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Advances in fabrication and control of quantum dots allow the realization of metastructures that may exhibit novel electrical transport phenomena. Here, we investigate the electrical current passing through one such metastructure, a system composed of quantum dots placed at the vertices of a triangle. The wave natural of quantum particles leads to internal current circulation within the metastructure in the absence of any external magnetic field. We uncover the relation between its steady-state total current and the internal circulation. By calculating the electronic correlations in quantum transport exactly, we present phase diagrams showing where different types of current circulation can be found as a function of the correlation strength and the coupling between the quantum dots. Finally, we show that the regimes of current circulation can be further enhanced or reduced depending on the local spatial distribution of the interactions, suggesting a single-particle scattering mechanism is at play even in the strongly-correlated regime. We suggest experimental realizations of actual quantum-dot metastructures where our predictions can be directly tested.

The quantum variance of an observable is a fundamental quantity in quantum mechanics, and the variance provides additional information other than the average itself. By examining the relation between the particle-current variance $(\delta J)^2$ and the average current $J$ in both closed and open interacting fermionic systems, we show the emergence of a multi-valued Lissajous curve between $\delta J$ and $J$ due to interactions. As a closed system we considered the persistent current in a benzene-like lattice enclosing an effective magnetic flux and solved it by exact diagonalization. For the open system, the steady-state current flowing through a few lattice sites coupled to two particle reservoirs was investigated using a Lindblad equation. In both cases, interactions open a loop and change the topology of the corresponding $\delta J$-$J$ Lissajous curve, showing that this effect is model-independent. We finally discuss how the predicted phenomena can be observed in ultracold atoms, thus offering an alternative way of probing the dynamics of many-body systems.

The geometry of optical lattices can be engineered allowing the study of atomic transport along paths arranged in patterns that are otherwise difficult to probe in the solid state. A question readily accessible to atomic systems is related to the speed of propagation of matter-waves as a function of the lattice geometry. To address this issue, we have investigated theoretically the quantum transport of non-interacting and weakly-interacting ultracold fermionic atoms in several 2D optical lattice geometries. We find that the triangular lattice has a higher propagation velocity compared to the square lattice, despite supporting longer paths. The body-centered square lattice has even longer paths, nonetheless the propagation velocity is yet faster. This apparent paradox arises from the mixing of the momentum states which leads to different group velocities in quantum systems. Standard band theory provides an explanation and allows for a systematic way to search and design systems with controllable matter-wave propagation. Moreover, the presence of a flat band such as in a two-leg ladder geometry leads to a dynamical density discontinuity, which contrasts the behavior of mobile and localized atoms in quantum transport. Our predictions are realizable with present experimental capability.

Ultracold atoms provide clues to an important many-body problem regarding the dependence of Bose-Einstein condensation (BEC) transition temperature $T_c$ on interactions. However, cold atoms are trapped in harmonic potentials and theoretical evaluations of the $T_c$ shift of trapped interacting Bose gases are challenging. While previous predictions of the leading-order shift have been confirmed, more recent experiments exhibit higher-order corrections beyond available mean-field theories. By implementing two large-N based theories with the local density approximation (LDA), we extract next-order corrections of the $T_c$ shift. The leading-order large-N theory produces results quantitatively different from the latest experimental data. The leading-order auxiliary field (LOAF) theory containing both normal and anomalous density fields captures the $T_c$ shift accurately in the weak interaction regime. However, the LOAF theory shows incompatible behavior with the LDA and forcing the LDA leads to density discontinuities in the trap profiles. We present a phenomenological model based on the LOAF theory, which repairs the incompatibility and provides a prediction of the $T_c$ shift in stronger interaction regime.

Memory effects can lead to history-dependent behavior of a system, and they are ubiquitous in our daily life and have broad applications. Here we explore possibilities of generating memory effects in simple isolated quantum systems. By utilizing geometrical effects from a class of lattices supporting flat-bands consisting of localized states, memory effects could be observed in ultracold atoms in optical lattices. As the optical lattice continuously transforms from a triangular lattice into a kagome lattice with a flat band, history-dependent density distributions manifest quantum memory effects even in noninteracting systems, including fermionic as well as bosonic systems in the proper ranges of temperatures. Rapid growth in ultracold technology predicts a bright future for quantum memory-effect systems, and here two prototypical applications of geometry-induced quantum memory effects are proposed: An accelerometer recording the mechanical change rate in a coupled system and a rate-controlled memvalve where the rate of ramping the lattice potential acts as a control of the remnant density in the lattice.

