Dispersion Spreading Research Articles

WRF4PALM v1.0: a mesoscale dynamical driver for the microscale PALM model system 6.0

Abstract. A set of Python-based tools, WRF4PALM, has been developed for offline nesting of the PALM model system 6.0 into the Weather Research and Forecasting (WRF) modelling system. Time-dependent boundary conditions of the atmosphere are critical for accurate representation of microscale meteorological dynamics in high-resolution real-data simulations. WRF4PALM generates initial and boundary conditions from WRF outputs to provide time-varying meteorological forcing for PALM. The WRF model has been used across the atmospheric science community for a broad range of multidisciplinary applications. The PALM model system 6.0 is a turbulence-resolving large-eddy simulation model with an additional Reynolds-averaged Navier–Stokes (RANS) mode for atmospheric and oceanic boundary layer studies at microscale (Maronga et al., 2020). Currently PALM has the capability to ingest output from the regional scale Consortium for Small-scale Modelling (COSMO) atmospheric prediction model. However, COSMO is not an open source model and requires a licence agreement for operational use or academic research (http://www.cosmo-model.org/, last access: 23 April 2021). This paper describes and validates the new free and open-source WRF4PALM tools (available at https://github.com/dongqi-DQ/WRF4PALM, last access: 23 April 2021). Two case studies using WRF4PALM are presented for Christchurch, New Zealand, which demonstrate successful PALM simulations driven by meteorological forcing from WRF outputs. The WRF4PALM tools presented here can potentially be used for micro- and mesoscale studies worldwide, for example in boundary layer studies, air pollution dispersion modelling, wildfire emissions and spread, urban weather forecasting, and agricultural meteorology.

Facile modification of polycaprolactone nanofibers with egg white protein

Synthetic polymers remain to be a major choice for scaffold fabrication due to their structural stability and mechanical strength. However, the lack of functional moieties limits their application for cell-based therapies which necessitate modification and functionalization. Blending synthetic polymers with natural components is a simple and effective way to achieve the desired biological properties for a scaffold. Herein, nanofibrous mats made of polycaprolactone (PCL) and egg white protein (EWP) blend were developed and further evaluated for use as a scaffold for tissue engineering applications. Homogeneous distribution of EWP was achieved throughout the nanofibrous mats, as shown by immunohistochemistry. ATR-FTIR analysis and contact angle measurements have further confirmed the presence of EWP on the surface of the samples. The swelling test showed that PCL/EWP nanofibers have higher water uptake than PCL nanofibrous mats. Also, EWP addition on the nanofibrous mats resulted in an increase in the tensile strength and Young’s modulus of the mats, indicating that the presence of protein can greatly enhance the mechanical properties of the mats. A significantly higher, more uniform, and dispersed cell spreading was observed on days 7 and 14 than that on neat PCL mats, demonstrating the importance of providing the required cues for cell homing by the availability of EWP. Hence, EWP is shown to be a simple and low-cost source for the functionalization of PCL nanofibrous mats. EWP is, therefore, a facile candidate to enhance cellular interactions of synthetic polymers for a wide range of tissue engineering applications.

Tailoring impact debris dispersion using intact or fragmented thermite projectiles

A high-velocity impact-ignition testing system was used to study the dynamic response of brittle thermite projectiles impacting an inert steel target at velocities of 850 and 1200 m/s. The projectiles included consolidated aluminum and bismuth trioxide that were launched by a propellant driven gun into a catch chamber equipped with high-speed imaging diagnostics. The projectiles passed through a break-screen at the entrance to the chamber and either fragmented upon penetrating the break-screen or remained intact prior to impacting the steel target. In all cases, the projectiles pulverized upon impact, and a reacting debris cloud spreads through the catch chamber. At lower impact velocities, the fragmented and intact projectiles produced similar flame spreading rates of 217–255 m/s. At higher impact velocities, the intact projectile produced the slowest average flame spreading rate of 179 m/s because debris rebounding was limited by the length of the projectile and the resulting debris field was highly consolidated in the radial direction. In contrast, the fragmented projectile rebounded into a well dispersed debris cloud with the highest, 353 m/s, flame spreading rate. A kinetic energy flux threshold was proposed as a means for describing the shift in observed debris dispersion and flame spreading rates. A reactivity model was developed based on particle burn times using a computational fluid dynamics code that incorporated heat transfer and particle combustion in a multiphase environment to understand how the particle size influenced flame spreading. Results from the model show a trade-off between faster reactivity and increased drag inhibiting movement for smaller particle debris.

