Low Initial Energy Research Articles

Distributed stable cluster head election (DSCHE) protocol for heterogeneous wireless sensor networks

During the last decade, wireless sensor networks (WSNs) have gained increasing attention for both the research community and actual users. The sensor nodes are mostly battery operated devices, the critical aspects to face concern how to reduce the energy consumption of nodes by using hierarchical clustered approach, so that the network lifetime and scalability can be extended. The key objective of this paper is to present a new distributed stable cluster head election (DSCHE) protocol to predict the network lifetime and stability of heterogeneous WSNs. In DSCHE, the cluster heads are selected by a weighted probability based on the ratio between residual energy of each node and the average energy of the network. The nodes with high initial and residual energy will have more chances to become the cluster heads as compared with other nodes with low initial and residual energy. The simulation results show that DSCHE balances the energy consumption better than the conventional existing routing protocols and al...

Attosecond Streaking in the Low-Energy Region as a Probe of Rescattering

The dynamics of low-energy photoelectrons (PEs) ionized by a single attosecond pulse in the presence of an intense infrared (IR) laser field is investigated. Whereas attosecond streaking usually involves momentum shifts of high-energy PEs, when PEs have low initial kinetic energies, the IR field can control the continuum-electron dynamics by inducing PE scattering from the residual ion. A semiclassical model is used to show that particular PE trajectories in the continuum involving electron-ion scattering explain the interference patterns exhibited in the low-energy PE spectrum. We confirm the effects of the trajectories by means of a full quantum simulation.

Transient Growth and Triggering in the Horizontal Rijke Tube

This theoretical paper examines a non-normal and non-linear model of a horizontal Rijke tube. Linear and non-linear optimal initial states, which maximize acoustic energy growth over a given time from a given energy, are calculated. It is found that non-linearity and non-normality both contribute to transient growth and that, for this model, linear optimal states are only a good predictor of non-linear optimal states for low initial energies. Two types of non-linear optimal initial state are found. The first has strong energy growth during the first period of the fundamental mode but loses energy thereafter. The second has weaker energy growth during the first period but retains high energy for longer. The second type causes triggering to self-sustained oscillations from lower energy than the first and has higher energy in the fundamental mode. This suggests, for instance, that low frequency noise will be more effective at causing triggering than high frequency noise.

Impact Resistance and Energy Absorption of Functionally Graded Cellular Structures

The dynamic response of functionally graded cellular structures subjected to impact of a finite mass was investigated in this paper. Compared to a cellular structure with a uniform cell size, the one with gradually changing cell sizes may improve many properties. Based on the two-dimensional random Voronoi technique, a two-dimensional topological configuration of cellular structures with a linear density-gradient in one direction was constructed by changing the cell sizes. The finite element method using ABAQUS/Explicit code was employed to investigate the energy absorption and the influence of gradient on stress wave propagation. Results show that functionally graded cellular structures studied are superior in energy absorption to the equivalent uniform cellular structures under low initial kinetic energy impacts, and the performance of such structures can be significantly improved when the density difference is enlarged. The stress levels at the impact and support ends may be reduced by introducing a gradual change of density in cellular structures when the initial impact velocity is low.

Heavy ion induced damage to plasmid DNA: plateau region vs. spread out Bragg-peak

We have investigated the damage of synthetic plasmid pBR322 DNA in dilute aqueous solutions induced by fast carbon ions. The relative contribution of indirect damage and direct damage to the DNA itself is expected to vary with linear energy transfer along the ion track, with the direct damage contribution increasing towards the Bragg peak. Therefore, 12C ions at the spread-out Bragg peak (dose averaged LET∞ = 189 ± 15 keV/μm) and in the plateau region of the Bragg curve (LET = 40 keV/μm) were employed and the radical scavenger concentration in the plasmid solution was varied to quantify the indirect effect. In order to minimize the influence of 12C break-up fragments, a relatively low initial energy of 90 MeV/nucleon was employed for the carbon ions. DNA damage has been quantified by subsequent electrophoresis on agarose gels. We find that strand breaks due to both indirect and direct effects are systematically higher in the plateau region as compared to the Bragg peak region with the difference being smallest at high scavenging capacities. In view of the fact that the relative biological effectiveness for many biological endpoints is maximum at the Bragg peak our findings imply that DNA damage at the Bragg peak is qualitatively most severe.

