not apply. For instance, energy does not flow in a meaningful way from a thermal bath to such systems. And energy need not be conserved. However, experiments and simulations have shown that there are well defined distributions for such important properties as forces, contact numbers, etc. And new theoretical constructions have been proposed, starting with Edwards et al. The present symposium highlights recent developments for the statistics of jammed matter. This talk reviews the overall field, and highlights recent work in granular systems[1]. Brian Tighe[2] will describe new results from a force ensemble approach proposed recently by Snoeijer et al. Silke Henkes will describe a different force-based ensemble approach that yields a generalized partition function[3]. Eric Corwin will describe state-of-the-art experiments on dense emulsions[4]. And Matthias Schr"oter will present novel experiments on fluidized suspensions that address the issue of jamming and glassy behavior[5]. So, do we have a complete description of jammed matter? Not yet, but these talks, as well as other exciting developments in the field, show that there has been enormous progress, towards that end. [4pt] [1] T. S. Majmudar et al., Nature 435, 1079 (2005); Phys. Rev. Lett. 98 058001 (2007). [0pt] [2] B. P. Tighe, A. R. T. van Eerd, and T. J. H. Vlugt , Phys. Rev. Lett. 100, 238001 (2008). [0pt] [3] S. Henkes, C. O'Hern and B. Chakrabory, Phys. Rev. Lett. 99, 038002 (2007). [0pt] [4] J. Bruji'c et al., Phys. Rev. Lett. 98, 248001 (2007). [0pt] [5] M. Schr"ooter, D. I. Goldman, and H. L. Swinney, Phys. Rev. E 71, 030301(R) (2005).

  7. Jamming of Cylindrical Grains in Vertical Channels

    NASA Astrophysics Data System (ADS)

    Baxter, G. William; Spier, Gregory; Barr, Nicholas; Steel, Fiona

    2012-02-01

    We study jamming of low aspect-ratio cylindrical Delrin grains in a vertical channel. These cylindrical grains resemble antacid tablets, poker chips, or coins since their height is less than their diameter. Grains are allowed to fall through a vertical channel with a square cross section where the channel width is greater than the diameter of a grain and constant throughout the length of the channel with no obstructions or constrictions. Within this channel, grains are sometimes observed to form jams, stable structures supported by the channel walls with no support beneath them. The probability of jam occurrence and the strength or robustness of a jam is effected by the grain dimensions and channel size. We will present experimental measurements of the jamming probability and jam strength in this system and discuss the relationship of these results to other experiments and theories.

  8. Tabletop Traffic Jams: Modeling Traffic Jams using Self Propelled Particles

    NASA Astrophysics Data System (ADS)

    Yadav, Vikrant; Kudrolli, Arshad

    2015-03-01

    We model behavior of traffic using Self Propelled Particles (SPPs). Granular rods with asymmetric mass distribution confined to move in a circular channel on a vibrated substrate and interact with each other through inelastic collision serve as our model vehicle. Motion of a single vehicle is observed to be composed of 2 parts, a linear velocity in the direction of lighter end of particle and a non-Gaussian random velocity. We find that the collective mean speed of the SPPs is constant over a wide range of line densities before decreasing rapidly as the maximum packing is approached indicating the spontaneous formation of Phantom jams. This decrease in speed is observed to be far greater than any small differences in the mean drift speed of individual SPPs , and occurs as the collision frequency between SPPs increase exponentially with line density. However the random velocity component of SPPs remain super-diffusive over entire range of line densities. While the collective motion at low densities is characterized by caravan following behind the slowest particle leading to clustering, at higher densities we see formation of jamming waves travelling in direction opposite to that of motion of particles.

  9. Hidden symmetries in jammed systems

    NASA Astrophysics Data System (ADS)

    Morse, Peter K.; Corwin, Eric I.

    2016-07-01

    There are deep, but hidden, geometric structures within jammed systems, associated with hidden symmetries. These can be revealed by repeated transformations under which these structures lead to fixed points. These geometric structures can be found in the Voronoi tesselation of space defined by the packing. In this paper we examine two iterative processes: maximum inscribed sphere (MIS) inversion and a real-space coarsening scheme. Under repeated iterations of the MIS inversion process we find invariant systems in which every particle is equal to the maximum inscribed sphere within its Voronoi cell. Using a real-space coarsening scheme we reveal behavior in geometric order parameters which is length-scale invariant.

  10. Dynamic shear jamming in granular suspensions

    NASA Astrophysics Data System (ADS)

    Peters, Ivo; Majumdar, Sayantan; Jaeger, Heinrich

    2014-11-01

    Jamming by shear allows a frictional granular packing to transition from an unjammed state into a jammed state while keeping the system volume and average packing fraction constant. Shear jamming of dry granular media can occur quasi-statically, but boundaries are crucial to confine the material. We perform experiments in aqueous starch suspension where we apply shear using a rheometer with a large volume (400 ml) cylindrical Couette cell. In our suspensions the packing fraction is sufficiently low that quasi-static deformation does not induce a shear jammed state. Applying a shock-like deformation however, will turn the suspension into a jammed solid. A fully jammed state is reached within tens of microseconds, and can be sustained for at least several seconds. High speed imaging of the initial process reveals a jamming front propagating radially outward through the suspension, while the suspension near the outer boundary remains quiescent. This indicates that granular suspensions can be shear jammed without the need of confining solid boundaries. Instead, confinement is most likely provided by the dynamics in the front region.

  11. FH/MFSK performance in multitone jamming

    NASA Technical Reports Server (NTRS)

    Levitt, B. K.

    1985-01-01

    The performance of frequency-hopped (FH) M-ary frequency-shift keyed (MFSK) signals in partial-band noise was analyzed in the open literature. The previous research is extended to the usually more effective class of multitone jamming. Some objectives researched are: (1) To categorize several different multitone jamming strategies; (2) To analyze the performance of FH/MSFK signaling, both uncoded with diversity, assuming a noncoherent energy detection metric with linear combining and perfect jamming state side information, in the presence of worst case interference for each of these multitone categories; and (3) To compare the effectiveness of the various multitone jamming techniques, and contrast the results with the partial band noise jamming case.

  12. Similarities between protein folding and granular jamming

    PubMed Central

    Jose, Prasanth P; Andricioaei, Ioan

    2012-01-01

    Grains and glasses, widely different materials, arrest their motions upon decreasing temperature and external load, respectively, in common ways, leading to a universal jamming phase diagram conjecture. However, unified theories are lacking, mainly because of the disparate nature of the particle interactions. Here we demonstrate that folded proteins exhibit signatures common to both glassiness and jamming by using temperature- and force-unfolding molecular dynamics simulations. Upon folding, proteins develop a peak in the interatomic force distributions that falls on a universal curve with experimentally measured forces on jammed grains and droplets. Dynamical signatures are found as a dramatic slowdown of stress relaxation upon folding. Together with granular similarities, folding is tied not just to the jamming transition, but a more nuanced picture of anisotropy, preparation protocol and internal interactions emerges. Results have implications for designing stable polymers and can open avenues to link protein folding to jamming theory. PMID:23093180

  13. Effect of friction on shear jamming

    NASA Astrophysics Data System (ADS)

    Wang, Dong; Bares, Jonathan; Dijksman, Joshua; Ren, Jie; Zheng, Hu; Behringer, Robert

    Shear jamming of granular materials was first found for systems of frictional disks, with a static friction coefficient μ ~ 0 . 6 (Bi et al. Nature (2011)). Jamming by shear is obtained by starting from a zero-stress state with a packing fraction ϕ between ϕJ (isotropic jamming) and a lowest ϕS for shear jamming. This phenomenon is associated with strong anisotropy in stress and the contact network in the form of force chains, which are stabilized and/or enhanced by the presence of friction. Whether shear jamming occurs for frictionless particles is under debate. The issue we address experimentally is how changing friction affects shear jamming. By applying a homogeneous simple shear, we study the effect of friction by using photoelastic disks either wrapped with Teflon to reduce friction or with fine teeth on the edge to increase friction. Shear jamming is still observed; however, the difference ϕJ -ϕS is smaller with lower friction. We also observe larger fluctuations due to initial configurations both at the lowest and the highest friction systems studied. Ongoing work is to use particles made of gelatin to reduce the friction coefficient to the order of 0.01. We acknowledge support from NSF Grant DMR1206351, NASA Grant NNX15AD38G and the William M. Keck Foundation.

  14. Effect of friction on shear jamming

    NASA Astrophysics Data System (ADS)

    Wang, Dong; Bares, Jonathan; Dijksman, Joshua; Ren, Jie; Zheng, Hu; Behringer, Robert

    2015-11-01

    Shear jamming of granular materials was first found for systems of frictional disks, with a static friction coefficient μ ~ 0 . 6. Jamming by shear is obtained by starting from a zero-stress state with a packing fraction ϕ between ϕJ (isotropic jamming) and a lowest ϕS for shear jamming. This phenomenon is associated with strong anisotropy in stress and the contact network in the form of force chains, which are stabilized and/or enhanced by the presence of friction. Whether shear jamming occurs for frictionless particles is under debate. The issue we address experimentally is how changing friction affects shear jamming. By applying a homogeneous simple shear, we study the effect of friction by using photoelastic disks either wrapped with Teflon to reduce friction or with fine teeth on the edge to increase friction. Shear jamming is still observed; however, the difference ϕJ -ϕS is smaller with lower friction. We also observe larger fluctuations due to initial configurations both at the lowest and the highest friction systems studied. Ongoing work is to characterize response from different friction systems under shear with information at local scale. We acknowledge support from NSF-DMR1206351, NASA NNX15AD38G and W.M. Keck Foundation.

  15. Effect of Friction on Shear Jamming

    NASA Astrophysics Data System (ADS)

    Wang, Dong; Ren, Jie; Dijksman, Joshua; Bares, Jonathan; Behringer, Robert

    2015-03-01

    Shear jamming of granular materials was first found for systems of frictional disks, with a static friction coefficient μ ~ 0 . 6 (Bi et al. Nature (2011)). Jamming by shear is obtained by starting from a zero-stress state with a packing fraction ϕ between ϕJ (isotropic jamming) and a lowest ϕS for shear jamming. This phenomenon is associated with strong anisotropy in stress and the contact network in the form of force chains, which are stabilized and/or enhanced by the presence of friction. Whether shear jamming occurs for frictionless particles is under debate. The issue we address experimentally is how reducing friction affects shear jamming. We put the Teflon-wrapped photoelastic disks, lowering the friction substantially from previous experiments, in a well-studied 2D shear apparatus (Ren et al. PRL (2013)), which provides a uniform simple shear. Shear jamming is still observed; however, the difference ϕJ -ϕS is smaller with lower friction. We also observe larger anisotropies in fragile states compared to experiments with higher friction particles at the same density. In ongoing work we are studying systems using photoelastic disks with fine gears on the edge to generate very large effective friction. We acknowledge support from NSF Grant DMR1206351, NSF Grant DMS-1248071, NASA Grant NNX10AU01G and William M. Keck Foundation.

  16. Electromagnetic anti-jam telemetry tool

    DOEpatents

    Ganesan, Harini; Mayzenberg, Nataliya

    2008-02-12

    A mud-pulse telemetry tool includes a tool housing, a motor disposed in the tool housing, and a magnetic coupling coupled to the motor and having an inner shaft and an outer shaft. The tool may also include a stator coupled to the tool housing, a restrictor disposed proximate the stator and coupled to the magnetic coupling, so that the restrictor and the stator adapted to generate selected pulses in a drilling fluid when the restrictor is selectively rotated. The tool may also include a first anti-jam magnet coupled to the too housing, and an second anti-jam magnet disposed proximate the first anti-jam magnet and coupled to the inner shaft and/or the outer shaft, wherein at least one of the first anti-jam magnet and the second anti-jam magnet is an electromagnet, and wherein the first anti-jam magnet and the second anti-jam magnet are positioned with adjacent like poles.

  17. Granular jamming transitions for a robotic mechanism

    NASA Astrophysics Data System (ADS)

    Jiang, Allen; Aste, Tomaso; Dasgupta, Prokar; Althoefer, Kaspar; Nanayakkara, Thrishantha

    2013-06-01

    The jamming transitions for granules growing field of interest in robotics for use in variable stiffness mechanisms. However, the traditional use of air pressure to control the jamming transition requires heavy vacuums, reducing the mobility of the robot. Thus, we propose the use of water as a hydraulic fluid to control the transition between free and clustered granules. This paper presents comparative studies that show that a hydraulic granular jammed finger joint can both achieve the same stiffness level and maintain the same hysteresis level of a pneumatic system, with only a small volume of fluid.

  18. Topological boundary modes in jammed matter.

    PubMed

    Sussman, Daniel M; Stenull, Olaf; Lubensky, T C

    2016-07-13

    Granular matter at the jamming transition is poised on the brink of mechanical stability, and hence it is possible that these random systems have topologically protected surface phonons. Studying two model systems for jammed matter, we find states that exhibit distinct mechanical topological classes, protected surface modes, and ubiquitous Weyl points. The detailed statistics of the boundary modes shed surprising light on the properties of the jamming critical point and help inform a common theoretical description of the detailed features of the transition. PMID:27345616

  19. Study on evaluation of photoelectric jamming effectiveness on ranging lidar

    NASA Astrophysics Data System (ADS)

    Che, Jinxi; Yang, Haiqiang; Gao, Bo

    2015-11-01

    Lidar (Light Detection and Range) is a brand-new field and research hotspot. Ranging lidar is studied in this paper. Specifically, its basic working principle and photoelectric jamming mechanism are introduced. Then, the ranging error jamming success rate rule is developed for laser distance deception jamming. And the effectiveness evaluation of laser blinding jamming is based on the influence level on ranging accuracy and ranging function. The results have some reference value to evaluation of jamming test effectiveness.

  20. Ice Jams the Ob River

    NASA Technical Reports Server (NTRS)

    2007-01-01

    Russia's Ob River flows from south to north, and each summer, it thaws in the same direction. The result is that an ice jam sits downstream from thawed portions of the river, which is laden with heavy runoff from melted snow. On June 29, 2007, the Moderate Resolution Imaging Spectroradiometer (MODIS) flying on NASA's Terra satellite captured this image of the almost completely thawed Ob River. The scene is typical for early summer. South of the ice jam, the Gulf of Ob is swollen with pent-up run-off, and upstream from that, the river is widened as well. Unable to carve through frozen land, the river has little choice but to overflow its banks. For a comparison of early summer and autumn conditions, see Flooding on the Ob River in the Earth Observatory's Natural Hazards section. Besides the annual overflow, this image captures other circumstances of early summer. Sea ice is retreating from the Kara Sea. A lingering line of snow cover snakes its way along the Ob River, to the west. And while the land is lush and green in the south, it appears barren and brown in the north. Near the mouth of the river and the Kara Sea, the land is cold-adapted tundra, with diminutive plants and a short growing season. Just as the ice plugging the river had yet to thaw in the Far North's short summer, the tundra had not yet to greened up either. In this image it still appears lifeless beige. NASA image courtesy Jeff Schmaltz, MODIS Rapid Response Team, Goddard Space Flight Center

  1. Scaling theory of the jamming transition

    NASA Astrophysics Data System (ADS)

    Liu, Andrea; Goodrich, Carl; Sethna, James; Nagel, Sidney

    The concept of jamming was first introduced at the University of Chicago by Sid Nagel and Tom Witten. By now we know that there is a zero-temperature critical jamming transition that marks the onset of rigidity in packings of soft repulsive spheres. In contrast to the perfect fcc crystal state, which is the maximally stable state for such systems, the jammed state is only marginally stable mechanically, and thus represents an opposite extreme to the perfect crystal. This marginal stability gives rise to power law scalings and diverging length scales at the transition. Here I will discuss recent developments that put the jamming transition in the same place that the Ising transition was when Leo Kadanoff introduced the ideas of coarse-graining and rescaling into critical phenomena. Supported by DOE-DE-FG02-05ER46199.

  2. Effect of friction on shear jamming

    NASA Astrophysics Data System (ADS)

    Wang, Dong; Ren, Jie; Dijksman, Joshua; Behringer, Robert

    2014-03-01

    Shear Jamming of granular materials was first found for systems of frictional disks, with a static friction coefficients μs ~= 0 . 6 . Jamming by shear is obtained by starting from a zero-stress state with a packing fraction ϕS <= ϕ <=ϕJ between ϕJ (isotropic jamming) and a lowest ϕS for shear jamming. This phenomenon is associated with strong anisotropy in stress and the contact network in the form of ``force chains,'' which are stabilized and/or enhanced by the presence of friction. We address experimentally how reducing friction affects shear jamming by using either teflon disks of teflon wrapped photoelastic particles. The teflon disks were placed in a wall driven 2D shear apparatus, in which we can probe shear stresses mechanically. Teflon-wrapped disks were placed in a bottom driven 2D shear apparatus (Ren et al., PRL 2013). Both apparatuses provide uniform simple shear. In all low- μ experiments, the shear jamming occurred, as observed through stress increases on the packing. However, the low- μ differences observed for ϕJ -ϕS were smaller than for higher friction particles. Ongoing work is studying systems using hydrogel disks, which have a lower friction coefficient than teflon. We acknowledge support from NSF Grant No. DMR12-06351, ARO Grant No. W911NF-1-11-0110, and NASA Grant No. NNX10AU01G.

  3. Effect of friction on shear jamming

    NASA Astrophysics Data System (ADS)

    Wang, Dong; Ren, Jie; Dijksman, Joshua; Behringer, Robert

    2014-11-01

    Shear Jamming of granular materials was first found for systems of frictional disks, with a static friction coefficients μs ~= 0 . 6 . Jamming by shear is obtained by starting from a zero-stress state with a packing fraction ϕS <= ϕ <=ϕJ between ϕJ (isotropic jamming) and a lowest ϕS for shear jamming. This phenomenon is associated with strong anisotropy in stress and the contact network in the form of ``force chains,'' which are stabilized and/or enhanced by the presence of friction. The issue that we address experimentally is how reducing friction affects shear jamming. We use photoelastic disks that have been wrapped with Teflon, lowering the friction coefficient substantially from previous experiments. The Teflon-wrapped disks were placed in a well-studied 2D shear apparatus (Ren et al., PRL, 110, 018302 (2013)), which provides uniform simple shear without generating shear bands. Shear jamming is still observed, but the difference ϕJ -ϕS is smaller than for higher friction particles. With Teflon-wrapped disks, we observe larger anisotropies compared to the previous experiment with higher friction particles at the same packing fraction, which indicates force chains tending to be straight in the low friction system. We acknowledge support from NSF Grant No. DMR12-06351, ARO Grant No. W911NF-1-11-0110, and NASA Grant No. NNX10AU01G.

  4. Jamming in Disordered and Ordered States: From RLP to FCC

    NASA Astrophysics Data System (ADS)

    Silbert, Leonardo

    2011-03-01

    The concept of jamming was originally introduced in the context of zero-temperature, frictionless sphere packings through which the jamming transition was identified with the more familiar idea of random close packing. More recently, the jamming behaviour for particles with friction has led to a practical definition of the less well-defined random loose packed limit. However, there are a number of subtleties associated with jamming that extend these concepts further. Here we implement a range of protocols to generate jammed packings both with and without friction, and find that the jamming transition actually consists of a finite region in packing fraction depending on the protocol used to create the jammed state. Furthermore, we examine how it is possible to tune the structural properties of jammed packings from the disordered regime through to the ordered face centred cubic lattice, and the subsequent changes in the jamming properties as the structure is manipulated. Supported by NSF CBET-0828359.

  5. Cultur(ally) Jammed: Culture Jams as a Form of Culturally Responsive Teaching

    ERIC Educational Resources Information Center

    Martinez, Ulyssa

    2012-01-01

    Does the person become the name or does the name become the person? This question was asked by a participant of my culture jam entitled, "What's my name?" In this culture jam, I asked people to discern the name of a person based solely on their appearance and a list of possible names below their picture. This article aims to show how culture jams…

  6. Fluctuations in flows near jamming.

    PubMed

    Woldhuis, Erik; Chikkadi, Vijayakumar; van Deen, Merlijn S; Schall, Peter; van Hecke, Martin

    2015-09-21

    Bubbles, droplets or particles in flowing complex media such as foams, emulsions or suspensions follow highly complex paths, with the relative motion of the constituents setting the energy dissipation rate. What is their dynamics, and how is this connected to the global rheology? To address these questions, we probe the statistics and spatio-temporal organization of the local particle motion and energy dissipation in a model for sheared disordered materials. We find that the fluctuations in the local dissipation vary from nearly Gaussian and homogeneous at low densities and fast flows, to strongly intermittent for large densities and slow flows. The higher order moments of the relative particle velocities reveal strong evidence for a qualitative difference between two distinct regimes which are nevertheless connected by a smooth crossover. In the critical regime, the higher order moments are related by novel multiscaling relations. In the plastic regime the relations between these moments take on a different form, with higher moments diverging rapidly when the flow rate vanishes. As these velocity differences govern the energy dissipation, we can distinguish two qualitatively different types of flow: an intermediate density, critical regime related to jamming, and a large density, plastic regime. PMID:26244633

  7. Sediment Movement Near a Tropical Wood Jam

    NASA Astrophysics Data System (ADS)

    Cadol, D.; Wohl, E.

    2008-12-01

    One mechanism by which wood interacts with sediment transport is the trapping of sediment behind jams. In tropical streams, higher discharge per unit of contributing area and higher microbial diversity relative to temperate zones are likely to cause in-stream wood to be more transient. This may reduce the residence time of jams, also reducing wood-induced sediment storage. To begin to evaluate this possibility, tracer clasts, scour chains, and wood pieces were surveyed four times from June 2007 to June 2008 at a wood jam in a stream in Costa Rica. At the study site the moderate gradient (3.2%) stream drains 1.6 km2 of preserved old-growth tropical wet forest of La Selva Biological Station. The mean grain size of the bed material is 205 mm, ranging from coarse sand to boulders, with discontinuous bedrock outcrops on both banks. Distance traveled by the tracer clasts was positively correlated with both maximum and average daily rainfall during the time between surveys. Between the first two surveys, a new accumulation of wood in the jam blocked the thalweg and redirected the majority of flow around the side of the jam. A 15-cm-thick wedge of sediment was deposited behind the blockage, and gravel bars adjacent to and immediately downstream of the jam were scoured by as much as 30 cm. The majority of the gravel sized tracer clasts placed upstream of the jam were not recovered and were presumably incorporated into the sediment wedge. Tracer clasts placed in the portion of the channel affected by the redirected flow were transported downstream as much as 47 m. Clasts larger than D55 (220 mm) were not transported in the course of the study. The jam and key pieces persisted for the entire study period, and the number of pieces in the jam stayed nearly constant. However, the structure was modified and only 46% of the original pieces were retained for the full year. The clast transport distance was positively correlated with wood turnover rate for the three inter

  8. City traffic jam relief by stochastic resonance

    NASA Astrophysics Data System (ADS)

    Castillo, F.; Toledo, B. A.; Muñoz, V.; Rogan, J.; Zarama, R.; Kiwi, M.; Valdivia, J. A.

    2014-06-01

    We simulate traffic in a city by means of the evolution of a row of interacting cars, using a cellular automaton model, in a sequence of traffic lights synchronized by a "green wave". When our initial condition is a small density jammed state, its evolution shows the expected scaling laws close to the synchronization resonance, with a uniform car density along the street. However, for an initial large density jammed state, we observe density variations along the streets, which results in the breakdown of the scaling laws. This spatial disorder corresponds to a different attractor of the system. As we include velocity perturbations in the dynamics of the cars, all these attractors converge to a statistically equivalent system for all initial jammed densities. However, this emergent state shows a stochastic resonance-like behavior in which the average traffic velocity increases with respect to that of the system without noise, for several initial jammed densities. This result may help in the understanding of dynamics of traffic jams in cities.

  9. Jamming threshold of dry fine powders.

    PubMed

    Valverde, J M; Quintanilla, M A S; Castellanos, A

    2004-06-25

    We report a novel experimental study on the jamming transition of dry fine powders with controlled attractive energy and particle size. Like in attractive colloids dry fine particles experience diffusion-limited clustering in the fluidlike regime. At the jamming threshold fractal clusters crowd in a metastable state at volume fractions depending on attractive energy and close to the volume fraction of hard nonattractive spheres at jamming. Near the phase transition the stress-(volume fraction) relationship can be fitted to a critical-like functional form for a small range of applied stresses sigma approximately (phi-phi(J))(beta) as measured on foams, emulsions, and colloidal systems and predicted by numerical simulations on hard spheres. PMID:15245067

  10. Pressure-driven suspension flow near jamming.

    PubMed

    Oh, Sangwon; Song, Yi-qiao; Garagash, Dmitry I; Lecampion, Brice; Desroches, Jean

    2015-02-27

    We report here magnetic resonance imaging measurements performed on suspensions with a bulk solid volume fraction (ϕ_{0}) up to 0.55 flowing in a pipe. We visualize and quantify spatial distributions of ϕ and velocity across the pipe at different axial positions. For dense suspensions (ϕ_{0}>0.5), we found a different behavior compared to the known cases of lower ϕ_{0}. Our experimental results demonstrate compaction within the jammed region (characterized by a zero macroscopic shear rate) from the jamming limit ϕ_{m}≈0.58 at its outer boundary to the random close packing limit ϕ_{rcp}≈0.64 at the center. Additionally, we show that ϕ and velocity profiles can be fairly well captured by a frictional rheology accounting for both further compaction of jammed regions as well as normal stress differences. PMID:25768782

  11. Laser jamming technique research based on combined fiber laser

    NASA Astrophysics Data System (ADS)

    Jie, Xu; Shanghong, Zhao; Rui, Hou; Shengbao, Zhan; Lei, Shi; Jili, Wu; Shaoqiang, Fang; Yongjun, Li

    2009-06-01

    A compact and light laser jamming source is needed to increase the flexibility of laser jamming technique. A novel laser jamming source based on combined fiber lasers is proposed. Preliminary experimental results show that power levels in excess of 10 kW could be achieved. An example of laser jamming used for an air-to-air missile is given. It shows that the tracking system could complete tracking in only 4 s and came into a steady state with its new tracking target being the laser jamming source.

  12. Dynamic jamming of iceberg-choked fjords

    NASA Astrophysics Data System (ADS)

    Peters, Ivo R.; Amundson, Jason M.; Cassotto, Ryan; Fahnestock, Mark; Darnell, Kristopher N.; Truffer, Martin; Zhang, Wendy W.

    2015-02-01

    We investigate the dynamics of ice mélange by analyzing rapid motion recorded by a time-lapse camera and terrestrial radar during several calving events that occurred at Jakobshavn Isbræ, Greenland. During calving events (1) the kinetic energy of the ice mélange is 2 orders of magnitude smaller than the total energy released during the events, (2) a jamming front propagates through the ice mélange at a rate that is an order of magnitude faster than the motion of individual icebergs, (3) the ice mélange undergoes initial compaction followed by slow relaxation and extension, and (4) motion of the ice mélange gradually decays before coming to an abrupt halt. These observations indicate that the ice mélange experiences widespread jamming during calving events and is always close to being in a jammed state during periods of terminus quiescence. We therefore suspect that local jamming influences longer timescale ice mélange dynamics and stress transmission.

  13. Disentangling the role of structure and friction in shear jamming

    NASA Astrophysics Data System (ADS)

    Vinutha, H. A.; Sastry, Srikanth

    2016-06-01

    Amorphous sphere packings have been intensely investigated to understand mechanical and flow behaviour of dense granular matter and to explore universal aspects of the jamming transition, from fluid to structurally arrested states. Considerable recent research has focused on anisotropic packings of frictional grains generated by shear deformation leading to shear jamming, occurring below the jamming density for isotropic packings of frictionless grains. Here, with the aim of disentangling the role of shear-deformation-induced structures and friction in generating shear jamming, we computationally study sheared assemblies of frictionless spheres, over a wide range of densities. We demonstrate that shear deformation alone leads to the emergence of geometric features characteristic of jammed packings, with the increase of shear strain. We also show that such emergent geometry, together with friction, leads to mechanically stable, shear-jammed, packings above a threshold density that lies well below the isotropic jamming point.

  14. Traffic jams, granular flow, and soliton selection

    SciTech Connect

    Kurtze, D.A.; Hong, D.C.

    1995-07-01

    The flow of traffic on a long section of road without entrances or exits can be modeled by continuum equations similar to those describing fluid flow. In a certain range of traffic density, steady flow becomes unstable against the growth of a cluster, or ``phantom`` traffic jam, which moves at a slower speed than the otherwise homogeneous flow. We show that near the onset of this instability, traffic flow is described by a perturbed Korteweg--de Vries (KdV) equation. The traffic jam can be identified with a soliton solution of the KdV equation. The perturbation terms select a unique member of the continuous family of KdV solitons. These results may also apply to the dynamics of granular relaxation.