Bifurcation analysis of a general activator-inhibitor model with nonlocal dispersal

In this paper, we are mainly concerned with the effect of nonlocal diffusion and dispersal spread on bifurcations of a general activator-inhibitor system in which the activator has a nonlocal dispersal. We find that spatially inhomogeneous patterns always exist if the dispersal rate of the activator is sufficiently small, while a larger dispersal spread and an increase of the activator diffusion inhibit the formation of patterns. Compared with the spatial averaging nonlocal dispersal model, our model admits a larger parameter region supporting pattern formations, which is also true if compared with the local reaction-diffusion one when the dispersal spread is small. We also study the existence of nonconstant positive steady states through bifurcation theory and find that there could exist finite or infinite steady state bifurcation points of the inhibitor diffusion constant. As an example of our results, we study a water-biomass model with nonlocal dispersal of plants and show that the water and plant distributions could be inphase and antiphase.

Functionalized nano diamond composites for photocatalytic hydrogen evolution and effective pollutant degradation

Development of superior heterogeneous photocatalyst for hydrogen (H2) evolution with promising pollutant degradable capacity is a significant feature but then again thought-provoking for shaping the energy and environmental issues. In this regard, a photocatalytic H2 evolution using nano diamond (ND) semiconducting materials having pollutant degradable capacity for Rhodamine B dye (RhB) has been rarely reported and hence predicted to the sustainable energy. Productive characteristics such good chemical stability, super hardness, nanometer size, biocompatibility and thermal conductivity, ND is a capable and highly valuable powder physical material. Non-uniform and agglomeration dispersion spread of ND in different solvents are the main problems preventing ND from the wide-use in commercial applications. Upon 535 nm solar light excitation, the fabricated ND sample exhibit remarkable photocatalytic H2 production with a HER of about 400 μmol h−1 than pristine ND (197 μmol h−1). Additionally, this H2 generation dramatically enhances the quantum yield, indicating the H2 terminated sites work as electron reservoirs. Precisely, the kinetic constant pseudo-order of FND for photodegradation of RhB was higher as compared with pristine ND. As such, the results show an important step toward tailor-designed and explain the vital role of FND composites for the rational motifs of fruitful photocatalyst with effective pollutant degradable capability for future demand.

Using spatial genetics to quantify mosquito dispersal for control programs

BackgroundHundreds of millions of people get a mosquito-borne disease every year and nearly one million die. Transmission of these infections is primarily tackled through the control of mosquito vectors. The accurate quantification of mosquito dispersal is critical for the design and optimization of vector control programs, yet the measurement of dispersal using traditional mark-release-recapture (MRR) methods is logistically challenging and often unrepresentative of an insect’s true behavior. Using Aedes aegypti (a major arboviral vector) as a model and two study sites in Singapore, we show how mosquito dispersal can be characterized by the spatial analyses of genetic relatedness among individuals sampled over a short time span without interruption of their natural behaviors.ResultsUsing simple oviposition traps, we captured adult female Ae. aegypti across high-rise apartment blocks and genotyped them using genome-wide SNP markers. We developed a methodology that produces a dispersal kernel for distance which results from one generation of successful breeding (effective dispersal), using the distance separating full siblings and 2nd- and 3rd-degree relatives (close kin). The estimated dispersal distance kernel was exponential (Laplacian), with a mean dispersal distance (and dispersal kernel spread σ) of 45.2 m (95% CI 39.7–51.3 m), and 10% probability of a dispersal > 100 m (95% CI 92–117 m). Our genetically derived estimates matched the parametrized dispersal kernels from previous MRR experiments. If few close kin are captured, a conventional genetic isolation-by-distance analysis can be used, as it can produce σ estimates congruent with the close-kin method if effective population density is accurately estimated. Genetic patch size, estimated by spatial autocorrelation analysis, reflects the spatial extent of the dispersal kernel “tail” that influences, for example, the critical radii of release zones and the speed of Wolbachia spread in mosquito replacement programs.ConclusionsWe demonstrate that spatial genetics can provide a robust characterization of mosquito dispersal. With the decreasing cost of next-generation sequencing, the production of spatial genetic data is increasingly accessible. Given the challenges of conventional MRR methods, and the importance of quantified dispersal in operational vector control decisions, we recommend genetic-based dispersal characterization as the more desirable means of parameterization.

