Central Density Research Articles

The Effect of Tobacco Smoking on Corneal Endothelium and Central Corneal Thickness

We aimed to study the impact of tobacco smoking towards central corneal thickness, morphology, and corneal endothelial cell density (ECD) in healthy subjects. This cross-sectional study recruited consecutive patients who visited the Ophthalmology Clinic, Universiti Kebangsaan Malaysia Medical Centre, from April 2017 to August 2018 who were active smokers and non-smokers. Active smokers were further divided into heavy and light smokers according to the number of pack-years smoked. The nicotine dependency level was measured using the Fagerstrom test and divided into low, moderate, and severe dependency. Non-contact specular microscopy was performed. Parameters studied included the ECD, percentage of hexagonality (HEX), coefficient of variation of cell size (COV), and central corneal thickness (CCT). A total of 84 eyes from 84 subjects were included, with 42 in the smoker and 42 in the non-smoker groups. The mean age was 38.3 ± 6.7 and 39.2 ± 10.7 years in the smoker and non-smoker groups, respectively. The mean ECD, HEX, and COV were 2783 ± 316 vs. 2877 ± 333 cells/mm2, 55.0 ± 6.7% vs. 55.0 ± 7.7% and 32.7 ± 4.4% vs. 32.2 ± 4.1% in the smoker and non-smoker group, respectively. However, none were statistically significant (p>0.05). The mean CCT was also not statistically different, with 532.6 ± 30.8 μm in the smoker group and 530.5 ± 30.8 μm in the non-smoker group. No statistically significant difference was found between light and heavy smokers and addiction levels. There was a statistically significant but weak negative correlation between ECD and duration of smoking (r = -.370, p = 0.016) and a weak positive correlation between COV and number of pack-years smoked (r = .344, p = 0.025). Smoking did not significantly affect corneal ECD, cellular morphology, or CCT.

Parametric characterization of arcs in semi-sealed splitter plate DC circuit breakers

Precisely assessing plasma parameters holds paramount importance in investigating the arc extinguishing mechanism of semi-sealed splitter plate DC circuit breakers, refining the configuration of splitter plates, and optimizing the overall structural design of circuit breakers. Based on the principle of the Langmuir probe, a double probe diagnostic method is proposed to investigate the air arc plasma in the opening process of a DC circuit breaker. The diagnostic circuit of the probes is designed, and three sets of double probes are arranged to trace the evolution of the plasma density during the opening process. The research reveals that the plasma center density, measured by the diagnostic system during the opening process of the DC circuit breaker, is about 1022 m−3–1023 m−3. This density is compared with the diagnostic results obtained by other methods, confirming the accuracy of the Langmuir double probe for plasma measurements in the DC circuit breaker. The study also revealed an exponential decay behavior of electron density along the radial direction of the arc. A mathematical model was employed to describe this phenomenon, establishing a relationship between the distribution of electron density and arc current.

Phacoemulsification versus Laser Peripheral Iridotomy for Treating Primary Angle Closure Glaucoma: A Systematic Review and Meta-Analysis.