  15. How do tiger moths jam bat sonar?

    PubMed

    Corcoran, Aaron J; Barber, Jesse R; Hristov, Nickolay I; Conner, William E

    2011-07-15

    The tiger moth Bertholdia trigona is the only animal in nature known to defend itself by jamming the sonar of its predators - bats. In this study we analyzed the three-dimensional flight paths and echolocation behavior of big brown bats (Eptesicus fuscus) attacking B. trigona in a flight room over seven consecutive nights to determine the acoustic mechanism of the sonar-jamming defense. Three mechanisms have been proposed: (1) the phantom echo hypothesis, which states that bats misinterpret moth clicks as echoes; (2) the ranging interference hypothesis, which states that moth clicks degrade the bats' precision in determining target distance; and (3) the masking hypothesis, which states that moth clicks mask the moth echoes entirely, making the moth temporarily invisible. On nights one and two of the experiment, the bats appeared startled by the clicks; however, on nights three through seven, the bats frequently missed their prey by a distance predicted by the ranging interference hypothesis (∼15-20 cm). Three-dimensional simulations show that bats did not avoid phantom targets, and the bats' ability to track clicking prey contradicts the predictions of the masking hypothesis. The moth clicks also forced the bats to reverse their stereotyped pattern of echolocation emissions during attack, even while bats continued pursuit of the moths. This likely further hinders the bats' ability to track prey. These results have implications for the evolution of sonar jamming in tiger moths, and we suggest evolutionary pathways by which sonar jamming may have evolved from other tiger moth defense mechanisms. PMID:21697434

  16. Designing Jammed Materials from the Particle Up

    NASA Astrophysics Data System (ADS)

    Miskin, Marc

    2015-03-01

    Identifying which microscopic features produce a desired macroscopic behavior is a problem at the forefront of materials science. This task is materials design, and within it, new challenges have emerged from tailoring packings of particles jammed into a rigid state. For these materials, particle shape is a key parameter by which the response of a packing can be tuned. Yet designing via shape faces two unique complications: first there is no general theory that calculates the response of an aggregate given a particle shape, and second, there is no straightforward way to explore the space of all particle geometries. This talk summarizes recent results that address these challenges to design jammed materials from the particle up. It shows how simulations, experiments, and state-of-the-art optimization engines come together to form a complete system that identifies extreme materials. As examples, it will show how this system can create particle shapes that form the stiffest, softest, densest, loosest, most dissipative and strain-stiffening aggregates. Finally, it will discuss the how these results relate to the general task of materials design and the exciting possibilities associated with optimizing, tuning and rationally constructing new breeds of jammed materials.

  17. Casimir forces in systems near jamming

    NASA Astrophysics Data System (ADS)

    Burton, Justin; Liétor-Santos, Juan-José

    Casimir forces arise when long-ranged fluctuations are geometrically confined between two surfaces. In most cases these fluctuations are quantum or thermal in nature, such as those near a classical critical point, yet this is not a requirement. The T = 0 jamming transition in frictionless, granular systems shares many properties with classical critical points, such as a diverging correlation length, although it has recently been identified as a unique example of a random first-order transition (RFOT). Here we show the existence of Casimir forces between two pinned particles immersed in systems near the frictionless jamming transition. We observe two components to the total force: a short-ranged, depletion force and a long-ranged, repulsive Casimir force. The Casimir force dominates when the pinned particles are much larger than the ambient jammed particles. In this case, we find that particles with the largest forces have the least number of contacts, and that these particles are clustered between the pinned particles, giving rise to a repulsive force which is independent of system preparation and inter-particle potential. We acknowledge support from NSF DMR-1455086.

  18. Spreading of Traffic Jam in a Traffic Flow Model

    NASA Astrophysics Data System (ADS)

    Nagatani, Takashi

    1993-04-01

    A cellular automaton (CA) model is presented to simulate the traffic jam induced by a traffic accident. The spreading of jamming cars induced by a car crash is investigated by computer simulation. An analogy is proposed between the crystal growth and the traffic-jam spreading. The scaling behavior of the traffic-jam spreading is studied. It is shown that the number N of jamming cars scales as N≈t2.34± 0.03 for p above the dynamical jamming transition pc{=}0.35 and N≈t1.07 below pc where t is the time and p is the density of cars. The time constant ts, which is the time required for all cars to stop, scales as ts≈p-1.07± 0.03 for p

  19. Critical slowing down and hyperuniformity on approach to jamming

    NASA Astrophysics Data System (ADS)

    Atkinson, Steven; Zhang, Ge; Hopkins, Adam B.; Torquato, Salvatore

    2016-07-01

    Hyperuniformity characterizes a state of matter that is poised at a critical point at which density or volume-fraction fluctuations are anomalously suppressed at infinite wavelengths. Recently, much attention has been given to the link between strict jamming (mechanical rigidity) and (effective or exact) hyperuniformity in frictionless hard-particle packings. However, in doing so, one must necessarily study very large packings in order to access the long-ranged behavior and to ensure that the packings are truly jammed. We modify the rigorous linear programming method of Donev et al. [J. Comput. Phys. 197, 139 (2004), 10.1016/j.jcp.2003.11.022] in order to test for jamming in putatively collectively and strictly jammed packings of hard disks in two dimensions. We show that this rigorous jamming test is superior to standard ways to ascertain jamming, including the so-called "pressure-leak" test. We find that various standard packing protocols struggle to reliably create packings that are jammed for even modest system sizes of N ≈103 bidisperse disks in two dimensions; importantly, these packings have a high reduced pressure that persists over extended amounts of time, meaning that they appear to be jammed by conventional tests, though rigorous jamming tests reveal that they are not. We present evidence that suggests that deviations from hyperuniformity in putative maximally random jammed (MRJ) packings can in part be explained by a shortcoming of the numerical protocols to generate exactly jammed configurations as a result of a type of "critical slowing down" as the packing's collective rearrangements in configuration space become locally confined by high-dimensional "bottlenecks" from which escape is a rare event. Additionally, various protocols are able to produce packings exhibiting hyperuniformity to different extents, but this is because certain protocols are better able to approach exactly jammed configurations. Nonetheless, while one should not generally

  20. Critical slowing down and hyperuniformity on approach to jamming.

    PubMed

    Atkinson, Steven; Zhang, Ge; Hopkins, Adam B; Torquato, Salvatore

    2016-07-01

    Hyperuniformity characterizes a state of matter that is poised at a critical point at which density or volume-fraction fluctuations are anomalously suppressed at infinite wavelengths. Recently, much attention has been given to the link between strict jamming (mechanical rigidity) and (effective or exact) hyperuniformity in frictionless hard-particle packings. However, in doing so, one must necessarily study very large packings in order to access the long-ranged behavior and to ensure that the packings are truly jammed. We modify the rigorous linear programming method of Donev et al. [J. Comput. Phys. 197, 139 (2004)JCTPAH0021-999110.1016/j.jcp.2003.11.022] in order to test for jamming in putatively collectively and strictly jammed packings of hard disks in two dimensions. We show that this rigorous jamming test is superior to standard ways to ascertain jamming, including the so-called "pressure-leak" test. We find that various standard packing protocols struggle to reliably create packings that are jammed for even modest system sizes of N≈10^{3} bidisperse disks in two dimensions; importantly, these packings have a high reduced pressure that persists over extended amounts of time, meaning that they appear to be jammed by conventional tests, though rigorous jamming tests reveal that they are not. We present evidence that suggests that deviations from hyperuniformity in putative maximally random jammed (MRJ) packings can in part be explained by a shortcoming of the numerical protocols to generate exactly jammed configurations as a result of a type of "critical slowing down" as the packing's collective rearrangements in configuration space become locally confined by high-dimensional "bottlenecks" from which escape is a rare event. Additionally, various protocols are able to produce packings exhibiting hyperuniformity to different extents, but this is because certain protocols are better able to approach exactly jammed configurations. Nonetheless, while one should

  1. Pebble Jammed in Rock Abrasion Tool

    NASA Technical Reports Server (NTRS)

    2004-01-01

    After the rock abrasion tool on NASA's Mars Exploration Rover Opportunity stopped working on sol 199 (Aug. 15, 2004), rover operators used the panoramic camera to take this image the next day for help in diagnosing the problem. The tool was closer than the camera could focus on sharply, but the image does show a dark spot just left of center, which engineers have determined is likely to be a pebble jammed between the cutting-blade rotor and the wire-brush rotor. If that diagnosis is confirmed by further analysis, the tool will likely be commanded to turn the rotors in reverse to release the pebble.

  2. And I hope you like jamming too

    PubMed Central

    Tambe, Dhananjay T.; Fredberg, Jeffrey J.

    2016-01-01

    Sorting of distinctly different cell types into specific tissue compartments has long been thought to be a problem in minimization of total free energy in immiscible fluids, wherein cell-cell adhesion, cell stiffness, and cell contraction combine to define an effective macroscopic tissue surface tension. Pawlizak et al. [11] now show not only that adhesion forces at interfaces unexpectedly fail to correlate with the density of adhesion molecules, but also that certain cancer cell lines unexpectedly fail to behave as a fluid, with cells becoming kinetically trapped in what might be a jammed, solid-like non-equilibrium state

  3. Molecular crowding creates traffic jams of kinesin motors on microtubules

    PubMed Central

    Leduc, Cécile; Padberg-Gehle, Kathrin; Varga, Vladimír; Helbing, Dirk; Diez, Stefan; Howard, Jonathon

    2012-01-01

    Despite the crowdedness of the interior of cells, microtubule-based motor proteins are able to deliver cargoes rapidly and reliably throughout the cytoplasm. We hypothesize that motor proteins may be adapted to operate in crowded environments by having molecular properties that prevent them from forming traffic jams. To test this hypothesis, we reconstituted high-density traffic of purified kinesin-8 motor protein, a highly processive motor with long end-residency time, along microtubules in a total internal-reflection fluorescence microscopy assay. We found that traffic jams, characterized by an abrupt increase in the density of motors with an associated abrupt decrease in motor speed, form even in the absence of other obstructing proteins. To determine the molecular properties that lead to jamming, we altered the concentration of motors, their processivity, and their rate of dissociation from microtubule ends. Traffic jams occurred when the motor density exceeded a critical value (density-induced jams) or when motor dissociation from the microtubule ends was so slow that it resulted in a pileup (bottleneck-induced jams). Through comparison of our experimental results with theoretical models and stochastic simulations, we characterized in detail under which conditions density- and bottleneck-induced traffic jams form or do not form. Our results indicate that transport kinesins, such as kinesin-1, may be evolutionarily adapted to avoid the formation of traffic jams by moving only with moderate processivity and dissociating rapidly from microtubule ends. PMID:22431622

  4. Intelligent cognitive radio jamming - a game-theoretical approach

    NASA Astrophysics Data System (ADS)

    Dabcevic, Kresimir; Betancourt, Alejandro; Marcenaro, Lucio; Regazzoni, Carlo S.

    2014-12-01

    Cognitive radio (CR) promises to be a solution for the spectrum underutilization problems. However, security issues pertaining to cognitive radio technology are still an understudied topic. One of the prevailing such issues are intelligent radio frequency (RF) jamming attacks, where adversaries are able to exploit on-the-fly reconfigurability potentials and learning mechanisms of cognitive radios in order to devise and deploy advanced jamming tactics. In this paper, we use a game-theoretical approach to analyze jamming/anti-jamming behavior between cognitive radio systems. A non-zero-sum game with incomplete information on an opponent's strategy and payoff is modelled as an extension of Markov decision process (MDP). Learning algorithms based on adaptive payoff play and fictitious play are considered. A combination of frequency hopping and power alteration is deployed as an anti-jamming scheme. A real-life software-defined radio (SDR) platform is used in order to perform measurements useful for quantifying the jamming impacts, as well as to infer relevant hardware-related properties. Results of these measurements are then used as parameters for the modelled jamming/anti-jamming game and are compared to the Nash equilibrium of the game. Simulation results indicate, among other, the benefit provided to the jammer when it is employed with the spectrum sensing algorithm in proactive frequency hopping and power alteration schemes.

  5. Intracellular mediators of JAM-A–dependent epithelial barrier function

    PubMed Central

    Monteiro, Ana C.; Parkos, Charles A.

    2012-01-01

    JAM-A is a critical signaling component of the apical junctional complex, a structure composed of several transmembrane and scaffold molecules that controls the passage of nutrients and solutes across epithelial surfaces. Observations from JAM-A–deficient epithelial cells and JAM-A knockout animals indicate that JAM-A is an important regulator of epithelial paracellular permeability, however the mechanism(s) linking JAM-A to barrier function are not understood. This review highlights recent findings relevant to JAM-A–mediated regulation of epithelial permeability, focusing on the role of upstream and downstream signaling candidates. We draw on what is known about proteins reported to associate with JAM-A in other pathways and on known modulators of barrier function to propose candidate effectors that may mediate JAM-A regulation of epithelial paracellular permeability. Further investigation of pathways highlighted in this review may provide ideas for novel therapeutics that target debilitating conditions associated with barrier dysfunction, such as inflammatory bowel disease. PMID:22671597

  6. Evolution of Traffic Jam in Traffic Flow Model

    NASA Astrophysics Data System (ADS)

    Fukui, Minoru; Ishibashi, Yoshihiro

    1993-11-01

    Traffic flow is simulated in a three-state cellular automaton model. In a two-dimensional cell without a crashed car, the ensemble average of the velocity of the cars is enhanced by the self-organization in the low-density phase of cars. In the high-density phase above p{=}0.5 of car density, the velocity is decreased and the system then degenerates into a global jamming phase in which all cars are stopped. A crashed car provides the seed of a jamming cluster, which grows into a global traffic jam even in the low-density phase. The growth of the jamming cluster is studied, and the time dependence of the number of jamming cars and the scaling law for the cell sizes are discussed.

  7. Jamming in finite systems: stability, anisotropy, fluctuations, and scaling.

    PubMed

    Goodrich, Carl P; Dagois-Bohy, Simon; Tighe, Brian P; van Hecke, Martin; Liu, Andrea J; Nagel, Sidney R

    2014-08-01

    Athermal packings of soft repulsive spheres exhibit a sharp jamming transition in the thermodynamic limit. Upon further compression, various structural and mechanical properties display clean power-law behavior over many decades in pressure. As with any phase transition, the rounding of such behavior in finite systems close to the transition plays an important role in understanding the nature of the transition itself. The situation for jamming is surprisingly rich: the assumption that jammed packings are isotropic is only strictly true in the large-size limit, and finite-size has a profound effect on the very meaning of jamming. Here, we provide a comprehensive numerical study of finite-size effects in sphere packings above the jamming transition, focusing on stability as well as the scaling of the contact number and the elastic response. PMID:25215719

  8. Direct observation of dynamic shear jamming in dense suspensions.

    PubMed

    Peters, Ivo R; Majumdar, Sayantan; Jaeger, Heinrich M

    2016-04-14

    Liquid-like at rest, dense suspensions of hard particles can undergo striking transformations in behaviour when agitated or sheared. These phenomena include solidification during rapid impact, as well as strong shear thickening characterized by discontinuous, orders-of-magnitude increases in suspension viscosity. Much of this highly non-Newtonian behaviour has recently been interpreted within the framework of a jamming transition. However, although jamming indeed induces solid-like rigidity, even a strongly shear-thickened state still flows and thus cannot be fully jammed. Furthermore, although suspensions are incompressible, the onset of rigidity in the standard jamming scenario requires an increase in particle density. Finally, whereas shear thickening occurs in the steady state, impact-induced solidification is transient. As a result, it has remained unclear how these dense suspension phenomena are related and how they are connected to jamming. Here we resolve this by systematically exploring both the steady-state and transient regimes with the same experimental system. We demonstrate that a fully jammed, solid-like state can be reached without compression and instead purely with shear, as recently proposed for dry granular systems. This state is created by transient shear-jamming fronts, which we track directly. We also show that shear stress, rather than shear rate, is the key control parameter. From these findings we map out a state diagram with particle density and shear stress as variables. We identify discontinuous shear thickening with a marginally jammed regime just below the onset of full, solid-like jamming. This state diagram provides a unifying framework, compatible with prior experimental and simulation results on dense suspensions, that connects steady-state and transient behaviour in terms of a dynamic shear-jamming process. PMID:27042934

  9. Direct observation of dynamic shear jamming in dense suspensions

    NASA Astrophysics Data System (ADS)

    Peters, Ivo R.; Majumdar, Sayantan; Jaeger, Heinrich M.

    2016-04-01

    Liquid-like at rest, dense suspensions of hard particles can undergo striking transformations in behaviour when agitated or sheared. These phenomena include solidification during rapid impact, as well as strong shear thickening characterized by discontinuous, orders-of-magnitude increases in suspension viscosity. Much of this highly non-Newtonian behaviour has recently been interpreted within the framework of a jamming transition. However, although jamming indeed induces solid-like rigidity, even a strongly shear-thickened state still flows and thus cannot be fully jammed. Furthermore, although suspensions are incompressible, the onset of rigidity in the standard jamming scenario requires an increase in particle density. Finally, whereas shear thickening occurs in the steady state, impact-induced solidification is transient. As a result, it has remained unclear how these dense suspension phenomena are related and how they are connected to jamming. Here we resolve this by systematically exploring both the steady-state and transient regimes with the same experimental system. We demonstrate that a fully jammed, solid-like state can be reached without compression and instead purely with shear, as recently proposed for dry granular systems. This state is created by transient shear-jamming fronts, which we track directly. We also show that shear stress, rather than shear rate, is the key control parameter. From these findings we map out a state diagram with particle density and shear stress as variables. We identify discontinuous shear thickening with a marginally jammed regime just below the onset of full, solid-like jamming. This state diagram provides a unifying framework, compatible with prior experimental and simulation results on dense suspensions, that connects steady-state and transient behaviour in terms of a dynamic shear-jamming process.

  10. Jamming and crystallization in athermal polymer packings

    NASA Astrophysics Data System (ADS)

    Karayiannis, Nikos Ch.; Foteinopoulou, Katerina; Laso, Manuel

    2013-11-01

    Dense packings of chains of hard spheres possess characteristic features that do not have a counterpart in corresponding packings of monomeric spheres especially near the maximally random jammed (MRJ) state. From the modelling perspective the additional requirement that spheres keep their connectivity while maximizing the occupied volume fraction imposes severe constraints on generation algorithms of dense chain configurations. The extremely sluggish dynamics imposed by the uncrossability of chains precludes the use of deterministic or stochastic dynamics to generate all but dilute polymer packings. As a viable alternative, especially tailored chain-connectivity-altering Monte Carlo (MC) algorithms have been developed that bypass this kinetic hindrance and have actually been able to produce packings of hard-sphere chains in a volume fraction range spanning from infinite dilution up to the MRJ state. Such very dense athermal polymer packings share a number of structural features with packings of monomeric hard spheres, but also display unique characteristics due to the constraints imposed by connectivity. We give an overview of the most relevant results of our recent modeling work on packings of freely-jointed chains of tangent hard spheres about the MRJ state, local structure, chain dimensions and their scaling with density, topological constraints in the form of entanglements and knots, contact network at jamming, and entropically driven crystallization.

  11. Rheology of Soft Suspensions near Jamming

    NASA Astrophysics Data System (ADS)

    Nordstrom, Kerstin; Verneuil, Emilie; Arratia, Paulo; Gollub, Jerry; Durian, Douglas

    2009-03-01

    The rheology of a suspension of soft colloidal particles is investigated using a pressure-driven flow in a deep 25 μm wide microchannel. The system is composed of N-isopropylacrylamide (NIPA) colloidal microgel particles, suspended in aqueous solution. NIPA is temperature-sensitive in that the hydrodynamic radius decreases as temperature increases [1]. Therefore, colloidal suspensions of different packing fraction can be obtained simply by varying the temperature using a temperature-controlled stage. We determine the velocity profile and the local shear rate of the suspension using particle image velocimetry (PIV). We have developed methods to accurately infer the suspension shear viscosity and shear stress as a function of shear rate. The dynamical range of shear rates probed is approximately 5 orders of magnitude, ranging from 10-4 to 10^1 s-1. Results show that as the packing fraction is increased towards the jamming point, the velocity profiles are markedly non-Newtonian. Further, above the jamming point, the stress versus shear rate curves show yield stress behavior. [1] Alsayed, A.M.;Islam, M.F.;Zhang, J.;Collings, P.J.;Yodh, A.J., Science 2005.

  12. Cell Jamming in the Airway Epithelium.

    PubMed

    Park, Jin-Ah; Fredberg, Jeffrey J

    2016-03-01

    Hallmarks of asthma include chronic airway inflammation, progressive airway remodeling, and airway hyperresponsiveness. The initiation and perpetuation of these processes are attributable at least in part to critical events within the airway epithelium, but the underlying mechanisms remain poorly understood. New evidence now suggests that epithelial cells derived from donors without asthma versus donors with asthma, even in the absence of inflammatory cells or mediators, express modes of collective migration that innately differ not only in the amount of migration but also in the kind of migration. The maturing cell layer tends to undergo a transition from a hypermobile, fluid-like, unjammed phase in which cells readily rearrange, exchange places, and flow, to a quiescent, solid-like, jammed phase in which cells become virtually frozen in place. Moreover, the unjammed phase defines a phenotype that can be perpetuated by the compressive stresses caused by bronchospasm. Importantly, in cells derived from donors with asthma versus donors without asthma, this jamming transition becomes substantially delayed, thus suggesting an immature or dysmature epithelial phenotype in asthma. PMID:27027955

  13. Love triangles, quantum fluctuations and spin jam

    NASA Astrophysics Data System (ADS)

    Lee, Seung-Hun

    When magnetic moments are interacting with each other in a situation resembling that of complex love triangles, called frustration, a large set of states that are energetically equivalent emerge. This leads to exotic spin states such as spin liquid and spin ice. Recently, we presented evidence for the existence of a topological glassy state, that we call spin jam, induced by quantum fluctuations. The case in point is SrCr9pGa12-9pO19 (SCGO(p)), a highly frustrated magnet, in which the magnetic Cr ions form a quasi-two-dimensional triangular system of bi-pyramids. This system has been an archetype in search for exotic spin states. Understanding the nature of the state has been a great intellectual challenge. Our new experimental data and theoretical spin jam model provide for the first time a coherent understanding of the phenomenon. Furthermore, the findings strongly support the possible existence of purely topological glassy states. Reference:

  14. Equilibrating temperaturelike variables in jammed granular subsystems.

    PubMed

    Puckett, James G; Daniels, Karen E

    2013-02-01

    Although jammed granular systems are athermal, several thermodynamiclike descriptions have been proposed which make quantitative predictions about the distribution of volume and stress within a system and provide a corresponding temperaturelike variable. We perform experiments with an apparatus designed to generate a large number of independent, jammed, two-dimensional configurations. Each configuration consists of a single layer of photoelastic disks supported by a gentle layer of air. New configurations are generated by cyclically dilating, mixing, and then recompacting the system through a series of boundary displacements. Within each configuration, a bath of particles surrounds a smaller subsystem of particles with a different interparticle friction coefficient than the bath. The use of photoelastic particles permits us to find all particle positions as well as the vector forces at each interparticle contact. By comparing the temperaturelike quantities in both systems, we find compactivity (conjugate to the volume) does not equilibrate between the systems, while the angoricity (conjugate to the stress) does. Both independent components of the angoricity are linearly dependent on the hydrostatic pressure, in agreement with predictions of the stress ensemble. PMID:23414047

  15. The first jamming crossover: geometric and mechanical features.

    PubMed

    Pica Ciamarra, Massimo; Sollich, Peter

    2013-03-28

    The jamming transition characterizes athermal systems of particles interacting via finite range repulsive potentials, and occurs on increasing the density when particles cannot avoid making contacts with those of their first coordination shell. We have recently shown [M. Pica Ciamarra and P. Sollich, e-print arXiv:1209.3334] that the same systems are also characterized by a series of jamming crossovers. These occur at higher volume fractions as particles are forced to make contact with those of subsequent coordination shells. At finite temperature, the crossovers give rise to dynamic and thermodynamic density anomalies, including a diffusivity anomaly and a negative thermal expansion coefficient. Density anomalies may therefore be related to structural changes occurring at the jamming crossovers. Here we elucidate these structural changes, investigating the evolution of the structure and of the mechanical properties of a jammed system as its volume fraction varies from the jamming transition to and beyond the first jamming crossover. We show that the first jamming crossover occurs at a well defined volume fraction, and that it induces a rearrangement of the force network causing a softening of the system. It also causes qualitative changes in the normal mode density of states and the spatial properties of the normal mode vectors. PMID:23556780

  16. The first jamming crossover: Geometric and mechanical features

    NASA Astrophysics Data System (ADS)

    Ciamarra, Massimo Pica; Sollich, Peter

    2013-03-01

    The jamming transition characterizes athermal systems of particles interacting via finite range repulsive potentials, and occurs on increasing the density when particles cannot avoid making contacts with those of their first coordination shell. We have recently shown [M. Pica Ciamarra and P. Sollich, e-print arXiv:1209.3334] that the same systems are also characterized by a series of jamming crossovers. These occur at higher volume fractions as particles are forced to make contact with those of subsequent coordination shells. At finite temperature, the crossovers give rise to dynamic and thermodynamic density anomalies, including a diffusivity anomaly and a negative thermal expansion coefficient. Density anomalies may therefore be related to structural changes occurring at the jamming crossovers. Here we elucidate these structural changes, investigating the evolution of the structure and of the mechanical properties of a jammed system as its volume fraction varies from the jamming transition to and beyond the first jamming crossover. We show that the first jamming crossover occurs at a well defined volume fraction, and that it induces a rearrangement of the force network causing a softening of the system. It also causes qualitative changes in the normal mode density of states and the spatial properties of the normal mode vectors.

  17. Confined disordered strictly jammed binary sphere packings

    NASA Astrophysics Data System (ADS)

    Chen, D.; Torquato, S.

    2015-12-01

    Disordered jammed packings under confinement have received considerably less attention than their bulk counterparts and yet arise in a variety of practical situations. In this work, we study binary sphere packings that are confined between two parallel hard planes and generalize the Torquato-Jiao (TJ) sequential linear programming algorithm [Phys. Rev. E 82, 061302 (2010), 10.1103/PhysRevE.82.061302] to obtain putative maximally random jammed (MRJ) packings that are exactly isostatic with high fidelity over a large range of plane separation distances H , small to large sphere radius ratio α , and small sphere relative concentration x . We find that packing characteristics can be substantially different from their bulk analogs, which is due to what we term "confinement frustration." Rattlers in confined packings are generally more prevalent than those in their bulk counterparts. We observe that packing fraction, rattler fraction, and degree of disorder of MRJ packings generally increase with H , though exceptions exist. Discontinuities in the packing characteristics as H varies in the vicinity of certain values of H are due to associated discontinuous transitions between different jammed states. When the plane separation distance is on the order of two large-sphere diameters or less, the packings exhibit salient two-dimensional features; when the plane separation distance exceeds about 30 large-sphere diameters, the packings approach three-dimensional bulk packings. As the size contrast increases (as α decreases), the rattler fraction dramatically increases due to what we call "size-disparity" frustration. We find that at intermediate α and when x is about 0.5 (50-50 mixture), the disorder of packings is maximized, as measured by an order metric ψ that is based on the number density fluctuations in the direction perpendicular to the hard walls. We also apply the local volume-fraction variance στ2(R ) to characterize confined packings and find that these

  18. Jamming and diode effects for vortices in Nanostructured Superconductors

    SciTech Connect

    Reichhardt, Charles; Reichhardt, C J

    2009-01-01

    We examine jamming and ratchet effects for vortex matter in superconductors with asymmetric funnel geometries. We show that the vortex-vortex interactions can induce a clogging or jamming effect where it becomes increasingly difficult for the vortices to move through the system. We also find that commensurability effects can arise when certain vortex configurations form highly symmetrical structures in the funnel plaquettes. Due to the asymmetry, the critical currents are different for driving in different directions, leading to a diode effect. We also discuss other possible geometries that could be used to explore jamming in vortex matter.

  19. Stress Relaxation for Granular Materials near Jamming under Cyclic Compression

    NASA Astrophysics Data System (ADS)

    Farhadi, Somayeh; Zhu, Alex Z.; Behringer, Robert P.

    2015-10-01

    We have explored isotropically jammed states of semi-2D granular materials through cyclic compression. In each compression cycle, systems of either identical ellipses or bidisperse disks transition between jammed and unjammed states. We determine the evolution of the average pressure P and structure through consecutive jammed states. We observe a transition point ϕm above which P persists over many cycles; below ϕm, P relaxes slowly. The relaxation time scale associated with P increases with packing fraction, while the relaxation time scale for collective particle motion remains constant. The collective motion of the ellipses is hindered compared to disks because of the rotational constraints on elliptical particles.

  20. Jamming anomaly in PT-symmetric systems

    NASA Astrophysics Data System (ADS)

    Barashenkov, I. V.; Zezyulin, D. A.; Konotop, V. V.

    2016-07-01

    The Schrödinger equation with a { P }{ T }-symmetric potential is used to model an optical structure consisting of an element with gain coupled to an element with loss. At low gain–loss amplitudes γ, raising the amplitude results in the energy flux from the active to the leaky element being boosted. We study the anomalous behaviour occurring for larger γ, where the increase of the amplitude produces a drop of the flux across the gain–loss interface. We show that this jamming anomaly is either a precursor of the exceptional point, where two real eigenvalues coalesce and acquire imaginary parts, or precedes the eigenvalue's immersion in the continuous spectrum.

  1. Traffic jam dynamics in stochastic cellular automata

    SciTech Connect

    Nagel, K. |; Schreckenberg, M.