Two-Dimensional Simulation on Propagation Mechanism of H2/O2 Cylindrical Detonation with a Detailed Reaction Model: Influence of Initial Energy and Propagation Mechanism

The authors studied cylindrical detonation (CD) induced by a direct initiation in the hydrogen/oxygen gas mixture using the 2-dimensional compressible Euler equations with a detailed chemical reaction model. As the result, a cellular structure of cylindrical detonation is obtained in the maximum pressure histories such as an open-shutter photograph and a smoked-foil record in the experimental results. The influence of the initiation energy on the propagation of cylindrical detonation is studied to obtain the subcritical and supercritical regimes: The generation of new transverse wave is observed and small cells during their propagation appear just after the detonation initiation. Furthermore, the number of transverse waves increases nonlinearly near the detonation front in each condition. The generation rate of the transverse wave under the high initiation energy becomes slow because the overdriven state which produces a strong shock wave is maintained longer than that under the low initiation energy.

Lipid mapping of colonic mucosa by cluster TOF-SIMS imaging and multivariate analysis in cftr knockout mice

The cftr knockout mouse model of cystic fibrosis (CF) shows intestinal obstruction; malabsorption and inflammation; and a fatty acid imbalance in intestinal mucosa. We performed a lipid mapping of colon sections from CF and control (WT) mice by cluster time of flight secondary-ion mass spectrometry (TOF-SIMS) imaging to localize lipid alterations. Data were processed either manually or by multivariate statistical methods. TOF-SIMS analysis showed a particular localization for cholesteryl sulfate at the epithelial border, C16:1 fatty acid in Lieberkühn glands, and C18:0 fatty acid in lamina propria and submucosa. Significant increases in vitamin E (vE) and C16:0 fatty acid in the epithelial border of CF colon were detected. Principal component analysis (PCA) and partitioning clustering allowed us to characterize different structural regions of colonic mucosa according to variations in C14:0, C16:0, C16:1, C18:0, C18:1, C18:2, C20:3, C20:4, and C22:6 fatty acids; phosphatidylethanolamine, phosphatidylcholine, and phosphatidylinositol glycerolipids; cholesterol; vitamin E; and cholesteryl sulfate. PCA on spectra from Lieberkühn glands led to separation of CF and WT individuals. This study shows for the first time the spatial distribution of lipids in colonic mucosa and suggests TOF-SIMS plus multivariate analyses as a powerful tool to investigate disease-related tissue spatial lipid signatures.

Approximate analytical solution for quasi-linear equations of synchrotron instability

We obtain an approximate analytical solution for the initial problem of quasi-linear relaxation of the synchrotron instability in a cold plasma for the case of a quasi-isotropic monoenergetic initial distribution of relativistic electrons and low initial radiation energy density. The key parameters of the analytical solution coincide with the results of the numerical calculation with 20% accuracy.

Non-existence of global solutions of a class of coupled non-linear Klein-Gordon equations with non-negative potentials and arbitrary initial energy

In the paper, we consider the non-existence of global solutions of Cauchy problem for coupled Klein-Gordon equations of the form u tt ― Δu + m 2 1 u + K 1 (x)u = a 1 |v| q+1 |u| p―1 u, v tt ― Δv + m 2 2 u + K 2 (x)u = a 2 |u| p+1 |v| q―1 v, u(0,x) = u 0 , u t (0,x) = u 1 (x), v(0,x) = v 0 , v t (0,x) = v 1 (x) on ℝ × ℝ n . First, for the case n = 2, 3, we prove the existence of ground state of the corresponding Lagrange―Euler equations of the above equations. Then, we establish a blow-up result with low initial energy, which leads to instability of standing waves of the system above. Moreover, as a byproduct we also discuss the global existence. Next, based on concavity method, we prove the blow-up result for the system with non-positive initial energy in the general case: 1 ≤ n < 6. Finally, when the initial energy is given arbitrarily positive, we show that if the initial datum satisfies some conditions, the corresponding solution blows up in a finite time. In other words, in this paper we establish the complete blow-up result for the Klein-Gordon equation above in the sense of the initial energy, ―∞ < E(0) < +∞.

