Dispersion Behavior Research Articles

Tailoring of structural, morphological, electrical, and magnetic properties of LaMn1-x Fe x O3 ceramics.

This study undertakes a comparative analysis of the structural, morphological, electrical, and magnetic characteristics of Fe-doped LaMnO3 ceramics. The solid-state reaction method was used to prepare Fe-doped LaMnO3 at different concentrations (0.00 ≤ x ≤ 1.00) and has been characterized using X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR), Field emission scanning electron microscopy (FE-SEM), energy-dispersive spectroscopy (EDS), and vibrating sample magnetometry (VSM). The structural transformation from rhombohedral to orthorhombic with Fe-doping is demonstrated by Rietveld's refined XRD patterns. The positive slope in Williamsons-Hall's (W-H) plots confirms the presence of tensile strain with increasing average crystallite size. Quasi-spherical morphology of all the compositions with similar uniformity was confirmed by FESEM images. The chemical distribution of all the elements has been identified by EDS mapping images. Normal dielectric dispersion behaviour of all the samples with NTCR response is confirmed by dielectric and impedance analysis respectively. Increasing lattice volume with Fe-concentration results is increasing E a. The presence of antiferromagnetic ordering, in addition to weak ferromagnetic ordering, is indicated by the unsaturated magnetization even up to a high external field. The decrease in M S and increase in H C values due to Fe-doping reflect the influence of particle size on various magnetic parameters.

Experimental Study on Distribution Characteristics and Leakage Detection of Hydrogen Release from Hydrogen Supply System of Fuel Cell Truck

The hydrogen supply system of a fuel cell truck is in a semi-enclosed space where hydrogen is easy to accumulate if a hydrogen leak occurs. The acquisition of hydrogen dispersion behavior data is essential to support the detection of hydrogen release. The purpose of this article is to present the characteristics of hydrogen concentration distribution and delay time of hydrogen leakage detection under different leakage parameters. The experiments have been performed in a hydrogen storage cabin with six hydrogen sensors arranged on the roof to measure hydrogen concentration. During the tests, hydrogen was released into the test cabin through standard leaks. Two different release rates (80 NL/min and 450 NL/min), three different release positions, and six release directions are investigated to analyze the effects on the distribution of hydrogen concentration and leakage detection delay time. This article presents both the experimental facility and results. The experimental results can help optimize the placement of hydrogen sensors and the design of a hydrogen leakage detection system.

MAGNETIC CORE APPLICATION IN A PLANAR RESONATOR WITH A YTTRIUM IRON GARNET FILM FOR ENHANCING STRONG PHOTON-MAGNON COUPLING

Subject and Purpose. This paper presents numerical simulation results on the transmission spectra of a split-ring resonator (SRR) loaded with a thin film of yttrium iron garnet (YIG). The application of a magnetic core in the SRR is proposed for increasing the photon-magnon (P-M) coupling strength. The anticrossing effect in the frequency dispersion behavior of the SRR modes and YIG film ferromagnetic resonance modes, namely SRR-YIG coupled modes, is identified. The dimensional parameters of the SRR with a magnetic core are calculated, taking care to preserve the design compactness and striving to obtain a maximum possible spin-number-normalized coupling strength for such a system. The work has been aimed at evaluating the efficiency of applying the magnetic core as a part of the planar microwave resonator to enhance the P-M coupling strength. Methods and Methodology. The transmission coefficient |S21| spectra of electromagnetic waves propagating through the planar resonator with the YIG film under the ferromagnetic resonance condition are numerically studied using the CST Studio Suite package in the frequency domain. The spatial distribution function of the magnetic field strength is calculated for the two scenarios of YIG film location: near the magnetic core (between the SRR and the feeding stripline) and inside the magnetic core (in the SRR center). Also, for each of these two scenarios, the transmission coefficient |S21| spectra of the wave propagation through the feeding stripline in the region of SRR-YIG coupled modes are simulated with and without the magnetic core. The dispersion curves of the SRR-YIG coupled modes are obtained in analytical terms. Results. It has been shown that the magnetic core application increases the P-M coupling strength 2.0 times in the scenario of YIG film location near the magnetic core (between the SRR and the feeding stripline). When the YIG film is inside the magnetic core (in the SRR center), the P-M coupling strength rises 2.3 times compared to similar cases without the magnetic core. Conclusions. The suggested magnetic core application can be used to increase the P-M coupling strength in the SRR — magnetic film resonant system, striving to develop effective microwave-to-optical converters and create efficient information exchange between quantum computers.