    1995-09-01

    Simple models for particles hopping on a grid (cellular automata) are used to simulate (single lane) traffic flow. Despite their simplicity, these models are astonishingly realistic in reproducing start-stop-waves and realistic fundamental diagrams. One can use these models to investigate traffic phenomena near maximum flow. A so-called phase transition at average maximum flow is visible in the life-times of jams. The resulting dynamic picture is consistent with recent fluid-dynamical results by Kuehne/Kerner/Konhaeuser, and with Treiterer`s hysteresis description. This places CA models between car-following models and fluid-dynamical models for traffic flow. CA models are tested in projects in Los Alamos (USA) and in NRW (Germany) for large scale microsimulations of network traffic.

  2. Creep and aging in jammed granular materials

    NASA Astrophysics Data System (ADS)

    Srivastava, Ishan; Fisher, Timothy

    Granular materials flow (or unjam) when stressed above the Coulomb yield stress, but a slow creep is observed when the applied stresses are low. In this work, using a recently introduced enthalpy-based variable-cell simulation method, we will present results on the creep and slow aging dynamics in granular systems comprised of soft particles of varying shape that are hydrostatically jammed and subjected to an external stress. We observe a two-stage creep with an initial fast exponential evolution followed by a slow logarithmic evolution over long time scales. We correlate the slow creeping dynamics with micromechanical evolution at the grain scale, such as increasing dynamical heterogeneity and force-chain rearrangements. Results will also be presented on the effect of grain shape (faceted vs. spherical) on the creep and aging dynamics. Finally, a continuum granular fluidity model is developed to rationalize these observations.

  3. Novel anti-jamming technique for OCDMA network through FWM in SOA based wavelength converter

    NASA Astrophysics Data System (ADS)

    Jyoti, Vishav; Kaler, R. S.

    2013-06-01

    In this paper, we propose a novel anti-jamming technique for optical code division multiple access (OCDMA) network through four wave mixing (FWM) in semiconductor optical amplifier (SOA) based wavelength converter. OCDMA signal can be easily jammed with high power jamming signal. It is shown that wavelength conversion through four wave mixing in SOA has improved capability of jamming resistance. It is observed that jammer has no effect on OCDMA network even at high jamming powers by using the proposed technique.

  4. Elasticity of frictionless particles near jamming.

    PubMed

    Karimi, Kamran; Maloney, Craig E

    2015-08-01

    We study the linear elastic response of harmonic disk packings near jamming via three types of probes: (i) point forcing, (ii) constrained homogeneous deformation of subregions of large systems, and (iii) unconstrained deformation of the full system subject to periodic boundary conditions. For the point forcing, our results indicate that the transverse component of the response is governed by a lengthscale ξT, which scales with the confining pressure, p, as ξT∼p-0.25, while the longitudinal component is governed by ξL, which scales as ξL∼p-0.4. The former scaling is precisely the transverse lengthscale, which has been invoked to explain the structure of normal modes near the density of states anomaly in sphere packings, while the latter is much closer to the rigidity length, l*∼p-0.5, which has been invoked to describe the jamming scenario. For the case of constrained homogeneous deformation, we find that μ(R), the value of the shear modulus measured in boxes of size R, gives a value much higher than the continuum result for small boxes and recedes to its continuum limit only for boxes bigger than a characteristic length, which scales like p-0.5, precisely the same way as l*. Finally, for the case of unconstrained homogeneous deformation, we find displacement fields with power spectra, which are consistent with independent, uncorrelated Eshelby transformations. The transverse sector is amazingly invariant with respect to p and very similar to what is seen in Lennard-Jones glasses. The longitudinal piece, however, is sensitive to p. It develops a plateau at long wavelength, the start of which occurs at a length that grows in the p→0 limit. Strikingly, the same behavior is observed both for applied shear and dilation. PMID:26382395

  5. Elasticity of frictionless particles near jamming

    NASA Astrophysics Data System (ADS)

    Karimi, Kamran; Maloney, Craig E.

    2015-08-01

    We study the linear elastic response of harmonic disk packings near jamming via three types of probes: (i) point forcing, (ii) constrained homogeneous deformation of subregions of large systems, and (iii) unconstrained deformation of the full system subject to periodic boundary conditions. For the point forcing, our results indicate that the transverse component of the response is governed by a lengthscale ξT, which scales with the confining pressure, p , as ξT˜p-0.25 , while the longitudinal component is governed by ξL, which scales as ξL˜p-0.4 . The former scaling is precisely the transverse lengthscale, which has been invoked to explain the structure of normal modes near the density of states anomaly in sphere packings, while the latter is much closer to the rigidity length, l*˜p-0.5 , which has been invoked to describe the jamming scenario. For the case of constrained homogeneous deformation, we find that μ (R ) , the value of the shear modulus measured in boxes of size R , gives a value much higher than the continuum result for small boxes and recedes to its continuum limit only for boxes bigger than a characteristic length, which scales like p-0.5, precisely the same way as l*. Finally, for the case of unconstrained homogeneous deformation, we find displacement fields with power spectra, which are consistent with independent, uncorrelated Eshelby transformations. The transverse sector is amazingly invariant with respect to p and very similar to what is seen in Lennard-Jones glasses. The longitudinal piece, however, is sensitive to p . It develops a plateau at long wavelength, the start of which occurs at a length that grows in the p →0 limit. Strikingly, the same behavior is observed both for applied shear and dilation.

  6. When do jammed sphere packings have a valid linear regime?

    NASA Astrophysics Data System (ADS)

    Goodrich, Carl; Liu, Andrea; Nagel, Sidney

    2014-03-01

    The physics of jamming can be studied in its purest form in packings of soft spheres at zero temperature. One of the successes of this approach is that bulk material properties, such as the elastic moduli or density of normal modes, can be predicted solely from the distance of the system to the jamming transition. Such properties are both defined and measured in the linear-response regime. It is thus tacitly assumed that the harmonic approximation to the local energy landscape can capture the meaningful physics, and it is therefore essential to delineate when this assumption is valid. We will examine the regime of validity of the harmonic approximation in jammed sphere packings as a function of system size and density. We will also discuss the crossover from linear response of the zero-temperature jammed solid to thermal behavior at nonzero temperatures.

  7. Preface: Special Issue on Structure in Glassy and Jammed Systems

    NASA Astrophysics Data System (ADS)

    Royall, C. Patrick; Speck, Thomas

    2016-05-01

    This special issue presents new developments in our understanding of the role of structure in dynamical arrest and jamming. Articles highlight local geometric motifs and other forms of amorphous order, in experiment, computer simulation and theory.

  8. Pinning Susceptibility: The Effect of Dilute, Quenched Disorder on Jamming

    NASA Astrophysics Data System (ADS)

    Graves, Amy L.; Nashed, Samer; Padgett, Elliot; Goodrich, Carl P.; Liu, Andrea J.; Sethna, James P.

    2016-06-01

    We study the effect of dilute pinning on the jamming transition. Pinning reduces the average contact number needed to jam unpinned particles and shifts the jamming threshold to lower densities, leading to a pinning susceptibility, χp . Our main results are that this susceptibility obeys scaling form and diverges in the thermodynamic limit as χp∝|ϕ -ϕc∞|-γp where ϕc∞ is the jamming threshold in the absence of pins. Finite-size scaling arguments yield these values with associated statistical (systematic) errors γp=1.018 ±0.026 (0.291 ) in d =2 and γp=1.534 ±0.120 (0.822 ) in d =3 . Logarithmic corrections raise the exponent in d =2 to close to the d =3 value, although the systematic errors are very large.

  9. Stability of Granular Packings Jammed under Gravity: Avalanches and Unjamming

    NASA Astrophysics Data System (ADS)

    Merrigan, Carl; Birwa, Sumit; Tewari, Shubha; Chakraborty, Bulbul

    Granular avalanches indicate the sudden destabilization of a jammed state due to a perturbation. We propose that the perturbation needed depends on the entire force network of the jammed configuration. Some networks are stable, while others are fragile, leading to the unpredictability of avalanches. To test this claim, we simulated an ensemble of jammed states in a hopper using LAMMPS. These simulations were motivated by experiments with vibrated hoppers where the unjamming times followed power-law distributions. We compare the force networks for these simulated states with respect to their overall stability. The states are classified by how long they remain stable when subject to continuous vibrations. We characterize the force networks through both their real space geometry and representations in the associated force-tile space, extending this tool to jammed states with body forces. Supported by NSF Grant DMR1409093 and DGE1068620.

  10. Experimental studies of contact networks in jammed colloidal systems

    NASA Astrophysics Data System (ADS)

    Kyeyune-Nyombi, Eru; Gilchrist, Lane; Makse, Hernán

    Recent theoretical advances in the statistical mechanics of jamming have provided a new outlook for thermodynamically characterizing packings of granular matter. Packing density, spatial ordering metrics, and the number of inter-particle contacts are a few fundamental parameters used in various theoretical models. However, experimental measurements of inter-particle forces have been illusive. Here, fluorescent molecular probes are used to identify inter-particle contacts in high resolution confocal images of jammed colloidal systems.

  11. Jam-absorption driving with a car-following model

    NASA Astrophysics Data System (ADS)

    Taniguchi, Yohei; Nishi, Ryosuke; Ezaki, Takahiro; Nishinari, Katsuhiro

    2015-09-01

    Jam-absorption driving (JAD) refers to the action performed by a single car to dynamically change its headway to remove a traffic jam. Because of its irregular motion, a car performing JAD perturbs other cars following it, and these perturbations may grow to become the so-called secondary traffic jams. A basic theory for JAD (Nishi et al. 2013) does not consider accelerations of cars or the stability of traffic flow. In this paper, by introducing car-following behaviors, we implement these elements in JAD. Numerous previous studies on the instability of traffic flow showed that even in a region whose density is below a critical density, perturbation may grow if its initial magnitude is large. According to these previous studies, we expect that the perturbations caused by JAD, if they are sufficiently small, do not grow to become secondary traffic jams. Using a microscopic car-following model, we numerically confirmed that the stability of a flow obeying the model depends on the magnitude of JAD perturbations. On the basis of this knowledge, numerical results indicate that parameter regions exist where JAD allows traffic jams to be removed without causing secondary traffic jams. Moreover, JAD is robust against a parameter of acceleration in the model, as well as the choice of car-following models.

  12. Thermal fluctuations, mechanical response, and hyperuniformity in jammed solids

    NASA Astrophysics Data System (ADS)

    Ikeda, Atsushi; Berthier, Ludovic

    2015-07-01

    Jamming is a geometric phase transition occurring in dense particle systems in the absence of temperature. We use computer simulations to analyze the effect of thermal fluctuations on several signatures of the transition. We show that scaling laws for bulk and shear moduli only become relevant when thermal fluctuations are extremely small, and propose their relative ratio as a quantitative signature of jamming criticality. Despite the nonequilibrium nature of the transition, we find that thermally induced fluctuations and mechanical responses obey equilibrium fluctuation-dissipation relations near jamming, provided the appropriate fluctuating component of the particle displacements is analyzed. This shows that mechanical moduli can be directly measured from particle positions in mechanically unperturbed packings, and suggests that the definition of a "nonequilibrium index" is unnecessary for amorphous materials. We find that fluctuations of particle displacements are spatially correlated, and define a transverse and a longitudinal correlation length scale which both diverge as the jamming transition is approached. We analyze the frozen component of density fluctuations and find that it displays signatures of nearly hyperuniform behavior at large length scales. This demonstrates that hyperuniformity in jammed packings is unrelated to a vanishing compressibility and explains why it appears remarkably robust against temperature and density variations. Differently from jamming criticality, obstacles preventing the observation of hyperuniformity in colloidal systems do not originate from thermal fluctuations.

  13. Jamming of Monodisperse Cylindrical Grains in Featureless Vertical Channels

    NASA Astrophysics Data System (ADS)

    Friedl, Nicholas; Baxter, G. William

    2014-03-01

    We study jamming of low aspect-ratio cylindrical Delrin grains falling through a featureless vertical channel under the influence of gravity. These grains have an aspect-ratio less than two (H/D < 2) and resemble aspirin tablets, 35mm film canisters, poker chips, or coins. Monodisperse grains are allowed to fall under the influence of gravity through a uniform channel of square cross-section where the channel width is greater than the grain size and constant along the length of the channel. No combination of grain heights and diameters is equal to the channel width. Collections of grains sometimes form jams, stable structures in which the grains are supported by the channel walls and not by grains or walls beneath them. The probability of a jam occurring and the jam's strength are influenced by the grain dimensions and channel width. We will present experimental measurements of the jamming probability and jam strength and discuss the relationship of these results to other experiments and theories. Supported by an Undergraduate Research Grant from Penn State Erie, The Behrend College.

  14. Jamming of Cylindrical Grains in Featureless Vertical Channels

    NASA Astrophysics Data System (ADS)

    Baxter, G. William; Barr, Nicholas; Weible, Seth; Friedl, Nicholas

    2013-03-01

    We study jamming of low aspect-ratio cylindrical Delrin grains falling through a featureless vertical channel. With a grain height less than the grain diameter, these grains resemble aspirin tablets, poker chips, or coins. Unidisperse grains are allowed to fall under the influence of gravity through a uniform channel of square cross-section where the channel width is greater than the grain size and constant along the length of the channel. Channel widths are chosen so that no combination of grain heights and diameters is equal to the channel width. Collections of grains sometimes form jams, stable structures in which the grains are supported by the channel walls and not by grains or walls beneath them. The probability of a jam occurring and the jam's strength are influenced by the grain dimensions and channel width. We will present experimental measurements of the jamming probability and jam strength and discuss the relationship of these results to other experiments and theories. Supported by an Undergraduate Research Grant from Penn State Erie, The Behrend College

  15. Countering GPS jamming and EW threat

    NASA Astrophysics Data System (ADS)

    Pereira, Carlos M.; Rastegar, J.; McLain, Clifford E.; Alanson, T.; McMullan, Charles; Nguyen, H.-L.

    2007-09-01

    Efforts at the U.S. Army Research, Development and Engineering Center (ARDEC) at Picatinny, New Jersey are focused on developing methods to counter GPS jamming and electronic warfare (EW) threat by eliminating GPS dependency entirely. In addition, the need for munitions cost reduction requires alternatives to expensive high-grade inertia components. Efforts at ARDEC include investigations of novel methods for onboard measurement of munitions full position and angular orientation independent of GPS signals or high-grade inertia components. Currently, two types of direct angular measurement sensors are being investigated. A first sensor, Radio Frequency Polarized Sensor (RFPS), uses an electromagnetic field as a reference. A second sensor is based on magnetometers, using the Earth magnetic field for orientation measurement. Magnetometers, however, can only provide two independent orientation measurements. The RFPS may also be used to make full object position and angular orientation measurement relative to a reference coordinate system, which may be moving or stationary. The potential applications of novel RFPS sensors is in providing highly effective inexpensive replacement for GPS, which could be used in a "Layered Navigation" scheme employing alternate referencing methods and reduce the current dependency on GPS as a primary reference for guided gun-fired munitions. Other potential applications of RFPSs is in UAVs, UGVs, and robotic platforms.

  16. Traffic jam driving with NMV avoidance

    NASA Astrophysics Data System (ADS)

    Milanés, Vicente; Alonso, Luciano; Villagrá, Jorge; Godoy, Jorge; de Pedro, Teresa; Oria, Juan P.

    2012-08-01

    In recent years, the development of advanced driver assistance systems (ADAS) - mainly based on lidar and cameras - has considerably improved the safety of driving in urban environments. These systems provide warning signals for the driver in the case that any unexpected traffic circumstance is detected. The next step is to develop systems capable not only of warning the driver but also of taking over control of the car to avoid a potential collision. In the present communication, a system capable of autonomously avoiding collisions in traffic jam situations is presented. First, a perception system was developed for urban situations—in which not only vehicles have to be considered, but also pedestrians and other non-motor-vehicles (NMV). It comprises a differential global positioning system (DGPS) and wireless communication for vehicle detection, and an ultrasound sensor for NMV detection. Then, the vehicle's actuators - brake and throttle pedals - were modified to permit autonomous control. Finally, a fuzzy logic controller was implemented capable of analyzing the information provided by the perception system and of sending control commands to the vehicle's actuators so as to avoid accidents. The feasibility of the integrated system was tested by mounting it in a commercial vehicle, with the results being encouraging.

  17. Development of kink jams in traffic flow

    NASA Astrophysics Data System (ADS)

    Kurtze, Douglas

    Near the threshold of absolute stability of uniform, steady traffic flow, car-following models can often be reduced to a modified Korteweg-deVries (mKdV) equation plus small corrections. The mKdV equation has a continuous family of hyperbolic-kink solutions describing boundaries between regions of different traffic densities, i.e. the edges of traffic jams. A solvability calculation picks out the one member of this family which is consistent with the correction terms; this is usually labelled the ``selected'' kink. This identification is problematic, however, since it must be the downstream boundary condition that determines which kink solution is realized. We display a two-parameter family of mKdV solutions which has the kink solutions as one limit and uniform flow as another, and show how the correction terms can lead to kinks developing from initially near-uniform traffic. We then clarify the meaning of the usual solvability calcuation and of the ``selected'' kink.

  18. Study of jamming of the frequency modulation infrared seekers

    NASA Astrophysics Data System (ADS)

    Qian, Fang; Guo, Jin; Shao, Jun-feng; Wang, Ting-feng

    2013-09-01

    The threat of the IR guidance missile is a direct consequence of extensive proliferation of the airborne IR countermeasure. The aim of a countermeasure system is to inject false information into a sensor system to create confusion. Many optical seekers have a single detector that is used to sense the position of its victim in its field of view. A seeker has a spinning reticle in the focal plane of the optical system that collects energy from the thermal scene and focuses it on to the detector. In this paper, the principle of the conical-scan FM reticle is analyzed. Then the effect that different amplitude or frequency modulated mid-infrared laser pulse acts on the reticle system is simulated. When the ratio of jamming energy to target radiation (repression) gradually increases, the azimuth error and the misalignment angle error become larger. The results show that simply increasing the intensity of the jamming light achieves little, but it increases the received signal strength of the FM reticle system ,so that the target will be more easily exposed. A slow variation of amplitude will warp the azimuth information received by the seeker, but the target can't be completely out of the missile tracking. If the repression and the jamming frequency change at the same time, the jamming effects can be more obvious. When the jamming signal's angular frequency is twice as large as the carrier frequency of the reticle system, the seeker will can't receive an accurate signal and the jamming can be achieved. The jamming mechanism of the conical-scan FM IR seeker is described and it is helpful to the airborne IR countermeasure system.

  19. Schwann cell-specific JAM-C-deficient mice reveal novel expression and functions for JAM-C in peripheral nerves.

    PubMed

    Colom, Bartomeu; Poitelon, Yannick; Huang, Wenlong; Woodfin, Abigail; Averill, Sharon; Del Carro, Ubaldo; Zambroni, Desirée; Brain, Susan D; Perretti, Mauro; Ahluwalia, Amrita; Priestley, John V; Chavakis, Triantafyllos; Imhof, Beat A; Feltri, M Laura; Nourshargh, Sussan

    2012-03-01

    Junctional adhesion molecule-C (JAM-C) is an adhesion molecule expressed at junctions between adjacent endothelial and epithelial cells and implicated in multiple inflammatory and vascular responses. In addition, we recently reported on the expression of JAM-C in Schwann cells (SCs) and its importance for the integrity and function of peripheral nerves. To investigate the role of JAM-C in neuronal functions further, mice with a specific deletion of JAM-C in SCs (JAM-C SC KO) were generated. Compared to wild-type (WT) controls, JAM-C SC KO mice showed electrophysiological defects, muscular weakness, and hypersensitivity to mechanical stimuli. In addressing the underlying cause of these defects, nerves from JAM-C SC KO mice were found to have morphological defects in the paranodal region, exhibiting increased nodal length as compared to WTs. The study also reports on previously undetected expressions of JAM-C, namely on perineural cells, and in line with nociception defects of the JAM-C SC KO animals, on finely myelinated sensory nerve fibers. Collectively, the generation and characterization of JAM-C SC KO mice has provided unequivocal evidence for the involvement of SC JAM-C in the fine organization of peripheral nerves and in modulating multiple neuronal responses. PMID:22090315

  20. Controllable surface haptics via particle jamming and pneumatics.

    PubMed

    Stanley, Andrew A; Okamura, Allison M

    2015-01-01

    The combination of particle jamming and pneumatics allows the simultaneous control of shape and mechanical properties in a tactile display. A hollow silicone membrane is molded into an array of thin cells, each filled with coffee grounds such that adjusting the vacuum level in any individual cell rapidly switches it between flexible and rigid states. The array clamps over a pressure-regulated air chamber with internal mechanisms designed to pin the nodes between cells at any given height. Various sequences of cell vacuuming, node pinning, and chamber pressurization allow the surface to balloon into a variety of shapes. Experiments were performed to expand existing physical models of jamming at the inter-particle level to define the rheological characteristics of jammed systems from a macroscopic perspective, relevant to force-displacement interactions that would be experienced by human users. Force-displacement data show that a jammed cell in compression fits a Maxwell model and a cell deflected in the center while supported only at the edges fits a Zener model, each with stiffness and damping parameters that increase at higher levels of applied vacuum. This provides framework to tune and control the mechanical properties of a jamming haptic interface. PMID:25594980

  1. Stochastic Model of Traffic Jam and Traffic Signal Control

    NASA Astrophysics Data System (ADS)

    Shin, Ji-Sun; Cui, Cheng-You; Lee, Tae-Hong; Lee, Hee-Hyol

    Traffic signal control is an effective method to solve the traffic jam. and forecasting traffic density has been known as an important part of the Intelligent Transportation System (ITS). The several methods of the traffic signal control are known such as random walk method, Neuron Network method, Bayesian Network method, and so on. In this paper, we propose a new method of a traffic signal control using a predicted distribution of traffic jam based on a Dynamic Bayesian Network model. First, a forecasting model to predict a probabilistic distribution of the traffic jam during each period of traffic lights is built. As the forecasting model, the Dynamic Bayesian Network is used to predict the probabilistic distribution of a density of the traffic jam. According to measurement of two crossing points for each cycle, the inflow and outflow of each direction and the number of standing vehicles at former cycle are obtained. The number of standing vehicle at k-th cycle will be calculated synchronously. Next, the probabilistic distribution of the density of standing vehicle in each cycle will be predicted using the Dynamic Bayesian Network constructed for the traffic jam. And then a control rule to adjust the split and the cycle to increase the probability between a lower limit and ceiling of the standing vehicles is deduced. As the results of the simulation using the actual traffic data of Kitakyushu city, the effectiveness of the method is shown.

  2. Jamming and chaotic dynamics in different granular systems

    NASA Astrophysics Data System (ADS)

    Maghsoodi, Homayoon; Luijten, Erik

    Although common in nature and industry, the jamming transition has long eluded a concrete, mechanistic explanation. Recently, Banigan et al. (Nat. Phys. 9, 288-292, 2013) proposed a method for characterizing this transition in a granular system in terms of the system's chaotic properties, as quantified by the largest Lyapunov exponent. They demonstrated that in a two-dimensional shear cell the jamming transition coincides with the bulk density at which the system's largest Lyapunov exponent changes sign, indicating a transition between chaotic and non-chaotic regimes. To examine the applicability of this observation to realistic granular systems, we study a model that includes frictional forces within an expanded phase space. Furthermore, we test the generality of the relation between chaos and jamming by investigating the relationship between jamming and the chaotic properties of several other granular systems, notably sheared systems (Howell, D., Behringer R. P., Veje C., Phys. Rev. Lett. 82, 5241-5244, 1999) and systems with a free boundary. Finally, we quantify correlations between the largest Lyapunov vector and collective rearrangements of the system to demonstrate the predictive capabilities enabled by adopting this perspective of jamming.

  3. Shape Effects on Jamming of Granular Materials

    NASA Astrophysics Data System (ADS)

    Farhadi, Somayeh

    In this work, we have focused on the jamming properties of systems composed of semi-2D elliptical shaped particles. In order to study these systems, we have performed three types of experiments: Couette shear, biaxial isotropic compression, and biaxial pure shear. In each experimental scheme, we take data for both systems of ellipses an bi-disperse disks, in order to probe the effect of broken spherical symmetry at the particle scale, on the global behavior. We use two synchronized cameras to capture the flow of particles and the local stress at the same time. In Couette experiments, we study the rheological properties, as well as the stress fluctuations for very large strains (up to 20 revolutions of the inner wheel). The system is sheared for densities below the isotropic jamming point (point J). From these studies we learn that over a small range of packing fractions, (0.85 ≤ φ ≤ 0.86), systems of ellipses demonstrate exceptionally slow dynamical evolution when they are sheared. For fixed density, and starting from an essentially unstressed state, the application of shear strain leads to first a growth of average particle displacements in the system through a Reynolds dilatancy effect, and then for very large strains, a steady decrease in particle displacements. In an intermediate range of shear strains, the system exists in effectively meta-stable states for a very long time before relaxing to an unjammed state, in which the flow of particles stops completely, and the stress fluctuations drop to zero. The strain scale for this relaxation depends on the global packing fraction. We characterize this slow dynamics by measuring the evolution of mean velocity, density, and orientational order throughout the experiments. In a similar set of experiments performed on disks, slow relaxation was observed as well. However, the increasing average displacement build-up before relaxation, which was observed in ellipses, did not occur for disks. This suggests that the

  4. Flow and jamming of granular suspensions in foams.

    PubMed

    Haffner, B; Khidas, Y; Pitois, O

    2014-05-14

    The drainage of particulate foams is studied under conditions where the particles are not trapped individually by constrictions of the interstitial pore space. The drainage velocity decreases continuously as the particle volume fraction φ(p) increases. The suspensions jam--and therefore drainage stops--for values φ*(p) which reveal a strong effect of the particle size. In accounting for the particular geometry of the foam, we show that φ*(p) accounts for unusual confinement effects when the particles pack into the foam network. We model quantitatively the overall behavior of the suspension--from flow to jamming--by taking into account explicitly the divergence of its effective viscosity at φ*(p). Beyond the scope of drainage, the reported jamming transition is expected to have a deep significance for all aspects related to particulate foams, from aging to mechanical properties. PMID:24633178

  5. Wireless Jamming Localization by Exploiting Nodes' Hearing Ranges

    NASA Astrophysics Data System (ADS)

    Liu, Zhenhua; Liu, Hongbo; Xu, Wenyuan; Chen, Yingying

    Jamming attacks are especially harmful when ensuring the dependability of wireless communication. Finding the position of a jammer will enable the network to actively exploit a wide range of defense strategies. Thus, in this paper, we focus on developing mechanisms to localize a jammer. We first conduct jamming effect analysis to examine how a hearing range, e.g., the area from which a node can successfully receive and decode the packet, alters with the jammer's location and transmission power. Then, we show that the affected hearing range can be estimated purely by examining the network topology changes caused by jamming attacks. As such, we solve the jammer location estimation by constructing a least-squares problem, which exploits the changes of the hearing ranges. Compared with our previous iterative-search-based virtual force algorithm, our proposed hearing-range-based algorithm exhibits lower computational cost (i.e., one-step instead of iterative searches) and higher localization accuracy.

  6. Solution of the Traffic Jam Problem through Fuzzy Applications

    NASA Astrophysics Data System (ADS)

    Fernandez, Shery

    2010-11-01

    The major hurdle of a city planning council is to handle the traffic jam problem. The number of vehicles on roads increases day by day. Also the number of vehicles is directly proportional to the width of the road (including that of parallel roads). But it is not always possible to make roads or to increase width of the road corresponding to the increase in the number of vehicles. Also we cannot tell a person not to buy a vehicle. So trying to minimise the traffic jam is the only possible way to overcome this hurdle. Here we try to develop a method to avoid traffic jam through a mathematical approach (through fuzzy applications). This method helps to find a suitable route from an origin to a destination with lesser time than other routes.

  7. Clogging and Jamming Transitions in Granular Matter Flowing Through Obstacles

    NASA Astrophysics Data System (ADS)

    Reichhardt, Cynthia Olson; Reichhardt, Charles

    2015-03-01

    We consider a two-dimensional system of bidisperse disks driven through a landscape of fixed obstacles. In the limit of a single obstacle, the disks cease moving when the disk density is increased to the jamming density. The threshold density value decreases as the number of obstacles increases, but we also observe a change in the nature of the frozen state. At low obstacle density we find a homogeneous jammed state, but for higher obstacle density we instead find a heterogeneous clogged state containing void areas and possessing a memory of the driving direction. The transition to the clogged state is strongly stochastic and we observe large fluctuations in clogging time both for clogging in the original driving direction and for transverse clogging when the drive is suddenly rotated by 90 degrees. We find evidence for a diverging clogging transition time at a critical disk density well below the jamming density in a clean system.

  8. The effect of jamming/deception on decision making

    NASA Astrophysics Data System (ADS)

    Felkey, M. A.; Monk, D. L.; Stec, L. J.

    1984-10-01

    The present experiment examined the capability of developing a simulation methodology for assessing the effects of Command, Control, and Communications CounterMeasures (C3CM) on a human operator. Primarily, the effects on human information jamming and deception were applied against a key decision maker in a simulated, air defense, C3 system were assessed. The man-in-the-loop simulation provides real human operator data and a methodology to assess human operator performance. The subjects' performance exhibited trends from which certain strategies were assessed. Results indicated that operator uncertainty and loss of confidence in ambiguous situations did not exist. Specifically, the subjects relied on the most timely information channel. Performance was worse when that channel was jammed. Also, the condition that degraded performance the most was when the most timely channel was jammed and the most precise channel contained deceptive information.