Kinetics of Surface-Induced Dissociation of N(CH 3) 4+ and N(CD 3) 4+ Using Silicon Nanoparticle Assisted Laser Desorption/Ionization and Laser Desorption/Ionization

The implementation of surface-induced dissociation (SID) to study the fast dissociation kinetics (sub-microsecond dissociation) of peptides in a MALDI TOF instrument has been reported previously. Silicon nanoparticle assisted laser desorption/ionization (SPALDI) now allows the study of small molecule dissociation kinetics for ions formed with low initial source internal energy and without MALDI matrix interference. The dissociation kinetics of N(CH(3))(4)(+) and N(CD(3))(4)(+) were chosen for investigation because the dissociation mechanisms of N(CH(3))(4)(+) have been studied extensively, providing well-characterized systems to investigate by collision with a surface. With changes in laboratory collision energy, changes in fragmentation timescale and dominant fragment ions were observed, verifying that these ions dissociate via unimolecular decay. At lower collision energies, methyl radical (CH(3)) loss with a sub-microsecond dissociation rate is dominant, but consecutive H loss after CH(3) loss becomes dominant at higher collision energies. These observations are consistent with the known dissociation pathways. The dissociation rate of CH(3) loss from N(CH(3))(4)(+) formed by SPALDI and dissociated by an SID lab collision energy of 15 eV corresponds to log k = 8.1, a value achieved by laser desorption ionization (LDI) and SID at 5 eV. The results obtained with SPALDI SID and LDI SID confirm that (1) the dissociation follows unimolecular decay as predicted by RRKM calculations; (2) the SPALDI process deposits less initial energy than LDI, which has advantages for kinetics studies; and (3) fluorinated self-assembled monolayers convert about 18% of laboratory collision energy into internal energy. SID TOF experiments combined with SPALDI and peak shape analysis enable the measurement of dissociation rates for fast dissociation of small molecules.

Computational Investigation of Wave Packet Scattering in the Complex Plane: Propagation on a Grid.

The time-dependent scattering of a wave packet from a Gaussian barrier is investigated computationally in the complex z-plane. The initial wave packet and the potential energy are obtained through analytic continuation from functions specified on the real-axis. The wave packet is then propagated on the two-dimensional grid. For a low initial wave packet energy, the time evolution is followed by plotting the following functions: |ψ(z,t)|, real(ψ(z,t)), and the quantum momentum function (QMF), p(z,t). In the reflected packet, an important role is played by ripples (quasi-nodes) forming above the real axis. As these quasi-nodes move down across the real axis, they are 'detected' as 'interference oscillations' in the density. In contrast, the component of the packet below the real axis makes a significant contribution to the transmitted packet. Vector maps of the QMF show hyperbolic flow around quasi-nodes and counterclockwise circular flow around transient stagnation points, where the QMF vanishes. However, when the Pólya vector field (defined by P(z,t) = p*(z,t)) is plotted, circular counterclockwise flow is obtained near the quasi-nodes. The real and imaginary parts of the quantum action function S(z,t) are plotted and the vorticity, defined by the curl of the Pólya field, is used to pinpoint regions of nonanalyticity in the QMF.

Differential cross-sections and energy transfer quantities in azulene/argon collisions

Computational results on collisional energy transfer between excited and cold azulene and Ar are reported under initial conditions similar to those of crossed molecular beam experiments (Liu, Hsu, Lyu and Ni, J. Chem. Phys. 125 204309 (2006)). The in-plane scattering cross-section is asymmetric with a preference for positive angles. The out-of-plane scattering angle is symmetric in both positive and negative angles with a strong forward scattering peak. In both T → V/R dominates over V → R/T. The double differential cross-section shows a high probability for forward, then sideways and finally, backward scattering. The latter shows relatively high probability for supercollisions. Average energy transfer quantities and collisional energy transfer probability density functions, P(E,E′), are presented and results for Ar and Kr as colliders are compared. At low initial relative translational energies the up-collision branch of P(E,E′) shows a peak. This peak, which is absent at higher relative translational energies, is due to the formation of a collision complex. Special attention is paid to the role of rotational energy in the energy transfer process. Changing the rotational temperature from 0.5 K to 2000 K changes the percentage of up and down collisions as well as the values of the average energy transferred quantities. The effect of the translational energy on energy transfer is discussed. There is broad agreement between experiment and computation.