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchive/

Plant cells can be sensitized toward a subsequent pathogen attack by avirulent pathogens or by chemicals such as beta aminobutyric acid (BABA). This process is called priming. Using a reverse genetic approach in Arabidopsis thaliana we demonstrate that the BABA responsive L type lectin receptor kinase VI. 2 (LecRK VI.2) contributes to disease resistance against the hemibiotrophic Pseudomonas syringae and the necrotrophic Pectobacterium carotovorum bacteria. Accordingly LecRK VI.2 mRNA levels increased after bacterial inoculation or treatments with microbe associated molecular patterns (MAMPs). We also show that LecRK VI.2 is required for full activation of pattern triggered immunity (PTI); notably lecrk VI.2 1 mutants show reduced upregulation of PTI marker genes impaired callose deposition and defective stomatal closure. Overexpression studies combined with genome wide microarray analyses indicate that LecRK VI.2 positively regulates the PTI response. LecRK VI.2 is demonstrated to act upstream of mitogen activated protein kinase signaling but independently of reactive oxygen production and BOTRYTIS INDUCED KINASE1 phosphorylation. In addition complex formation between the MAMP receptor FLAGELLIN SENSING2 and its signaling partner BRASSINOSTEROID INSENSITIVE1 ASSOCIATED KINASE1 is observed in flg22 treated lecrk VI.2 1 mutants. LecRK VI.2 is also required for full BABA induced resistance and priming of PTI. Our work identifies LecRK VI.2 as a novel mediator of the Arabidopsis PTI response and provides insight into molecular mechanisms governing priming.

This study compared the agronomic properties of rice husk biochar (RHB) and wood biochar (WB) and investigated their effect on the growth rate of water spinach in a field experiment. Each biochar type was tested at 5 different rates of 4.0, 3.0, 2.0, 1.0 and 0.5 kg m3, respectively. The results detailing the growth of water spinach showed that the application of rice husk biochar improves biomass production. The WB added to soil increased the plant weight of water spinach by increasing the root size and leaf width, whereas RHB added to soil increased plant weight by increasing the stem size and leaf length of the water spinach. In addition, the stem size of water spinach was proportional to the WHC/silt ratio; whereas the root size of water spinach was proportional to the OM/OC ratio of soil. We also proposed that the working mechanism of WB and RHB in soil would be such, that the decomposition of OC in biochar-added soil to OM resulted in increased WHC and decreased silt in biochar-added soil. The decomposition of WB biochar was faster than RHB under a lower dosage amount (< 1.5 kg m3), but this trend was inversed with a higher dosage ( > 3.0 kg m3).

A new variable structure longitudinal controller is designed and analyzed for an autonomous intelligent vehicle. The proposed controller not only guarantees individual vehicle stability but also platoon stability. Moreover, the achieved platoon stability is proven to be robust with respect to vehicle parameter uncertainties and unknown time varying disturbances. Explicit transient bounds are obtained which indicate ways of choosing controller parameters for comfortable driving. 3 2431 2436 Sponsors: IEEE Computer Society ACM SIGSOFT IEE IFIP Working Group 2.9 Conference code: 42972 Cited By :11

We compute the shear viscosity, $\eta$, at general temperatures $T$, in a BCS-BEC crossover scheme which is demonstrably consistent with conservation laws. The study of $\eta$ is important because it constrains microscopic theories by revealing the excitation spectra. The onset of a normal state pairing gap and the contribution from pair degrees of freedom imply that $\eta$ at low $T$ becomes small, rather than exhibiting the upturn predicted by most others. Using the local density approximation, we find quite reasonable agreement with just-published experiments., Comment: 4 pages, 2 figures

During manual driving, most human drivers often use information about the speed and position of the preceding and following vehicles in order to adjust the position and speed of their vehicles. The purpose of this paper is to design an autonomous intelligent cruise control (AICC) which mimics this human driving behavior. The proposed AICC law uses relative speed and spacing information from the preceding and following vehicles in order to choose the proper control action for smooth vehicle following and for maintaining a desired intervehicle spacing specified by the driver. The vehicle stability and platoon stability (in the case of multiple vehicles) in both directions (backward and forward) are guaranteed by the proposed AICC law. Furthermore, platoon stability is guaranteed for a speed-dependent desired spacing (time headway approach) as well as for a constant desired spacing at all speeds. 48 1 319 328 Cited By :45

