Giant Acceleration Research Articles

Giant acceleration of polaron transport by ultrafast laser-induced coherent phonons.

Polaron formation is ubiquitous in polarized materials, but severely hampers carrier transport for which effective controlling methods are urgently needed. Here, we show that laser-controlled coherent phonon excitation enables orders of magnitude enhancement of carrier mobility via accelerating polaron transport in a prototypical material, lithium peroxide (Li2O2). The selective excitation of specific phonon modes, whose vibrational pattern directly overlap with the polaronic lattice deformation, can remarkably reduce the energy barrier for polaron hopping. The strong nonadiabatic couplings between the electronic and ionic subsystem play a key role in triggering the migration of polaron, via promoting phonon-phonon scattering in q space within sub-picoseconds. These results extend our understanding of polaron transport dynamics to the nonequilibrium regime and allow for optoelectronic devices with ultrahigh on-off ratio and ultrafast responsibility, competitive with those of state-of-the-art devices fabricated based on free electron transport.

Composites “lithium chloride/vermiculite” for adsorption thermal batteries: Giant acceleration of sorption dynamics

Adsorption thermal batteries have been proposed for storing heat from renewable and waste energy sources. Composites “salt in porous matrix” based on expanded vermiculite have extraordinary methanol sorption and heat storage capacities. However, their practical implementation is restricted by slow desorption, leading to low battery power. This paper aims to accelerate methanol desorption from a composite LiCl/vermiculite through its modification by an aluminum-oxygen containing additive. First, the dynamics of methanol sorption/desorption is studied for a pristine LiCl/vermiculite to reveal the factors braking sorption. Slow heterogeneous nucleation and sluggish growth of crystalline LiCl are shown to dramatically inhibit the methanol desorption from the pristine LiCl/vermiculite composite. To accelerate the nucleation, the vermiculite is modified by 2.5–8.9 wt% of aluminum-oxygen containing additive. Both pristine and modified sorbents are characterized by XRD, SEM, DSC, and BET techniques. The modification allows a giant acceleration of methanol desorption. The characteristic time corresponding to conversion 0.8 reduces by a factor of 2–12 as compared with the pristine composite. The dynamics acceleration affords fourfold increase in the specific power of the heat storage stage of adsorption thermal batteries employing the new composite. In a broader sense, the proposed approach could help accelerate the sorption of methanol, water, and ammonia on composites based on macroporous matrixes and could be advantageous for various adsorption applications.

Hybrid CPG–FRI dynamic walking algorithm balancing agility and stability control of biped robot

Dynamic walking fulfill agility and stability simultaneously is one of the most difficulty for biped robot control. The traditional zero moment point (ZMP) is the most commonly used reference point for biped robot static and quasi dynamic walking control. However, human walking experimental results indicate that during walking process of human beings, the ZMP trajectory is not always conformed to the requirement of stability, such as giant strides, acceleration walking or fast walking. In order to reveal the mechanism of the biped dynamic walking, this paper proposed a novel stability criterion for the biped walking by tuning the conventional fixed support polygon area to an adjustable one. This method includes the tiptoe underactuated phase of the support foot during the biped walking. A new algorithm for the real-time biped walking generation by combining central pattern generation (CPG) with foot rotation indicator (FRI) is presented. The FRI monitor establishes the mapping function between the center of mass of the biped robot with the boundary of the elastic support polygon. By introducing FRI information, the CPG parameters can be adjusted in real time to generate a rhythmic and stable walking pattern. Numerical simulation results show that the proposed algorithm extends the application area of the ZMP criterion and improves the walking velocity of the biped robot. Moreover, the algorithm builds a bridge for the dynamic biped walking from the robot agility to motor parameters. This means that the agility of the biped robot can be quantitative controlled by modulating the motor parameters.

Possible Experiment for the Demonstration of Neutron Waves Interaction with Spatially Oscillating Potential

A wide range of problems in neutron optics is well described by a theory based on application of the effective potential model. It was assumed that the concept of the effective potential in neutron optics have a limited region of validity and ceases to be correct in the case of the giant acceleration of a matter. To test this hypothesis a new Ultra Cold neutron experiment for the observation neutron interaction with potential structure oscillating in space was proposed. The report is focused on the model calculations of the topography of sample surface that oscillate in space. These calculations are necessary to find an optimal parameters and geometry of the planned experiment.

Transport and diffusion properties of Brownian particles powered by a rotating wheel.