Lipid mapping in human dystrophic muscle by cluster-time-of-flight secondary ion mass spectrometry imaging

Human striated muscle samples, from male control and Duchenne muscular dystrophy-affected children, were subjected to cluster-time-of-flight secondary ion mass spectrometry (cluster-ToF-SIMS) imaging using a 25 keV Bi(3)(+) liquid metal ion gun under static SIMS conditions. Spectra and ion density maps, or secondary ion images, were acquired in both positive and negative ion mode over several areas of 500 x 500 microm(2) (image resolution, 256 x 256 pixels). Characteristic distributions of various lipids were observed. Vitamin E and phosphatidylinositols were found to concentrate within the cells, whereas intact phosphocholines accumulated over the most damaged areas of the dystrophic muscles, together with cholesterol and sphingomyelin species. Fatty acyl chain composition varied depending on the region, allowing estimation of the local damage extent.

Quasi-linear stage of synchrotron instability I. The limit of low initial radiation energy density

We consider the initial problem of quasi-linear relaxation of synchrotron instability in a spatially homogeneous system of relativistic electrons embedded in a cold plasma. We analyze evolution of the energy spectrum of electrons and the frequency spectrum of radiation at the limit of low initial radiation energy density. At this limit, the problem is reduced to the solution of a diffusion equation with a stationary diffusion coefficient for the electron distribution over momentum which does not depend on the initial radiation energy density. The radiation frequency spectrum is approximated by the Gaussian profile, and its parameters are expressed via the electron energy density at the given and initial instants of time.

Energy transfer between azulene and krypton: Comparison between experiment and computation

Trajectory calculations of collisional energy transfer between excited azulene and Kr are reported, and the results are compared with recent crossed molecular beam experiments by Liu et al. [J. Chem. Phys. 123, 131102 (2005); 124, 054302 (2006)]. Average energy transfer quantities are reported and compared with results obtained before for azulene-Ar collisions. A collisional energy transfer probability density function P(E,E'), calculated at identical initial conditions as experiments, shows a peak at the up-collision branch of P(E,E') at low initial relative translational energy. This peak is absent at higher relative translational energies. There is a supercollision tail at the down-collision side of the probability distribution. Various intermolecular potentials are used and compared. There is broad agreement between experiment and computation, but there are some differences as well.

Lipid imaging by gold cluster time-of-flight secondary ion mass spectrometry: application to Duchenne muscular dystrophy

Imaging with time-of-flight secondary ion mass spectrometry (TOF-SIMS) has expanded very rapidly with the development of gold cluster ion sources (Au(3+)). It is now possible to acquire ion density maps (ion images) on a tissue section without any treatment and with a lateral resolution of few micrometers. In this article, we have taken advantage of this technique to study the degeneration/regeneration process in muscles of a Duchenne muscular dystrophy model mouse. Specific distribution of different lipid classes (fatty acids, triglycerides, phospholipids, tocopherol, coenzyme Q9, and cholesterol) allows us to distinguish three different regions on a mouse leg section: one is destroyed, another is degenerating (oxidative stress and deregulation of the phosphoinositol cycle), and the last one is stable. TOF-SIMS imaging shows the ability to localize directly on a tissue section a great number of lipid compounds that reflect the state of the cellular metabolism.