  9. JAM-A mediates neutrophil transmigration in a stimulus-specific manner in vivo: evidence for sequential roles for JAM-A and PECAM-1 in neutrophil transmigration.

    PubMed

    Woodfin, Abigail; Reichel, Christoph Andreas; Khandoga, Andrej; Corada, Monica; Voisin, Mathieu-Benoit; Scheiermann, Christoph; Haskard, Dorian O; Dejana, Elisabetta; Krombach, Fritz; Nourshargh, Sussan

    2007-09-15

    Junctional adhesion molecule-A (JAM-A) is a transmembrane protein expressed at tight junctions of endothelial and epithelial cells and on the surface of platelets and leukocytes. The role of JAM-A in leukocyte transmigration in vivo was directly investigated by intravital microscopy using both a JAM-A-neutralizing monoclonal antibody (mAb) (BV-11) and JAM-A-deficient (knockout [KO]) mice. Leukocyte transmigration (but not adhesion) through mouse cremasteric venules as stimulated by interleukin 1beta (IL-1beta) or ischemia/reperfusion (I/R) injury was significantly reduced in wild-type mice treated with BV-11 and in JAM-A KO animals. In contrast, JAM-A blockade/genetic deletion had no effect on responses elicited by leukotriene B(4) (LTB(4)) or platelet-activating factor (PAF). Furthermore, using a leukocyte transfer method and mice deficient in endothelial-cell JAM-A, evidence was obtained for the involvement of endothelial-cell JAM-A in leukocyte transmigration mediated by IL-1beta. Investigation of the functional relationship between JAM-A and PECAM-1 (CD31) determined that dual blockade/deletion of these proteins does not lead to an inhibitory effect greater than that seen with blockade/deletion of either molecule alone. The latter appeared to be due to the fact that JAM-A and PECAM-1 can act sequentially to mediate leukocyte migration through venular walls in vivo. PMID:17505016

  10. A study of optimal abstract jamming strategies vs. noncoherent MFSK

    NASA Technical Reports Server (NTRS)

    Mceliece, R. J.; Rodemich, E. R.

    1983-01-01

    The present investigation is concerned with the performance of uncoded MFSK modulation in the presence of arbitrary additive jamming, taking into account the objective to devise robust antijamming strategies. An abstract model is considered, giving attention to the signal strength as a nonnegative real number X, the employment of X as a random variable, its distribution function G(x), the transmitter's strategy G, the jamming noise as an M-dimensional random vector Z, and the error probability. A summary of previous work on the considered problem is provided, and the results of the current study are presented.

  11. Rigid Cluster Decomposition Reveals Criticality in Frictional Jamming

    NASA Astrophysics Data System (ADS)

    Henkes, Silke; Quint, David A.; Fily, Yaouen; Schwarz, J. M.

    2016-01-01

    We study the nature of the frictional jamming transition within the framework of rigidity percolation theory. Slowly sheared frictional packings are decomposed into rigid clusters and floppy regions with a generalization of the pebble game including frictional contacts. Our method suggests a second-order transition controlled by the emergence of a system-spanning rigid cluster accompanied by a critical cluster size distribution. Rigid clusters also correlate with common measures of rigidity. We contrast this result with frictionless jamming, where the rigid cluster size distribution is noncritical.

  12. Contact nonlinearities and linear response in jammed particulate packings.

    PubMed

    Goodrich, Carl P; Liu, Andrea J; Nagel, Sidney R

    2014-08-01

    Packings of frictionless athermal particles that interact only when they overlap experience a jamming transition as a function of packing density. Such packings provide the foundation for the theory of jamming. This theory rests on the observation that, despite the multitude of disordered configurations, the mechanical response to linear order depends only on the distance to the transition. We investigate the validity and utility of such measurements that invoke the harmonic approximation and show that, despite particles coming in and out of contact, there is a well-defined linear regime in the thermodynamic limit. PMID:25215727

  13. Standoff jamming in the 21st century - The EC multiplier

    NASA Astrophysics Data System (ADS)

    McBride, Lance; Black, Al

    1987-02-01

    Consideration is given to a jamming aircraft screening friendly aircraft in the presence of threat radars such as missile-associated radars and radars employed in guiding interceptor aircraft. In these ranks are early warning (EW), acquisition, target tracking, and ground and air controlled intercept radars. A 21st century standoff jamming (SOJ) system block diagram is given. Transmitters, electronic support measures, and EW command and control are discussed as well as reliability, maintainability, and cost. It is concluded that several megawatts of EW ERP (effective radiated power) will be required to enable each SOJ platform to effectively counter multiple radars from the protection afforded by long standoff range.

  14. An EW technology research of jamming IR imaging guided missiles

    NASA Astrophysics Data System (ADS)

    Wu, Xiu-qin; Rong, Hua; Liang, Jing-ping; Chen, Qi; Chen, Min-rong

    2009-07-01

    The IR-Imaging-Guided Weapons have been playing an important role in the modern warfare by means of select attacking the vital parts of targets with the features of highly secret attacking, high precision, and excellent anti-jamming capability ,therefore, they are viewed to be one of the promising precisely guided weapons ,receiving great concern through out the world. This paper discusses the characteristics of IR-Imaging guidance systems at the highlight of making a study of correlated technologies of jamming IR-Imaging-Guided Weapons on the basis of elaborating the operational principles of IR-Imaging-guided Weapons.

  15. Basic Helix-Loop-Helix Transcription Factors JASMONATE-ASSOCIATED MYC2-LIKE1 (JAM1), JAM2, and JAM3 Are Negative Regulators of Jasmonate Responses in Arabidopsis1[W][OPEN

    PubMed Central

    Sasaki-Sekimoto, Yuko; Jikumaru, Yusuke; Obayashi, Takeshi; Saito, Hikaru; Masuda, Shinji; Kamiya, Yuji; Ohta, Hiroyuki; Shirasu, Ken

    2013-01-01

    Jasmonates regulate transcriptional reprogramming during growth, development, and defense responses. Jasmonoyl-isoleucine, an amino acid conjugate of jasmonic acid (JA), is perceived by the protein complex composed of the F-box protein CORONATINE INSENSITIVE1 (COI1) and JASMONATE ZIM DOMAIN (JAZ) proteins, leading to the ubiquitin-dependent degradation of JAZ proteins. This activates basic helix-loop-helix-type MYC transcription factors to regulate JA-responsive genes. Here, we show that the expression of genes encoding other basic helix-loop-helix transcription factors, JASMONATE ASSOCIATED MYC2-LIKE1 (JAM1), JAM2, and JAM3, is positively regulated in a COI1- and MYC2-dependent manner in Arabidopsis (Arabidopsis thaliana). However, contrary to myc2, the jam1jam2jam3 triple mutant exhibited shorter roots when treated with methyl jasmonate (MJ), indicating enhanced responsiveness to JA. Our genome-wide expression analyses revealed that key jasmonate metabolic genes as well as a set of genes encoding transcription factors that regulate the JA-responsive metabolic genes are negatively regulated by JAMs after MJ treatment. Consistently, loss of JAM genes resulted in higher accumulation of anthocyanin in MJ-treated plants as well as higher accumulation of JA and 12-hydroxyjasmonic acid in wounded plants. These results show that JAMs negatively regulate the JA responses in a manner that is mostly antagonistic to MYC2. PMID:23852442

  16. Reliability of a jammed binary transmission over a Nakagami channel

    NASA Astrophysics Data System (ADS)

    Zenon, Syroka

    2014-05-01

    This study presents a mathematic and numerical analysis of the probability of error in a binary transmission over a fading radio channel described by Nakagami-m distribution and its special cases. The transmission is jammed by a signal occupying the entire (or comparable) band before detection.

  17. Wall slip across the jamming transition of soft thermoresponsive particles

    NASA Astrophysics Data System (ADS)

    Divoux, Thibaut; Lapeyre, Véronique; Ravaine, Valérie; Manneville, Sébastien

    2015-12-01

    Flows of suspensions are often affected by wall slip, that is, the fluid velocity vf in the vicinity of a boundary differs from the wall velocity vw due to the presence of a lubrication layer. While the slip velocity vs=|vf-vw| robustly scales linearly with the stress σ at the wall in dilute suspensions, there is no consensus regarding denser suspensions that are sheared in the bulk, for which slip velocities have been reported to scale as a vs∝σp with exponents p inconsistently ranging between 0 and 2. Here we focus on a suspension of soft thermoresponsive particles and show that vs actually scales as a power law of the viscous stress σ -σc , where σc denotes the yield stress of the bulk material. By tuning the temperature across the jamming transition, we further demonstrate that this scaling holds true over a large range of packing fractions ϕ on both sides of the jamming point and that the exponent p increases continuously with ϕ , from p =1 in the case of dilute suspensions to p =2 for jammed assemblies. These results allow us to successfully revisit inconsistent data from the literature and pave the way for a continuous description of wall slip above and below jamming.

  18. JAMS - a software platform for modular hydrological modelling

    NASA Astrophysics Data System (ADS)

    Kralisch, Sven; Fischer, Christian

    2015-04-01

    Current challenges of understanding and assessing the impacts of climate and land use changes on environmental systems demand for an ever-increasing integration of data and process knowledge in corresponding simulation models. Software frameworks that allow for a seamless creation of integrated models based on less complex components (domain models, process simulation routines) have therefore gained increasing attention during the last decade. JAMS is an Open-Source software framework that has been especially designed to cope with the challenges of eco-hydrological modelling. This is reflected by (i) its flexible approach for representing time and space, (ii) a strong separation of process simulation components from the declarative description of more complex models using domain specific XML, (iii) powerful analysis and visualization functions for spatial and temporal input and output data, and (iv) parameter optimization and uncertainty analysis functions commonly used in environmental modelling. Based on JAMS, different hydrological and nutrient-transport simulation models were implemented and successfully applied during the last years. We will present the JAMS core concepts and give an overview of models, simulation components and support tools available for that framework. Sample applications will be used to underline the advantages of component-based model designs and to show how JAMS can be used to address the challenges of integrated hydrological modelling.

  19. FIJI: Fighting Implicit Jamming in 802.11 WLANs

    NASA Astrophysics Data System (ADS)

    Broustis, Ioannis; Pelechrinis, Konstantinos; Syrivelis, Dimitris; Krishnamurthy, Srikanth V.; Tassiulas, Leandros

    The IEEE 802.11 protocol inherently provides the same long-term throughput to all the clients associated with a given access point (AP). In this paper, we first identify a clever, low-power jamming attack that can take advantage of this behavioral trait: the placement of a low-power jammer in a way that it affects a single legitimate client can cause starvation to all the other clients. In other words, the total throughput provided by the corresponding AP is drastically degraded. To fight against this attack, we design FIJI, a cross-layer anti-jamming system that detects such intelligent jammers and mitigates their impact on network performance. FIJI looks for anomalies in the AP load distribution to efficiently perform jammer detection. It then makes decisions with regards to optimally shaping the traffic such that: (a) the clients that are not explicitly jammed are shielded from experiencing starvation and, (b) the jammed clients receive the maximum possible throughput under the given conditions. We implement FIJI in real hardware; we evaluate its efficacy through experiments on a large-scale indoor testbed, under different traffic scenarios, network densities and jammer locations. Our measurements suggest that FIJI detects such jammers in real-time and alleviates their impact by allocating the available bandwidth in a fair and efficient way.

  20. Shear modulus and dilatancy softening in granular packings above jamming.

    PubMed

    Coulais, C; Seguin, A; Dauchot, O

    2014-11-01

    We investigate experimentally the mechanical response to shear of a monolayer of bidisperse frictional grains across the jamming transition. We inflate an intruder inside the packing and use photoelasticity and tracking techniques to measure the induced shear strain and stresses at the grain scale. We quantify experimentally the constitutive relations for strain amplitudes as low as 10(-3) and for a range of packing fractions within 2% variation around the jamming transition. At the transition strong nonlinear effects set in: both the shear modulus and the dilatancy shear soften at small strain until a critical strain is reached where effective linearity is recovered. The scaling of the critical strain and the associated critical stresses on the distance to jamming are extracted. We check that the constitutive laws, together with mechanical equilibrium, correctly predict to the observed stress and strain profiles. These profiles exhibit a spatial crossover between an effective linear regime close to the inflater and the truly nonlinear regime away from it. The crossover length diverges at the jamming transition. PMID:25415925

  1. A theoretical framework for jamming in confluent biological tissues

    NASA Astrophysics Data System (ADS)

    Manning, M. Lisa

    2015-03-01

    For important biological functions such as wound healing, embryonic development, and cancer tumorogenesis, cells must initially rearrange and move over relatively large distances, like a liquid. Subsequently, these same tissues must undergo buckling and support shear stresses, like a solid. Our work suggests that biological tissues can accommodate these disparate requirements because the tissues are close to glass or jamming transition. While recent self propelled particle models generically predict a glass/jamming transition that is driven by packing density φ and happens at some critical φc less than unity, many biological tissues that are confluent with no gaps between cells appear to undergo a jamming transition at a constant density (φ = 1). I will discuss a new theoretical framework for predicting energy barriers and rates of cell migration in 2D tissue monolayers, and show that this model predicts a novel type of rigidity transition, which takes place at constant φ = 1 and depends only on single cell properties such as cell-cell adhesion, cortical tension and cell elasticity. This model additionally predicts that an experimentally observable parameter, the ratio between a cell's perimeter and the square root of its cross-sectional area, attains a specific, critical value at the jamming transition. We show that this prediction is precisely realized in primary epithelial cultures from human patients, with implications for asthma pathology.

  2. Physical-scale models of engineered log jams in rivers

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Stream restoration and river engineering projects are employing engineered log jams increasingly for stabilization and in-stream improvements. To further advance the design of these structures and their morphodynamic effects on corridors, the basis for physical-scale models of rivers with engineere...

  3. Responses of experimental river corridors to engineered log jams

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Physical models of the Big Sioux River, SD, were constructed to assess the impact on flow, drag, and bed erosion and deposition in response to the installation of two different types of engineered log jams (ELJs). A fixed-bed model focused on flow velocity and forces acting on an instrumented ELJ, a...

  4. Jamming transition and inherent structures of hard spheres and disks.

    PubMed

    Ozawa, Misaki; Kuroiwa, Takeshi; Ikeda, Atsushi; Miyazaki, Kunimasa

    2012-11-16

    Recent studies show that volume fractions φ(J) at the jamming transition of frictionless hard spheres and disks are not uniquely determined but exist over a continuous range. Motivated by this observation, we numerically investigate the dependence of φ(J) on the initial configurations of the parent fluid equilibrated at a volume fraction φ(eq), before compressing to generate a jammed packing. We find that φ(J) remains constant when φ(eq) is small but sharply increases as φ(eq) exceeds the dynamic transition point which the mode-coupling theory predicts. We carefully analyze configurational properties of both jammed packings and parent fluids and find that, while all jammed packings remain isostatic, the increase of φ(J) is accompanied with subtle but distinct changes of local orders, a static length scale, and an exponent of the finite-size scaling. These results are consistent with the scenario of the random first-order transition theory of the glass transition. PMID:23215507

  5. Armoring a droplet: Soft jamming of a dense granular interface

    NASA Astrophysics Data System (ADS)

    Lagubeau, Guillaume; Rescaglio, Antonella; Melo, Francisco

    2014-09-01

    Droplets and bubbles protected by armors of particles have found vast applications in encapsulation, stabilization of emulsions and foams, or flotation processes. The liquid phase stores capillary energy, while concurrently the solid contacts of the granular network induce friction and energy dissipation, leading to hybrid interfaces of combined properties. By means of nonintrusive tensiometric methods and structural measurements, we distinguish three surface phases of increasing rigidity during the evaporation of armored droplets. The emergence of surface rigidity is reminiscent of jamming of granular matter, but it occurs differently since it is marked by a step by step hardening under surface compression. These results show that the concept of the effective surface tension remains useful only below the first jamming transition. Beyond this point, the surface stresses become anisotropic.

  6. High-order jamming crossovers and density anomalies.

    PubMed

    Pica Ciamarra, Massimo; Sollich, Peter

    2013-10-28

    We demonstrate that particles interacting via core-softened potentials exhibit a series of successive density anomalies upon isothermal compression, leading to oscillations in the diffusivity and thermal expansion coefficient, with the latter reaching negative values. These finite-temperature density anomalies are then shown to correspond to zero-temperature high-order jamming crossovers. These occur when particles are forced to come into contact with neighbours in successive coordination shells upon increasing the density. The crossovers induce anomalous behavior of the bulk modulus, which oscillates with density. We rationalize the dependence of these crossovers on the softness of the interaction potential, and relate the jamming crossovers and the anomalous diffusivity via the properties of the vibrational spectrum. PMID:26029762

  7. On adaptive robustness approach to Anti-Jam signal processing

    NASA Astrophysics Data System (ADS)

    Poberezhskiy, Y. S.; Poberezhskiy, G. Y.

    An effective approach to exploiting statistical differences between desired and jamming signals named adaptive robustness is proposed and analyzed in this paper. It combines conventional Bayesian, adaptive, and robust approaches that are complementary to each other. This combining strengthens the advantages and mitigates the drawbacks of the conventional approaches. Adaptive robustness is equally applicable to both jammers and their victim systems. The capabilities required for realization of adaptive robustness in jammers and victim systems are determined. The employment of a specific nonlinear robust algorithm for anti-jam (AJ) processing is described and analyzed. Its effectiveness in practical situations has been proven analytically and confirmed by simulation. Since adaptive robustness can be used by both sides in electronic warfare, it is more advantageous for the fastest and most intelligent side. Many results obtained and discussed in this paper are also applicable to commercial applications such as communications in unregulated or poorly regulated frequency ranges and systems with cognitive capabilities.

  8. A general analysis of anti-jam communication systems

    NASA Technical Reports Server (NTRS)

    Omura, J. K.; Levitt, B. K.

    1981-01-01

    A general error bound is derived for a general anti-jam communication system which will serve as the basis for evaluating the performance of all such complex communication systems. The two most common spread spectrum techniques, coherent DS/BPSK and noncoherent FH/MFSK, are analyzed. Pulse jamming represents the worst type of jammer for DS/BPSK systems, and several receiver structures against such a jammer are examined. It is found that for low values of chip energy-to-noise ratios of O dB or less there is little difference between having or not having jammer state knowledge with a hard decision receiver. Soft decision receivers are shown to be useless against very narrow pulses without jammer state knowledge. Partial band jammers are close to the worst case jammer for FH/MFSK systems. The conclusions found for these systems are similar to those for the DS/BPSK systems.

  9. On variational arguments for vibrational modes near jamming

    NASA Astrophysics Data System (ADS)

    Yan, Le; DeGiuli, Eric; Wyart, Matthieu

    2016-04-01

    Amorphous solids tend to present an abundance of soft elastic modes, which diminish their transport properties, generate heterogeneities in their elastic response, and affect non-linear processes like thermal activation of plasticity. This is especially true in packings of particles near their jamming transition, for which effective medium theory and variational arguments can both predict the density of vibrational modes. However, recent numerics support that one hypothesis of the variational argument does not hold. We provide a novel variational argument which overcomes this problem, and correctly predicts the scaling properties of soft modes near the jamming transition. Soft modes are shown to be related to the response to a local strain in more connected networks, and to be characterized by a volume 1/δ z , where δ z is the excess coordination above the Maxwell threshold. These predictions are verified numerically.

  10. Spatial Distributions of Local Elastic Moduli Near the Jamming Transition

    NASA Astrophysics Data System (ADS)

    Mizuno, Hideyuki; Silbert, Leonardo E.; Sperl, Matthias

    2016-02-01

    Recent progress on studies of the nanoscale mechanical responses in disordered systems has highlighted a strong degree of heterogeneity in the elastic moduli. In this contribution, using computer simulations, we study the elastic heterogeneities in athermal amorphous solids—composed of isotropic static sphere packings—near the jamming transition. We employ techniques based on linear response methods that are amenable to experimentation. We find that the local elastic moduli are randomly distributed in space and are described by Gaussian probability distributions, thereby lacking any significant spatial correlations, that persist all the way down to the transition point. However, the shear modulus fluctuations grow as the jamming threshold is approached, which is characterized by a new power-law scaling. Through this diverging behavior we are able to identify a characteristic length scale, associated with shear modulus heterogeneities, that distinguishes between bulk and local elastic responses.

  11. RJARS: RAND's version of the jamming aircraft and radar simulation

    NASA Astrophysics Data System (ADS)

    Sollfrey, William

    1991-06-01

    RJARS is an engagement level model that simulates air-to-ground and ground-to-air combat, primarily the latter, treating the combatants as individuals rather than aggregating. It has been designed to consider terrain masking, multipath and clutter, and flight dynamics in order to more carefully evaluate jamming effectiveness and mission attrition. The model is an extensive development of JARS (Jamming Aircraft and Radar Simulation). The current version of RJARS considers sorties in which aircraft carrying warning receivers, jammers, anti-radiation missiles, and air-launched cruise missiles fly against a defensive system with search, acquisition, and tracking radars, IR and optical systems, surface-to-air missiles, artillery, and a command, control, and communications system. All equipment parameters and scenarios can be varied.

  12. Jammed Clusters and Non-locality in Dense Granular Flows

    NASA Astrophysics Data System (ADS)

    Kharel, Prashidha; Rognon, Pierre

    We investigate the micro-mechanisms underpinning dense granular flow behaviour from a series of DEM simulations of pure shear flows of dry grains. We observe the development of transient clusters of jammed particles within the flow. Typical size of such clusters is found to scale with the inertial number with a power law that is similar to the scaling of shear-rate profile relaxation lengths observed previously. Based on the simple argument that transient clusters of size l exist in the dense flow regime, the formulation of steady state condition for non-homogeneous shear flow results in a general non-local relation, which is similar in form to the non-local relation conjectured for soft glassy flows. These findings suggest the formation of jammed clusters to be the key micro-mechanism underpinning non-local behaviour in dense granular flows. Particles and Grains Laboratory, School of Civil Engineering, The University of Sydney, Sydney, NSW 2006, Australia.

  13. Spatial Distributions of Local Elastic Moduli Near the Jamming Transition.

    PubMed

    Mizuno, Hideyuki; Silbert, Leonardo E; Sperl, Matthias

    2016-02-12

    Recent progress on studies of the nanoscale mechanical responses in disordered systems has highlighted a strong degree of heterogeneity in the elastic moduli. In this contribution, using computer simulations, we study the elastic heterogeneities in athermal amorphous solids--composed of isotropic static sphere packings--near the jamming transition. We employ techniques based on linear response methods that are amenable to experimentation. We find that the local elastic moduli are randomly distributed in space and are described by Gaussian probability distributions, thereby lacking any significant spatial correlations, that persist all the way down to the transition point. However, the shear modulus fluctuations grow as the jamming threshold is approached, which is characterized by a new power-law scaling. Through this diverging behavior we are able to identify a characteristic length scale, associated with shear modulus heterogeneities, that distinguishes between bulk and local elastic responses. PMID:26919018

  14. The jamming elasticity of emulsions stabilized by ionic surfactants.

    PubMed

    Scheffold, Frank; Wilking, James N; Haberko, Jakub; Cardinaux, Frédéric; Mason, Thomas G

    2014-07-28

    Oil-in-water emulsions composed of colloidal-scale droplets are often stabilized using ionic surfactants that provide a repulsive interaction between neighboring droplet interfaces, thereby inhibiting coalescence. If the droplet volume fraction is raised rapidly by applying an osmotic pressure, the droplets remain disordered, undergo an ergodic-nonergodic transition, and jam. If the applied osmotic pressure approaches the Laplace pressure of the droplets, then the jammed droplets also deform. Because solid friction and entanglements cannot play a role, as they might with solid particulate or microgel dispersions, the shear mechanical response of monodisperse emulsions can provide critical insight into the interplay of entropic, electrostatic, and interfacial forces. Here, we introduce a model that can be used to predict the plateau storage modulus and yield stress of a uniform charge-stabilized emulsion accurately if the droplet radius, interfacial tension, surface potential, Debye screening length, and droplet volume fraction are known. PMID:24913542

  15. T-structured fluid and jamming in driven Brownian rotators

    NASA Astrophysics Data System (ADS)

    Kirchhoff, R.; Löwen, H.

    2005-01-01

    The dynamics of two-dimensional suspensions of Brownian rods which are driven by an external torque are explored by computer simulation and instability theory. For increasing density the system self-organizes into a "T-structured fluid", where neighbouring rods preferentially orient perpendicular to each other until an overlap density is reached. Then a sharp jamming transition occurs towards a dynamically blocked state with parallel neighbouring rods.

  16. Bispectrum modulation for jamming rejection on satellite communication channels

    NASA Astrophysics Data System (ADS)

    Barton, Richard J.

    1995-05-01

    The Global Grid communications environment is designed to provide a high-data-rate network that supports the full complement of DoD communications needs. Satellite links are an integral part of the Global Grid concept which extends the connectivity to individual mobile units and jointly operating forces at isolated locations. However, satellite channels are vulnerable to jamming, in particular when a high data rate is required. To overcome the jamming problem, the traditional approach is to design modulation techniques such that, on the average, the spectrum of the signal looks like the spectrum of a white noise process. This together with channel coding provides immunity against jamming. The main problem with this approach is that it requires a much larger spectrum than that of the data sequence; hence, the available spectrum on the link is used mostly for jamming protection and not for data communications. The traditional modulation techniques employed on satellite communication links are based on various properties of the second-order spectrum of the modulation wave form. In this study we have explored the utility and performance of a new family of modulation schemes that exploit the properties of the higher-order cumulant sequences and associated polyspectra of the waveform. In particular, we have investigated an approach in which the third-order polyspectrum, which is generally referred to as the bispectrum, is modulated. To determine the performance characteristics of this bispectral modulation scheme, we have considered two different detector structures, for which we have completed both theoretical and simulated performance analyses.

  17. Navigating the Race to the Top Traffic Jam

    ERIC Educational Resources Information Center

    National Council on Teacher Quality, 2010

    2010-01-01

    Early last week the U.S. Department of Education announced an unexpected 16 finalists for the first round of Race to the Top (RTT) funding--a veritable traffic jam in the Race to the Top. The finalists have requested a total of $6.5 billion in funds, but only $4.3 billion is up for grabs, and that needs to be spread over two rounds of competition.…

  18. Spin jam induced by quantum fluctuations in a frustrated magnet.

    PubMed

    Yang, Junjie; Samarakoon, Anjana; Dissanayake, Sachith; Ueda, Hiroaki; Klich, Israel; Iida, Kazuki; Pajerowski, Daniel; Butch, Nicholas P; Huang, Q; Copley, John R D; Lee, Seung-Hun

    2015-09-15

    Since the discovery of spin glasses in dilute magnetic systems, their study has been largely focused on understanding randomness and defects as the driving mechanism. The same paradigm has also been applied to explain glassy states found in dense frustrated systems. Recently, however, it has been theoretically suggested that different mechanisms, such as quantum fluctuations and topological features, may induce glassy states in defect-free spin systems, far from the conventional dilute limit. Here we report experimental evidence for existence of a glassy state, which we call a spin jam, in the vicinity of the clean limit of a frustrated magnet, which is insensitive to a low concentration of defects. We have studied the effect of impurities on SrCr9pGa12-9pO19 [SCGO(p)], a highly frustrated magnet, in which the magnetic Cr(3+) (s = 3/2) ions form a quasi-2D triangular system of bipyramids. Our experimental data show that as the nonmagnetic Ga(3+) impurity concentration is changed, there are two distinct phases of glassiness: an exotic glassy state, which we call a spin jam, for the high magnetic concentration region (p > 0.8) and a cluster spin glass for lower magnetic concentration (p < 0.8). This observation indicates that a spin jam is a unique vantage point from which the class of glassy states of dense frustrated magnets can be understood. PMID:26324917

  19. Sculpting Pickering Emulsion Droplets by Arrest and Jamming

    NASA Astrophysics Data System (ADS)

    Burke, Christopher; Wei, Zengyi; Caggioni, Marco; Spicer, Patrick; Atherton, Tim

    Pickering emulsion droplets can be arrested into non-spherical shapes--useful for applications such as active delivery--through a general mechanism of deformation followed by absorption of additional colloidal particles onto the interface, relaxation of the droplet caused by surface tension and arrest at some point due to crowding of the particles. We perform simulations of the arrest process to clarify the relative importance of diffusive rearrangement of particles and collective forcing due to surface evolution. Experiment and theory are compared, giving insight into the stability of the resulting capsules and the robustness of the production process for higher-throughput production in, for example, microfluidic systems. We adapt theoretical tools from the jamming literature to better understand the arrested configurations and long timescale evolution of the system: using linear programming and a penalty function approach, we identify unjamming motions in kinetically arrested states. We propose a paradigm of ``metric jamming'' to describe the limiting behavior of this class of system: a structure is metric-jammed if it is stable with respect to collective motion of the particles as well as evolution of the hypersurface on which the packing is embedded. Supported by a Cottrell Award from the Research Corporation for Science Advancement.