Diffusion and rectification of Brownian particles powered by a rotating wheel are numerically investigated in a two-dimensional channel. The nonequilibrium driving comes from the rotating wheel, which can break thermodynamical equilibrium and induce the directed transport in an asymmetric potential. It is found that the direction of the transport along the potential is determined by the asymmetry of the potential and the position of the wheel. The average velocity is a peaked function of the angular speed (or the diffusion coefficient) and the position of the peak shifts to large angular speed (or diffusion coefficient) when the diffusion coefficient (or the angular speed) increases. There exists an optimal angular speed (or diffusion coefficient) at which the effective diffusion coefficient takes its maximal value. Remarkably, the giant acceleration of diffusion is observed by suitably adjusting the system parameters. The parameters corresponding to the maximum effective diffusion coefficient are not the same as the parameters at which average velocity is maximum.

Giant Acceleration of DNA Diffusion in an Array of Entropic Barriers.

We investigate with experiments and computer simulations the nonequilibrium dynamics of DNA polymers crossing arrays of entropic barriers in nanofluidic devices in a pressure-driven flow. With increasing driving pressure, the effective diffusivity of DNA rises and then peaks at a value that is many times higher than the equilibrium diffusivity. This is an entropic manifestation of "giant acceleration of diffusion." The phenomenon is sensitive to the effective energy landscape; thus, it offers a unique probe of entropic barriers in a system driven away from equilibrium.

Experiment proposed for the observation of UCN interaction with matter moving with giant acceleration

It was assumed that in neutron optics the concept of the effective potential has a limited region of validity, which is unlikely in the case of giant acceleration of matter. In the current work an experimental approach to test this hypothesis has been proposed.

Ultracold neutrons and the interaction of waves with moving matter

The present review is focused on the problem of interaction of neutron waves with moving matter. The validity of the 1/v law for ultracold neutrons and the possibility to characterize the interaction of neutrons with matter using the effective potential were verified in the so-called null Fizeau experiments. A neutron wave in such experiments propagates through a flat sample that moves parallel to its edges. The observation of effects caused by this motion provides evidence that the concept of constant effective potential is not correct. The second part of the review deals with the prediction and the first observation of the accelerated matter effect (a change in the energy of neutrons in passing through a refractive sample that moves with an acceleration directed along or opposite the direction of neutron propagation). The characteristic features of this phenomenon in the case of birefringent material are considered. In conclusion, the problem of propagation of neutron waves in matter moving with giant acceleration is discussed.

Energetic electrons generated during solar flares

The Sun is a giant particle accelerator. During solar flares, magnetic field energy stored in the corona is suddenly released and transferred to local heating of the coronal plasma, mass motions (e.g. jets) and the generation of energetic particles, i.e. electrons, protons and heavy ions. Basically, a flare occurs as a local enhancement of the emission of electromagnetic radiation from the radio up to the ${\it\gamma}$-ray range on the Sun. That indicates the production of energetic electrons during flares. NASA’s RHESSI mission has the aim to investigate electron acceleration processes by studying the Sun’s X-ray and ${\it\gamma}$-ray emission with high spatial, temporal and spectral resolution, i.e. by means of imaging spectroscopy. A substantial part of the energy released during a flare is carried by these energetic electrons. Apart from them, solar energetic particles, i.e. protons and heavy ions, and coronal mass ejections play an important role in the energy budget of a flare. Here, we focus on electron acceleration. The way in which $10^{36}$ electrons are accelerated up to energies beyond 30 keV is one of the open questions in solar physics. A flare is considered as the manifestation of magnetic reconnection in the solar corona. Which mechanisms lead to the production of energetic electrons in the magnetic reconnection region is discussed in this paper. Two of them are described in more detail.

Giant Acceleration of Diffusion Observed in a Single-Molecule Experiment on F(1)-ATPase.

The giant acceleration (GA) of diffusion is a universal phenomenon predicted by the theoretical analysis given by Reimann et al. [Phys. Rev. Lett. 87, 010602 (2001)]. Here we apply the theory of the GA of diffusion to a single-molecule experiment on a rotary motor protein, F(1), which is a component of F(o)F(1) adenosine triphosphate synthase. We discuss the energetic properties of F(1) and identify a high energy barrier of the rotary potential to be 20k(B)T, with the condition that the adenosine diphosphates are tightly bound to the F(1) catalytic sites. To conclude, the GA of diffusion is useful for measuring energy barriers in nonequilibrium and single-molecule experiments.