Primary Angle Closure Glaucoma (PACG), is caused by narrowing the iridocorneal angle and increases the risk of blockage in the trabecular meshwork. Phacoemulsification and laser peripheral iridotomy (LPI) effectively control IOP elevation and widen the angle. This systematic review and meta-analysis compared Phacoemulsification and LPI Effectiveness for PACG. We searched Medline, Embase, and CENTRAL. We included randomized controlled trials (RCTs) that compared Phacoemulsification and LPI for individuals with PACG. We sought to evaluate the following outcomes: mean IOP, number of glaucoma medications, visual acuity (VA), visual field (VF) progression, peripheral anterior synechiae (PAS), Shaffer gonioscopy grading, central corneal thickness (CCT), central endothelial cell density (CECD), and poor response to surgery. The standardized mean difference (SMD) was used to represent continuous outcomes, while the risk ratio (RR) was used to represent dichotomous outcomes. 5 RCTs that enrolled 917 participants were deemed eligible. The phacoemulsification group showed statistically significance lower mean CCT and CECD and lower risk of poor response to surgery compared to LPI (SMD = -1.10; 95% -1.50, -0.70; P<0.001, SMD -366.12; 95% -652.59, -79.65; P=0.01, and RR 0.35; 95% 0.23, 0.54; P<0.001 respectively). There were no significant improvement in IOP and number of medications between both groups (SMD = -0.74; 95% CI = -2.26, 0.78; P=0.34, and SMD -17.58; 95% CI = -50.28, 15.12; P=0.29 respectively). Finally, there were also no significant differences in VA, VF progression, PAS, and mean Shaffer gonioscopy grading between both groups. Phacoemulsification showed statistically significant lower mean corneal thickness, central endothelial cell density, and lower risk of poor response to surgery compared to LPI. However, there were no significant differences in mean IOP, number of medications, VA, VF progression, PAS, and mean Shaffer gonioscopy grading between Phacoemulsification and LPI.

The Initial Conditions of Clustered Core Collapse: Multiwavelength Analysis of Oph A SM1N and N6 at 100 au Resolution

We present new Atacama Large Millimeter/submillimeter Array (ALMA) continuum and NH2D, N2D+, and H2D+ line emission at matched, ∼100 au resolution toward the dense star-forming cores SM1N and N6 within the Ophiuchus molecular cloud. We determine the density and temperature structure of SM1N based on radiative transfer modeling and simulated observations of the multiwavelength continuum emission at 0.8, 2, and 3 mm. We show that SM1N is best fit by either a broken power-law or Plummer-like density profile with high central densities (n ∼ 108 cm−3), and an inner transition radius of only ∼80–300 au. The free-fall time of the inner region is only a few ×103 yr. The continuum modeling rules out the presence of an embedded first hydrostatic core (FHSC) or protostar. SM1N is therefore a dynamically unstable but still starless core. We find that NH2D is likely depleted at high densities within SM1N. The nonthermal velocity dispersions increase from NH2D to N2H+ and H2D+, possibly tracing increasing (but still subsonic) infall speeds at higher densities as predicted by some models of starless core contraction. Toward N6, we confirm the previous ALMA detection of a faint, embedded point source (N6-mm) in 0.8 mm continuum emission. NH2D and N2D+ avoid N6-mm within ∼100 au, while H2D+ is not strongly detected toward N6. The distribution of these tracers is consistent with heating by a young, warm object. N6-mm thus remains one of the best candidate FHSCs detected so far, although its observed (sub)millimeter luminosity remains below predictions for FHSCs.

Basic Analysis of Physical Determinants Affecting the Distribution Density of Senior Citizen Centers around Small Apartment Complexes, Focusing on Administrative Districts in Busan

The role of senior citizen centers is becoming more important, with a greater emphasis placed on ensuring that these establishments facilitate leisure and communication for older adults. These developments are taking place as population aging has now become an irreversible global trend. However, there is still a lack of systematic research on predicting the distribution density of senior citizen centers based on physical factors in urban planning. Therefore, this study set each administrative district in Busan as a unit and investigated physical factors affecting the distribution density of senior citizen centers around small apartment complexes to validate their effectiveness. First, the spatial hierarchy of each administrative district in Busan was examined. The city was divided into administrative districts while focusing on the distribution density of senior citizen centers (the dependent variable) around small apartment complexes where older adults live (within a 500 m radius). The spatial accessibility of senior citizen centers and the number of apartments in each administrative district were set as independent variables. This selection was made to verify the effectiveness of the physical factors by conducting an independent sample t-test, normality test, Friedman test, and two-way ANOVA. The chief findings of this study are as follows. (1) The spatial awareness of each administrative district was low, and there were large disparities in the land development density relative to the spatial scale of the administrative districts. (2) Regarding the physical factors affecting the distribution density of senior citizen centers, the spatial accessibility of senior residences was more significant than the number of small apartment complexes nearby. (3) Personal and social factors may have indirectly influenced the distribution density of senior citizen centers more than physical factors, depending on the type of house in which the older adults live. The findings will provide a theoretical basis for determining the location and distribution density of senior citizen centers in urban planning considering physical factors, as well as serve as a reference for public policy decisions related to the allocation of such centers in the future.