  20. Self-driven jamming in growing microbial populations

    NASA Astrophysics Data System (ADS)

    Delarue, Morgan; Hartung, Jörn; Schreck, Carl; Gniewek, Pawel; Hu, Lucy; Herminghaus, Stephan; Hallatschek, Oskar

    2016-08-01

    In natural settings, microbes tend to grow in dense populations where they need to push against their surroundings to accommodate space for new cells. The associated contact forces play a critical role in a variety of population-level processes, including biofilm formation, the colonization of porous media, and the invasion of biological tissues. Although mechanical forces have been characterized at the single-cell level, it remains elusive how collective pushing forces result from the combination of single-cell forces. Here, we reveal a collective mechanism of confinement, which we call self-driven jamming, that promotes the build-up of large mechanical pressures in microbial populations. Microfluidic experiments on budding yeast populations in space-limited environments show that self-driven jamming arises from the gradual formation and sudden collapse of force chains driven by microbial proliferation, extending the framework of driven granular matter. The resulting contact pressures can become large enough to slow down cell growth, to delay the cell cycle in the G1 phase, and to strain or even destroy the micro-environment through crack propagation. Our results suggest that self-driven jamming and build-up of large mechanical pressures is a natural tendency of microbes growing in confined spaces, contributing to microbial pathogenesis and biofouling.

  1. Dynamic jamming fronts in iceberg-choked fjords

    NASA Astrophysics Data System (ADS)

    Peters, Ivo; Amundson, Jason; Cassotto, Ryan; Fahnestock, Mark; Darnell, Kristopher; Truffer, Martin; Zhang, Wendy

    2015-03-01

    During summertime at the glacier terminus at Jakobshavn Isbræ, Greenland, calving events are followed by rapid motion in the ice mélange in front of the terminus. Understanding the dynamics of ice mélange is important because it acts as a resisting force to calving events. We analyze this motion using time-lapse photography and terrestrial radar images. Large calving events last for approximately 5 minutes, during which ~1014 J of potential energy is released. Motion in the ice mélange quickly spreads out over at least 16 km down the fjord, and relaxes in about 1 hour. The ice mélange can be viewed as a dense granular system, which is packed close to the jamming point. A jammed ice mélange resists expansion of the glacier terminus much more strongly and reduces iceberg calving, which may therefore play a significant role in glacier evolution. In our images, we observe dynamic jamming fronts, which propagate one order of magnitude faster than the instantaneous speed of the calving iceberg. From the ratio between the speed of the front and the calving iceberg we calculate a compaction that agrees with estimated compaction that we observe directly.

  2. Spin jam induced by quantum fluctuations in a frustrated magnet

    PubMed Central

    Yang, Junjie; Samarakoon, Anjana; Dissanayake, Sachith; Ueda, Hiroaki; Klich, Israel; Iida, Kazuki; Pajerowski, Daniel; Butch, Nicholas P.; Huang, Q.; Copley, John R. D.; Lee, Seung-Hun

    2015-01-01

    Since the discovery of spin glasses in dilute magnetic systems, their study has been largely focused on understanding randomness and defects as the driving mechanism. The same paradigm has also been applied to explain glassy states found in dense frustrated systems. Recently, however, it has been theoretically suggested that different mechanisms, such as quantum fluctuations and topological features, may induce glassy states in defect-free spin systems, far from the conventional dilute limit. Here we report experimental evidence for existence of a glassy state, which we call a spin jam, in the vicinity of the clean limit of a frustrated magnet, which is insensitive to a low concentration of defects. We have studied the effect of impurities on SrCr9pGa12-9pO19 [SCGO(p)], a highly frustrated magnet, in which the magnetic Cr3+ (s = 3/2) ions form a quasi-2D triangular system of bipyramids. Our experimental data show that as the nonmagnetic Ga3+ impurity concentration is changed, there are two distinct phases of glassiness: an exotic glassy state, which we call a spin jam, for the high magnetic concentration region (p>0.8) and a cluster spin glass for lower magnetic concentration (p<0.8). This observation indicates that a spin jam is a unique vantage point from which the class of glassy states of dense frustrated magnets can be understood. PMID:26324917

  3. Jamming Behavior of Domain Walls in an Antiferromagnetic Film

    NASA Astrophysics Data System (ADS)

    Sinha, Sunil

    2014-03-01

    Over the last few years, attempts have been made to unify many aspects of the freezing behavior of glasses, granular materials, gels, supercooled liquids, etc. into a general conceptual framework of what is called jamming behavior. This occurs when particles reach packing densities high enough that their motions become highly restricted. A general phase diagram has been proposed onto which various materials systems, e.g glasses or granular materials, can be mapped. We will discuss some recent applications of resonant and non-resonant soft X-ray Grazing Incidence Scattering to mesoscopic science, for example the study of magnetic domain wall fluctuations in thin films. For these studies, we use resonant magnetic x-ray scattering with a coherent photon beam and the technique of X-ray Photon Correlation Spectroscopy. find that at the ordering temperature the domains of an antiferromagnetic system, namely Dysprosium metal, behave very much also like a jammed system and their associated fluctuations exhibit behavior which exhibit some of the universal characteristics of jammed systems, such as non-exponential relaxation and Vogel-Fulcher type freezing. Work supported by Basic Energy Sciences, U.S. Dept. of Energy under Grant Number: DE-SC0003678.

  4. Laser-jamming effectiveness analysis of combined-fiber lasers for airborne defense systems.

    PubMed

    Jie, Xu; Shanghong, Zhao; Rui, Hou; Shengbao, Zhan; Lei, Shi; Jili, Wu; Shaoqiang, Fang; Yongjun, Li

    2008-12-20

    The laser-jamming effectiveness of combined fiber lasers for airborne defense systems is analyzed in detail. Our preliminary experimental results are proof of the concept of getting a high-power laser through a beam combination technique. Based on combined fiber lasers, the jamming effectiveness of four-quadrant guidance and imaging guidance systems are evaluated. The simulation results have proved that for a four-quadrant guidance system, the tracking system takes only two seconds to complete tracking, and the new tracking target is the jamming laser; for the imaging guidance system, increasing the power of the jamming laser or the distance between the target and the jamming laser are both efficient ways to achieve a successful laser jamming. PMID:19104536

  5. Dysregulation of JAM-A plays an important role in human tumor progression

    PubMed Central

    Zhao, Chen; Lu, Funian; Chen, Hongxia; Zhao, Xianda; Sun, Jun; Chen, Honglei

    2014-01-01

    Junctional adhesion molecule A (JAM-A) is a transmembrane protein that belongs to the immunoglobulin (Ig) superfamily. Evidence determines that JAM-A plays a role in numerous cellular processes, including tight junction assembly, leukocyte migration, platelet activation, angiogenesis and virus binding. Recent research suggests that JAM-A is dysregulated in various cancers and is vital for tumor progression. JAM-A is implicated in carcinogenesis via different signal pathways such as TGF-β1 signaling. Furthermore, JAM-A expression in cancers is usually associated with certain outcome of patients and might be a prognostic indicator. In this review, the correlation between JAM-A expression and human cancers will be described. PMID:25400822

  6. Jamming, Self-Filtration and Cake Growth in Concentrated Particle Suspensions

    NASA Astrophysics Data System (ADS)

    Guo, Youjing; Li, Shoubo; Yang, Donglei; Mi, Yongli; Wang, Xiaorong

    2015-03-01

    We study the flows of concentrated particle suspensions driven through a circular orifice. Above a critical concentration, a jammed structure (i.e., quasi-solid sphere) often forms in the flow and at the entrance of the geometrical constriction. Once occurred this jammed structure grows fast as time t passes and produces a reduction in the solid concentration downstream. Our analysis shows that a combination of the particle jamming, the self-filtration, and the cake-formation with the flow passing through the pores of the jammed solid is responsible for the occurrence of such phenomena. Based on this mechanism, we establish a mathematical model to show how the jammed structure is propagated. Our results suggest that the size D of the jammed structure in this case is proportional to a 1/3 power of the time t. Experiments also support this conclusion.

  7. Self-Organization in 2D Traffic Flow Model with Jam-Avoiding Drive

    NASA Astrophysics Data System (ADS)

    Nagatani, Takashi

    1995-04-01

    A stochastic cellular automaton (CA) model is presented to investigate the traffic jam by self-organization in the two-dimensional (2D) traffic flow. The CA model is the extended version of the 2D asymmetric exclusion model to take into account jam-avoiding drive. Each site contains either a car moving to the up, a car moving to the right, or is empty. A up car can shift right with probability p ja if it is blocked ahead by other cars. It is shown that the three phases (the low-density phase, the intermediate-density phase and the high-density phase) appear in the traffic flow. The intermediate-density phase is characterized by the right moving of up cars. The jamming transition to the high-density jamming phase occurs with higher density of cars than that without jam-avoiding drive. The jamming transition point p 2c increases with the shifting probability p ja. In the deterministic limit of p ja=1, it is found that a new jamming transition occurs from the low-density synchronized-shifting phase to the high-density moving phase with increasing density of cars. In the synchronized-shifting phase, all up cars do not move to the up but shift to the right by synchronizing with the move of right cars. We show that the jam-avoiding drive has an important effect on the dynamical jamming transition.

  8. An information theoretic study of communication in the presence of jamming

    NASA Astrophysics Data System (ADS)

    McEliece, R. J.; Stark, W. E.

    An information theoretic analysis of communications in the presence of a hostile jammer is presented. Under certain restrictions coding and jamming strategies which are simultaneously optimal for both the coder and jammer are shown to exist. When the coder and jammer both have average power constraints the minimax strategies are shown to be Gaussian input, Gaussian jamming. By considering pulsed jamming strategies, Gaussian jamming is shown not to be a saddle point strategy when the input is restricted to be binary. However provided a modest amount of bandwidth expansion is tolerable, suitable coding can neutralize a pulsed jammer.

  9. Approach jamming effectiveness evaluation for surface-type infrared decoy in network centric warship formation

    NASA Astrophysics Data System (ADS)

    Lv, Mingshan

    2015-10-01

    The passive and photoelectrical jamming to anti-ship missile in the condition of network centric warship formation is an important research issue of fleet EW operation. An approach jamming method of shipborne surface-type infrared decoy countering the infrared image guided anti-ship missile is put forward. By analyzing the countering process the jamming effectiveness evaluation model is constructed. By simulation the method is proved t reasonable and effective. This method breaks through the traditional restrict that the passive and photoelectricity jamming measure can only be used in the end self-defence and provides a new method for network centric worship formation to support each other.

  10. Title: Flushed Away: Linking Carbon Storage and Log Jams in Colorado's Front Range

    NASA Astrophysics Data System (ADS)

    Beckman, N. D.; Wohl, E. E.

    2011-12-01

    Historical documents and recent field studies suggest that resource use within the Colorado Rockies during the past two centuries has reduced the wood loads and frequency of wood jams along most forested streams. Recent research has also shown that streams play a significant role in the sequestration and transport of organic carbon, and wood jams are a key component of storage and biological processing in mountain headwater streams. Log jams tend to slow the transport of carbon and encourage its uptake in the riverine environment and therefore may have effects which extend beyond streams and into the global carbon cycle. The paper aims to quantify the effects of past and present resource management on instream wood loads and logjam frequency along Colorado's Front Range. We hypothesize that more highly impacted reaches (as measured by recent fire, logging, and high flow regulation) will demonstrate lower wood loads, lower jam densities and lower overall volume of stored sediment. In addition, we hypothesize that soils stored behind log jams will have a higher OM and TC content. If these hypothesis hold true, then by implication areas with younger forests and higher impacts will have higher carbon flux and lower return of carbon and nutrients to the surrounding ecosystem. Wood loads and jam frequency are compared based on stream characteristics, forest age, and flow alteration. In addition, sediment samples from reaches with and without log jams are compared based on organic matter (OM) content and Total Carbon (TC) content. Samples taken from behind log jams are compared to samples taken from other backwater areas along a river reach. Preliminary results of the 2010/2011 field seasons indicate that sediment samples taken from log jams (regardless of forest age) have an overall average of 5% OM, as compared to an average of 1% OM in samples taken from non-jam areas. Samples taken from log jams on streams draining old growth forests (more than 250 years since last

  11. Mars Science Laboratory Rover Integrated Pump Assembly Bellows Jamming Failure

    NASA Technical Reports Server (NTRS)

    Johnson, Michael R.; Johnson, Joel; Birur, Gajanana; Bhandari, Pradeep; Karlmann, Paul

    2012-01-01

    The Mars Science Laboratory rover and spacecraft utilize two mechanically pumped fluid loops for heat transfer to and from the internal electronics assemblies and the Radioisotope Thermo-Electric Generator (RTG). The heat transfer fluid is Freon R-11 (CFC-11) which has a large coefficient of thermal expansion. The Freon within the heat transfer system must have a volume for safe expansion of the fluid as the system temperature rises. The device used for this function is a gas-over-liquid accumulator. The accumulator uses a metal bellows to separate the fluid and gas sections. During expansion and contraction of the fluid in the system, the bellows extends and retracts to provide the needed volume change. During final testing of a spare unit, the bellows would not extend the full distance required to provide the needed expansion volume. Increasing the fluid pressure did not loosen the jammed bellows either. No amount of stroking the bellows back and forth would get it to pass the jamming point. This type of failure, if it occurred during flight, would result in significant overpressure of the heat transfer system leading to a burst failure at some point in the system piping. A loss of the Freon fluid would soon result in a loss of the mission. The determination of the source of the jamming of the bellows was quite elusive, leading to an extensive series of tests and analyses. The testing and analyses did indicate the root cause of the failure, qualitatively. The results did not provide a set of dimensional limits for the existing hardware design that would guarantee proper operation of the accumulator. In the end, a new design was developed that relied on good engineering judgment combined with the test results to select a reliable enough solution that still met other physical constraints of the hardware, the schedule, and the rover system.

  12. Mitigation of Control Channel Jamming via Combinatorial Key Distribution

    NASA Astrophysics Data System (ADS)

    Falahati, Abolfazl; Azarafrooz, Mahdi

    The problem of countering control channel jamming against internal adversaries in wireless ad hoc networks is addressed. Using combinatorial key distribution, a new method to secure the control channel access is introduced. This method, utilizes the established keys in the key establishment phase to hide the location of control channels without the need for a secure BS. This is in obtained by combination of a collision free one-way function and a combinatorial key establishment method. The proposed scheme can be considered as a special case of the ALOHA random access schemes which uses the common established keys as its seeds to generate the pattern of transmission.

  13. Jamming and pattern formation in models of segregation

    NASA Astrophysics Data System (ADS)

    Rogers, Tim; McKane, Alan J.

    2012-04-01

    We investigate the Schelling model of social segregation, formulated as an intrinsically nonequilibrium system, in which the agents occupy districts (or patches) rather than sites on a grid. We show that this allows the equations governing the dynamical behavior of the model to be derived. Analysis of these equations reveals a jamming transition in the regime of low-vacancy density, and inclusion of a spatial dimension in the model leads to a pattern forming instability. Both of these phenomena exhibit unusual characteristics which may be studied through our approach.

  14. First JAM results on the determination of polarized parton distributions

    SciTech Connect

    Accardi, Alberto; Jimenez-Delgado, Pedro; Melnitchouk, Wally

    2014-01-01

    The Jefferson Lab Angular Momentum (JAM) Collaboration is a new initiative to study the angular momentum dependent structure of the nucleon. First results on the determination of spin-dependent parton distribution functions at intermediate and large x from world data on polarized deep-inelastic scattering are presented. Different aspects of global QCD analysis are discussed, including the effects of nuclear structure of deuterium and {sup 3}He targets, target mass corrections and higher twist contributions to the g{sub 1} and g{sub 2} structure functions.

  15. Traffic jams and hysteresis in driven one-dimensional systems

    NASA Astrophysics Data System (ADS)

    Braun, O. M.; Hu, B.; Filippov, A.; Zeltser, A.

    1998-08-01

    The driven underdamped chain of anharmonically interacting atoms in the sinusoidal external potential is studied. It is shown that due to the interatomic interaction the system exhibits hysteresis for any nonzero rate of changing of the dc driving force. Before the transition to the running state the system passes through the traffic-jam inhomogeneous state. The system behavior is explained with the help of two simple models, the discrete lattice-gas model with two states of atoms, and the continuum mean-field model based on the Fokker-Planck equation.

  16. On-board recordings reveal no jamming avoidance in wild bats.

    PubMed

    Cvikel, Noam; Levin, Eran; Hurme, Edward; Borissov, Ivailo; Boonman, Arjan; Amichai, Eran; Yovel, Yossi

    2015-01-01

    Animals often deal with situations in which vast sensory input is received simultaneously. They therefore must possess sophisticated mechanisms to select important input and ignore the rest. In bat echolocation, this problem is at its extreme. Echolocating bats emit sound signals and analyse the returning echoes to sense their environment. Bats from the same species use signals with similar frequencies. Nearby bats therefore face the difficulty of distinguishing their own echoes from the signals of other bats, a problem often referred to as jamming. Because bats commonly fly in large groups, jamming might simultaneously occur from numerous directions and at many frequencies. Jamming is a special case of the general phenomenon of sensory segregation. Another well-known example is the human problem of following conversation within a crowd. In both situations, a flood of auditory incoming signals must be parsed into important versus irrelevant information. Here, we present a novel method, fitting wild bats with a miniature microphone, which allows studying jamming from the bat's 'point of view'. Previous studies suggested that bats deal with jamming by shifting their echolocation frequency. On-board recordings suggest otherwise. Bats shifted their frequencies, but they did so because they were responding to the conspecifics as though they were nearby objects rather than avoiding being jammed by them. We show how bats could use alternative measures to deal with jamming instead of shifting their frequency. Despite its intuitive appeal, a spectral jamming avoidance response might not be the prime mechanism to avoid sensory interference from conspecifics. PMID:25429017

  17. 77 FR 71746 - Artificially Sweetened Fruit Jelly and Artificially Sweetened Fruit Preserves and Jams; Proposed...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-12-04

    ... fruit preserves and jams (artificially sweetened preserves and jams) (21 CFR 150.161) (24 FR 8896... for their use in food labeling (58 FR 2302; January 6, 1993). FDA also prescribed at the same time in... a traditional standardized food term (58 FR 2431; January 6, 1993). A nutrient content claim...

  18. Jamming effectiveness analysis of IR smoke projectile based on sight optical observation

    NASA Astrophysics Data System (ADS)

    Wang, Longtao; Liu, Zhenxing; Wang, Falong

    2013-09-01

    This text makes use of the similar of the principle between IR imaging guided missile detection system and the general sight optics probe. In this text, the synopsis analysis on the jamming effectiveness of the IR smoke projectile resist the IR imaging guided missile is discussed. This research of the jamming technique to IR imaging guided missile have a very realistic meaning.

  19. Geometric order parameters derived from the Voronoi tessellation show signatures of the jamming transition.

    PubMed

    Morse, Peter K; Corwin, Eric I

    2016-01-28

    A jammed packing of frictionless spheres at zero temperature is perfectly specified by the network of contact forces from which mechanical properties can be derived. However, we can alternatively consider a packing as a geometric structure, characterized by a Voronoi tessellation which encodes the local environment around each particle. We find that this local environment characterizes systems both above and below jamming and changes markedly at the transition. A variety of order parameters derived from this tessellation carry signatures of the jamming transition, complete with scaling exponents. Furthermore, we define a real space geometric correlation function which also displays a signature of jamming. Taken together, these results demonstrate the validity and usefulness of a purely geometric approach to jamming. PMID:26611105

  20. Positioning of jamming aircraft using the integrated refractive effects prediction system

    NASA Astrophysics Data System (ADS)

    White, T. W.

    1982-10-01

    Tactical ECM planning has historically considered only horizontal positioning of self-protection and standoff jamming systems. Failure to consider vertical positioning of the jammer, and how the environment affects that positioning, can lead to substantially reduced jamming effectiveness. The effects of radar and jamming system antenna patterns and environmental considerations are discussed. The Integrated Refractive Effects Prediction System (IREPS) incorporates these effects, but not in a form that is convenient for ECM planning. However, as it is now configured, IREPS can be a useful tool. A step-by-step approach for using IREPS and the jamming equations to assist the ECM planner is given. Sample calculations for self-protection and standoff jamming under actual environmental conditions are provided.

  1. Self-organization of traffic jams in cities: Effects of stochastic dynamics and signal periods

    NASA Astrophysics Data System (ADS)

    Chowdhury, Debashish; Schadschneider, Andreas

    1999-02-01

    We propose a cellular automata model for vehicular traffic in cities by combining (and appropriately modifying) ideas borrowed from the Biham-Middleton-Levine (BML) model of city traffic and the Nagel-Schreckenberg (NS) model of highway traffic. We demonstrate a phase transition from the ``free-flowing'' dynamical phase to the completely ``jammed'' phase at a vehicle density which depends on the time periods of the synchronized signals and the separation between them. The intrinsic stochasticity of the dynamics, which triggers the onset of jamming, is similar to that in the NS model, while the phenomenon of complete jamming through self-organization as well as the final jammed configurations are similar to those in the BML model. Using our model, we have made an investigation of the time dependence of the average speeds of the cars in the ``free-flowing'' phase as well as the dependence of flux and jamming on the time period of the signals.

  2. Angoricity and compactivity describe the jamming transition in soft particulate matter

    NASA Astrophysics Data System (ADS)

    Wang, Kun; Song, Chaoming; Wang, Ping; Makse, Hernán A.

    2010-09-01

    The application of concepts from equilibrium statistical mechanics to out-of-equilibrium systems has a long history of describing diverse systems ranging from glasses to granular materials. For dissipative jammed systems —particulate grains or droplets— a key concept is to replace the energy ensemble describing conservative systems by the volume-stress ensemble. Here, we test the applicability of the volume-stress ensemble to describe the jamming transition by comparing the jammed configurations obtained by dynamics with those averaged over the ensemble as a probe of ergodicity. Agreement between both methods suggests the idea of "thermalization" at a given angoricity and compactivity. We elucidate the thermodynamic order of the jamming transition by showing the absence of critical fluctuations in static observables like pressure and volume. The approach allows to calculate observables such as the entropy, volume, pressure, coordination number and distribution of forces to characterize the scaling laws near the jamming transition from a statistical mechanics viewpoint.

  3. Study on electro-optical jamming effect on TV seekers by flight test

    NASA Astrophysics Data System (ADS)

    Gao, Wei; Sun, Yifan; Wei, Yanling

    2014-07-01

    The effect and mechanism of smokescreen and stealth jamming on TV seekers are investigated by seeker captive flight jamming test. Based on a comprehensive analysis of large amounts of test results, we have discovered the laws of smokescreen and stealth jamming effect on the performance of TV seekers, such as tracking status, tracking error, measurement of line-of-sight angle and its angular rate. A rational explanation for the laws has also been presented based on the principle of stabilization of seeker optical axis. The results are not only useful for evaluating smokescreen and stealth jamming effect on TV guidance missiles, but also referential for the study of smokescreen and stealth mechanism and the anti-jamming design of imaging seekers.

  4. Differential mouse-strain specific expression of Junctional Adhesion Molecule (JAM)-B in placental structures.

    PubMed

    Stelzer, Ina Annelies; Mori, Mayumi; DeMayo, Francesco; Lydon, John; Arck, Petra Clara; Solano, Maria Emilia

    2016-03-01

    The junctional adhesion molecule (JAM)-B, a member of the immunoglobulin superfamily, is involved in stabilization of interendothelial cell-cell contacts, formation of vascular tubes, homeostasis of stem cell niches and promotion of leukocyte adhesion and transmigration. In the human placenta, JAM-B protein is abundant and mRNA transcripts are enriched in first-trimester extravillous trophoblast in comparison to the villous trophoblast. We here aimed to elucidate the yet unexplored spatio-temporal expression of JAM-B in the mouse placenta. We investigated and semi-quantified JAM-B protein expression by immunohistochemistry in early post-implantation si tes and in mid- to late gestation placentae of various murine mating combinations. Surprisingly, the endothelium of the placental labyrinth was devoid of JAM-B expression. JAM-B was mainly present in spongiotrophoblast cells of the junctional zone, as well as in the fetal vessels of the chorionic plate, the umbilical cord and in maternal myometrial smooth muscle. We observed a strain-specific placental increase of JAM-B protein expression from mid- to late gestation in Balb/c-mated C57BL/6 females, which was absent in DBA/2J-mated Balb/c females. Due to the essential role of progesterone during gestation, we further assessed a possible modulation of JAM-B in mid-gestational placentae deficient in the progesterone receptor (Pgr(-/-)) and observed an increased expression of JAM-B in Pgr(-/-) placentae, compared to Pgr(+/+) tissue samples. We propose that JAM-B is an as yet underappreciated trophoblast lineage-specific protein, which is modulated via the progesterone receptor and shows unique strain-specific kinetics. Future work is needed to elucidate its possible contribution to placental processes necessary to ensuring its integrity, ultimately facilitating placental development and fetal growth. PMID:26914234

  5. Jamming Attack in Wireless Sensor Network: From Time to Space

    NASA Astrophysics Data System (ADS)

    Sun, Yanqiang; Wang, Xiaodong; Zhou, Xingming

    Classical jamming attack models in the time domain have been proposed, such as constant jammer, random jammer, and reactive jammer. In this letter, we consider a new problem: given k jammers, how does the attacker minimize the pair-wise connectivity among the nodes in a Wireless Sensor Network (WSN)? We call this problem k-Jammer Deployment Problem (k-JDP). To the best of our knowledge, this is the first attempt at considering the position-critical jamming attack against wireless sensor network. We mainly make three contributions. First, we prove that the decision version of k-JDP is NP-complete even in the ideal situation where the attacker has full knowledge of the topology information of sensor network. Second, we propose a mathematical formulation based on Integer Programming (IP) model which yields an optimal solution. Third, we present a heuristic algorithm HAJDP, and compare it with the IP model. Numerical results show that our heuristic algorithm is computationally efficient.

  6. Three-dimensional jamming and flows of soft glassy materials.

    PubMed

    Ovarlez, G; Barral, Q; Coussot, P

    2010-02-01

    Various disordered dense systems, such as foams, gels, emulsions and colloidal suspensions, undergo a jamming transition from a liquid state (they flow) to a solid state below a yield stress. Their structure, which has been thoroughly studied with powerful means of three-dimensional characterization, shows some analogy with that of glasses, which led to them being named soft glassy materials. However, despite its importance for geophysical and industrial applications, their rheological behaviour, and its microscopic origin, is still poorly known, in particular because of its nonlinear nature. Here we show from two original experiments that a simple three-dimensional continuum description of the behaviour of soft glassy materials can be built. We first show that when a flow is imposed in some direction there is no yield resistance to a secondary flow: these systems are always unjammed simultaneously in all directions of space. The three-dimensional jamming criterion seems to be the plasticity criterion encountered in most solids. We also find that they behave as simple liquids in the direction orthogonal to that of the main flow; their viscosity is inversely proportional to the main flow shear rate, as a signature of shear-induced structural relaxation, in close similarity to the structural relaxations driven by temperature and density in other glassy systems. PMID:20062046

  7. Motility-Driven Glass and Jamming Transitions in Biological Tissues

    NASA Astrophysics Data System (ADS)

    Bi, Dapeng; Yang, Xingbo; Marchetti, M. Cristina; Manning, M. Lisa

    2016-04-01

    Cell motion inside dense tissues governs many biological processes, including embryonic development and cancer metastasis, and recent experiments suggest that these tissues exhibit collective glassy behavior. To make quantitative predictions about glass transitions in tissues, we study a self-propelled Voronoi model that simultaneously captures polarized cell motility and multibody cell-cell interactions in a confluent tissue, where there are no gaps between cells. We demonstrate that the model exhibits a jamming transition from a solidlike state to a fluidlike state that is controlled by three parameters: the single-cell motile speed, the persistence time of single-cell tracks, and a target shape index that characterizes the competition between cell-cell adhesion and cortical tension. In contrast to traditional particulate glasses, we are able to identify an experimentally accessible structural order parameter that specifies the entire jamming surface as a function of model parameters. We demonstrate that a continuum soft glassy rheology model precisely captures this transition in the limit of small persistence times and explain how it fails in the limit of large persistence times. These results provide a framework for understanding the collective solid-to-liquid transitions that have been observed in embryonic development and cancer progression, which may be associated with epithelial-to-mesenchymal transition in these tissues.