Improving Inhalation Performance with Particle Agglomeration via Combining Mechanical Dry Coating and Ultrasonic Vibration.

Agglomerate formulations for dry powder inhalation (DPI) formed with fine particles are versatile means for the highly efficient delivery of budesonide. However, uncontrolled agglomeration induces high deposition in the upper airway, causing local side effects due to high mechanical strength, worse deagglomeration, and poor fine-particle delivery. In the present study, fine lactose was mechanically dry-coated prior to particle agglomeration, and the agglomerates were then spheroidized via ultrasonic vibration to improve their aerosol performance. The results showed that the agglomerate produced with the surface-enriched hydrophobic magnesium stearate and ultrasonic vibration demonstrated improved aerosolization properties, benefiting from their lower mechanical strength, less interactive cohesive force, and improved fine powder dispersion behavior. After dispersion utilizing a Turbuhaler® with a pharmaceutical cascade impactor test, a fine particle fraction (FPF) of 71.1 ± 1.3% and an artificial throat deposition of 19.3 ± 0.4% were achieved, suggesting the potential to improve the therapeutic outcomes of budesonide with less localized infections of the mouth and pharynx.

Regulating hollow structure of CL-20 microspheres using microjet droplet technology to enhance safety and combustion performance

Hollow energetic microspheres have attracted great attention in the field of materials due to their wide application potential. However, scalable, simple, and low-cost production methods have not been achieved yet. In this study, using nitrocellulose (NC) as a binder, hollow and porous hollow CL-20 microspheres were prepared by the assist of microjet droplet technology. The effects of receiving liquid temperature, solution concentration, and solvent type on the morphology, particle size, shell thickness, and pore size of the CL-20 microspheres were systematically investigated. Furthermore, the influences of shell thickness and pore size on the dispersibility, crystal structure, thermal decomposition, mechanical sensitivity, and combustion behavior of CL-20 microspheres were further studied. The results showed that precise control over the shell thickness and pore size of CL-20 microspheres could be achieved by adjusting the process parameters. Compared to raw CL-20, the CL-20 microspheres exhibited excellent dispersibility and improved thermal and safety performance (raw CL-20 vs CL-20 microspheres, 40.3° vs 27.1° ∼ 29.1°; 240.4℃ vs 241.1 ∼ 246.2℃; 2 J vs 25 ∼ 32.5 J). Ignition experiments demonstrated that the hollow and porous hollow structures significantly enhanced the combustion flame of CL-20, shortened the burning time, and thereby improved energy release efficiency. This preparation method is simple and efficient, providing a new approach for the fabrication of multi-structured hollow energetic microspheres.

Electrochemical investigation of an anticancer drug 5-Fluorouracil in the presence of Theophylline using low-cost and disposable poly(GLY) modified pencil graphite electrode