Reevaluating the Origin of Detectable Cataclysmic Variables in Globular Clusters: Testing the Importance of Dynamics

Based on the current detectable cataclysmic variable (CV) population in Galactic globular clusters (GCs), we show that there is not a clear relation between the number of sources per unit of mass and the stellar encounter rate, the cluster mass, or the cluster central density. If any, only in the case of core-collapsed GCs could there be an anticorrelation with the stellar encounter rate. Our findings contrast with previous studies where clear positive correlations were identified. Our results suggest that correlations between faint X-ray sources, from which often conclusions for the CV population are drawn, and the GC parameters considered here, are likely influenced by other type of X-ray sources, including other types of compact binaries, which have X-ray luminosities similar to CVs. The findings presented here also suggest that the role of primordial systems is more important than previously believed and that dynamical formation has less influence in the current detectable CV population. The long-standing paradigm that GCs are efficient factories of CVs formed via dynamical interactions does not seem to be supported by current observations.

Comparative assessment of the corneal endothelium following phacoemulsification surgery in patients with type II diabetes and nondiabetes

Abstract: PURPOSE: The purpose is to assess the corneal endothelial changes after phacoemulsification surgery in diabetic patients and compare with those of nondiabetic subjects. METHODS: The study compared the corneal endothelial changes in diabetics and nondiabetics after phacoemulsification surgery. The study population included 40 patients with diabetes mellitus with good glycemic control and 40 nondiabetic patients who underwent uneventful phacoemulsification surgery. Central corneal endothelial cell density (ECD), central corneal thickness (CCT), and percentage of hexagonality percentage coefficient of variation (%CV) were measured preoperatively and postoperatively (at 4 and 12 weeks) using a specular microscope. RESULTS: Mean ECD loss (%) was measured as 9.85% and 8.41% at 4 weeks and 12 weeks postoperatively in the diabetic group while ECD loss percentage was 7.09% and 5.74% in the control group at the same time intervals, respectively. Furthermore, a significant difference was noted on comparing mean ECD measurements between the two groups at the postsurgical visits (4 weeks and 12 weeks). While the CCT was found to be similar in both diabetic and nondiabetic patients, increase was observed in the values of (%CV in both the groups at postoperative 4 weeks’ and 12 weeks’ follow-up. The values of both %CV and percentage hexagonality showed statistically significant differences between the diabetic and nondiabetic group before surgery and at 4 weeks’ and 12 weeks’ postoperative examinations. CONCLUSION: The patients with diabetes suffered greater endothelial damage despite good glycemic control as compared to nondiabetic patients which indicates the necessity of far more care to protect cornea endothelium in patients with diabetes.

Excited-State Lifetime of NV Centers for All-Optical Magnetic Field Sensing.

We investigate the magnetic field-dependent fluorescence lifetime of microdiamond powder containing a high density of nitrogen-vacancy centers. This constitutes a non-intensity quantity for robust, all-optical magnetic field sensing. We propose a fiber-based setup in which the excitation intensity is modulated in a frequency range up to 100MHz. The change in magnitude and phase of the fluorescence relative to B=0 is recorded where the phase shows a maximum in magnetic contrast of 5.8∘ at 13MHz. A lock-in amplifier-based setup utilizing the change in phase at this frequency shows a 100 times higher immunity to fluctuations in the optical path compared to the intensity-based approach. A noise floor of 20μT/Hz and a shot-noise-limited sensitivity of 0.95μT/Hz were determined.