Pest survey card on Geosmithia morbida and its vector Pityophthorus juglandis

This pest survey card was prepared in the context of the EFSA mandate on plant pest surveillance (M-2017-0137) at the request of the European Commission. Its purpose is to guide the Member States in preparing data and information for Geosmithia morbida and Pityophthorus juglandis surveys. These are required to design statistically sound and risk-based pest surveys, in line with current international standards.Geosmithia morbida and its vector P. juglandis are clearly defined taxonomic entitiesand the combined activity of the fungus and the insect causes the disease complex thousand canker disease on the plant genera Juglans and Pterocarya. The pest and its vector originate in North America and currently have a restricted distribution in the EU, limited to the northern parts of Italy.However, they are potentially able to become established everywhere in the EU where their host plants occur.Currently, the spread capacity ofP.juglandis is unknown, but the insect vectormay cover large distances by passive dispersal or human-assisted spread. Risk locations include entry points (e.g. seaports, airports), loading stations, storage facilities and wood processing companies that deal withheat-treated wood, bark or woodchips of the genera Juglans and Pterocarya originating from countries where the fungus and its vector occur.Trapping is the recommended method for detecting the vector inthe early stages of an epidemic. Following insect trapping, a specific tree inspection should be carried out, looking for external symptoms(e.g. penetration and exit holes, cankers and wilting). The trapping should start when the mean air temperature exceeds 18°C.Morphological identification of the pathogen and its vector should be performed by experts. Molecular assays are also available for both fungal and vector identification.

Control of undulator radiation using a Laser Plasma Acceleration Source

Spontaneous undulator radiation emission, after the COXINEL line using a Laser Plasma acceleration (LPA) source, has been observed. The line enables to manipulate the electron beam phase space such as emittance, dispersion and energy spread along a 10 m long transport. The large divergence is handled at a very early stage to mitigate the chromatic emittance, using high gradient permanent magnet based quadrupoles mounted on translation tables. The operating energy is between 161-180 MeV focused in a 2-m long cryo-ready undulator with a period of 18 mm emitting light in the Ultra-Violet range. The spectral flux is characterized using a spectrometer. The wavelength is tuned by either changing the electron beam energy or by adjusting the undulator gap. The radiation pattern signature is illustrated alongside its dependence on the energy spread that is modified by introducing a slit in a magnetic chicane where a small relative bandwidth of 5% has been achieved.

Transformer Ratio at Wakefield Excitation by Train of Electron Bunches with Linear Growth of Current in Dielectric Resonator Electron–Positron Collider