Herein this study, a facile, efficient and disposable electrochemical sensor has been prepared by electropolymerization of glycine (poly(GLY)) on the surface of pencil graphite electrode (PGE). The surface topology of the equipped poly(GLY) modified pencil graphite electrode (poly(GLY)/PGE) and bare pencil graphite electrode (BPGE) has been characterized by the scanning electron microscopy (SEM) combined with energy dispersive x-ray analysis (EDX) and charge transfer behaviour was measured by electron impedance spectroscopy (EIS) method. The voltammetric behaviour of anticancer, 5-fluorouracil (5-FU) in the presence of theophylline (THP) has been carried out in 0.1 M phosphate buffer solution (PBS) of physiological pH 7.0 using different techniques such as cyclic voltammetry (CV), linear sweep voltammetry (LSV) and differential pulse voltammetry (DPV). The proposed poly(GLY)/PGE shows augmented peak current for 5-FU at lower potential side over the BPGE due to the electrocatalytic behaviour of modifier layers wrapped on the electrode surface. The kinetic behaviour of 5-FU at modified electrode surface was studied by varying different parameters such as pH, scan rate and concentration study in 0.1 M PBS used as a supporting electrolyte. The limit of detection (LOD) for 5-FU was attained using DPV method with different concentrations (1.0–13.0 μM) and it was found to be 0.012 μM. The possible electrochemical reaction of 5-FU was proposed and it was incorporated by two electrons and two protons mechanism at modified electrode surface. The voltammetric response of poly(GLY)/PGE towards the determination of 5-FU was unaffected in the presence of some excipients in addition to the remarkable stability and reproducibility. The applicability of the proposed sensor has been performed by real sample investigation of 5-FU with a substantial percentage of recovery results in all optimized conditions.

A Comparative Study of Influence of Different Polymers on Lumefantrine: Piperine Solid Dispersion

To improve the oral delivery of biopharmaceutical classification system (BCS) class II drugs, solid dispersions techniques are generally adopted in drug product develooment in pharmaceuticals. The choice of polymer in these designs significantly affects a drug’s solubility and dissolution properties. The crystalline nature and the involvement of P-glycoprotein in active ingredient efflux further hinder drug absorption and bioavailability. In this study, solid dispersion (SD) of an antimalarial drug (lumefantrine) combined with piperine (a P-gp and CYP3A4 inhibitor), was created using different polymeric carriers: Soluplus, Klucel, Poloxamer, Povidone/PVP K30 (PVP), and Copovidone/Kollidon® VA64 (KOL). Among these, LUMF-PIP solid dispersion with SOL exhibited the maximum water solvency and fastest release across various media. These findings indicate that the choice of polymeric carrier significantly impacts LUMF’s solubility and dissolution behavior in solid dispersion. SOL emerges as the most promising polymer for enhancing LUMF’s solubility and dissolution, ultimately leading to improved bioavailability upon oral administration.

Improved gas influx distribution estimation using interfacial area transport equation (IATE) enabled two-fluid model: An advanced modeling and full-scale experimental study

Gas influx management is a critical aspect of petroleum drilling operations, which aims to prevent the uncontrolled outflow of formation gas and the potential consequences caused by blowouts. This study investigates the distribution of gas influx and the interfacial area concentration (IAC) during gas influx circulation operations through a combination of full-scale experiments and advanced numerical simulations.Experiments were conducted to simulate downhole gas influxes by injecting Nitrogen gas into the base of a 5,160-foot-deep experimental wellbore, which was filled with water. A Distributed Fiber-Optic Sensing (DFOS) system was installed in the wellbore to obtain high-resolution acoustic and temperature data and monitor the gas influx behaviors when circulated out of the annulus. Various types of measurements were obtained to analyze the gas influx length, slip velocities, void fraction distribution, and dispersion behaviors. In addition, an advanced numerical simulator was developed based on a modified Two-Fluid Model and the Interfacial Area Transport Equation (IATE) to simulate the gas influx behaviors. The model estimations were compared to the experimental measurements for validation of accuracy and further insights.The numerical modeling framework, based on the interfacial area transport equation, effectively captured bubble interactions, including mechanisms including bubble breakage and coalescence, by estimating the interfacial area distribution. The gas influx dispersion during circulation was analyzed using both model estimations and experimental data. Good agreement was observed between the model predictions and experimental data, including multi-depths gauge measurements and the DFOS data.This is a novel application of the IATE in well-scale multiphase flow simulations, which has proved to be an effective tool for predicting the dynamics of gas influx distributions. The outcomes of this study provide critical insights into the design and optimization of gas influx management during Managed Pressure Drilling (MPD).