Hot ion implantation to create dense NV center ensembles in diamond

Creating dense and shallow nitrogen-vacancy (NV) ensembles with good spin properties is a prerequisite for developing diamond-based quantum sensors exhibiting better performance. Ion implantation is a key enabling tool for precisely controlling spatial localization and density of NV color centers in diamond. However, it suffers from a low creation yield, while higher ion fluences significantly damage the crystal lattice. In this work, we realize N2+ ion implantation in the 30–40 keV range at high temperatures. At 800 °C, NV's ensemble photoluminescence emission is three to four times higher than room temperature implanted films, while narrow electron spin resonance linewidths of 1.5 MHz, comparable to well-established implantation techniques, are obtained. In addition, we found that ion fluences above 2 × 1014 ions/cm2 can be used without graphitization of the diamond film, in contrast to room temperature implantation. This study opens promising perspectives in optimizing diamond films with implanted NV ensembles that could be integrated into quantum sensing devices.

The influence of heterogeneous catalytic processes on the heat flux to the surface and the chemical composition of the shock layer at high-speed flow around blunt bodies

Numerical modeling of the high-speed flow of a multicomponent dissociated gas around a blunt body was carried out for the flow regime corresponding to the thermally stressed point of the gliding trajectory of entry into the Earth's atmosphere in the surface temperature range of 800–2000 K. As boundary conditions, a stage-by-stage model of heterogeneous catalysis of the interaction of dissociated air with the thermal protection material SiO2 was used, previously developed by the authors on the basis of transition state theory and quantum mechanical calculations. The dependence of the modes of heterogeneous chemical reactions on the surface temperature and the density of surface adsorption centers and their influence on the chemical composition of the shock layer and the convective heat flux to the streamlined surface are analyzed. The contributions of individual mechanisms of heterogeneous recombination to the total rate of formation of molecules on the surface are estimated. The possibility of using the density of adsorption sites as an effective parameter when setting boundary conditions on a real thermal protection surface in flow problems is shown.

Investigation of phonon lifetimes and magnon–phonon coupling in YIG/GGG hybrid magnonic systems in the diffraction limited regime

Quantum memories facilitate the storage and retrieval of quantum information for on-chip and long-distance quantum communications. Thus, they play a critical role in quantum information processing and have diverse applications ranging from aerospace to medical imaging fields. Bulk acoustic wave (BAW) phonons are attractive candidates for quantum memories because of their long lifetimes and high operating frequencies. In this study, we establish a modeling approach to design hybrid magnonic high-overtone bulk acoustic wave resonator (HBAR) structures for high-density, long-lasting quantum memories, and efficient quantum transduction devices. We illustrate the approach by investigating a hybrid magnonic system, consisting of a gadolinium iron garnet (GGG) thick film and a patterned yttrium iron garnet (YIG) thin film. The BAW phonons are excited in GGG thick film via coupling with magnons in the YIG thin film. We present theoretical and numerical analyses of the diffraction-limited BAW phonon lifetimes, modeshapes, and magnon–phonon coupling strengths in YIG/GGG planar and confocal HBAR (CHBAR) structures. We utilize Fourier beam propagation and Hankel transform eigenvalue problem methods and compare the two methods. We discuss strategies to improve the phonon lifetimes in the diffraction-limited regime, since increased lifetimes have direct implications on the storage times of quantum states for quantum memory applications. We find that ultra-high cooperativities and phonon lifetimes on the order of ∼105 and ∼10 milliseconds, respectively, could be achieved using a CHBAR structure with 10μm YIG lateral area. Additionally, high integration density of on-chip memory or transduction centers is naturally desired for high-density memory or transduction devices. The proposed CHBAR structure will offer more than 100-fold improvement of integration density relative to a recently demonstrated YIG/GGG device. Our results will have direct applicability for devices operating in the cryogenic or milliKelvin regimes. For example, our study will inform the design of HBAR devices that could couple with superconducting qubits for promising quantum information platforms.

