Jumping Mode Research Articles

State estimation for discrete-time Markovian jumping neural networks with mixed mode-dependent delays

In this Letter, we investigate the state estimation problem for a new class of discrete-time neural networks with Markovian jumping parameters as well as mode-dependent mixed time-delays. The parameters of the discrete-time neural networks are subject to the switching from one mode to another at different times according to a Markov chain, and the mixed time-delays consist of both discrete and distributed delays that are dependent on the Markovian jumping mode. New techniques are developed to deal with the mixed time-delays in the discrete-time setting, and a novel Lyapunov–Krasovskii functional is put forward to reflect the mode-dependent time-delays. Sufficient conditions are established in terms of linear matrix inequalities (LMIs) that guarantee the existence of the state estimators. We show that both the existence conditions and the explicit expression of the desired estimator can be characterized in terms of the solution to an LMI. A numerical example is exploited to show the usefulness of the derived LMI-based conditions.

Design of [formula omitted] filter for Markov jumping linear systems with non-accessible mode information

For Markov jumping linear systems (MJLS), it is often encountered that the jumping mode cannot be accessible for filtering. Therefore it is strongly desirable to design a filter which is independent of the jumping model. In this paper, a new deterministic filter design procedure is proposed, which shows less conservatism than existing results. The whole design procedure can be accomplished by solving a set of linear matrix inequalities (LMIs). Finally, numerical examples are given to illustrate the effectiveness of the proposed approach.

Unbinding Molecular Recognition Force Maps of Localized Single Receptor Molecules by Atomic Force Microscopy

Atomic force microscopy is a technique capable to study biological recognition processes at the single-molecule level. In this work we operate the AFM in a force-scan based mode, the jumping mode, where simultaneous topographic and tip-sample adhesion maps are acquired. This approach obtains the unbinding force between a well-defined receptor molecule and a ligand attached to the AFM tip. The method is applied to the avidin-biotin system. In contrast with previous data, we obtain laterally resolved adhesion maps of avidin-biotin unbinding forces highly correlated with single avidin molecules in the corresponding topographic map. The scanning rate 250 pixel s(-1) (2 min for a 128 x 128 image) is limited by the hydrodynamic drag force. We are able to build a rupture-force distribution histogram that corresponds to a single defined molecule. Furthermore, we find that due to the motility of the polymer used as spacer to anchor the ligand to the tip, its direction at rupture does not generally coincide with the normal to the tip-sample, this introduces an appreciable error in the measured force.

“Frictionless” and “frictional” ThermoElastic Dynamic Instability (TEDI) of sliding contacts

Recently, we found that a new form of coupled instability, named ThermoElastic Dynamic Instability (TEDI), can occur by interaction between frictional heating and the natural dynamic modes of sliding bodies. This is distinct from the classical dynamic instabilities (DI) which is produced by an interaction between the frictional forces at the sliding interface and the natural modes of vibration of the bodies if the friction coefficient is sufficiently high, and also from ThermoElastic Instability (TEI), which is due to the interaction of frictional heating and thermal expansion, leading for example to low pitched brake noise above some critical speed. This result was relative to an highly idealized system, comprising an elastic layer sliding over a rigid plane including both dynamic and thermoelastic effects, but neglecting shear waves at the interface due to frictional tractions (from which the denomination “frictionless TEDI”). We demonstrate here that including these shear waves destabilizes both the shear and dilatational vibration modes of the system at arbitrarily small friction coefficients and speeds, where DI and TEI are predicted to be stable. A detailed study of the new modes and transient simulations show that for low pressures and high speed, the system tends towards the results of the previous model (“ frictionless TEDI”), i.e. the tendency to a state in which the layer bounces over the plane, with alternating periods of sliding contact and separation. In the case of low speeds and high pressures, viceversa, the system is dominated by the modes near the resonance of the shear and dilatational modes, with a resulting complex behaviour, but generally leading to stick-slip regimes, reducing the jumping mode of “ frictionless TEDI”, because stick reduces or stops frictional heating production.

Take-off and landing forces in jumping frogs

Anurans use a saltatorial (jumping) mode of locomotion. A jumping cycle can be divided into four subphases: propulsion, flight, landing and recovery. We studied the landing phase during locomotion in Rana esculenta by measuring the ground reaction forces during propulsion and landing over a range of distances. Landing performance affects locomotor ability in jumping frogs. Landing and recovery together take up one third of the locomotor cycle. Peak landing forces are on average almost three times larger than propulsive forces. The forelimbs appear to be fully extended when they make contact with the substrate and absorb the first impact peak. The height of this peak varies depending on arm positioning and jumping distance. Since the stiffness of the arms stays constant over the full jumping range, it is possible that this is a limiting factor in the ability of the forelimbs to work as dampers. A spring-dashpot model is used to model the effect of arm angle at touch down. Damping during landing is performed by placing the forelimbs at an optimal angle to cancel frictional forces effectively.