  8. Spatiotemporal chaotic unjamming and jamming in granular avalanches.

    PubMed

    Wang, Ziwei; Zhang, Jie

    2015-01-01

    We have investigated the spatiotemporal chaotic dynamics of unjamming and jamming of particles in a model experiment - a rotating drum partially filled with bidisperse disks to create avalanches. The magnitudes of the first Lyapunov vector δu(t) and velocity v(t) of particles are directly measured for the first time to yield insights into their spatial correlation Cδu,v, which is on statistical average slightly larger near the unjamming than the value near the jamming transition. These results are consistent with the recent work of Banigan et al (Nature Phys. 2013), and it is for the first time to validate their theoretical models in a real scenario. v(t) shows rich dynamics: it grows exponentially for unstable particles and keeps increasing despite stochastic interactions; after the maximum, it decays with large fluctuations. Hence the spatiotemporal chaotic dynamics of avalanche particles are entangled, causing temporal correlations of macroscopic quantities of the system. We propose a simple model for these observations. PMID:25634753

  9. Multifrequency OFDM SAR in Presence of Deception Jamming

    NASA Astrophysics Data System (ADS)

    Schuerger, Jonathan; Garmatyuk, Dmitriy

    2010-12-01

    Orthogonal frequency division multiplexing (OFDM) is considered in this paper from the perspective of usage in imaging radar scenarios with deception jamming. OFDM radar signals are inherently multifrequency waveforms, composed of a number of subbands which are orthogonal to each other. While being employed extensively in communications, OFDM has not found comparatively wide use in radar, and, particularly, in synthetic aperture radar (SAR) applications. In this paper, we aim to show the advantages of OFDM-coded radar signals with random subband composition when used in deception jamming scenarios. Two approaches to create a radar signal by the jammer are considered: instantaneous frequency (IF) estimator and digital-RF-memory- (DRFM-) based reproducer. In both cases, the jammer aims to create a copy of a valid target image via resending the radar signal at prescribed time intervals. Jammer signals are derived and used in SAR simulations with three types of signal models: OFDM, linear frequency modulated (LFM), and frequency-hopped (FH). Presented results include simulated peak side lobe (PSL) and peak cross-correlation values for random OFDM signals, as well as simulated SAR imagery with IF and DRFM jammers'-induced false targets.

  10. Spatial structure of states of self stress in jammed systems.

    PubMed

    Sussman, Daniel M; Goodrich, Carl P; Liu, Andrea J

    2016-05-01

    States of self stress, organizations of internal forces in many-body systems that are in equilibrium with an absence of external forces, can be thought of as the constitutive building blocks of the elastic response of a material. In overconstrained disordered packings they have a natural mathematical correspondence with the zero-energy vibrational modes in underconstrained systems. While substantial attention in the literature has been paid to diverging length scales associated with zero- and finite-energy vibrational modes in jammed systems, less is known about the spatial structure of the states of self stress. In this work we define a natural way in which a unique state of self stress can be associated with each bond in a disordered spring network derived from a jammed packing, and then investigate the spatial structure of these bond-localized states of self stress. This allows for an understanding of how the elastic properties of a system would change upon changing the strength or even existence of any bond in the system. PMID:26996807

  11. Universal robotic gripper based on the jamming of granular material

    PubMed Central

    Brown, Eric; Rodenberg, Nicholas; Amend, John; Mozeika, Annan; Steltz, Erik; Zakin, Mitchell R.; Lipson, Hod; Jaeger, Heinrich M.

    2010-01-01

    Gripping and holding of objects are key tasks for robotic manipulators. The development of universal grippers able to pick up unfamiliar objects of widely varying shape and surface properties remains, however, challenging. Most current designs are based on the multifingered hand, but this approach introduces hardware and software complexities. These include large numbers of controllable joints, the need for force sensing if objects are to be handled securely without crushing them, and the computational overhead to decide how much stress each finger should apply and where. Here we demonstrate a completely different approach to a universal gripper. Individual fingers are replaced by a single mass of granular material that, when pressed onto a target object, flows around it and conforms to its shape. Upon application of a vacuum the granular material contracts and hardens quickly to pinch and hold the object without requiring sensory feedback. We find that volume changes of less than 0.5% suffice to grip objects reliably and hold them with forces exceeding many times their weight. We show that the operating principle is the ability of granular materials to transition between an unjammed, deformable state and a jammed state with solid-like rigidity. We delineate three separate mechanisms, friction, suction, and interlocking, that contribute to the gripping force. Using a simple model we relate each of them to the mechanical strength of the jammed state. This advance opens up new possibilities for the design of simple, yet highly adaptive systems that excel at fast gripping of complex objects.

  12. Spatiotemporal chaotic unjamming and jamming in granular avalanches

    PubMed Central

    Wang, Ziwei; Zhang, Jie

    2015-01-01

    We have investigated the spatiotemporal chaotic dynamics of unjamming and jamming of particles in a model experiment – a rotating drum partially filled with bidisperse disks to create avalanches. The magnitudes of the first Lyapunov vector δu(t) and velocity v(t) of particles are directly measured for the first time to yield insights into their spatial correlation Cδu,v, which is on statistical average slightly larger near the unjamming than the value near the jamming transition. These results are consistent with the recent work of Banigan et al (Nature Phys. 2013), and it is for the first time to validate their theoretical models in a real scenario. v(t) shows rich dynamics: it grows exponentially for unstable particles and keeps increasing despite stochastic interactions; after the maximum, it decays with large fluctuations. Hence the spatiotemporal chaotic dynamics of avalanche particles are entangled, causing temporal correlations of macroscopic quantities of the system. We propose a simple model for these observations. PMID:25634753

  13. Jamming effect analysis of infrared reticle seeker for directed infrared countermeasures

    NASA Astrophysics Data System (ADS)

    Bae, Tae-Wuk; Kim, Byoung-Ik; Kim, Young-Choon; Ahn, Sang-Ho

    2012-09-01

    In directed infrared countermeasures (DIRCM), the purpose of jamming toward missiles is making missiles miss the target (aircraft of our forces) in the field of view. Since the DIRCM system directly emits the pulsing flashes of infrared (IR) energy to missiles, it is more effective than present flare method emitting IR source to omni-direction. In this paper, we implemented a reticle seeker simulation tool using MATLAB-SIMULINK, in order to analyze jamming effect of spin-scan and con-scan reticle missile seeker used widely in the world, though it was developed early. Because the jammer signal has influence on the missile guidance system using its variable frequency, it is very important technique among military defense systems protecting our forces from missiles of enemy. Simulation results show that jamming effect is greatly influenced according to frequency, phase and intensity of jammer signal. Especially, jammer frequency has the largest influence on jamming effect. Through our reticle seeker simulation tool, we can confirm that jamming effect toward missiles is significantly increased when jammer frequency is similar to reticle frequency. Finally, we evaluated jamming effect according to jammer frequencies, by using correlation coefficient as an evaluation criterion of jamming performance in two reticle missile seekers.

  14. Confocal Microscopy of Jammed Matter: From Elasticity to Granular Thermodynamics

    NASA Astrophysics Data System (ADS)

    Jorjadze, Ivane

    Packings of particles are ubiquitous in nature and are of interest not only to the scientific community but also to the food, pharmaceutical, and oil industries. In this thesis we use confocal microscopy to investigate packing geometry and stress transmission in 3D jammed particulate systems. By introducing weak depletion attraction we probe the accessible phase-space and demonstrate that a microscopic approach to jammed matter gives validity to statistical mechanics framework, which is intriguing because our particles are not thermally activated. We show that the fluctuations of the local packing parameters can be successfully captured by the recently proposed 'granocentric' model, which generates packing statistics according to simple stochastic processes. This model enables us to calculate packing entropy and granular temperature, the so-called 'compactivity', therefore, providing a basis for a statistical mechanics of granular matter. At a jamming transition point at which there are formed just enough number of contacts to guarantee the mechanical stability, theoretical arguments suggest a singularity which gives rise to the surprising scaling behavior of the elastic moduli and the microstructure, as observed in numerical simulations. Since the contact network in 3D is typically hidden from view, experimental test of the scaling law between the coordination number and the applied pressure is lacking in the literature. Our data show corrections to the linear scaling of the pressure with density which takes into account the creation of contacts. Numerical studies of vibrational spectra, in turn, reveal sudden features such as excess of low frequency modes, dependence of mode localization and structure on the pressure. Chapter four describes the first calculation of vibrational density of states from the experimental 3D data and is in qualitative agreement with the analogous computer simulations. We study the configurational role of the pressure and demonstrate

  15. Effect of aronia berry honey syrup used for sweetening jams on their quality.

    PubMed

    Kmiecik, W; Lisiewska, Z; Jaworska, G

    2001-08-01

    The effects of sweetening agents on the quality of low sweetened jams were compared with respect to blackcurrant, raspberry, sour cherry, strawberry, and bilberry jams. The sweetening agents were sucrose, aronia berry honey syrup, and sucrose + honey syrup at a ratio of 1:1. The level of physicochemical indices, especially the content of vitamin C and anthocyanins determined directly after production and after 3- and 6-month storage, was used as the quality criterion for the evaluation of jams. Moreover, after 6-month storage the products were subjected to sensorial analysis. According to the accepted method of the investigation the produced jams were characterized by a 32-33% content of extract. During the production and 6-month storage the content of acids slightly and that of pectin considerably (from 26 to 46%) decreased, although the consistency of the jams was not affected thereby. In the case of vitamin C, its pronounced losses concerned raspberry (62-67% of the initial value), strawberry (57-61%), and sour cherry (57-58%), being distinctly smaller in blackcurrant (13-16%) and bilberry (15-35%) jams. With respect to anthocyanins a similar regularity was observed, the losses reaching 49-63% in strawberry jam, 40-56% in raspberry, 33-39% in sour cherry, 30-36% in blackcurrant, and 28-36% in bilberries. In almost all the products the losses of vitamin C and anthocyanins were higher when sweetening agent was aronia berry honey syrup. The organoleptic evaluation showed that the addition of aronia berry honey syrup to raspberry and strawberry jams slightly spoiled their colour but improved the aroma and taste. In the final score the significant differentiation in favour of the addition of aronia berry honey syrup concerned only blackcurrant, sour cherry, and bilberry jams. PMID:11534468

  16. Topology-selective jamming of fully-connected, code-division random-access networks

    NASA Technical Reports Server (NTRS)

    Polydoros, Andreas; Cheng, Unjeng

    1990-01-01

    The purpose is to introduce certain models of topology selective stochastic jamming and examine its impact on a class of fully-connected, spread-spectrum, slotted ALOHA-type random access networks. The theory covers dedicated as well as half-duplex units. The dominant role of the spatial duty factor is established, and connections with the dual concept of time selective jamming are discussed. The optimal choices of coding rate and link access parameters (from the users' side) and the jamming spatial fraction are numerically established for DS and FH spreading.

  17. Equilibrium Sampling of Hard Spheres up to the Jamming Density and Beyond.

    PubMed

    Berthier, Ludovic; Coslovich, Daniele; Ninarello, Andrea; Ozawa, Misaki

    2016-06-10

    We implement and optimize a particle-swap Monte Carlo algorithm that allows us to thermalize a polydisperse system of hard spheres up to unprecedentedly large volume fractions, where previous algorithms and experiments fail to equilibrate. We show that no glass singularity intervenes before the jamming density, which we independently determine through two distinct nonequilibrium protocols. We demonstrate that equilibrium fluid and nonequilibrium jammed states can have the same density, showing that the jamming transition cannot be the end point of the fluid branch. PMID:27341260

  18. Equilibrium Sampling of Hard Spheres up to the Jamming Density and Beyond

    NASA Astrophysics Data System (ADS)

    Berthier, Ludovic; Coslovich, Daniele; Ninarello, Andrea; Ozawa, Misaki

    2016-06-01

    We implement and optimize a particle-swap Monte Carlo algorithm that allows us to thermalize a polydisperse system of hard spheres up to unprecedentedly large volume fractions, where previous algorithms and experiments fail to equilibrate. We show that no glass singularity intervenes before the jamming density, which we independently determine through two distinct nonequilibrium protocols. We demonstrate that equilibrium fluid and nonequilibrium jammed states can have the same density, showing that the jamming transition cannot be the end point of the fluid branch.

  19. Critical scaling in linear response of frictionless granular packings near jamming.

    PubMed

    Ellenbroek, Wouter G; Somfai, Ellák; van Hecke, Martin; van Saarloos, Wim

    2006-12-22

    We study the origin of the scaling behavior in frictionless granular media above the jamming transition by analyzing their linear response. The response to local forcing is non-self-averaging and fluctuates over a length scale that diverges at the jamming transition. The response to global forcing becomes increasingly nonaffine near the jamming transition. This is due to the proximity of floppy modes, the influence of which we characterize by the local linear response. We show that the local response also governs the anomalous scaling of elastic constants and contact number. PMID:17280395

  20. Self organization and shear-jamming in magnetic photoelastic particles

    NASA Astrophysics Data System (ADS)

    Cox, Meredith; Wang, Dong; Bares, Jonathan; Behringer, Bob

    Many experimental studies of simple particles in granular systems have been conducted, but the behavior of complex particles in such systems has not been addressed. There has been a growing interest in functionalized microparticles, and the study of these complex particles may reveal interesting analogues between micro- and macroparticles. We perform experiments to investigate magnetic particles in a 2D granular material close to the jamming transition. We incrementally compress and shear photoelastic particles containing magnets and image the interparticle forces in each compression using a photoelastic technique. To track the orientation of individual particles, we draw UV-visible bars on each particle and image each compression of the system under ultraviolet light. We repeat the experimental procedure using varying ratios of magnetic to nonmagnetic particles from 0% magnetic to 100% magnetic. By using custom software to resolve particle deformations, we extract particle contact and pressure.

  1. Soliton and kink jams in traffic flow with open boundaries.

    PubMed

    Muramatsu, M; Nagatani, T

    1999-07-01

    Soliton density wave is investigated numerically and analytically in the optimal velocity model (a car-following model) of a one-dimensional traffic flow with open boundaries. Soliton density wave is distinguished from the kink density wave. It is shown that the soliton density wave appears only at the threshold of occurrence of traffic jams. The Korteweg-de Vries (KdV) equation is derived from the optimal velocity model by the use of the nonlinear analysis. It is found that the traffic soliton appears only near the neutral stability line. The soliton solution is analytically obtained from the perturbed KdV equation. It is shown that the soliton solution obtained from the nonlinear analysis is consistent with that of the numerical simulation. PMID:11969749

  2. Controlled assembly of jammed colloidal shells on fluid droplets.

    PubMed

    Subramaniam, Anand Bala; Abkarian, Manouk; Stone, Howard A

    2005-07-01

    Assembly of colloidal particles on fluid interfaces is a promising technique for synthesizing two-dimensional microcrystalline materials useful in fields as diverse as biomedicine, materials science, mineral flotation and food processing. Current approaches rely on bulk emulsification methods, require further chemical and thermal treatments, and are restrictive with respect to the materials used. The development of methods that exploit the great potential of interfacial assembly for producing tailored materials have been hampered by the lack of understanding of the assembly process. Here we report a microfluidic method that allows direct visualization and understanding of the dynamics of colloidal crystal growth on curved interfaces. The crystals are periodically ejected to form stable jammed shells, which we refer to as colloidal armour. We propose that the energetic barriers to interfacial crystal growth and organization can be overcome by targeted delivery of colloidal particles through hydrodynamic flows. Our method allows an unprecedented degree of control over armour composition, size and stability. PMID:15937488

  3. A dynamic jamming point for shear thickening suspensions

    NASA Astrophysics Data System (ADS)

    Brown, Eric; Jaeger, Heinrich

    2008-11-01

    Densely packed suspensions can shear thicken, in which the viscosity increases with shear rate. We performed rheometry measurements on two model systems: corn starch in water and glass spheres in oils. In both systems we observed shear thickening up to a critical packing fraction φc (=0.55 for spherical grains) above which the flow abruptly transitions to shear thinning. The viscosity and yield stress diverge as power laws at φc. Extrapolating the dynamic ranges of shear rate and stress in the shear thickening regime up to φc suggests a finite change in shear stress with zero change in shear rate. This is a dynamic analog to the jamming point with a yield stress at zero shear rate.

  4. Elastic moduli and vibrational modes in jammed particulate packings

    NASA Astrophysics Data System (ADS)

    Mizuno, Hideyuki; Saitoh, Kuniyasu; Silbert, Leonardo E.

    2016-06-01

    When we elastically impose a homogeneous, affine deformation on amorphous solids, they also undergo an inhomogeneous, nonaffine deformation, which can have a crucial impact on the overall elastic response. To correctly understand the elastic modulus M , it is therefore necessary to take into account not only the affine modulus MA, but also the nonaffine modulus MN that arises from the nonaffine deformation. In the present work, we study the bulk (M =K ) and shear (M =G ) moduli in static jammed particulate packings over a range of packing fractions φ . The affine MA is determined essentially by the static structural arrangement of particles, whereas the nonaffine MN is related to the vibrational eigenmodes. We elucidate the contribution of each vibrational mode to the nonaffine MN through a modal decomposition of the displacement and force fields. In the vicinity of the (un)jamming transition φc, the vibrational density of states g (ω ) shows a plateau in the intermediate-frequency regime above a characteristic frequency ω*. We illustrate that this unusual feature apparent in g (ω ) is reflected in the behavior of MN: As φ →φc , where ω*→0 , those modes for ω <ω* contribute less and less, while contributions from those for ω >ω* approach a constant value which results in MN to approach a critical value MN c, as MN-MN c˜ω* . At φc itself, the bulk modulus attains a finite value Kc=KA c-KN c>0 , such that KN c has a value that remains below KA c. In contrast, for the critical shear modulus Gc, GN c and GA c approach the same value so that the total value becomes exactly zero, Gc=GA c-GN c=0 . We explore what features of the configurational and vibrational properties cause such a distinction between K and G , allowing us to validate analytical expressions for their critical values.

  5. Beyond linear elasticity: jammed solids at finite shear strain and rate.

    PubMed

    Boschan, Julia; Vågberg, Daniel; Somfai, Ellák; Tighe, Brian P

    2016-06-28

    The shear response of soft solids can be modeled with linear elasticity, provided the forcing is slow and weak. Both of these approximations must break down when the material loses rigidity, such as in foams and emulsions at their (un)jamming point - suggesting that the window of linear elastic response near jamming is exceedingly narrow. Yet precisely when and how this breakdown occurs remains unclear. To answer these questions, we perform computer simulations of stress relaxation and shear start-up tests in athermal soft sphere packings, the canonical model for jamming. By systematically varying the strain amplitude, strain rate, distance to jamming, and system size, we identify characteristic strain and time scales that quantify how and when the window of linear elasticity closes, and relate these scales to changes in the microscopic contact network. PMID:27212139

  6. Feedback control scheme of traffic jams based on the coupled map car-following model

    NASA Astrophysics Data System (ADS)

    Zhou, Tong; Sun, Di-Hua; Zhao, Min; Li, Hua-Min

    2013-09-01

    Based on the pioneering work of Konishi et al. [Phys. Rev. E (1999) 60 4000], a new feedback control scheme is presented to suppress traffic jams based on the coupled map car-following model under the open boundary condition. The effect of the safe headway on the traffic system is considered. According to the control theory, the condition under which traffic jams can be suppressed is analyzed. The results are compared with the previous results concerning congestion control. The simulations show that the suppression performance of our scheme on traffic jams is better than those of the previous schemes, although all the schemes can suppress traffic jams. The simulation results are consistent with theoretical analyses.

  7. Use of oil-in-water emulsions to control fungal deterioration of strawberry jams.

    PubMed

    Ribes, Susana; Fuentes, Ana; Talens, Pau; Barat, José M

    2016-11-15

    This work aimed to control the fungal deterioration of strawberry jams. The antifungal activity of the clove, cinnamon leaf, lemon and mandarin essential oils and their effectiveness in oil-in-water emulsions were evaluated. According to the results obtained, only clove and cinnamon leaf oils were selected to prepare emulsions. All the tested emulsions were stable, independently the amount of polymer and essential oil used. Essential oil loss was affected by the amount of polymer employed to prepare the emulsions. The oil-in-water emulsions with 5.0mg/g xanthan gum, and with 0.55mg/g clove or 0.65mg/g cinnamon leaf essential oil, were used for the in vivo tests. The jams prepared with the oil-in-water emulsions showed a lower fungal decay compared with jams without emulsion. The present work demonstrated that emulsions can be employed to prevent strawberry jam mould spoilage. PMID:27283611

  8. Random walk theory of jamming in a cellular automaton model for traffic flow

    NASA Astrophysics Data System (ADS)

    Barlovic, Robert; Schadschneider, Andreas; Schreckenberg, Michael

    2001-05-01

    The jamming behavior of a single lane traffic model based on a cellular automaton approach is studied. Our investigations concentrate on the so-called VDR model which is a simple generalization of the well-known Nagel-Schreckenberg model. In the VDR model one finds a separation between a free flow phase and jammed vehicles. This phase separation allows to use random walk like arguments to predict the resolving probabilities and lifetimes of jam clusters or disturbances. These predictions are in good agreement with the results of computer simulations and even become exact for a special case of the model. Our findings allow a deeper insight into the dynamics of wide jams occuring in the model.

  9. DMP: Detouring Using Multiple Paths against Jamming Attack for Ubiquitous Networking System

    PubMed Central

    Kim, Mihui; Chae, Kijoon

    2010-01-01

    To successfully realize the ubiquitous network environment including home automation or industrial control systems, it is important to be able to resist a jamming attack. This has recently been considered as an extremely threatening attack because it can collapse the entire network, despite the existence of basic security protocols such as encryption and authentication. In this paper, we present a method of jamming attack tolerant routing using multiple paths based on zones. The proposed scheme divides the network into zones, and manages the candidate forward nodes of neighbor zones. After detecting an attack, detour nodes decide zones for rerouting, and detour packets destined for victim nodes through forward nodes in the decided zones. Simulation results show that our scheme increases the PDR (Packet Delivery Ratio) and decreases the delay significantly in comparison with rerouting by a general routing protocol on sensor networks, AODV (Ad hoc On Demand Distance Vector), and a conventional JAM (Jammed Area Mapping) service with one reroute. PMID:22319316

  10. DMP: detouring using multiple paths against jamming attack for ubiquitous networking system.

    PubMed

    Kim, Mihui; Chae, Kijoon

    2010-01-01

    To successfully realize the ubiquitous network environment including home automation or industrial control systems, it is important to be able to resist a jamming attack. This has recently been considered as an extremely threatening attack because it can collapse the entire network, despite the existence of basic security protocols such as encryption and authentication. In this paper, we present a method of jamming attack tolerant routing using multiple paths based on zones. The proposed scheme divides the network into zones, and manages the candidate forward nodes of neighbor zones. After detecting an attack, detour nodes decide zones for rerouting, and detour packets destined for victim nodes through forward nodes in the decided zones. Simulation results show that our scheme increases the PDR (Packet Delivery Ratio) and decreases the delay significantly in comparison with rerouting by a general routing protocol on sensor networks, AODV (Ad hoc On Demand Distance Vector), and a conventional JAM (Jammed Area Mapping) service with one reroute. PMID:22319316

  11. Real-time traffic jam detection and localization running on a smart camera

    NASA Astrophysics Data System (ADS)

    Lipetski, Yuriy; Loibner, Gernot; Ulm, Michael; Ponweiser, Wolfgang; Sidla, Oliver

    2014-03-01

    Reliable automatic detection of traffic jam occurrences is of big significance for traffic flow analysis related applications. We present our work aimed at the application of video based real-time traffic jam detection. Our method can handle both calibrated and un-calibrated scenarios, operating in world and in image coordinate systems respectively. The method is designed to be operated on a smart camera, but is also suitable for a standard personal computer. The combination of state-of-the-art algorithms for vehicle detections and velocity estimation allows robust long-term system operation in due to the high recall rate and very low false alarm rate. The proposed method not only detects traffic jam events in real-time, but also precisely localizes traffic jams by their start and end positions per road lane. We describe also our strategy in making computationally heavy algorithms real-time capable even on hardware with a limited computing power.

  12. The role of JAM-B in cancer and cancer metastasis (Review).

    PubMed

    Zhao, Huishan; Yu, Hefen; Martin, Tracey A; Teng, Xu; Jiang, Wen G

    2016-07-01

    The junctional adhesion molecule B (JAM-B) is a multifunctional transmembrane protein, which belongs to the immunoglobulin superfamily (IgSF). JAM-B is localized to cell-cell contacts and enriched at cell junctions in epithelial and endothelial cells, as well as on the surface of erythrocytes, leukocytes, and platelets. Recent research in this field has shown that JAM-B plays an important role in numerous cellular processes, such as tight junction assembly, spermatogenesis, regulation of paracellular permeability, leukocytic transmigration, angiogenesis, tumor metastasis and cell proliferation. This study provides a new research direction for the diagnosis and treatment of relevant diseases. In this review, we briefly focus on what is currently known about the structure, function, and mechanism of JAM-B, with particular emphasis on cancer. PMID:27121546

  13. Dissipation and velocity distribution at the shear-driven jamming transition

    NASA Astrophysics Data System (ADS)

    Olsson, Peter

    2016-04-01

    We investigate energy dissipation and the distribution of particle velocities at the jamming transition for overdamped shear-driven frictionless disks in two dimensions at zero temperature. We find that the dissipation is caused by the fastest particles and that the fraction of particles responsible for the dissipation decreases towards zero as jamming is approached. These particles belong to an algebraic tail of the velocity distribution that approaches ˜v-3 as jamming is approached. We further find that different measures of the velocity diverge differently, which means that concepts such as typical velocity may no longer be used, a finding that should have implications for analytical approaches to shear-driven jamming.

  14. The role of JAM-B in cancer and cancer metastasis (Review)

    PubMed Central

    ZHAO, HUISHAN; YU, HEFEN; MARTIN, TRACEY A.; TENG, XU; JIANG, WEN G.

    2016-01-01

    The junctional adhesion molecule B (JAM-B) is a multifunctional transmembrane protein, which belongs to the immunoglobulin superfamily (IgSF). JAM-B is localized to cell-cell contacts and enriched at cell junctions in epithelial and endothelial cells, as well as on the surface of erythrocytes, leukocytes, and platelets. Recent research in this field has shown that JAM-B plays an important role in numerous cellular processes, such as tight junction assembly, spermatogenesis, regulation of paracellular permeability, leukocytic transmigration, angiogenesis, tumor metastasis and cell proliferation. This study provides a new research direction for the diagnosis and treatment of relevant diseases. In this review, we briefly focus on what is currently known about the structure, function, and mechanism of JAM-B, with particular emphasis on cancer. PMID:27121546

  15. On-board recordings reveal no jamming avoidance in wild bats

    PubMed Central

    Cvikel, Noam; Levin, Eran; Hurme, Edward; Borissov, Ivailo; Boonman, Arjan; Amichai, Eran; Yovel, Yossi

    2015-01-01

    Animals often deal with situations in which vast sensory input is received simultaneously. They therefore must possess sophisticated mechanisms to select important input and ignore the rest. In bat echolocation, this problem is at its extreme. Echolocating bats emit sound signals and analyse the returning echoes to sense their environment. Bats from the same species use signals with similar frequencies. Nearby bats therefore face the difficulty of distinguishing their own echoes from the signals of other bats, a problem often referred to as jamming. Because bats commonly fly in large groups, jamming might simultaneously occur from numerous directions and at many frequencies. Jamming is a special case of the general phenomenon of sensory segregation. Another well-known example is the human problem of following conversation within a crowd. In both situations, a flood of auditory incoming signals must be parsed into important versus irrelevant information. Here, we present a novel method, fitting wild bats with a miniature microphone, which allows studying jamming from the bat's ‘point of view’. Previous studies suggested that bats deal with jamming by shifting their echolocation frequency. On-board recordings suggest otherwise. Bats shifted their frequencies, but they did so because they were responding to the conspecifics as though they were nearby objects rather than avoiding being jammed by them. We show how bats could use alternative measures to deal with jamming instead of shifting their frequency. Despite its intuitive appeal, a spectral jamming avoidance response might not be the prime mechanism to avoid sensory interference from conspecifics. PMID:25429017

  16. Divergent JAM-C Expression Accelerates Monocyte-Derived Cell Exit from Atherosclerotic Plaques

    PubMed Central

    Miljkovic-Licina, Marijana; Lee, Boris P.; Fischer, Nicolas; Fish, Richard J.; Kwak, Brenda; Fisher, Edward A.; Imhof, Beat A.