Simulations of galaxy cluster mergers with velocity-dependent, rare, and frequent self-interactions

ABSTRACT Self-interacting dark matter (SIDM) has been proposed to solve small-scale problems in $\rm {\Lambda CDM}$ cosmology. In previous work, constraints on the self-interaction cross-section of dark matter have been derived assuming that the self-interaction cross-section is independent of velocity. However, a velocity-dependent cross-section is more natural in most theories of SIDM. Using idealized N-body simulations without baryons, we study merging clusters with velocity-dependent SIDM. In addition to the usual rare scattering in the isotropic limit, we also simulate these systems with anisotropic, small-angle (frequent) scatterings. We find that the collisionless brightest cluster galaxy (BCG) has an offset from the DM peak that grows at later stages. Finally, we also extend the existing upper bounds on the velocity-independent, isotropic self-interaction cross-section to the parameter space of rare and frequent velocity-dependent self-interactions by studying the central densities of dark matter-only isolated haloes. For these upper-bound parameters, the DM-BCG offsets just after the first pericentre in the dark matter-only simulations are found to be ≲10 kpc. On the other hand, because of BCG oscillations, we speculate that the distribution of BCG offsets in a relaxed cluster is a statistically viable probe. Therefore, this motivates further studies of BCG off-centring in hydrodynamic cosmological simulations.

Building stellar bulges and halo cores from massive clumps observed in the DYNAMO-HST sample

ABSTRACT We present N-body simulations of the process of bulge formation in disc galaxies due to inward migration of massive stellar clumps. The process is accompanied by dark halo heating, with a quasi-isothermal core replacing the initial central density cusp, transforming an initially dark matter dominated central region into a baryon dominated one. The characteristics of the clumps are chosen to be compatible with low redshift observations of stellar clumps in DYNAMO-HST galaxies, which may be relatively long lived in terms of being robust against internal starburst-instigated disruption. We thus test for disruption due to tidal stripping using different clump internal radial profiles; Plummer, Hernquist, and Jaffe, in ascending order of see per central density profile. Our calculations predict that in order for clump migration to be effective in building galactic bulges and dark halo cores, steeply increasing central clump profiles, or a less massive or less concentrated haloes, are preferred. The dependence on such factors may contribute to the diversity in observed total mass distributions and resulting rotation curves in galaxies. When the process is most efficient, a ‘bulge-halo conspiracy’, with a singular isothermal total density akin to that observed bright galaxies, results.

Symmetry energy and neutron star properties constrained by chiral effective field theory calculations

We investigate the nuclear symmetry energy and neutron star properties using a Bayesian analysis based on constraints from different chiral effective field theory calculations using new energy density functionals that allow for large variations at high densities. Constraints at high densities are included from observations of GW170817 and from NICER. In particular, we show that both NICER analyses lead to very similar posterior results for the symmetry energy and neutron star properties when folded into our equation-of-state framework. Using the posteriors, we provide results for the symmetry energy and the slope parameter, as well as for the proton fraction, the speed of sound, and the central density in neutron stars. Moreover, we explore correlations of neutron star radii with the pressure and the speed of sound in neutron stars. Our 95% credibility ranges for the symmetry energy Sv, the slope parameter L, and the radius of a 1.4M⊙ neutron star, R1.4, are Sv=(30.6–33.9)MeV, L=(43.7–70.0)MeV, and R1.4=(11.6–13.2)km. Our analysis for the proton fraction shows that larger and/or heavier neutron stars are more likely to cool rapidly via the direct Urca process. Within our equation-of-state framework a maximum mass of neutron stars Mmax&gt;2.1M⊙ indicates that the speed of sound needs to exceed the conformal limit. Published by the American Physical Society 2024