Traffic flow instabilities such as traffic congestion are often caused by ad hoc and inappropriate speeds and headways that humans choose when they operate their vehicles. In an automated highway system (AHS) environment, the driver's actions are replaced by those of a computer control system that is designed to optimize traffic flow. On the microscopic level, each vehicle is driven by a computer control system, which, based on the actions of the surrounding vehicles, sends the appropriate commands to the throttle/brake/steering actuators. On the macroscopic level, a roadway controller calculates the desired speed commands to be followed by vehicles in each section of the freeway lanes in order to achieve desired traffic density distributions that lead to optimum traffic flow conditions. In this paper, we design, analyze and simulate a roadway controller for an automated highway that achieves desired traffic densities along the lane. A macroscopic traffic flow model that is modified for AHS operation is used for control design and analysis. We show that the proposed roadway controller guarantees exponential convergence of the traffic density at each section to the desired density. Simulation results are used to illustrate the effectiveness of the proposed controller and the significant benefits AHS may bring to traffic flow. © 1997 Elsevier Science Ltd. 33 7 1273 1285 Cited By :56

A new class of adaptive control schemes for minimum-phase linear time invariant (LTI) systems has recently been developed using nonlinear design techniques which guarantee improved transient performance in addition to closed-loop stability and asymptotic tracking. In this paper we establish the parameter convergence properties of this new class of schemes in the presence of persistently exciting signals and compare them with the properties of the traditional adaptive controllers. We show that the new class of adaptive controllers has stronger parameter convergence properties in the presence of overparameterization. © 1996 IEEE. 41 10 1489 1493 Cited By :32

In this paper, a roadway controller is designed, analyzed and simulated for a single automated highway lane that achieves desired traffic densities along the lane. A macroscopic traffic flow model that is modified for AHS (Automated Highway Systems) operation is used for control design and analysis. The authors show that the proposed roadway controller guarantees exponential convergence of the traffic density at each section of the lane to the desired density. Simulation results are used to illustrate the effectiveness of the proposed controller and the significant benefits AHS may bring to traffic flow.

In this paper, a fuzzy traffic density homogenizer is proposed to alleviate or avoid congestion by smoothing the traffic density distribution profile over freeway lanes. The proposed fuzzy homogenizer consists of two parts: the fuzzy mean speed controller and the fuzzy on- ramp controller. Simulation results are used to demonstrate that the proposed controllers can eliminate traffic flow instabilities leading to smooth traffic flows.

This paper investigates two different longitudinal control policies for automatically controlled vehicles. One is based on maintaining a constant spacing between the vehicles while the other is based upon maintaining a constant headway (or time) between successive vehicles. To avoid collisions in the platoon, controllers have to be designed to ensure string stability, i.e the spacing errors should not get amplified as they propagate upstream from vehicle to vehicle. A measure of string stability is introduced and a systematic method of designing constant spacing controllers which guarantee string stability is presented. The constant headway policy does not require inter-vehicle communication to assure string stablity. Also, since inter-vehicle communication is not required it can be used in systems with mixed automated-nonautomated vehicles, e.g for AICC (Autonomous Intelligent Cruise Control). It is shown in this paper that for all the autonomous headway control laws, the desired control torques are inversely proportional to the headway time. © 1994, Taylor & Francis Group, LLC. All rights reserved. 23 1 597 625 Cited By :28

Entrainment and vehicle following controllers are proposed for autonomous intelligent vehicles in both non-tight and tight vehicle following maneuvers. A nonlinear vehicle model is used for designing the controllers. The proposed vehicle following controller is designed based on a constant time headway policy whereas, the proposed entrainment controller is designed based on a k-factor headway policy. The proposed vehicle following controller not only provides local individual vehicle stability but also guarantees asymptotic platoon stability without the availability of feedforward information. Furthermore, the achieved asymptotic platoon stability is shown to be theoretically robust with respect to sensor delays. Computer simulations demonstrate the performance of the proposed controllers. 1 6 10 Sponsors: AACC Conference code: 21446 Cited By :37

In this paper, a fuzzy traffic density homogenizer is proposed to alleviate or avoid the congestion by smoothing the traffic density distribution profile over the freeway. The proposed fuzzy traffic density homogenizer consists of two parts which are fuzzy mean speed controller and fuzzy on-ramp controller. The fuzzy mean speed controller is designed to determine the evolution rate of the mean speed in each section to achieve smooth traffic flow and the fuzzy on-ramp controller is designed to determine the maximum allowable on-ramp traffic volume in the sense that the on-ramp traffic flow does not lead to an amplification of the congestion of freeways. 2 968 973 Sponsors: IEEE Conference code: 42534 Cited By :3

For manual driving, the traffic flow is often irregular, unstable leading to congestion and to low traffic flow rate during minor incidents. These irregularities are due to variation of vehicle speeds and headways that are selected by the individual drivers. It is expected that the congestion could be reduced and traffic flow rate could be increased, if the speed and density of the vehicles along a lane can be properly controlled by a roadway controller. In this paper we propose a roadway controller and investigate the benefits of controlling the density and speed of the vehicles along a lane by using the proposed roadway controller. The roadway controller sends the appropriate speed commands to vehicles in each section of the lane. The vehicles are equipped to follow each other automatically and respond to the roadway commands without any driver intervention. A macroscopic traffic flow model is used for analysis and simulations. Our results demonstrate significant benefits in terms of smooth and stable traffic flow that reduce congestion considerably. 3 2425 2430 Sponsors: IEEE Computer Society ACM SIGSOFT IEE IFIP Working Group 2.9 Conference code: 42972 Cited By :6