Therapeutic potential of atmospheric neutrons

Background Glioblastoma multiform (GBM) is the most common and most aggressive type of primary brain tumour in humans. It has a very poor prognosis despite multi-modality treatments consisting of open craniotomy with surgical resection, followed by chemotherapy and/or radiotherapy. Recently, a new treatment has been proposed – Boron Neutron Capture Therapy (BNCT) – which exploits the interaction between Boron-10 atoms (introduced by vector molecules) and low energy neutrons produced by giant accelerators or nuclear reactors. Methods The objective of the present study is to compute the deposited dose using a natural source of neutrons (atmospheric neutrons). For this purpose, Monte Carlo computer simulations were carried out to estimate the dosimetric effects of a natural source of neutrons in the matter, to establish if atmospheric neutrons interact with vector molecules containing Boron-10. Results The doses produced (an average of 1 μGy in a 1 g tumour) are not sufficient for therapeutic treatment of in situ tumours. However, the non-localised yet specific dosimetric properties of 10B vector molecules could prove interesting for the treatment of micro-metastases or as (neo)adjuvant treatment. On a cellular scale, the deposited dose is approximately 0.5 Gy/neutron impact. Conclusion It has been shown that BNCT may be used with a natural source of neutrons, and may potentially be useful for the treatment of micro-metastases. The atmospheric neutron flux is much lower than that utilized during standard NBCT. However the purpose of the proposed study is not to replace the ordinary NBCT but to test if naturally occurring atmospheric neutrons, considered to be an ionizing pollution at the Earth's surface, can be used in the treatment of a disease such as cancer. To finalize this study, it is necessary to quantify the biological effects of the physically deposited dose, taking into account the characteristics of the incident particles (alpha particle and Lithium atom) and radio-induced effects (by-stander and low dose effect). One of the aims of the presented paper is to propose to experimental teams (which would be interested in studying the phenomena) a simple way to calculate the dose deposition (allometric fit of free path, transmission factor of brain).

Research on dynamic characteristics of giant magnetostrictive acceleration sensors

This paper studies the dynamic response performance of giant magnetostrictive acceleration sensors. A magneto- mechanical strongly coupled dynamic model is presented, which is calculated by means of the finite element method. Accor ding to the proposed model, the time characteristic of the induced voltage for the acceleration sensor built with rare earth g iant magnetostrictive alloy is calculated. A comparison between the calculated results and measured ones has been carried out to examine the validity of the proposed dynamic model and the FE implementation. It is found that they are in an agreement. This indicates that the proposed FE model can reflect dynamic resp onse performance of giant magnetostrictive acceleration sensors.

Dynamic Model of Giant Magnetostrictive Acceleration Sensors Including Eddy-Current Effects

Compared with other types of acceleration sensors, the rare-earth giant magnetostrictive acceleration sensors have obvious advantages. In order to analyze performance of the giant magnetostrictive acceleration sensors, this paper presents a magneto-mechanical strongly coupled dynamic model for the giant magnetostrictive acceleration sensors, which includes eddy-current effects. Using the proposed model, the time characteristic of the induced voltage for the acceleration sensors is calculated by finite element method (FED). In order to validate the presented model, an experiment of the relation between the induced voltage and time for the acceleration sensors has been done. A comparison between the calculated results and measured ones has been carried out to examine the validity of the proposed model and the FED implementation. It is found that both of them are qualitatively in an agreement. This indicates that the proposed FED model can reflect dynamic response performance of the giant magnetostrictive acceleration sensors.

LHC switches on

Giant accelerator sees first beam circulate successfully.

Understanding the differences in molecular conformation of carbohydrate and protein in endosperm tissues of grains with different biodegradation kinetics using advanced synchrotron technology