Quantum-chemical calculations of thermodynamic characteristics of some heterogeneous catalytic processes with the use of multilayer cluster models

The approaches to estimating the changes in enthalpy, entropy, and Gibbs energy of adsorption processes and heterogeneous catalytic reactions on the basis of the quantum chemical calculation data were studied. By comparing with the experimental data on CO adsorption on the anatase (TiO2) surface, the applicability of the developed multilayer cluster model for calculation of the adsorption energy (enthalpy) was shown. The data on the calculation methods of the entropy change in heterogeneous processes were analyzed. The use of the theories of an ideal two-dimensional gas and an ideal two-dimensional lattice gas for estimating a configuration contribution to the entropy of a heterogeneous process was studied. The density of adsorption centers on the (101) anatase surface and the population corresponding to the standard state of an ideal two-dimensional gas were calculated. The consistency of the studied models at low populations was shown, and the limits of their applicability were established.

Numerical analyses of M31 dark matter profiles

In this paper, we reproduce the rotation curve of the Andromeda galaxy (M31) by taking into account its bulge, disk and halo components, considering the last one to contain the major part of dark matter mass. Hence, our prescription is to split the galactic bulge into two components, namely, the inner and main bulges, respectively. Both bulges are thus modeled by exponential density profiles since we underline that the widely accepted de Vaucouleurs law fails to reproduce the whole galactic bulge rotation curve. In addition, we adopt various well-known phenomenological dark matter profiles to estimate the dark matter mass in the halo region. Moreover, we apply the least-squares fitting method to determine from the rotation curve the model free parameters, namely, the characteristic (central) density, scale radius and consequently the total mass. To do so, we perform Markov chain Monte Carlo statistical analyses based on the Metropolis algorithm, maximizing our likelihoods adopting velocity and radii data points of the rotation curves. We do not fit separately the components for bulges, disk and halo, but we perform an overall fit including all the components and employing all the data points. Thus, we critically analyze our corresponding findings and, in particular, we employ the Bayesian information criterion to assess the most accredited model to describe M31 dark matter dynamics.

Quantitative Measurement and Analysis of the Radial Peripapillary and Central Macular Microvasculature Density in Early Open-Angle Glaucoma Using OCT Angiography

Background Glaucoma is a prevalent cause of visual impairment, and early detection is critical to prevent progressive vision loss. Optical coherence tomography angiography (OCT-A) enables visualization of retinal and optic nerve microvasculature and holds promise for early glaucoma detection. Aims This study aims to assess microvasculature density alterations in glaucoma using OCT-A. Methods An observational cross-sectional case–control study was conducted at Benghazi Eye Hospital in Libya from December 2022 to August 2023. It included 160 eyes of 126 patients diagnosed with primary open-angle glaucoma and 120 eyes of 96 control subjects. OCT-A was performed using the Swept-Source OCT DRI Triton. Vessel density measurements were obtained from OCT-A images using new built-in software within the device. The data presented as mean ± standard deviation and percentages were analyzed using SPSS. The statistical significance of the differences between different groups was determined using independent t-tests, and the level of significance was set at p-value less than 0.05. Results OCT-A demonstrated significantly reduced microvasculature density in glaucoma eyes across all optic nerve sectors including the inferior (29.0%), superior (25.2%), central (23.5%), nasal (9.9%), and temporal sectors (9.3%; p &lt; 0.02). Moreover, glaucoma patients exhibited a significant reduction in vessel density in the superior macula (17% reduction), the temporal (15.7%,), nasal (12.9%), and inferior sectors (12.6%) (p &lt; 0.002). No statistical difference was seen with vessel density of the central sector (0.49%, p &gt;0.05). Conclusion OCT-A demonstrated significant reductions in microvasculature density in glaucoma patients compared with healthy controls. These findings support the association between glaucoma and vascular changes. Additionally, the TOPCON Swept-Source OCT DRI Triton new software shows promise as a valuable tool for early detection and monitoring of glaucoma-related vascular changes.