Collision induced ion ejection in an FTICR trapped-ion cell

A collision algorithm was used with SimIon to evaluate collision-mediated ion ejection mechanisms in the ICR MS experiment. These mechanisms were characterized based on kinetic energy, ion mass, applied trapping potential, and collision gas mass. It was found that there are three collision-based energy regimes for ion loss from a trapped-ion cell. The first region is characterized by low initial cyclotron kinetic energy, a radial ejection mode, and a very high collision ratio (>100 collisions per ejection). The second region is characterized by a medium to high initial cyclotron kinetic energy leading to axial ejection at low collision ratio (1 to 10 collisions per ejection). The third region is characterized by a high initial cyclotron kinetic energy, a radial ejection mode, and a collision ratio of unity. It was also determined that there is a radial cyclotron mode limit, approximately 40% of the cell radius, after which an ion is ejected after a single collision. This has important consequences on the damping of the FTICR signal, various cooling techniques, ion activation techniques, and the remeasurement experiment.

Hydrogen-Induced Lattice Relaxation Effects on the Absorption and Desorption of H on a Li(100) Surface

Here, we investigate and discuss the effects of H-induced lattice relaxation on the H absorption into (desorption from) a Li(100) surface. Using the coupled-channel method via the local reflection matrix scheme, we performed quantum dynamics calculations to obtain the H absorption and desorption probability plots as functions of the H initial translational energy and the Li initial vibrational state. Our results show that the hydrogen motion and the surface lattice relaxation are dynamically coupled and, depending on the initial conditions, the surface lattice motion either promotes or hinders the penetration of hydrogen into (desorptin from) the surface (subsurface). At low initial translational energy of H, the Li lattice has sufficient time to relax effectively reducing the energy barrier for H absorption and desorption.

H/Pd(111) Absorption and Desorption Dynamics -Hydrogen-Induced Lattice Relaxation Effects-

We investigate the effects of hydrogen-induced surface lattice relaxation on the dynamics of hydrogen absorption into the surface and desorption from the subsurface to the Pd(111) surface. We perform quantum dynamics calculations with and without surface lattice motion. From the results of both hydrogen absorption and desorption probability, we can see that the hydrogen motion and the surface lattice relaxation are dynamically coupled and, depending on the initial conditions, the surface lattice motion either promotes or hinders the penetration of hydrogen into (desorption from) the surface (subsurface). We observe tunneling of hydrogen through the energy barrier hindering the hydrogen from penetration into (desorption from) the surface (subsurface). We also investigate the surface temperature dependence of hydrogen absorption dynamics. From the results, we can see that the absorption probability increases (decreases) as the surface temperature increases in the low (high) hydrogen's initial translational energy regions.

Reduction of polymerization contraction stress for dental composites by two-step light-activation

Objectives: The goal of this study was to assess the reduction of polymerization contraction stress of composites during a two-step light-activation process and to relate this reduction to the process of polymerization shrinkage and specimen thickness. Methods: Three test procedures were performed to compare two-step light-activation with delay with one-step continuous irradiation of composites: polymerization contraction stress using a closed-loop servohydraulic testing instrument, polymerization shrinkage by a mercury dilatometer, and degree of conversion by FTIR. For the one-step continuous curing method, the samples were light-activated for 60 s at 330 mW/cm 2. For the two-step curing method, a 5 s light exposure at 60 mW/cm 2 was followed by 2 min without light exposure, and then a second light exposure for 60 s at 330 mW/cm 2. The same light parameters were used for measurements of stress, shrinkage, and degree of conversion. Three composites, Heliomolar, Herculite and Z100 were evaluated. The contraction stress experiments were repeated with varying thickness for Herculite using the one-step and two different two-step techniques. Results: Polymerization contraction stress 10 min after light-activation was significantly reduced ( P<0.05) by the two-step method: 29.7% for Heliomolar, 26.5% for Herculite, and 19.0% for Z100. Total volumetric shrinkage and degree of conversion were not significantly different for composites cured by the two different techniques. Increasing the thickness of the composite sample reduced the measured contraction stress, especially for one of the two-step curing methods. Significance: A combination of low initial energy density followed by a lag period before a final high-intensity light irradiation provides a reduction of polymerization contraction stresses in dental composites. The stress reductions cannot be attributed to reductions in degree of conversion or unrestrained volumetric shrinkage.