The dispersion and ignition behavior of zirconium particles under the effect of a shock wave

Experiments of the interaction process between shock waves and zirconium particles have been carried out using a self-designed shock tube. The interaction process was recorded using a high-speed shadowgraph imaging system, pressure testing system, and infrared thermal imager. The wave-systems structures resulting from the interaction between shock waves and accumulated zirconium powders have been characterized. Generally, the axial distance of the powder cloud reduces with the increase in accumulation thickness, which in turn increases with the addition of shock Mach number. The incident shock wave with an intensity of 1.53 Ma was enough to ignite zirconium powders under these experimental conditions. The ignition delay time for zirconium powders decreases with the addition of shock Mach number, while it decreases for thinner accumulations. Besides, the flame propagation characteristics and the ignition mechanism of zirconium powders are discussed in detail. The results can serve as a supplementary guide for the utilization and safe operation of zirconium powders.

Spin and charge persistent currents in a Kane Mele α-T 3 quantum ring

We conduct a thorough study of different persistent currents in a spin-orbit coupled α-T 3 (pseudospin-1) fermionic quantum ring (QR) that smoothly interpolates between graphene (α = 0, pseudospin-1/2) and a dice lattice (α = 1, pseudospin-1) in presence of an external perpendicular magnetic field. In particular, we have considered effects of intrinsic (ISOC) and Rashba spin-orbit couplings (RSOC) that are both inherent to two dimensional quantum structures and yield interesting consequences. The energy levels of the system comprise of the conduction bands, valence bands, and flat bands which show non-monotonic dependencies on the radius, R of the QR, in the sense that, for small R, the energy levels vary as 1/R , while the variation is linear for large R. The dispersion spectra corresponding to zero magnetic field are benchmarked with those for finite fields to enumerate the role played by the spin–orbit coupling terms therein. Further, it is noted that the flat bands demonstrate dispersive behavior, and hence is able to contribute to the transport properties only for finite ISOC. Moreover, RSOC yields spin-split bands, thereby contributing to the spin-resolved currents. The charge and the spin-polarized persistent currents are hence computed in presence of these spin-orbit couplings. The persistent currents in both the charge and spin sectors oscillate as a function of the magnetic field with a period equal to the flux quantum, as they should be; although they now depend upon the spin–orbit coupling parameters. Interestingly, the ISOC distorts the current profiles, owing to the distribution of the flat band caused by it, whereas RSOC alone preserves the flat band and hence a perfect periodicity of the current characteristic is maintained. Further, we have explored the role played by the parameter α in our entire analysis to enable studies while interpolating from graphene to a dice lattice.

Partial migration in Magellanic penguins

We studied the migration of Magellanic penguins near the southern tip of the breeding distribution, and for the first time found evidence of partial migration for this species within the same colony. Forty‐three percent of the penguins studied stayed within ~ 290 km of the colony (residents), while others went northwards as far as 2000 km. All penguins spent the same amount of time at sea and traveled similar total distances, but residents experienced colder waters (2°C lower) and habitats with lower Chlorophyll‐a concentrations than migrants. The two habitats are inhabited by different prey items, consequently offering the penguins distinct prey options. We have shown high variability in the non‐breeding dispersion behavior of Magellanic penguins within the same colony; nonetheless, further research is required to understand the proximate and ultimate causes, and the consequences, of this behavior.

Microwave synthesis of high-entropy alloy catalysts on graphene oxide sheets for oxygen reduction and evolution reactions

High-entropy alloys (HEAs) are commonly synthesized through solid-state reactions and solution-mediated techniques. In this work, HEA nanoparticles were synthesized using an ultra-efficient pulse microwave (PM) method at relatively low temperatures (∼100 °C) with superior catalytic activities. During the PM synthesis process, the precursors of the reaction activate and accelerate the reaction owing to the release of localized and excessive energy. This leads to the formation of a crystallized high-entropy alloy (HEA). Pt30Al15Mn15Co10Ni15Cu15 and Pt30Al15Mn15Co10Ni15Fe15 HEA nanoparticles were synthesized without requiring additional external heat treatments. Furthermore, the synthesized entropically stable HEA nanoparticles showed excellent dispersion behavior towards graphene oxide (GO) sheets (particle size: 4–10 nm), this enhanced dispersion resulted in improved catalytic activity and long-term durability for various processes including H2 adsorption/desorption, oxygen reduction reaction (ORR), and oxygen evolution reaction (OER). The robust design of Cu-HEA-GO catalytic nanoparticles leads to increased synergistic interactions, which play a critical role in enhancing the ORR/OER activity. We firmly believe that the framework established in this study paves the way for the development of various high-performance catalysts based on HEAs for applications in fuel cells, metal-air batteries, and other electrochemical devices.