Jumping mode atomic force microscopy obtains reproducible images of Alzheimer paired helical filaments in liquids

Alzheimer paired helical filaments (PHF) have been investigated with atomic force microscopy (AFM) under physiological conditions. Dynamic mode (DM) and jumping mode (JM) AFM have been employed as imaging techniques. Data obtained in solution have been compared to data obtained in ambient air with DM. In liquids, PHF particles show distortion and irreversible damage when imaged with DM. On the contrary, JM images of PHF particles are reproducible and out of apparent damage. Dimensions of the PHF particles measured with JM, are in agreement with previously reported electron microscopy data. We have found that the forces involved in DM imaging are larger than those involved in JM imaging and hence we believe that this is the main reason of the damage caused by the tip when using DM in solution.

Characterization by Atomic Force Microscopy of Alzheimer Paired Helical Filaments under Physiological Conditions

Paired helical filaments (PHF) is an aberrant structure present in the brain of Alzheimer's disease patients which has been correlated with their degree of dementia. In order to determine the structure of PHF, several studies have been performed using atomic force microscopy (AFM). However, those studies have the limitation that they have not been done in solution and the sample could be far from the real physiological conditions. In this work we present an AFM analysis of PHF in liquid environment and we compare that analysis with that performed in dry conditions. PHF imaging in liquid was only possible by using jumping mode AFM as the imaging technique. Jumping mode AFM images of PHF in solution show first, a notable increase in the absolute values of the height of the filament, and second, a smaller ratio between the height measured at the upper and at the lower part of the PHF. Direct comparison of the experimental data with structural models has been performed. From this we conclude that the PHF structure is compatible with two coupled ribbons with an overall height of 20 nm and a width of 10 nm.

Jumping mode scanning force microscopy: a suitable technique for imaging DNA in liquids

In this work, we introduce jumping mode (JM) scanning force microscopy (SFM) as a suitable technique for imaging soft samples in liquid environment like DNA adsorbed on mica. JM reveals as a non-intrusive technique where shear forces are minimized by performing the scanning motion without tip–sample contact. We find no visible damage on DNA samples and the nominal height of 2 nm of the molecules is achieved when imaging applying a maximum normal force of ∼150 pN. In addition to topographic images, adhesion maps of DNA are simultaneously recorded showing that the minimum adhesion force occurs on top of the DNA molecules.

DNA height in scanning force microscopy

The measured height of DNA molecules adsorbed on a mica substrate by scanning probe microscopy is always less than the theoretical diameter. In this paper we show that, when imaged in ambient conditions, the molecules are usually immersed in the salt layer used to adsorb them to the substrate. This layer distorts the measurement of DNA height and is the main source of error but not the only one. We have performed different experiments to study this problem using two scanning force techniques: non-contact tapping mode in air and jumping mode in aqueous solution, where the dehydration phenomena is minimized. Height measurements of DNA in air using tapping mode reveal a height of 0.7±0.2 nm. This value increases up to 1.5±0.2 nm when the salt layer, in which the molecules are embedded, is removed. Jumping experiments in water give a value of 1.4±0.3 nm when the maximum applied force is 300 pN and 1.8±0.2 nm at very low forces, which confirms the removal of the salt layer. Still, in all our experiments, the measured height of the DNA is less than the theoretical value. Our results show that although the salt layer present is important, some sample deformation due to either the loading force of the tip or the interaction with the substrate is also present.

Probing electrical transport in nanowires: current maps of individual V2O5nanofibres with scanning force microscopy

In this work we present two scanning force microscopy (SFM) techniquesapplied to the electrical characterization of V2O5 nanofibres with one endconnected to a metallic electrode: first a non-contact imaging techniquecombined with the acquisition of current versus voltage curves in a selectedspot, and second jumping mode SFM that allows simultaneous acquisitionof topograhic images and current maps with nanometric resolution.Both the conductivity (∼20 S cm−1) and the contact resistance (∼ 62MΩ)of the fibres are determined. A non-linear behaviour of the conductivityis observed for large applied electrical fields (E > 105 V cm−1)as found previously for V2O5 films.