Numerical study on dust particle charging and dynamics in continuous and pulsed radio frequency argon discharges

AbstractCharging and dynamics of a spherical dust grain injected into a continuous and pulsed radio frequency (RF) discharge have been studied using a one‐dimensional fluid model. First, the plasma characteristics of the two types of discharges are computed and compared. In the pulsed discharge, it is found that the central electron density exhibits a periodic variation while the averaged electron density is lower compared to that in the continuous discharge due to the decrease in the total ionization rate. Further, the dust charge is computed using the plasma characteristics. It is found that the dust charge negatively increases as the duty cycle ratio increases. Also, the charge in the pulsed discharge is lower in comparison to the continuous discharge due to the shorter duration of the pulsed RF discharge limiting the amount of energy transferred to electrons. On the other hand, the dust particle remains in the powered sheath region exhibiting a damped oscillation in the two discharges with higher oscillation frequency in the continuous discharge.

Revealing the Impact of Critical Stellar Central Density on Galaxy Quenching through Cosmic Time

In a previous work, we investigated the structural and environmental dependence on quenching in the nearby universe. In this work, we extend our investigations to higher redshifts by combining galaxies from the Sloan Digital Sky Survey and The FourStar Galaxy Evolution surveys. In low density, we find a characteristic Σ1 kpc above which the quenching is initiated as indicated by their population-averaged color. Σ1kpccrit shows only a weak mass dependency at all redshifts, which suggests that the internal quenching process is more related to the physics that acts in the central region of galaxies. In high density, Σ1kpccrit for galaxies at z > 1 is almost indistinguishable from their low-density counterparts. At z < 1, Σ1kpccrit for low-mass galaxies becomes progressively strongly mass dependent, which is due to the increasingly stronger environmental effects at lower redshifts. Σ1kpccrit in low density shows strong redshift evolution with ∼1 dex decrement from z = 2.5–0. It is likely that at a given stellar mass, the host halo is on average more massive and gas-rich at higher redshifts; hence, a higher level of integrated energy from a more massive black hole (BH) is required to quench. As the halo evolves from the cold to hot accretion phase at lower redshifts, the gas is shock-heated and becomes more vulnerable to the feedback processes from active galactic nucleus as predicted by theory. Meanwhile, angular momentum quenching also becomes more effective at low redshifts, which complements a lower level of integrated energy from the BH to quench.

Increasing planting density increases fruit mass and reduces the dispersal ability of a range‐expanding invasive plant, Mikania micrantha

AbstractAimInvasive plants may evolve a suite of distinctive traits during spread in the new range. Among these traits, dispersal ability is an important trait determining the invasion speed of exotic plants. There is evidence that higher dispersal ability is favoured at the invasion front, where population density may be low. However, no study has explicitly tested how planting density in a common garden affects the dispersal ability of invasive plants.LocationHainan island of China.MethodsIn this study, using 27 populations of an invasive plant, Mikania micrantha, which is expanding its range on Hainan island of China, we examine how three dispersal‐related traits (i.e. dispersal ability, fruit mass, and pappus radius) change with distance from invasion centre and field population density, and how planting density in a common garden affects dispersal traits.ResultsDispersal traits did not change with distance from the invasion centre and field population cover either in the natural environment or in the common garden. In the common garden, increasing planting density from one to five plants per pot increased fruit mass and decreased dispersal ability, indicating that the effect of density on dispersal traits could not be detected in the field. The relationship between dispersal ability in the natural environment and that in the common garden was positive but significant only under the five plants per pot treatment, possibly because dispersal traits in natural conditions were selected under high‐density growth conditions.Main ConclusionsOur results indicate that increasing population density may increase fruit mass and reduce the dispersal ability of range‐expanding invasive plants. We suggest that further studies exploring the patterns of dispersal traits in range‐expanding invasive plants in a common garden should consider intraspecific competition.