    2016-01-01

    Atherosclerosis, caused in part by monocytes in plaques, continues to be a disease that afflicts the modern world. Whilst significant steps have been made in treating this chronic inflammatory disease, questions remain on how to prevent monocyte and macrophage accumulation in atherosclerotic plaques. Junctional Adhesion Molecule C (JAM-C) expressed by vascular endothelium directs monocyte transendothelial migration in a unidirectional manner leading to increased inflammation. Here we show that interfering with JAM-C allows reverse-transendothelial migration of monocyte-derived cells, opening the way back out of the inflamed environment. To study the role of JAM-C in plaque regression we used a mouse model of atherosclerosis, and tested the impact of vascular JAM-C expression levels on monocyte reverse transendothelial migration using human cells. Studies in-vitro under inflammatory conditions revealed that overexpression or gene silencing of JAM-C in human endothelium exposed to flow resulted in higher rates of monocyte reverse-transendothelial migration, similar to antibody blockade. We then transplanted atherosclerotic, plaque-containing aortic arches from hyperlipidemic ApoE-/- mice into wild-type normolipidemic recipient mice. JAM-C blockade in the recipients induced greater emigration of monocyte-derived cells and further diminished the size of atherosclerotic plaques. Our findings have shown that JAM-C forms a one-way vascular barrier for leukocyte transendothelial migration only when present at homeostatic copy numbers. We have also shown that blocking JAM-C can reduce the number of atherogenic monocytes/macrophages in plaques by emigration, providing a novel therapeutic strategy for chronic inflammatory pathologies. PMID:27442505

  17. Cancer-Related Constituents of Strawberry Jam as Compared with Fresh Fruit.

    PubMed

    Flores, Gema; Ruiz Del Castillo, Maria Luisa

    2016-01-01

    The health awareness recently shown by consumers has led to a demand for health beneficial products. In particular, researchers are currently focusing their studies on the search for foods for cancer prevention activity. In the present work, we study comparatively the effect of two different processing methods on the contents of phenolic compounds (i.e., ellagic acid, myricetin, quercetin and kaempferol) with antioxidant and antitumor properties in strawberry jams. In turn, the results obtained were compared with those of unprocessed fruit. Additionally carcinogenic heat-induced compounds formed by the two jam making methods were evaluated. Decreases of total ellagic acid from 138.4 µg/g to 86.5 µg/g were measured in jam as compared with the intact fruit. Even higher losses of up to 90% of total flavonols were found in strawberry after the jam-making process. A comparison between the two processing methods proved shorter heating periods (around 60 min) even at temperatures as high as 100 °C enabled losses of antioxidant phenolics to be minimized. Carcinogenic heat-induced volatile compounds, mainly Maillard reaction products, were formed as a result of thermal treatment during jam processing. However, shorter heating periods also helped reduce the formation of these harmful compounds. These results are deeply discussed. From a practical standpoint, the processing conditions here proposed can be used by industry to obtain strawberry jam with higher content of antioxidant flavonoids and, at the same time, reduced amounts of carcinogenic compounds. PMID:26784230

  18. Cancer-Related Constituents of Strawberry Jam as Compared with Fresh Fruit

    PubMed Central

    Flores, Gema; Ruiz del Castillo, Maria Luisa

    2016-01-01

    The health awareness recently shown by consumers has led to a demand for health beneficial products. In particular, researchers are currently focusing their studies on the search for foods for cancer prevention activity. In the present work, we study comparatively the effect of two different processing methods on the contents of phenolic compounds (i.e., ellagic acid, myricetin, quercetin and kaempferol) with antioxidant and antitumor properties in strawberry jams. In turn, the results obtained were compared with those of unprocessed fruit. Additionally carcinogenic heat-induced compounds formed by the two jam making methods were evaluated. Decreases of total ellagic acid from 138.4 µg/g to 86.5 µg/g were measured in jam as compared with the intact fruit. Even higher losses of up to 90% of total flavonols were found in strawberry after the jam-making process. A comparison between the two processing methods proved shorter heating periods (around 60 min) even at temperatures as high as 100 °C enabled losses of antioxidant phenolics to be minimized. Carcinogenic heat-induced volatile compounds, mainly Maillard reaction products, were formed as a result of thermal treatment during jam processing. However, shorter heating periods also helped reduce the formation of these harmful compounds. These results are deeply discussed. From a practical standpoint, the processing conditions here proposed can be used by industry to obtain strawberry jam with higher content of antioxidant flavonoids and, at the same time, reduced amounts of carcinogenic compounds. PMID:26784230

  19. Elastic moduli and vibrational modes in jammed particulate packings.

    PubMed

    Mizuno, Hideyuki; Saitoh, Kuniyasu; Silbert, Leonardo E

    2016-06-01

    When we elastically impose a homogeneous, affine deformation on amorphous solids, they also undergo an inhomogeneous, nonaffine deformation, which can have a crucial impact on the overall elastic response. To correctly understand the elastic modulus M, it is therefore necessary to take into account not only the affine modulus M_{A}, but also the nonaffine modulus M_{N} that arises from the nonaffine deformation. In the present work, we study the bulk (M=K) and shear (M=G) moduli in static jammed particulate packings over a range of packing fractions φ. The affine M_{A} is determined essentially by the static structural arrangement of particles, whereas the nonaffine M_{N} is related to the vibrational eigenmodes. We elucidate the contribution of each vibrational mode to the nonaffine M_{N} through a modal decomposition of the displacement and force fields. In the vicinity of the (un)jamming transition φ_{c}, the vibrational density of states g(ω) shows a plateau in the intermediate-frequency regime above a characteristic frequency ω^{*}. We illustrate that this unusual feature apparent in g(ω) is reflected in the behavior of M_{N}: As φ→φ_{c}, where ω^{*}→0, those modes for ω<ω^{*} contribute less and less, while contributions from those for ω>ω^{*} approach a constant value which results in M_{N} to approach a critical value M_{Nc}, as M_{N}-M_{Nc}∼ω^{*}. At φ_{c} itself, the bulk modulus attains a finite value K_{c}=K_{Ac}-K_{Nc}>0, such that K_{Nc} has a value that remains below K_{Ac}. In contrast, for the critical shear modulus G_{c}, G_{Nc} and G_{Ac} approach the same value so that the total value becomes exactly zero, G_{c}=G_{Ac}-G_{Nc}=0. We explore what features of the configurational and vibrational properties cause such a distinction between K and G, allowing us to validate analytical expressions for their critical values. PMID:27415345

  20. A Geometric-Structure Theory for Maximally Random Jammed Packings

    PubMed Central

    Tian, Jianxiang; Xu, Yaopengxiao; Jiao, Yang; Torquato, Salvatore

    2015-01-01

    Maximally random jammed (MRJ) particle packings can be viewed as prototypical glasses in that they are maximally disordered while simultaneously being mechanically rigid. The prediction of the MRJ packing density ϕMRJ, among other packing properties of frictionless particles, still poses many theoretical challenges, even for congruent spheres or disks. Using the geometric-structure approach, we derive for the first time a highly accurate formula for MRJ densities for a very wide class of two-dimensional frictionless packings, namely, binary convex superdisks, with shapes that continuously interpolate between circles and squares. By incorporating specific attributes of MRJ states and a novel organizing principle, our formula yields predictions of ϕMRJ that are in excellent agreement with corresponding computer-simulation estimates in almost the entire α-x plane with semi-axis ratio α and small-particle relative number concentration x. Importantly, in the monodisperse circle limit, the predicted ϕMRJ = 0.834 agrees very well with the very recently numerically discovered MRJ density of 0.827, which distinguishes it from high-density “random-close packing” polycrystalline states and hence provides a stringent test on the theory. Similarly, for non-circular monodisperse superdisks, we predict MRJ states with densities that are appreciably smaller than is conventionally thought to be achievable by standard packing protocols. PMID:26568437

  1. A Geometric-Structure Theory for Maximally Random Jammed Packings

    NASA Astrophysics Data System (ADS)

    Tian, Jianxiang; Xu, Yaopengxiao; Jiao, Yang; Torquato, Salvatore

    2015-11-01

    Maximally random jammed (MRJ) particle packings can be viewed as prototypical glasses in that they are maximally disordered while simultaneously being mechanically rigid. The prediction of the MRJ packing density ϕMRJ, among other packing properties of frictionless particles, still poses many theoretical challenges, even for congruent spheres or disks. Using the geometric-structure approach, we derive for the first time a highly accurate formula for MRJ densities for a very wide class of two-dimensional frictionless packings, namely, binary convex superdisks, with shapes that continuously interpolate between circles and squares. By incorporating specific attributes of MRJ states and a novel organizing principle, our formula yields predictions of ϕMRJ that are in excellent agreement with corresponding computer-simulation estimates in almost the entire α-x plane with semi-axis ratio α and small-particle relative number concentration x. Importantly, in the monodisperse circle limit, the predicted ϕMRJ = 0.834 agrees very well with the very recently numerically discovered MRJ density of 0.827, which distinguishes it from high-density “random-close packing” polycrystalline states and hence provides a stringent test on the theory. Similarly, for non-circular monodisperse superdisks, we predict MRJ states with densities that are appreciably smaller than is conventionally thought to be achievable by standard packing protocols.

  2. Jamming transitions in force-based models for pedestrian dynamics.

    PubMed

    Chraibi, Mohcine; Ezaki, Takahiro; Tordeux, Antoine; Nishinari, Katsuhiro; Schadschneider, Andreas; Seyfried, Armin

    2015-10-01

    Force-based models describe pedestrian dynamics in analogy to classical mechanics by a system of second order ordinary differential equations. By investigating the linear stability of two main classes of forces, parameter regions with unstable homogeneous states are identified. In this unstable regime it is then checked whether phase transitions or stop-and-go waves occur. Results based on numerical simulations show, however, that the investigated models lead to unrealistic behavior in the form of backwards moving pedestrians and overlapping. This is one reason why stop-and-go waves have not been observed in these models. The unrealistic behavior is not related to the numerical treatment of the dynamic equations but rather indicates an intrinsic problem of this model class. Identifying the underlying generic problems gives indications how to define models that do not show such unrealistic behavior. As an example we introduce a force-based model which produces realistic jam dynamics without the appearance of unrealistic negative speeds for empirical desired walking speeds. PMID:26565291

  3. Wall slip of foams close to the jamming transition

    NASA Astrophysics Data System (ADS)

    Cohen-Addad, S.; Le Merrer, M.; Lespiat, R.; Hohler, R.

    2014-11-01

    Aqueous foams are dense packings of gas bubbles in a surfactant solution. They exhibit unique rheological properties. When they flow along a solid smooth wall, they slip and experience viscous drag. This feature is crucial in many applications involving flow through microfluidic channels, pipes or spreading on surfaces. We focus on foams in the vicinity of the jamming transition where the bubbles are quasi spherical with small contact films at the wall and thick liquid channels between bubbles. What are the mechanisms of friction at play at the scale of the films, the channels and the bubbles that are at the origin of the macroscopic friction law? To address this question, we measure the velocity of a bubble monolayer or a wet 3D foam as it creeps along an immersed inclined plane, as a function of the inclination angle, bubble size and confinement. Two regimes of friction are evidenced: In addition to a previously reported non-linear Bretherton-like drag, we present the first direct evidence for a linear Stokes-like drag. We show that the key parameter governing the transition between the regimes is set by the Bond number for the monolayer or the confinement pressure for the foam. Institut des NanoSciences de Paris, sylvie.cohen-addad@insp.upmc.fr.

  4. Self organization and jamming in magnetic photoelastic particles

    NASA Astrophysics Data System (ADS)

    Cox, Meredith; Bares, Jonathan; Wang, Dong; Behringer, Robert

    2015-11-01

    Many experimental studies of simple particles in granular systems have been conducted, but the behavior of complex particles in such systems has not been addressed. There has been a growing interest in functionalized microparticles, and the study of these complex particles may reveal interesting analogues between micro- and macroparticles. We perform experiments to investigate magnetic particles in a 2D granular material close to the jamming transition. We incrementally compress photoelastic particles containing magnets and image the interparticle forces in each compression using a photoelastic technique. To track the orientation of individual particles, we draw UV-visible bars on each particle and image each compression of the system under ultraviolet light. We repeat the experimental procedure using varying ratios of magnetic to nonmagnetic particles from 0% magnetic to 100% magnetic. By using custom software to resolve particle deformations, we extract particle contact forces and demonstrate that as the concentration of nonmagnetic particles grows, the rate of increase of pressure with strain also grows. We acknowledge support from NSF DMR1206351, NASA NNX15AD38G and W. M. Keck Foundation.

  5. Jamming under rapid pulling in dense granular suspensions

    NASA Astrophysics Data System (ADS)

    Majumdar, Sayantan; Peters, Ivo R.; Jaeger, Heinrich

    2015-03-01

    It requires a lot of force to quickly pull out an object immersed in a bath of dense granular suspension like corn starch in water. To understand such striking force response, we experimentally measure the normal force required for pulling out a cylindrical rod vertically from the suspension at a controlled pulling velocity. We observe that for slow pulling velocities the force response is similar to that of highly viscous fluids but above a certain threshold velocity the force show a diverging behavior soon after the initial viscous-like response. The time delay between the initial viscous-like and the diverging force response crucially depends on the proximity of the container walls from the initial contact region of the pulling rod with the suspension. We use in-situ X-ray radiography techniques to map out the local velocity profiles inside the suspension using metallic tracer particles which reveals that the force divergence takes place under pulling when the motion inside the suspension extends up to the container walls. Although the exact mechanism remains to be explained, our experiments suggest that both the magnitude and the delay in force response under pulling are reminiscent of dynamic jamming under impact in dense granular suspensions. S.M. acknowledges support from a Kadanoff-Rice Post Doctoral fellowship from MRSEC, University of Chicago

  6. Rake receiver performance in the presence of narrowband jamming

    NASA Astrophysics Data System (ADS)

    Meng, Julian; Ding, Xin

    2005-06-01

    Direct-sequence spread spectrum (DSSS) modulation offers many properties that make it well suited for a mobile environment including some inherent narrowband interference or jamming (NBJ) suppression capability and resistance to multipath fading. The estimation and filtering of unwanted narrowband signals in DSSS systems has been extensively addressed in previous work but has given limited insight to system performance when multipath fading is introduced and a diversity solution such as the ubiquitous Rake receiver is implemented. In this case, multiple correlators (or fingers) are used to extract the desired signal replicas from the individual delay path components. For the maximum ratio combiner (MRC) version of the Rake receiver, the signal replicas from each finger are then combined in some weighted sense to formulate the final decision threshold. The focus of this study is twofold: to investigate the inaccuracies incurred on path delay estimation due to the presence of NBJ and its impact on the system Bit Error Rate (BER). In order to reduce the impact of NBJ, some adaptive NBJ suppression filters are suggested.

  7. Self-Driven Jamming of Growing Microbial Populations

    NASA Astrophysics Data System (ADS)

    Schreck, Carl; Delarue, Morgan; Gneiwek, Pawel; Hallatschek, Oskar

    When cells grow in confined spaces, they assemble into dense populations that interact both chemically and physically. Although in recent years scientists have uncovered a previously hidden layer of mechanical regulation in mammalian tissues that impacts gene expression and development, little is known about the consequences of mechanical constraints on single-celled microbes. This is largely due to a lack of appropriate culturing techniques and accurate computational models. Using physically explicit computer models that are developed alongside microfluidic experiments, we address two fundamental questions: (1) what structures self-assemble in confined geometries due to the cell growth and division process? and (2) how do those structures and associated stresses feed back on to cell physiology? We find that microbial growth in confinement can lead to jamming, heterogeneous stress fields, and intermittent flow that in turn result in spatially and temporally heterogeneous physiological responses. With computer simulations, we further explore the differences between this 'active' flow that is driven internally by cell growth and 'inactive' flow, such as shear and hopper flow, that is driven externally.

  8. Jamming transitions in force-based models for pedestrian dynamics

    NASA Astrophysics Data System (ADS)

    Chraibi, Mohcine; Ezaki, Takahiro; Tordeux, Antoine; Nishinari, Katsuhiro; Schadschneider, Andreas; Seyfried, Armin

    2015-10-01

    Force-based models describe pedestrian dynamics in analogy to classical mechanics by a system of second order ordinary differential equations. By investigating the linear stability of two main classes of forces, parameter regions with unstable homogeneous states are identified. In this unstable regime it is then checked whether phase transitions or stop-and-go waves occur. Results based on numerical simulations show, however, that the investigated models lead to unrealistic behavior in the form of backwards moving pedestrians and overlapping. This is one reason why stop-and-go waves have not been observed in these models. The unrealistic behavior is not related to the numerical treatment of the dynamic equations but rather indicates an intrinsic problem of this model class. Identifying the underlying generic problems gives indications how to define models that do not show such unrealistic behavior. As an example we introduce a force-based model which produces realistic jam dynamics without the appearance of unrealistic negative speeds for empirical desired walking speeds.

  9. Jamming and free energy landscapes for three caged soft disks

    NASA Astrophysics Data System (ADS)

    Du, Xin; Weeks, Eric

    2015-03-01

    We use a Monte Carlo simulation to study jamming in a model of three soft Brownian disks with harmonic repulsive potential confined in a circular corral. For large corrals, the disks can freely rearrange where one particle passes in between the other two, but for small corrals rearrangements become rare. Rearrangement events correspond to the system crossing over the energy barrier. With low temperature and/or small corral size, the energy barrier becomes larger and the system approaches a glass transition. We calculate the Helmholtz free energy from the distribution of configurations in the system and quantify both the entropic and potential components of the free energy barrier. In a hard disk model, the free energy barrier for rearrangements is entirely entropic. By comparing the entropic component of the soft model to a model of hard disks, we model the soft disks as hard disks with a temperature-dependent effective size. We find that our results are generalizable to other soft disk potentials as well.

  10. Rearrangements during slow compression of a jammed 2D emulsion

    NASA Astrophysics Data System (ADS)

    Du, Xin; Orellana, Carlos; Hong, Xia; Weeks, Eric

    We experimentally study non-affine motion within an evaporating quasi two-dimensional emulsion system. Our samples are oil-in-water emulsions confined between two close-spaced parallel plates, so that the oil droplets are deformed into pancake shapes. In this system, water slowly evaporates from an open edge of the chamber and, as a consequence, the volume fraction of oil droplets gradually increases. By means of microscopy, we analyzed the motion of droplets and measure the deformation of the droplet's outlines. Based on this information, we calculate the force network and the Voronoi cell when the system approaching jamming state. Using a recently proposed method (J. Rieser et al., arXiv:1509.05496), we calculate the Voronoi cell anisotropy vectors which point from the center of each particle to the corresponding Voronoi cell centroid, and identify void spaces where droplets may be more likely to move toward according to the field of the vectors. These allow us to study the correlations between the force network, the Voronoi vector field, and the non-affine displacements of droplets in our evaporating system.

  11. Method for preventing jamming conditions in a compression device

    DOEpatents

    Williams, Paul M.; Faller, Kenneth M.; Bauer, Edward J.

    2002-06-18

    A compression device for feeding a waste material to a reactor includes a waste material feed assembly having a hopper, a supply tube and a compression tube. Each of the supply and compression tubes includes feed-inlet and feed-outlet ends. A feed-discharge valve assembly is located between the feed-outlet end of the compression tube and the reactor. A feed auger-screw extends axially in the supply tube between the feed-inlet and feed-outlet ends thereof. A compression auger-screw extends axially in the compression tube between the feed-inlet and feed-outlet ends thereof. The compression tube is sloped downwardly towards the reactor to drain fluid from the waste material to the reactor and is oriented at generally right angle to the supply tube such that the feed-outlet end of the supply tube is adjacent to the feed-inlet end of the compression tube. A programmable logic controller is provided for controlling the rotational speed of the feed and compression auger-screws for selectively varying the compression of the waste material and for overcoming jamming conditions within either the supply tube or the compression tube.

  12. Characterizing and distinguishing free and jammed traffic flows from the distribution and correlation of experimental speed data

    NASA Astrophysics Data System (ADS)

    Tadaki, Shin-ichi; Kikuchi, Macoto; Nakayama, Akihiro; Shibata, Akihiro; Sugiyama, Yuki; Yukawa, Satoshi

    2016-08-01

    From a physics point of view, the emergence of a traffic jam is considered to be a dynamical phase transition. To verify this, we performed a series of circuit experiments. In previous work, Tadaki et al (2013 New J. Phys 15 103034), we confirmed the occurrence of this phase transition and estimated the critical density between free and jammed flows by analyzing the fundamental diagram. In this paper, we characterize and distinguish free and jammed flows, beyond the analyses of fundamental diagrams, according to the distribution and correlation of experimental speed data. We find that the speed in free flow does not correlate and its distribution has a narrow single peak at the average. The distribution of speed in jammed flow has two peaks or a single broad peak. The two peaks indicate the car speeds inside and outside of jam clusters. The broad single peak appears as a result of the appearance and disappearance of jam clusters. We also find that the formation of jam clusters induces a long correlation in speed. We can identify the size of jam clusters and the relative distance between coexisting jam clusters from this speed correlation.

  13. Quince (Cydonia oblonga Miller) fruit (pulp, peel, and seed) and Jam: antioxidant activity.

    PubMed

    Silva, Branca M; Andrade, Paula B; Valentão, Patrícia; Ferreres, Federico; Seabra, Rosa M; Ferreira, Margarida A

    2004-07-28

    To study the antioxidant activity of quince fruit (pulp, peel, and seed) and jam, methanolic extracts were prepared. Each extract was fractionated into a phenolic fraction and an organic acid fraction and was analyzed by high-performance liquid chromatography (HPLC)/diode array detection and HPLC/UV, respectively. Antiradical activities of the extracts and fractions were evaluated by a microassay using 1,1'-diphenyl-2-picrylhydrazyl. The phenolic fraction always exhibited a stronger antioxidant activity than the whole methanolic extract. Organic acid extracts were always the weakest in terms of antiradical activity, which seems to indicate that the phenolic fraction gives a higher contribution for the antioxidant potential of quince fruit and jam. The evaluation of the antioxidant activity of methanolic extracts showed that peel extract was the one presenting the highest antioxidant capacity. The IC50 values of quince pulp, peel, and jam extracts were correlated with the caffeoylquinic acids total content. Among the phenolic fractions, the seed extract was the one that exhibited the strongest antioxidant activity. The IC50 values of quince pulp, peel, and jam phenolic extracts were strongly correlated with caffeoylquinic acids and phenolics total contents. For organic acid fractions, the peel extract was the one that had the strongest antiradical activity. The IC50 values of quince pulp, peel, and jam organic acid fractions were correlated with the ascorbic acid and citric acid contents. PMID:15264903

  14. Simulation and Experimental Studies of Jamming for Model Two-Dimensional Particles Under Flow

    NASA Astrophysics Data System (ADS)

    Guariguata, A.; Wu, D. T.; Koh, C. A.; Sum, A. K.; Sloan, E. D.

    2009-06-01

    Jamming and plugging of flowlines with gas hydrates is the most critical issue in the flow assurance of oil and gas production lines. Because solid hydrate particles are often suspended in a fluid, the pipeline jamming and flow constriction formed by hydrates depend not only on particle/wall properties, such as friction, binding forces and mechanical characteristics, but also on the concentration of particles upstream of the restriction, flow velocity, fluid viscosity, and forces between the particles. Therefore, to gain insight into the jamming phenomena, both experiments and computer simulations on two-dimensional model systems have been carried out to characterize the flow of particles in a channel, with the eventual goal of applying that knowledge to gas hydrates jamming. Using the simulation software PFC2d®, we studied the effect of restriction geometry and flow velocity on the jamming process of particles. Results from the simulations were compared to experimental measurements on polyethylene discs floating on water flowing in an open channel.

  15. Measurement of growing dynamical length scales and prediction of the jamming transition in a granular material

    NASA Astrophysics Data System (ADS)

    Keys, Aaron S.; Abate, Adam R.; Glotzer, Sharon C.; Durian, Douglas J.

    2007-04-01

    Supercooled liquids and dense colloidal suspensions exhibit anomalous behaviour known as `spatially heterogeneous dynamics' (SHD), which becomes increasingly pronounced as the system approaches the glass transition. Recently, the observation of SHD in confined granular packings under slow shear near the onset of jamming has bolstered speculation that the two transitions are related. Here, we report measurements of SHD in a system of air-driven granular beads, as a function of both density and effective temperature. On approach to jamming, the dynamics becomes progressively slower and more spatially heterogeneous. The rapid growth of timescales and dynamical length scales characterizing the heterogeneities can be described both by mode-coupling theory and the Vogel-Tammann-Fulcher (VTF) equation, such as in glass-forming liquids. The value of the control variable at the VTF transition coincides with point J (refs 9, 10), the random close-packed jamming density at which all motion ceases, in analogy to a zero-temperature ideal glass transition. Our findings demonstrate further universality of the jamming concept and provide a significant step forward in the quest for a unified theory of jamming in disparate systems.

  16. Characteristics of physico-chemical properties of bilberry (Vaccinium myrtillus L.) jams with added herbs.

    PubMed

    Korus, Anna; Jaworska, Grażyna; Bernaś, Emilia; Juszczak, Lesław

    2015-05-01

    Low-sugar bilberry jams without added herbs and those with added mentha (1 %) and lemon balm (1 %) were examined for levels of selected physico-chemical indicators, antioxidant activity, colour and texture. Jams were obtained by two methods: cooked in an open pan and cooked in a vacuum evaporator. 100 g fresh mass contained 0.076-0.481 mg HMF, 5.8-7.1 mg vitamin C, 176-232 mg total polyphenols, 122-156 mg total flavonoids, 73-96 mg total anthocyanins, with antioxidant activity per 1 g of 405-575 μM Trolox (ABTS), 71-89 μM Trolox (DPPH) and 120-176 μM Fe(2+) (FRAP). Jams cooked in a vacuum evaporator had higher levels of the indicators examined, better colour and worse texture. Jams with added herbs generally showed higher levels of all indicators, but their colour and texture were slightly worse. Storing jams for 8 months caused a reduction in antioxidant constituents of 7-20 % along with a deterioration of colour and texture. PMID:25892779

  17. Research on the laser angle deception jamming technology of laser countermeasure

    NASA Astrophysics Data System (ADS)

    Ma, Shi-wei; Chen, Wen-jian; Gao, Wei; Duan, Yuan-yuan

    2015-10-01

    In recent years , laser guided weapons behave very well at destroying the military goals in the local wars, the single-shot probability, effective range and hitting precision getting better. And the semi-active laser guided weapons are the most widely used laser guided weapons. In order to improve the viability and protect important military goals, it's necessary to study the technology to against the semi-active guided weapons. This paper studies the working principle, the advantages and disadvantages of the semi-active guided weapons at first, and analyze the possibility of laser angle deception jamming system working. Then it analyzes the working principle and process of laser angle deception jamming technology. Finally it designs a half-real simulation system of laser angle deception jamming, which consists of semi-active laser guided weapons simulation system and laser angle deception jamming system. The simulation system demonstrates the working process of the laser angle deception jamming system. This paper provides fundamental base for the research on the countermeasure technology of semi-active laser guided weapons.

  18. Jamming dynamics of stretch-induced surfactant release by alveolar type II cells.

    PubMed

    Majumdar, Arnab; Arold, Stephen P; Bartolák-Suki, Erzsébet; Parameswaran, Harikrishnan; Suki, Béla

    2012-03-01

    Secretion of pulmonary surfactant by alveolar epithelial type II cells is vital for the reduction of interfacial surface tension, thus preventing lung collapse. To study secretion dynamics, rat alveolar epithelial type II cells were cultured on elastic membranes and cyclically stretched. The amounts of phosphatidylcholine, the primary lipid component of surfactant, inside and outside the cells, were measured using radiolabeled choline. During and immediately after stretch, cells secreted less surfactant than unstretched cells; however, stretched cells secreted significantly more surfactant than unstretched cells after an extended lag period. We developed a model based on the hypothesis that stretching leads to jamming of surfactant traffic escaping the cell, similar to vehicular traffic jams. In the model, stretch increases surfactant transport from the interior to the exterior of the cell. This transport is mediated by a surface layer with a finite capacity due to the limited number of fusion pores through which secretion occurs. When the amount of surfactant in the surface layer approaches this capacity, interference among lamellar bodies carrying surfactant reduces the rate of secretion, effectively creating a jam. When the stretch stops, the jam takes an extended time to clear, and subsequently the amount of secreted surfactant increases. We solved the model analytically and show that its dynamics are consistent with experimental observations, implying that surfactant secretion is a fundamentally nonlinear process with memory representing collective behavior at the level of single cells. Our results thus highlight the importance of a jamming dynamics in stretch-induced cellular secretory processes. PMID:22033531

  19. Characterization of maximally random jammed sphere packings: Voronoi correlation functions.

    PubMed

    Klatt, Michael A; Torquato, Salvatore

    2014-11-01

    We characterize the structure of maximally random jammed (MRJ) sphere packings by computing the Minkowski functionals (volume, surface area, and integrated mean curvature) of their associated Voronoi cells. The probability distribution functions of these functionals of Voronoi cells in MRJ sphere packings are qualitatively similar to those of an equilibrium hard-sphere liquid and partly even to the uncorrelated Poisson point process, implying that such local statistics are relatively structurally insensitive. This is not surprising because the Minkowski functionals of a single Voronoi cell incorporate only local information and are insensitive to global structural information. To improve upon this, we introduce descriptors that incorporate nonlocal information via the correlation functions of the Minkowski functionals of two cells at a given distance as well as certain cell-cell probability density functions. We evaluate these higher-order functions for our MRJ packings as well as equilibrium hard spheres and the Poisson point process. It is shown that these Minkowski correlation and density functions contain visibly more information than the corresponding standard pair-correlation functions. We find strong anticorrelations in the Voronoi volumes for the hyperuniform MRJ packings, consistent with previous findings for other pair correlations [A. Donev et al., Phys. Rev. Lett. 95, 090604 (2005)PRLTAO0031-900710.1103/PhysRevLett.95.090604], indicating that large-scale volume fluctuations are suppressed by accompanying large Voronoi cells with small cells, and vice versa. In contrast to the aforementioned local Voronoi statistics, the correlation functions of the Voronoi cells qualitatively distinguish the structure of MRJ sphere packings (prototypical glasses) from that of not only the Poisson point process but also the correlated equilibrium hard-sphere liquids. Moreover, while we did not find any perfect icosahedra (the locally densest possible structure in which a

  20. Climbing, falling, and jamming during ant locomotion in confined environments

    PubMed Central

    Gravish, Nick; Monaenkova, Daria; Goodisman, Michael A. D.; Goldman, Daniel I.