The efficiency of electron bunch acceleration by wakefield, excited in two-beam electron-positron dielectric resonator collider by train of electron bunches is determined by transformer ratio (TR). The train of homogeneous bunches, in which current grows linearly along a train, is considered. The length of homogeneous bunch equals to half of excited wavelength 0.5λ. Interval between bunches is ρλ, p = 1, 2,… The conditions have been formulated, when the wakefield pulses from all electron bunches are added. Bunch is injected in dielectric resonator, when the back wavefront of the wakefield pulse is on the bunch-injection boundary of the resonator/cavity. Bunch leaves the resonator, when the first wavefront of wakefield pulse is on the end of the resonator. The conditions for a large TR have been formulated. The wakefield and TR have been derived after N bunch. The computer simulation has been performed taking into account wakefield pulse dispersion spreading and electron bunch transition radiations. The results of analytical investigation are compared with the results of computer simulation. It has been shown that the dependence TR = 2N is performed. Advantage of this mode with large transformer ratio that some injected bunch with decreased current becomes witness. When this bunch is injected it gets in maximum accelerating field.The infinite periodical mode of accelerator operation has been proposed. In this mode, witness-bunches and driver-bunches are injected according to periodic mode. In the infinite periodical mode, short shaped trains of driver-bunches are alternated with witnesses. Large transformer ratio and identical decelerating field for all driver-bunches are provided by this long periodic train.

Influence of lead-manganese naphthenate on changes in the dynamic edge wetting angle upon spreading of styrene-acrylic dispersion

The effect of lead-manganese naphthenate on the change in the dynamic contact angle during spreading of a styrene-acrylic dispersion is studied. The dependences of the change in the dynamic contact angle in time are obtained for various concentrations of lead-manganese naphthenate in solution. As a result of the analysis of the experimental data, a concentration region was revealed in which the dynamic wetting angle varies in the widest range with the lowest speed compared to solutions of other concentrations. The results of the research will be used to optimize the composition of the polymer-mineral composite material and will make it possible to obtain a polymer matrix that most wetts the mineral fillers, and the resulting composite will have the greatest mobility and vitality.

The generalised principal eigenvalue of time-periodic nonlocal dispersal operators and applications

This paper is mainly concerned with the generalised principal eigenvalue for time-periodic nonlocal dispersal operators. We first establish the equivalence between two different characterisations of the generalised principal eigenvalue. We further investigate the dependence of the generalised principal eigenvalue on the frequency of the periodic oscillation, the dispersal rate and the dispersal spread. Finally, these qualitative results for time-periodic linear operators are applied to time-periodic nonlinear KPP equations with nonlocal dispersal, focusing on the effects of the frequency of the periodic oscillation, the dispersal rate and the dispersal spread on the existence and stability of positive time-periodic solutions to nonlinear equations.

Asymptotic behaviors for nonlocal diffusion equations about the dispersal spread

This paper studies the effects of the dispersal spread, which characterizes the dispersal range, on nonlocal diffusion equations with the nonlocal dispersal operator [Formula: see text] and Neumann boundary condition in the spatial heterogeneity environment. More precisely, we are mainly concerned with asymptotic behaviors of generalized principal eigenvalue to the nonlocal dispersal operator, positive stationary solutions and solutions to the nonlocal diffusion KPP equation in both large and small dispersal spread. For large dispersal spread, we show that their asymptotic behaviors are unitary with respect to the cost parameter [Formula: see text]. However, small dispersal spread can lead to different asymptotic behaviors as the cost parameter [Formula: see text] is in a different range. In particular, for the case [Formula: see text], we should point out that asymptotic properties for the nonlocal diffusion equation with Neumann boundary condition are different from those for the nonlocal diffusion equation with Dirichlet boundary condition.

EFFECT OF TRANSITION RADIATION AND DISPERSION SPREADING AT ACHIEVEMENT OF A LARGE TRANSFORMER RATIO OF DRIVER-BUNCH ENERGY INTO WAKEFIELD IN A DIELECTRIC RESONATOR ACCELERATOR

Possibility of increase of transformer ratio TR in the case of the profiled sequence of bunches at their injection in a two-beam electron-positron dielectric-resonator collider is considered. Unlike considered earlier the waveguide case, for which TR is equal to the doubled number of bunches of sequence which provide a contribution to the total wakefield, and which is limited by the effect of the group velocity, in a resonator this limitation is absent. For derivation in the case of resonator of TR, proportional to the number of bunches, as well as in the waveguide, the ratio of bunch charges is selected to be equal 1:3:5: … , lengths of bunches, equal to the half of wavelength, interval between bunches is multiple to the wavelength. The effect of transition radiation and dispersion spreading on the transformer ratio is studied by numerical simulation.