Vehicle following and its effects on traffic flow has been an active area of research. Human driving involves reaction times, delays, and human errors that affect traffic flow adversely. One way to eliminate human errors and delays in vehicle following is to replace the human driver with a computer control system and sensors. The purpose of this paper is to develop an autonomous intelligent cruise control (AICC) system for automatic vehicle following, examine its effect on traffic flow, and compare its performance with that of the human driver models. The AICC system developed is not cooperative i.e., it does not exchange information with other vehicles and yet is not susceptible to oscillations and “slinky” effects. The elimination of the “slinky” effect is achieved by using a safety distance separation rule that is proportional to the vehicle velocity (constant time headway) and by designing the control system appropriately. The performance of the AICC system is found to be superior to that of the human driver models considered. It has a faster and better transient response that leads to a much smoother and faster traffic flow. Computer simulations are used to study the performance of the proposed AICC system and analyze vehicle following in a single lane, without passing, under manual and automatic control. In addition, several emergency situations that include emergency stopping and cut-in cases were simulated. The simulation results demonstrate the effectiveness of the AICC system and its potentially beneficial effects on traffic flow. © 1993 IEEE 42 4 657 672 Cited By :259

Vehicle following and its effects on traffic flow has been an active area of research. Human driving involves reaction times, delays and human errors that affect traffic flow adversely. One way to eliminate human errors and delays in vehicle following is to replace the human driver with a computer control system and sensors. The purpose of this paper is to come up with a control system for automatic vehicle following, examine its effect on traffic flow and compare its performance with that of the human driver models. We proposed a control law for automatic vehicle following that is not cooperative i.e. it does not exchange information with other vehicles and yet is free of oscillations and slinky-effects. The elimination of the slinky-effect is achieved by using a safety distance separation rule that is proportional to the vehicle velocity (constant time headway). The performance of automatic vehicle following is found to be superior to that of the human driver models considered. It has a faster and better transient response that leads to a much smoother and faster traffic flow. Traffic flow rates can be improved considerably with automation due to the elimination of human delays and errors and the potential of using smaller and safer intervehicle spacings than those assumed by human drivers. 2 1748 1752 Conference code: 17380 Cited By :65

We report recent advances in hard-x-ray optics-including record spatial resolution-and in staining techniques that enable synchrotron microradiology to produce neurobiology images of quality comparable to electron and visible microscopy. In addition, microradiology offers excellent penetration and effective three-dimensional detection as required for many neuron studies. Our tests include tomographic reconstruction based on projection image sets.

Our experimental results demonstrate that full-field hard-X-ray microscopy is finally able to investigate the internal structure of cells in tissues. This result was made possible by three main factors: the use of a coherent (synchrotron) source of X-rays, the exploitation of contrast mechanisms based on the real part of the refractive index and the magnification provided by high-resolution Fresnel zone-plate objectives. We specifically obtained high-quality microradiographs of human and mouse cells with 29 nm Rayleigh spatial resolution and verified that tomographic reconstruction could be implemented with a final resolution level suitable for subcellular features. We also demonstrated that a phase retrieval method based on a wave propagation algorithm could yield good subcellular images starting from a series of defocused microradiographs. The concluding discussion compares cellular and subcellular hard-X-ray microradiology with other techniques and evaluates its potential impact on biomedical research. (C) 2012 Elsevier Inc. All rights reserved.

We demonstrate that, with appropriate staining, high-resolution X-ray microscopy can image complicated tissue structures-cerebellum and liver-and resolve large or small amounts of Au nanoparticles in these tissues. Specifically, images of tumor tissue reveal high concentrations of accumulated Au nanoparticles. PEG (poly(ethylene glycol)) coating is quite effective in enhancing this accumulation and significantly modifies the mechanism of uptake by reticuloendothelial system (RES) organs.

Substantial improvements in the nanofabrication and characteristics of gold Fresnel zone plates yielded unprecedented resolution levels in hard-x-ray microscopy. Tests performed on a variety of specimens with 8-10 keV photons demonstrated a first-order lateral resolution below 40 nm based on the Rayleigh criterion. Combined with the use of a phase contrast technique, this makes it possible to view features in the 30 nm range; good-quality images can be obtained at video rate, down to 50 ms/frame. The important repercussions on materials science, nanotechnology, and the life sciences are discussed. (C) 2008 American Institute of Physics.