Conventional “wet” chemical analyses rely heavily on the use of harsh chemicals and derivatization, thereby altering native seed structures leaving them unable to detect any original inherent structures within an intact tissue sample. A synchrotron is a giant particle accelerator that turns electrons into light (million times brighter than sunlight) which can be used to study the structure of materials at the molecular level. Synchrotron radiation-based Fourier transform IR microspectroscopy (SR-FTIRM) has been developed as a rapid, direct, non-destructive and bioanalytical technique. This technique, taking advantage of the brightness of synchrotron light and a small effective source size, is capable of exploring the molecular chemistry within the microstructures of a biological tissue without the destruction of inherent structures at ultraspatial resolutions within cellular dimensions. This is in contrast to traditional ‘wet’ chemical methods, which, during processing for analysis, often result in the destruction of the intrinsic structures of feeds. To date there has been very little application of this technique to the study of plant seed tissue in relation to nutrient utilization. The objective of this study was to use novel synchrotron radiation-based technology (SR-FTIRM) to identify the differences in the molecular chemistry and conformation of carbohydrate and protein in various plant seed endosperms within intact tissues at cellular and subcellular level from grains with different biodegradation kinetics. Barley grain (cv. Harrington) with a high rate (31.3%/h) and extent (78%), corn grain (cv. Pioneer) with a low rate (9.6%/h) and extent of (57%), and wheat grain (cv. AC Barrie) with an intermediate rate (23%/h) and extent (72%) of ruminal DM degradation were selected for evaluation. SR-FTIRM evaluations were performed at the National Synchrotron Light Source at the Brookhaven National Laboratory (Brookhaven, NY). The molecular structure spectral analysis involved the fingerprint regions of ca. 1720–1485 cm −1 (attributed to protein amide I C O and C N stretching; amide II N H bending and C N stretching), ca. 1650–950 cm −1 (non-structural CHO starch in endosperms), and ca. 1185–800 cm −1 (attributed to total CHO C O stretching vibrations) together with agglomerative hierarchical cluster and principal component analyses. Analyses involving the protein amide I features consistently identified differences between all three grains. Other analyses involving carbohydrate features were able to differentiate between wheat and barley but failed however to differentiate between wheat and corn. These results suggest that SR-FTIRM plus the multivariate analyses can be used to identify spectral features associated with the molecular structure of endosperm from grains with different biodegradation kinetics, especially in relation to protein structure. The Novel synchrotron radiation-based bioanalytical technique provides a new approach for plant seed structural molecular studies at ultraspatial resolution and within intact tissue in relation to nutrient availability.

Giant acceleration in slow-fast space-periodic Hamiltonian systems

The motion of an ensemble of particles in a space-periodic potential well with a weak wavelike perturbation imposed is considered. We found that slow oscillations of the wave number of the perturbation lead to the occurrence of directed particle current. This current is amplified with time due to the giant acceleration of some particles. It is shown that giant acceleration is linked to the existence of resonant channels in phase space.

Mechanism of Improvement Effect of Ultrasonically Activated Coolant on Finished Surface Roughness in Cylindrical Grinding

The use of an ultrasonically activated coolant improves the roughness of a ground surface compared with that of an ordinary coolant. By evaluating the change in working surface conditions, it has been clarified that the ultrasonically activated coolant suppresses loading and wheel wear, and maintains a good the working surface condition. The flushing effect of the ultrasonically activated coolant, promoted by giant vibration acceleration, prevents the deposition and welding of chips on the working surface. Since the density of kinetic energy in the coolant stream increases, the activation helps the coolant to overcome the airflow due to wheel rotation and to reach the grinding point efficiently. This promotes the cooling and lubricating effects of coolant, and then protects the cutting edges from crushing, falling off and dulling. On the basis of the results, it can be said that the effects of coolant activation suppress the generation of scratches, and consequently improve the finished surface roughness.

Spontaneous emission in a high-contrast one-dimensional photonic crystal

In a high-contrast one-dimensional photonic crystal (PC) spontaneous emission (SE) can resonantly excite evanescent modes that are guided by the high-index layers. Giant acceleration of SE takes place – as high as 76 (50) times the free-space value for a single atom (gas). Analogous SE in two-dimensional PCs, that resonantly excites waves guided by the dielectric cylinders, could lead to improvement of PC lasers. The radiative modes can have exotic radiation patterns and can be totally suppressed for TE polarization in certain spectral ranges. The SE rate is extremely sensitive to the atom’s position at the interfaces, with possible applications in surface science.

Giant acceleration of free diffusion by use of tilted periodic potentials.

The effective diffusion coefficient for the overdamped Brownian motion in a tilted periodic potential is calculated in closed analytical form. Universality classes and scaling properties for weak thermal noise are identified near the threshold tilt where deterministic running solutions set in. In this regime the diffusion may be greatly enhanced, as compared to free thermal diffusion with, for a realistic experimental setup, an enhancement of up to 14 orders of magnitude.

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