The role of dispersion in the mechanism of femtosecond pulse self-shortening in Kerr media

We investigate the influence of material dispersion on the mechanism of self-shortening of femtosecond pulses interacting with fused silica plates having thicknesses an order of magnitude smaller than the dispersion length for the initial 72-fs pulse. The femtosecond pulse self-shortening is observed at large values of the B integral, when small-scale self-focusing develops in the central part of the pulse; this self-focusing plays the role of an optical shutter selecting the unperturbed radiation of the pulse leading edge. A study of the femtosecond pulse self-shortening in 1- and 3-mm-thick fused silica samples reveals that, under the experimental conditions in use, the self-phase modulation enhances the role of dispersion in the formation of a shortened pulse. With an increase in the sample thickness, the shortened pulse width increases as a result of the dispersion spread of the initial pulse in time. At the same time, this shortened pulse remains close to the transform-limited one, independent of the sample thickness.

Gaia DR 2 and VLT/FLAMES search for new satellites of the LMC

A wealth of tiny galactic systems populates the surroundings of the Milky Way. However, some of these objects might have originated as former satellites of the Magellanic Clouds, in particular of the Large Magellanic Cloud (LMC). Examples of the importance of understanding how many systems are genuine satellites of the Milky Way or the LMC are the implications that the number and luminosity-mass function of satellites around hosts of different mass have for dark matter theories and the treatment of baryonic physics in simulations of structure formation. Here we aim at deriving the bulk motions and estimates of the internal velocity dispersion and metallicity properties in four recently discovered distant southern dwarf galaxy candidates, Columba I, Reticulum III, Phoenix II, and Horologium II. We combined Gaia DR2 astrometric measurements, photometry, and new FLAMES/GIRAFFE intermediate-resolution spectroscopic data in the region of the near-IR Ca II triplet lines; this combination is essential for finding potential member stars in these low-luminosity systems. We find very likely member stars in all four satellites and are able to determine (or place limits on) the bulk motions and average internal properties of the systems. The systems are found to be very metal poor, in agreement with dwarf galaxies and dwarf galaxy candidates of similar luminosity. Of these four objects, we can only firmly place Phoenix II in the category of dwarf galaxies because of its resolved high velocity dispersion (9.5 −4.4+6.8 km s−1) and intrinsic metallicity spread (0.33 dex). For Columba I we also measure a clear metallicity spread. The orbital pole of Phoenix II is well constrained and close to that of the LMC, suggesting a prior association. The uncertainty on the orbital poles of the other systems is currently very large, so that an association cannot be excluded, except for Columba I. Using the numbers of potential former satellites of the LMC identified here and in the literature, we obtain for the LMC a dark matter mass of M200 = 1.9 −0.9+1.3 × 1011 M⊙.

Frequency transformation of ultrafast laser pulses in metamaterials

The nonstationary parametric interaction of waves in negative-index metamaterials is studied in the second-order dispersion theory. A nonlinear interaction between a long pulse of a strong pump wave and an ultrashort pulse with quadratic phase modulation is considered. The results of calculating the shape of the spectrum of an excited signal wave are presented. A comparison is made with the case of interaction in an ordinary medium. It is shown that the effects of group-velocity dispersion and dispersive spreading in such materials lead to a narrowing of the spectrum of the excited wave. The presence of phase modulation of the exciting idler pulse promotes broadening of the central maximum of the spectrum of the excited signal wave. As the modulation factor increases, the fragmentation of the excited pulse is observed.