    2013-01-01

    Locomotion emerges from effective interactions of an individual with its environment. Principles of biological terrestrial locomotion have been discovered on unconfined vertical and horizontal substrates. However, a diversity of organisms construct, inhabit, and move within confined spaces. Such animals are faced with locomotor challenges including limited limb range of motion, crowding, and visual sensory deprivation. Little is known about how these organisms accomplish their locomotor tasks, and such environments challenge human-made devices. To gain insight into how animals move within confined spaces, we study the locomotion of the fire ant Solenopsis invicta, which constructs subterranean tunnel networks (nests). Laboratory experiments reveal that ants construct tunnels with diameter, D, comparable to body length, L = 3.5 ± 0.5 mm. Ants can move rapidly (> 9 bodylengths per s) within these environments; their tunnels allow for effective limb, body, and antennae interaction with walls, which facilitate rapid slip-recovery during ascending and descending climbs. To examine the limits of slip-recovery in artificial tunnels, we perform perturbations consisting of rapid downward accelerations of the tunnels, which induce falls. Below a critical tunnel diameter, Ds = 1.31 ± 0.02 L, falls are always arrested through rapid interaction of appendages and antennae with tunnel walls to jam the falls. Ds is comparable to the size of incipient nest tunnels (D = 1.06 ± 0.23 L), supporting our hypothesis that fire ants construct environments that simplify their control task when moving through the nest, likely without need for rapid nervous system intervention. PMID:23690589

  1. Climbing, falling, and jamming during ant locomotion in confined environments.

    PubMed

    Gravish, Nick; Monaenkova, Daria; Goodisman, Michael A D; Goldman, Daniel I

    2013-06-11

    Locomotion emerges from effective interactions of an individual with its environment. Principles of biological terrestrial locomotion have been discovered on unconfined vertical and horizontal substrates. However, a diversity of organisms construct, inhabit, and move within confined spaces. Such animals are faced with locomotor challenges including limited limb range of motion, crowding, and visual sensory deprivation. Little is known about how these organisms accomplish their locomotor tasks, and such environments challenge human-made devices. To gain insight into how animals move within confined spaces, we study the locomotion of the fire ant Solenopsis invicta, which constructs subterranean tunnel networks (nests). Laboratory experiments reveal that ants construct tunnels with diameter, D, comparable to body length, L = 3.5 ± 0.5 mm. Ants can move rapidly (> 9 bodylengths per s) within these environments; their tunnels allow for effective limb, body, and antennae interaction with walls, which facilitate rapid slip-recovery during ascending and descending climbs. To examine the limits of slip-recovery in artificial tunnels, we perform perturbations consisting of rapid downward accelerations of the tunnels, which induce falls. Below a critical tunnel diameter, Ds = 1.31 ± 0.02 L, falls are always arrested through rapid interaction of appendages and antennae with tunnel walls to jam the falls. Ds is comparable to the size of incipient nest tunnels (D = 1.06 ± 0.23 L), supporting our hypothesis that fire ants construct environments that simplify their control task when moving through the nest, likely without need for rapid nervous system intervention. PMID:23690589

  2. A novel junctional adhesion molecule A (CgJAM-A-L) from oyster (Crassostrea gigas) functions as pattern recognition receptor and opsonin.

    PubMed

    Liu, Conghui; Wang, Mengqiang; Jiang, Shuai; Wang, Lingling; Chen, Hao; Liu, Zhaoqun; Qiu, Limei; Song, Linsheng

    2016-02-01

    Junctional adhesion molecule (JAM), a subfamily of immunoglobulin superfamily (IgSF) with a couple of immunoglobulin domains, can act as regulator in homeostasis and inflammation of vertebrates. In the present study, a structural homolog of JAM-A (designated CgJAM-A-L) was screened out from oyster, Crassostrea gigas, through a search of JAM-A D1 domain (N-terminal Ig domain in JAM-A). The cDNA of CgJAM-A-L was of 1188 bp encoding a predicted polypeptide of 395 amino acids. The immunoreactive area of CgJAM-A-L mainly distributed over the plasma membrane of hemocytes. After Vibro splendidus or tumor necrosis factor (CgTNF-1) stimulation, the mRNA transcripts of CgJAM-A-L in hemocytes increased significantly by 4.46-fold and 9.00-fold (p < 0.01) of those in control group, respectively. The recombinant CgJAM-A-L protein (rCgJAM-A-L) could bind multiple PAMPs including lipopolysaccharides (LPS), peptidoglycan (PGN), lipoteichoic acid (LTA), mannose (MAN), β-glucan (GLU) and poly(I:C), and various microorganisms including Micrococcus luteus, Staphylococcus aureus, Escherichia coli, Vibro anguillarum, V. splendidus, Pastoris pastoris and Yarrowia lipolytica. The phagocytic rates of oyster hemocytes towards Gram-negative bacteria V. anguillarum and yeast P. pastoris were significantly enhanced after the incubation of rCgJAM-A-L, and even increased more significantly after the pre-incubation of rCgJAM-A-L with microbes (p < 0.01). The results collectively indicated that CgJAM-A-L functioned as an important pattern recognition receptor (PRR) and opsonin in the immune defense against invading pathogen in oyster. Moreover, as the most primitive specie with homolog of JAMs, the information of CgJAM-A-L in oyster would provide useful clues for the evolutionary study of JAMs and immunoglobulins. PMID:26434620

  3. Free amino acid composition of quince (Cydonia oblonga Miller) fruit (pulp and peel) and jam.

    PubMed

    Silva, Branca M; Casal, Susana; Andrade, Paula B; Seabra, Rosa M; Oliveira, M Beatriz P P; Ferreira, Margarida A

    2004-03-10

    Twenty-one free amino acids present in several samples of quince fruit (pulp and peel) and quince jam (homemade and industrially manufactured) were analyzed by GC/FID. The analyses showed some differences between quince pulps and peels. Generally, the highest content in total free amino acids and in glycine was found in peels. As a general rule, the three major free amino acids detected in pulps were aspartic acid, asparagine, and hydroxyproline. For quince peels, usually, the three most abundant amino acids were glycine, aspartic acid, and asparagine. Similarly, for quince jams the most important free amino acids were aspartic acid, asparagine, and glycine or hydroxyproline. This study suggests that the free amino acid analysis can be useful for the evaluation of quince jam authenticity. It seems that glycine percentage can be used for the detection of quince peel addition while high alanine content can be related to pear addition. PMID:14995121

  4. Stability of micronutrients and phytochemicals of grapefruit jam as affected by the obtention process.

    PubMed

    Igual, M; García-Martínez, E; Camacho, M M; Martínez-Navarrete, N

    2016-04-01

    Fruits are widely revered for their micronutrient properties. They serve as a primary source of vitamins and minerals as well as of natural phytonutrients with antioxidant properties. Jam constitutes an interesting way to preserve fruit. Traditionally, this product is obtained by intense heat treatment that may cause irreversible loss of these bioactive compounds responsible for the health-related properties of fruits. In this work, different grapefruit jams obtained by conventional, osmotic dehydration (OD) without thermal treatment and/or microwave (MW) techniques were compared in terms of their vitamin, organic acid and phytochemical content and their stability through three months of storage. If compared with heating, osmotic treatments lead to a greater loss of organic acids and vitamin C during both processing and storage. MW treatments permit jam to be obtained which has a similar nutritional and functional value than that obtained when using a conventional heating method, but in a much shorter time. PMID:25956906

  5. Modeling the capability of penetrating a jammed crowd to eliminate freezing transition

    NASA Astrophysics Data System (ADS)

    Mohammed Mahmod, Shuaib

    2016-05-01

    Frozen state from jammed state is one of the most interesting aspects produced when simulating the multidirectional pedestrian flow of high density crowds. Cases of real life situations for such a phenomenon are not exhaustively treated. Our observations in the Hajj crowd show that freezing transition does not occur very often. On the contrary, penetrating a jammed crowd is a common aspect. We believe the kindness of pedestrians facing others whose walking is blocked is a main factor in eliminating the frozen state as well as in relieving the jammed state. We refine the social force model by incorporating a new social force to enable the simulated pedestrians to mimic the real behavior observed in the Hajj area. Simulations are performed to validate the work qualitatively.

  6. Junctional adhesion molecule-C (JAM-C) regulates polarized neutrophil transendothelial cell migration in vivo

    PubMed Central

    Woodfin, Abigail; Voisin, Mathieu-Benoit; Beyrau, Martina; Colom, Bartomeu; Caille, Dorothée; Diapouli, Frantzeska-Maria; Nash, Gerard B; Chavakis, Triantafyllos; Albelda, Steven M.; Rainger, G Ed; Meda, Paolo; Imhof, Beat A.; Nourshargh, Sussan

    2011-01-01

    Neutrophil migration into inflamed tissues is a fundamental component of innate immunity. A decisive step in this process is the polarised migration of blood neutrophils through endothelial cells (ECs) lining the venular lumen (transendothelial cell migration; TEM) in a luminal to abluminal direction. Using real-time confocal imaging we report that neutrophils can exhibit disrupted polarised TEM (“hesitant” and “reverse”) in vivo. These events were noted in inflammation following ischemia-reperfusion injury, characterised by reduced expression of junctional adhesion molecule C (JAM-C) from EC junctions, and were enhanced by EC JAM-C blockade or genetic deletion. The results identify JAM-C as a key regulator of polarised neutrophil TEM in vivo and suggest that reverse TEM neutrophils can contribute to dissemination of systemic inflammation. PMID:21706006

  7. Jamming and percolation in random sequential adsorption of extended objects on a triangular lattice with quenched impurities

    NASA Astrophysics Data System (ADS)

    Budinski-Petković, Lj; Lončarević, I.; Jakšić, Z. M.; Vrhovac, S. B.

    2016-05-01

    Random sequential adsorption (RSA) on a triangular lattice with defects is studied by Monte Carlo simulations. The lattice is initially randomly covered by point-like impurities at a certain concentration p. The deposited objects are formed by self-avoiding random walks on the lattice. Jamming coverage {θ\\text{jam}} and percolation threshold θ \\text{p}\\ast are determined for a wide range of impurity concentrations p for various object shapes. Rapidity of the approach to the jamming state is found to be independent on the impurity concentration. The jamming coverage {θ\\text{jam}} decreases with the impurity concentration p and this decrease is more prominent for objects of larger size. For a certain defect concentration, decrease of the jamming coverage with the length of the walk \\ell making the object is found to obey an exponential law, {θ\\text{jam}}={θ0}+{θ1}{{\\text{e}}-\\ell /r} . The results for RSA of polydisperse mixtures of objects of various sizes suggest that, in the presence of impurities, partial jamming coverage of small objects can have even larger values than in the case of an ideal lattice. Percolation in the presence of impurities is also studied and it is found that the percolation threshold θ \\text{p}\\ast is practically insensitive to the concentration of point defects p. Percolation can be reached at highest impurity concentrations with angled objects, and the critical defect concentration p c is lowest for the most compact objects.

  8. Combined osmodehydration and high pressure processing on the enzyme stability and antioxidant capacity of a grapefruit jam

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A combined osmodehydration process and high pressure treatment (OD-HHP) was developed for grapefruit jam preservation. The inactivation kinetics of pectinmethylesterase (PME) and peroxidase (POD) in the osmodehydrated (OD) jam treated by combined thermal (45-75°C) and high pressure (550–700 MPa) pro...

  9. Auditory detection of paired pulses by a dolphin in the presence of a pulse jam

    NASA Astrophysics Data System (ADS)

    Sukhoruchenko, M. N.

    2004-07-01

    From behavioral studies of a bottlenose dolphin ( Tursiops truncatus), the audibility thresholds were measured for a single pair of equal-amplitude pulses, i.e., clicks, presented to the dolphin in combination with a pulse jam. The pulse jam consisted of pairs of identical pulses with a pulse spacing τj within the pairs and a pair repetition rate f j. Series of pulses were interrupted by a pause R>1/ f j, within which the pulse jam was absent while a pair of test pulses was supplied to one of the two channels at random. Each series had a duration T, and the total stimulation cycle was J= T+ R. The dependence of the test pair detection threshold on the pulse spacing τj was studied at different fixed values of the pulse spacing in the test pair: τt=50, 100, 200, and 500 µs. Preliminary measurements performed with τj=τt=100 µs were used to adjust the parameters of the pulse jam. The threshold shift at τj=τt=100 µs reached 35 dB above the audibility threshold of the test pair in the absence of the pulse jam. On both sides of the point τj=τt=100 µs the thresholds decreased with varying τj to approximately 20 dB above the detection threshold of the test pair in the absence of the jam. However, in the course of training, the threshold curves gradually shifted downwards approaching the detection level of the test pair in the absence of the jam and becoming progressively flatter (the selectivity with respect to the pulse jam vanished). A decrease in the pause duration R restored the dependence of the test pair detection threshold on τj. In this case, a statistically significant maximum was obtained at τj=τt for τj within the critical interval (for τt<500 µs). Beyond the critical interval (for τt>500 µs), even with the smallest pause duration ( R=15 ms), no dependence of the test pair detection thresholds on τj could be observed.

  10. Adductor pollicis jamming injuries in the professional baseball player: 2 case reports.

    PubMed

    Altobelli, Grant G; Ruchelsman, David E; Belsky, Mark R; Graham, Thomas; Asnis, Peter; Leibman, Matthew I

    2013-06-01

    We characterize a mechanism of injury, injury pattern, and treatment algorithm for adductor pollicis myotendinous injuries in 2 professional baseball players. Similar to myotendinous eccentric injuries in other anatomical areas, the adductor pollicis sustains a sudden forceful eccentric load during a jammed swing, resulting in intramuscular strain or tendon rupture. Based on the reported injury mechanism, and magnetic resonance imaging features of these myotendinous injuries, the thumb of the top hand during a jammed swing was suddenly and forcefully eccentrically abducted from a contracted and adducted position, resulting in injury patterns. PMID:23707017

  11. Percolation and jamming transitions in particulate systems with and without cohesion

    NASA Astrophysics Data System (ADS)

    Kovalcinova, L.; Goullet, A.; Kondic, L.

    2015-09-01

    We consider percolation and jamming transitions for particulate systems exposed to compression. For the systems built of particles interacting by purely repulsive forces in addition to friction and viscous damping, it is found that these transitions are influenced by a number of effects, and in particular by the compression rate. In a quasistatic limit, we find that for the considered type of interaction between the particles, percolation and jamming transitions coincide. For cohesive systems, however, or for any system exposed to even slow dynamics, the differences between the considered transitions are found and quantified.

  12. Jamming efficiency evaluation of the IR smoke screen against high-orbit IR detector

    NASA Astrophysics Data System (ADS)

    Gao, Gui-qing; Li, Yong-xiang

    2011-08-01

    In order to lower the orientating capability of the DSP satellite, at first the paper analyzes early warning missile satellite detective system, introduces the jamming mechanism of infrared smoke screen, and a model of jamming efficiency evaluation of the IR smoke screen against early warning satellite was built from three sides of absorbency of smoke screen to infrared radiation, dispersion ability and infrared radiation from smoke screen self. At last the correlative conclusion was got based on the brief depiction of Early-warning Satellite.

  13. Edwards thermodynamics of the jamming transition for frictionless packings: ergodicity test and role of angoricity and compactivity.

    PubMed

    Wang, Kun; Song, Chaoming; Wang, Ping; Makse, Hernán A

    2012-07-01

    This paper illustrates how the tools of equilibrium statistical mechanics can help to describe a far-from-equilibrium problem: the jamming transition in frictionless granular materials. Edwards ideas consist of proposing a statistical ensemble of volume and stress fluctuations through the thermodynamic notion of entropy, compactivity, X, and angoricity, A (two temperature-like variables). We find that Edwards thermodynamics is able to describe the jamming transition (J point) in frictionless packings. Using the ensemble formalism we elucidate the following: (i) We test the combined volume-stress ensemble by comparing the statistical properties of jammed configurations obtained by dynamics with those averaged over the ensemble of minima in the potential energy landscape as a test of ergodicity. Agreement between both methods supports the idea of ergodicity and "thermalization" at a given angoricity and compactivity. (ii) A microcanonical ensemble analysis supports the maximum entropy principle for grains. (iii) The intensive variables A and X describe the approach to jamming through a series of scaling relations as A → 0+ and X → 0-. Due to the force-strain coupling in the interparticle forces, the jamming transition is probed thermodynamically by a "jamming temperature" T(J) composed of contributions from A and X. (iv) The thermodynamic framework reveals the order of the jamming phase transition by showing the absence of critical fluctuations at jamming in static observables like pressure and volume, and we discuss other critical scenarios for the jamming transition. (v) Finally, we elaborate on a comparison with relevant studies by Gao, Blawzdziewicz, and O'Hern [Phys. Rev. E 74, 061304 (2006)], showing a breakdown of equiprobability of microstates obtained via fast quenches. A network analysis of the energy landscape reveals the origin of the inhomogeneities in the uneven distribution of the areas of the basins. Such inhomogeneities are also found in other

  14. Flow and Geometry Control the Onset of Jamming in Fractures with High Solid-Fraction Fluids

    NASA Astrophysics Data System (ADS)

    Medina, R.; Elkhoury, J. E.; Shannon, L. J.; Detwiler, R. L.; Morris, J.; Prioul, R.; Desroches, J.

    2013-12-01

    Fluids containing a large fraction of suspended solids are common in the subsurface. Examples include fluids used for environmental remediation, hydraulic fracturing fluids and magma. These fluid-solid mixtures behave as non-Newtonian fluids where interactions between fluid, suspended solids, and pore walls can lead to jamming of the suspended solids. Jamming causes the velocity of the solid to decrease locally to zero causing a rapid decrease in permeability as the fluid is forced to flow through the pore space within the immobilized solid. Here we present results from experiments that quantify the flow of non-Newtonian suspensions in an analog parallel-plate fracture (transparent 15cm x 15cm with ~3-mm aperture) and explore the dependence of jamming on flow conditions, fracture geometry, and the action of gravity. We used guar gum mixed with water (0.75%) as the fluid and added 50% by volume of crushed silica (< 300μm). Flow rates ranged from 0.2ml/min to 6.0ml/min, cell orientation varied from horizontal to vertical (bottom to top) flow and a transducer provided continuous measurement of differential pressure across the cell. A strobed LED panel backlit the cell and a high-resolution CCD camera captured frequent (0.2 Hz) images during all experiments. Particle image velocimetry (PIV) yielded measurements of the evolving velocity field during experiments (see Figure). In the vertical orientation during the initial period of high flow rate, outflow decreased rapidly and the differential pressure increased indicating jamming within the cell. Subsequent efforts to flush solids from the cell suggested that jamming occurred at the inlet of the cell. This was likely due to settling of solids within the flow field indicating that the time scale associated with settling was shorter than the time scale of advection through the cell. In the horizontal orientation, localized jamming occurred at the lowest flow rate in a region near the outlet. This suggests that when

  15. Deceptive jamming for countering UWB-SAR based on Doppler frequency phase template of false target

    NASA Astrophysics Data System (ADS)

    He, Xiaodong; Tang, Bin

    2016-04-01

    A false target deceptive jamming method for countering ultra-wideband synthetic aperture radar (UWB-SAR) is proposed in this paper, which is based on dechirp processing to intercepted UWB-SAR signal and inverse dechirp to jamming signal. The jammer quadrature down-converts and dechirps the intercepted UWB-SAR signal using a linear frequency modulation (LFM) signal oscillator, which could reduce the bandwidth and sample rate of analog-to-digital converter. Then, the jammer utilises the azimuth direction Doppler frequency phase between the false target and the jammer, and backward reflection coefficient template to modulate the phase of the intercepted UWB-SAR signal, and then delayed the modulated phase and also modulated the range direction Doppler frequency phase to the that. Finally, the jammer uses LFM signal oscillator to up-convert the narrowband jamming signal in order to recover the bandwidth of the signal. Parameter errors analysis and simulation results have shown that the detected parameters and motion characteristic errors reduce the resolution and offset the expected position of the false target, but it still could obtain an expected false target image. Theoretical analysis and simulation results indicated that the jamming signal proposed in this paper could produce a false target in the UWB-SAR image, which provide a feasible method for countering UWB-SAR in real time.

  16. Popular Culture, Cultural Resistance, and Anticonsumption Activism: An Exploration of Culture Jamming as Critical Adult Education

    ERIC Educational Resources Information Center

    Sandlin, Jennifer A.

    2007-01-01

    This chapter examines popular culture as a site of cultural resistance. Specifically, it explores how "culture jamming," a cultural-resistance activity, can be a form of adult education. It examines adult education and learning as it intersects with both consumerism and popular culture. Focus is placed on a growing social movement of individuals…

  17. Dynamic jamming effects on code synchronization of frequency-hop spread-spectrum

    NASA Astrophysics Data System (ADS)

    van Grouw, M. G.; Wickert, M. A.

    1989-06-01

    A general scheme for the code synchronization of Frequency-Hop Spread-Spectrum (FHSS) is presented. Synchronization performance is observed in the presence of channel dynamics and is characterized by mean synchronization time and mean time to loss of lock. A fixed-threshold multiple-dwell synchronization scheme is shown to adequately mitigate the effects of random hop jamming.

  18. Jelly Jam, the People Preserver. An Environmental Self-Teaching Activity Book.

    ERIC Educational Resources Information Center

    Friedman, Judi

    Designed for students in grades 2 through 4, this self-teaching, interdisciplinary reading and activity program comprises a complete supplemental reading, science, and social studies approach to the problems of environmental pollution. Jelly Jam, a caring little animal, helps children understand how air, water, and land pollution affects their own…

  19. Jelly Jam, the People Preserver. Teaching Guide. An Environmental Manual for Teachers and Parents. Revised Edition.

    ERIC Educational Resources Information Center

    Friedman, Judi

    Designed for teachers of students in grades 2 through 4, this teaching guide for a self-teaching, interdisciplinary reading and activity program comprises a complete supplemental reading, science, and social studies approach to the problems of environmental pollution. Jelly Jam, a caring little animal, helps children understand how air, water, and…

  20. Resistance to HF jamming interference in mobile radio networks by an adaptive, distributed reconfiguration technique

    NASA Astrophysics Data System (ADS)

    Baker, D. J.; Wieselthier, J. E.; Ephremides, A.; McGregor, D. N.

    1984-08-01

    In radio communication, interference (and in particular jamming) represents an important limitation to the rate and range of information transfer. In a radio network environment, a combination of relaying and other classes of interference-combatting methods, such as spread spectrum signaling, may achieve highly robust resistance to jamming. Since the presence of relays is an inherent characteristic of a network, it is possible to use some nodes as relays when previously existing direct links are disabled as a result of jamming. The purpose of this report is to show how a distributed algorithm can enable an HF radio network to reconfigure itself to combat various jamming threats. We present models for the communication range that is achievable through the use of HF groundwave signals under both benign and stressed conditions and for cases of narrowband and wideband signaling. The models are used in our simulations. These simulations show that the choice of best frequency for communication in an HF network should not depend solely on communication range in a benign environment.

  1. Jelly Jam, the People Preserver. An Environmental Self-Teaching Activity Book. Bermuda Edition.

    ERIC Educational Resources Information Center

    Friedman, Judi

    Designed for students in grades 2 through 4, this self-teaching, interdisciplinary reading and activity program approaches the environmental conditions, the state of natural resources, and the problems of pollution in Bermuda. A caring little animal named Jelly Jam is used to help children understand how air, water, and land pollution affect their…

  2. Complete genome sequence of the xylan-degrading subseafloor bacterium Microcella alkaliphila JAM-AC0309.

    PubMed

    Kurata, Atsushi; Hirose, Yuu; Misawa, Naomi; Wakazuki, Sachiko; Kishimoto, Noriaki; Kobayashi, Tohru

    2016-03-10

    Here we report the complete genome sequence of Microcella alkaliphila JAM-AC0309, which was newly isolated from the deep subseafloor core sediment from offshore of the Shimokita Peninsula of Japan. An array of genes related to utilization of xylan in this bacterium was identified by whole genome analysis. PMID:26808869

  3. Research on power measurement device of jamming bomb based on Infrared Radiation

    NASA Astrophysics Data System (ADS)

    Chang, Shuai; Tong, Shoufeng; Song, Yansong; Dong, Yan

    2013-12-01

    In order to realize the non-connect measurement on the power and character of jamming bomb, we carried out the research on power measurement device of jamming bomb based on Infrared Radiation. First, the power and infrared radiant band of the jamming bomb was summarized and refined. Then, ensuring the feature and power of jamming bomb was characterized by the magnitude of Infrared Radiation. Afterwards, based on the theory of the above, a power measurement device of Infrared Radiation was simulated and developed. Including the selection of detector and the detector application design, analog signal processing and digital signal processing, using correlation measurement method to detect and calculate the power of device. Finally, the specific method and advantage of the device was introduced. The results of the experiment show that: the response time of the device is less than 3ms; the detection sensitivity is better than 3 x 108cm √HZ / W . The device successfully accomplished the accuracy measurement of Infrared Radiation between 1 to 20um wavelength with higher detection sensitivity and lower response time.

  4. Magic at the Marketplace: Choice Blindness for the Taste of Jam and the Smell of Tea

    ERIC Educational Resources Information Center

    Hall, Lars; Johansson, Petter; Tarning, Betty; Sikstrom, Sverker; Deutgen, Therese

    2010-01-01

    We set up a tasting venue at a local supermarket and invited passerby shoppers to sample two different varieties of jam and tea, and to decide which alternative in each pair they preferred the most. Immediately after the participants had made their choice, we asked them to again sample the chosen alternative, and to verbally explain why they chose…

  5. 21 CFR 150.161 - Artificially sweetened fruit preserves and jams.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 2 2011-04-01 2011-04-01 false Artificially sweetened fruit preserves and jams. 150.161 Section 150.161 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN CONSUMPTION FRUIT BUTTERS, JELLIES, PRESERVES, AND RELATED...

  6. 21 CFR 150.161 - Artificially sweetened fruit preserves and jams.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 2 2010-04-01 2010-04-01 false Artificially sweetened fruit preserves and jams. 150.161 Section 150.161 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN CONSUMPTION FRUIT BUTTERS, JELLIES, PRESERVES, AND RELATED PRODUCTS Requirements for Specific Standardized...

  7. Analysis of acesulfame-K, saccharin and preservatives in beverages and jams by HPLC.

    PubMed

    Hannisdal, A

    1992-06-01

    A method is described that permits the simultaneous determination of acesulfame-K, saccharin and benzoic and sorbic acid in beverages and jams. The results of the HPLC analysis, using an RP-C 18 separation system with UV detection at 227 nm are reported. PMID:1496858

  8. Flow, turbulence, and drag associated with engineered log jams in a fixed-bed experimental channel

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Engineered log jams (ELJs) have become attractive alternatives for river restoration and bank stabilization programs. Yet the effects of ELJs on turbulent flow and the fluid forces acting on the ELJs are not well known, and such information could inform design criteria. In this study, a fixed-bed ph...

  9. Models in frequency-hopping-based proactive jamming mitigation for space communication networks

    NASA Astrophysics Data System (ADS)

    Shen, Dan; Chen, Genshe; Pham, Khanh; Blasch, Erik; Tian, Zhi

    2012-06-01

    In this paper, we consider a cognitive radio based space communication system in a game-theoretical framework, where players dynamically interact through wireless channels to utilize the wideband spectrum for their objectives. The performance indices include data rate, covertness, jamming, and anti-jamming; each of which relate to an effective signal-nose-ratio (SNR). The game players have different intents and asymmetric and hierarchical information about the frequency spectrum which are modeled as three different types of players: primary users, secondary users, and hostile active jammers. We consider the informational asymmetry in two situations: (1) different information sets for friendly users and jammers and (2) even among the friendly sensors; some sensors may only have partial or little information about others due to jammed observations. Such an asymmetric information pattern naturally partitions the sensors into leaders and followers. In our hierarchical anti-jammer approach, a two level approach includes a pursuit-evasion game and a Stackelberg game. At the higher-level, a non-cooperative pursuit-evasion game is constructed to model the interactions between jammer and primary users in the frequency-location domains. At the lower level, primary and secondary users play a dynamic Stackelberg game in the presence of jammers. Theoretical game solutions are provided to demonstrate the proposed proactive jamming mitigation strategy.

  10. Single DNA molecule jamming and history-dependent dynamics during motor-driven viral packaging

    NASA Astrophysics Data System (ADS)

    Keller, Nicholas; Grimes, Shelley; Jardine, Paul J.; Smith, Douglas E.

    2016-08-01

    In many viruses, molecular motors forcibly pack single DNA molecules to near-crystalline density into ~50-100 nm prohead shells. Unexpectedly, we found that packaging frequently stalls in conditions that induce net attractive DNA-DNA interactions. Here, we present findings suggesting that this stalling occurs because the DNA undergoes a nonequilibrium jamming transition analogous to that observed in many soft-matter systems, such as colloidal and granular systems. Experiments in which conditions are changed during packaging to switch DNA-DNA interactions between purely repulsive and net attractive reveal strongly history-dependent dynamics. An abrupt deceleration is usually observed before stalling, indicating that a transition in DNA conformation causes an abrupt increase in resistance. Our findings suggest that the concept of jamming can be extended to a single polymer molecule. However, compared with macroscopic samples of colloidal particles we find that single DNA molecules jam over a much larger range of densities. We attribute this difference to the nanoscale system size, consistent with theoretical predictions for jamming of attractive athermal particles.