Scanning force microscopy jumping and tapping modes in liquids

In this work theoretical considerations of the performance of scanning force microscopy jumping mode and tapping mode in liquids are discussed. A priori, jumping mode should improve in a liquid environment compared to in air while the situation for tapping mode should become worse. In order to confirm this we present jumping and tapping mode images of DNA molecules absorbed on a mica substrate immersed in water. The experiments demonstrate that jumping mode is a suitable scanning force microscopy method by which to image soft samples in liquid and that it has similar or even better performance than those exhibited by tapping, but without the complex experimental requirements of this mode.

Nonlinear shape oscillations of axisymmetric magnetic fluid columns in a magnetic field

Nonlinear axisymmetric shape oscillations have been revealed through experiments conducted with large-amplitude forced vertical vibrations of a magnetic fluid column supported by a magnetic field in the presence of gravity. Those nonlinear shape oscillations are characterized by the jumping phenomena, mode transition, and subharmonic motions.

Measurement of the isotopic composition and atomic weight of an isotopic reference material of platinum, IRMM-010

An isotopic reference material (IRM), IRMM-010, was prepared as a metallic platinum wire and certified for isotopic composition of platinum. The measurements were carried out with a quadrupole inductively coupled plasma mass spectrometer (ICP-MS) in peak jumping mode using a secondary electron multiplier as detector. Five synthetic isotope mixtures with certified isotope amount ratios of n( 196Pt)/ n( 195Pt) were prepared in order to calibrate the measurements. The synthetic isotope mixtures, the natural platinum reference material as well as the isotopically enriched materials were measured in a 2% HNO 3 and 2% H 2O 2 matrix in order to reduce memory effects during the measurements. These measurements resulted in certified isotope amount ratios and isotopic composition of a platinum reference material with natural isotopic composition. The relative abundances of the different platinum isotopes were determined as: 0.0117±0.0012 amount % of 190Pt, 0.782±0.016 amount % of 192Pt, 32.86±0.27 amount % of 194Pt, 33.77+0.16 amount % of 195Pt, 25.21+0.23 amount % of 196Pt, and 7.356±0.087 amount % of 198Pt. This lead to an atomic weight equal to 195.0844±0.0058 for this material. The purity of IRMM-010 was measured, the total impurity was found to be 140±140 μg·g −1. Uncertainties are expanded combined uncertainties expressed with a coverage factor k=2.

Different stages of water adsorption on Au studied by dynamic SFM and jumping mode

Adsorption of water on solid surfaces is a phenomenon always present at ambient conditions. In the present work, we study adsorption of water on different sites of a Au surface. We combine imaging and acquisition of the force vs. distance curve at different relative humidities to characterise the physics of this process. We find two different sites of adsorption: terraces and grain boundaries, each with typical features.

The role of shear forces in scanning force microscopy: a comparison between the jumping mode and tapping mode

Shear forces are known to be one of the main causes of sample damage in scanning force microscopy. In this work, we compare two related imaging methods: jumping mode and tapping mode. These methods have been used in the imaging of two delicate samples such as DNA on mica and single-wall carbon nanotubes on silicon oxide. The results of these experiments show that while the tapping mode does not produce any visible modification, the jumping mode introduces irreversible sample damage. In the jumping mode case, the damage is explained assuming the presence of lateral force components derived from the normal force. In the tapping mode and under our usual experimental conditions, normal forces are found to be extremely weak, and thus, lateral contributions are negligible. From the experiments, we conclude that the absence of friction forces introduced by the tip scanning is not sufficient to obtain non-intrusive images.

Manipulation for low back pain.

SUMMARY Anurans use a saltatorial (jumping) mode of locomotion. A jumping cycle can be divided into four subphases: propulsion, flight, landing and recovery. We studied the landing phase during locomotion in Rana esculenta by measuring the ground reaction forces during propulsion and landing over a range of distances. Landing performance affects locomotor ability in jumping frogs. Landing and recovery together take up one third of the locomotor cycle. Peak landing forces are on average almost three times larger than propulsive forces. The forelimbs appear to be fully extended when they make contact with the substrate and absorb the first impact peak. The height of this peak varies depending on arm positioning and jumping distance. Since the stiffness of the arms stays constant over the full jumping range, it is possible that this is a limiting factor in the ability of the forelimbs to work as dampers. A spring-dashpot model is used to model the effect of arm angle at touch down. Damping during landing is performed by placing the forelimbs at an optimal angle to cancel frictional forces effectively.