Extra pulmonary vein driver mapping and ablation in paroxysmal atrial fibrillation by electrogram dispersion analysis

The adjunctive approach is still unknown for atrial fibrillation (AF), which cannot be terminated after pulmonary vein isolation (PVI). We hypothesized that the driver ablation plus PVI was superior to PVI alone. A total of 98 patients with paroxysmal AF were enrolled in this study and were divided into two groups, with one group undergoing PVI (n = 49) and the other group undergoing PVI + driver ablation (n = 49). The driver regions were defined as clusters of bipolar electrograms that displayed spatial dispersion spread over mean AF cycle length at a minimum of three adjacent bipolars of a PentaRay catheter. During the procedure, the most prominent driver regions before PVI were the roof (n = 27; 55.1%), PV antrum (n = 23; 46.9%), and the inferoposterior wall (n = 11; 22.4%). PVI can eliminate all drivers at PV antrum, but only terminate 30.4% of AF in the driver group. The AF termination rate in the driver ablation group was significantly higher than that in conventional ablation (93.9% vs 40.6%; P < 0.001). The rate of freedom from atrial tachyarrhythmia episodes by a single procedure at 6 months was significantly higher in the driver group than in the conventional group (91.6% vs 72.4%; P = 0.02). The present method is effective for AF driver identification. It guided ablation adjunctive to PVI increasing the rate of AF termination and improving the outcomes in patients with paroxysmal AF.

Ultrashort spatiotemporal optical solitons in waveguide arrays: the effect of combined linear and nonlinear couplings

We investigate the propagation of Gaussian spatiotemporal inputs in arrays of parallel optical waveguides, assuming both linear and nonlinear non-dispersive coupling between adjacent guides. The numerical simulations employ a discrete version of the modified Korteweg–de Vries equation that adequately describe the propagation of few-cycle spatiotemporal solitons in coupled waveguide arrays. It is shown that depending on the numerical values of the key parameters of the spatiotemporal Gaussian input, the combined effect of linear and nonlinear couplings leads to either the diffraction and dispersion spreading effect or to the formation of different types of (2 + 1)-dimensional ultrashort spatiotemporal solitons such as one or many single-channel few-cycle solitons, and half-cycle (single-humped) ones.

An initial study of deep learning for mangrove classification

Deep Learning is a new breakthrough in the area of neural network. One of it methodology is Deep Neural Network. Usually, deep neural network is a method that can solve problems such as classification or prediction. Here in this study, we collect data for mangrove classification, and we see an opportunity to classify the type of mangrove based on its features using deep neural network. Research on mangrove plants related to classification is more widely used in mangrove dispersal spread through spectral and hyperspectral satellite images than using real value data such as morphological data, thus providing blank space for researchers to use mangrove morphological data. This initial study is to build a deep neural network architecture and analyze it in term of mangrove sprout plant classification. The result from our architectural methodology of this research is reaching the lowest training error of 0.1345 and the highest testing accuracy value of 98%.

Fish dispersal in flowing waters: A synthesis of movement‐ and genetic‐based studies

AbstractEnhancing our understanding of fish dispersal is central to the success of modern‐day conservation efforts in freshwater ecosystems. However, methods seeking to estimate dispersal are diverse; ranging from direct estimation of individual movements, computation of dispersal kernels, to indirect assessment using measures of gene flow across riverscapes. An important question is whether results from these different approaches provide a consistent picture of the spatial scales of dispersal. Here, we performed a review and meta‐analysis of the literature reporting both individual movements and genetic data to characterize patterns of dispersal for riverine fishes globally. Across all the studies considered (Ndirect = 206; Nindirect = 205), our results suggest restricted magnitudes of dispersal for riverine fishes, but highlight a large heterogeneity among species, taxonomic orders and geographies. For instance, we found that the maximum parent–offspring dispersal distances varied from 69 m to 1,086 km (median = 12 km; Nspecies = 107), whereas the dispersal spread derived from isolation‐by‐distance slopes (σIBD) from genetic data ranged from 19 m to 250 km (median = 1 km; Nspecies = 56). Comparisons of species‐specific values also revealed significant and positive relationships between direct and indirect estimates of dispersal distances, indicating that organismal movement ability often translates into effective transmission of genes. Finally, this global overview pointed to important geographic and taxonomic disparities in the study of dispersal for riverine fishes. We thus encourage researchers to broaden the taxonomic and geographical scope of future investigations and identify emerging research frontiers where new scientific efforts are needed.