Large eddy simulation of particle hydrodynamic characteristics in a dense gas-particle bubbling fluidized bed

A subgrid scale particle kinetic turbulent energy model coupled with a second order moment model is developed to describe the particle hydrodynamic characteristics in dense gas-particle fluidized bed. Anisotropic behaviors of particle dispersions and interactions between gas and particle are fully revealed by means of two-phase Reynolds stresses transport eqs. A four-way coupling strategy for the consideration of particle-particle collisions is modeled by frictional granular temperature transport equation. Simulation results by large eddy simulation are validated by experimental measurement with acceptable agreement. Heterogenous flow structures, anisotropic characteristics of particle dispersions and wider-size distribution behaviors of bubbles are indicated. At the height of 0.2 m, the largest dominant frequency of porosity is 25.0 Hz at lateral 0.375 cm away from center, it is approximately 5.0 times larger than that of lateral 9.375 cm. Compared to 0.45 m, the standard deviations of 82.5 cm/s at lateral region is approximately 1.5 times larger than that of center region.

Experimental and Numerical Study for Gas Release and Dispersion on Offshore Platforms

Accidental gas release is a major triggering event for the offshore oil and gas industry. This paper focuses on the experimental and numerical investigation for dispersion behavior of released gas on offshore platforms. For this purpose, an experimental system is designed and developed to investigate gas release and dispersion. A series of experiments are carried out, among which the scenarios with constant leakage rates and time-varying leakage rates are both emphasized. The gas concentrations at different sampling points are obtained to study the dispersion behavior and accumulation characteristics of the released gas. Furthermore, a numerical computational fluid dynamics model is established to replicate the experimental scenarios. Good agreement between experimental data and CFD simulation results is observed by calculating a series of statistical performance measures. The developed numerical model is subsequently utilized to investigate a gas release scenario on a practical offshore platform, in which a fully transient leakage rate is adopted considering the response of process protection measures. The developed numerical model could provide support for risk assessment and optimization of contingency plans against gas release accidents in offshore facilities.

Dispersion behaviour of molybdenum disulfide (MoS2) nanosheets in different exposure media and determination of its toxicity using in-vitro and in-silico approaches

MoS2 nanocomposites have been used in a wide range of environmental, biomedical, and energy-related applications due to their unique physicochemical properties. On the contrary, fewer attempts were made to understand its environmental sustainability, fate, and toxicity. The present study reports the synthesis, characterisation, dispersion behaviour, cellular uptake, toxicity, and in-silico docking of trigonal prismatic (2H) defect-rich MoS2 nanosheets. The applicability of a common European approach to the regulatory testing of nanomaterials (NANoREG) was employed to understand the dispersion stability of MoS2 nanosheets. Particle size analysis was used to understand the interaction between MoS2 nanosheets and biomolecules present in the environmental matrices. Prolonged exposure (48 h) of MoS2 nanosheets to HepG2 cells resulted in a significant increase in cellular uptake of Mo compared to that in cells exposed for 1 h. Significant reduction in the cell viability was noticed in HepG2 cells exposed to 500 mg/L (p ≤ 0.05) and HL-60 cells exposed to 1000 mg/L (p ≤ 0.01) and 500 mg/L (p ≤ 0.05) of MoS2 nanosheets concentrations for 48 h. Forward/side scatter plots in flow cytometric assays (apoptosis and mitochondrial permeability) revealed alterations in cellular morphology of HL-60 cells treated with higher concentrations (≥100 mg/L) of MoS2 nanosheets for 48 h. Loss of mitochondrial membrane potential (ΔΨm) was observed in cells treated with higher concentrations (≥100 mg/L) of MoS2 nanosheets. The results obtained by in vitro analysis suggest that MoS2 nanosheets are toxic at higher doses and not at environmentally relevant concentrations. To the best of our knowledge, this is the first study of its kind that demonstrates the cellular and molecular toxicity of MoS2 nanosheets, along with its in silico interactions with the key sixteen macro-molecules involved in programmed cell death.

Habitat specialisation and resource availability determine dispersal behaviour in four afro‐tropical butterflies

Abstract Ecological demands, such as sex and environmental conditions, determine species' behaviour, such as dispersal, and shape local population structures. However, only marginal knowledge of these factors exists for afro‐tropical insects so far. Therefore, we performed a mark–release–recapture study in the coastal region of Kenya over a period of 2 months, covering the dry and the rainy seasons. As study species, we used four co‐occurring but ecologically diverging butterfly species, the forest species Bicyclus safitza and Junonia natalica and the savannah species Junonia oenone and Byblia ilithyia. The study area represents an ecosystem mosaic consisting of anthropogenic habitats as well as natural forest and savannah, assessed by detailed landscape mapping. We obtained 1701 capture events, comprising 1224 individuals with an overall recapture rate of 24% (ranging from 15% to 48%). The analyses based on these results allowed an assessment of the population ecology, dispersal behaviour and habitat preferences of these species. Demographic models inferred different patterns of population dynamics among species. All species preferred the habitats they were known for. The observed dispersal distances were rather low ranging from a mean of 25 to 72 m, referring to taxa and sexes. The dispersal extrapolations were unreliably low for the negative exponential function, while the values for inverse power function were credible. The latter predicted a considerably higher long‐distance dispersal capacity in males than in females of the forest species B. safitza and J. natalica, while females dispersed more than males in the savannah species J. oenone and B. ilithyia. Our results obtained from these four ecologically diverging afro‐tropical butterfly species underline that species’ behaviour, such as dispersal, is strongly determined by habitat preferences, sex and the availability of resources.

Taylor dispersion in arbitrarily shaped axisymmetric channels

Advective dispersion of solutes in long thin axisymmetric channels is important to the analysis and design of a wide range of devices, including chemical separation systems and microfluidic chips. Despite extensive analysis of Taylor dispersion in various scenarios, most studies focus on long-term dispersion behaviour and cannot capture the transient evolution of the solute zone across the spatial variations in the channel. In the current study, we analyse the Taylor–Aris dispersion for arbitrarily shaped axisymmetric channels. We derive an expression for solute dynamics in terms of two coupled ordinary differential equations, which allow prediction of the time evolution of the mean location and axial (standard deviation) width of the solute zone as a function of the channel geometry. We compare and benchmark our predictions with Brownian dynamics simulations for a variety of cases, including linearly expanding/converging channels and periodic channels. We also present an analytical description of the physical regimes of transient positive versus negative axial growth of solute width. Finally, to further demonstrate the utility of the analysis, we demonstrate a method to engineer channel geometries to achieve desired solute width distributions over space and time. We apply the latter analysis to generate a geometry that results in a constant axial width and a second geometry that results in a sinusoidal axial variance in space.

Insights into the Unanticipated Chemical Reactivity of Functionalized Nanosheets Derived from TiB2.

Titanium diboride (TiB2) is a member of the AlB2-type layered metal boride family; the materials of this family are receiving renewed research interest owing to their amenability to nanoscaling. Earlier, we showed that TiB2 can be nanoscaled to yield quasi 2D nanostructures following a dissolution-recrystallization approach. This approach yielded nanosheets that were chemically functionalized with oxy-functional groups. Also, these nanosheets could inherently form a gel-like substance. In this work, we show that these functionalized nanosheets can interact with ascorbic acid in a way that first imparts a characteristic orange hue to the original yellowish nanosheet dispersion. Second, this interaction results in the loss of gel-like behavior of the nanosheet dispersion. We utilize several spectroscopic techniques such as UV-visible, FT-IR, NMR, EPR, XPS, and XANES to unravel this unexplored chemical interaction. The findings show that both titania as well as oxy-boron species react with ascorbic acid, leading to a profound modification of the nanosheets. This modification results in an augmented electrochemical response, implying that the modified nanosheets can be used in novel applications. This study is therefore a step toward gaining an even deeper understanding of the chemical opportunities that these nanoscaled borides can provide.

Factors shaping the abundance of two butterflies sharing resources and enemies across a biogeographic region

AbstractAimIntraspecific variation in species relative abundance is shaped by a complex interplay of abiotic and biotic factors, making it both necessary and challenging to assess their combined relative importance in explaining variations across space and time. We used two congeneric butterfly species for which extensive count data and a deep understanding of their natural history is available to test three hypotheses explaining intraspecific variation in their abundance: (H1) seasonal dispersal behaviour driven by climate, (H2) resource availability and (H3) apparent competition mediated via shared parasitoids.TaxonGonepteryx rhamni (Brimstone) and G. cleopatra (Cleopatra).LocationNE Iberian Peninsula, where both species coexist, and a nearby archipelago (Balearic Islands), where only Cleopatra occurs.MethodsWe analysed spatial abundance variations for both species in the mainland and island–mainland differences in the abundance of Cleopatra. Abiotic and biotic factors, including temperature, host plant and overwintering habitat availability, larval parasitism and density dependence, were tested to explain the observed variations.ResultsH1 can explain variation in butterfly abundance between mainland regions since in warmer summers populations increased in cooler areas but decreased in warmer areas. H2 explains the variation within mainland climate regions with a strong positive relationship between resource availability and abundance but is unlikely to explain the island–mainland variation in the abundance of Cleopatra. H3 could neither explain biogeographical variation in abundance because although richer parasitoid communities were found on the mainland, larval mortality rates were similar or lower on the mainland than in the islands.Main ConclusionsClimate and resource availability jointly account for variation in butterfly abundance across the mainland, but neither these factors nor parasitism can explain island–mainland differences. Both coexisting butterfly species and their larval parasitoids may have undergone evolutionary processes, resulting in spatial segregation that promotes the coexistence of the two butterfly species on the mainland.

Minimal Mechanisms Responsible for the Dispersive Behavior of the Madden–Julian Oscillation

An attempt has been made to explore the relative contributions of moisture feedback processes on tropical intraseasonal oscillation or Madden–Julian Oscillation (MJO). We focused on moisture feedback processes, including evaporation wind feedback (EWF) and moisture convergence feedback (MCF), which integrate the mechanisms of convective interactions into the tropical atmosphere. The dynamical framework considered here is a moisture-coupled, single-layer linear shallow-water model on an equatorial beta-plane with zonal momentum damping. With this approach, we aimed to recognize the minimal physical mechanisms responsible for the existence of the essential dispersive characteristics of the MJO, including its eastward propagation (k>0), the planetary-scale (small zonal wavenumbers) instability, and the slow phase speed of about ≈5 m/s. Furthermore, we extended our study to determine each feedback mechanism’s influence on the simulated eastward dispersive mode. Our model emphasized that the MJO-like eastward mode is a possible outcome of the combined effect of moisture feedback processes without requiring additional complex mechanisms such as cloud radiative feedback and boundary layer dynamics. The results substantiate the importance of EWF as a primary energy source for developing an eastward moisture mode with a planter-scale instability. The eastward moisture mode exhibits the highest growth rate at the largest wavelengths and is also sensitive to the strength of the EWF, showing a significant increase in the growth rate with the increasing strength of the EWF; however, the eastward moisture mode remains unstable at planetary-scale wavelengths. Moreover, our model endorses that the MCF alone could not produce instability without surface fluxes, although it has a significant role in developing deep convection. It was found that the MCF exhibits a damping mechanism by regulating the frequency and growth rate of the eastward moisture mode at shorter wavelengths.