Variable Dispersion Research Articles

Geochemical methods to prospect for gold mineralization in Shamkhyia area : northern state-Sudan

Geochemical methods to prospect for gold mineralization in Shamkhyia area : northern state-Sudan
 The study area is located in the northern border of Buyda Desert at the lobe of the River Nile at coordinates: latitude 19° 27 25" N, longitude 32° 59’ 37'.
 Unconsolidates samples were collected from areas of the suspected Au bearing sector to reveal secondary dispersion patterns.
 The results which were obtained for Au and accompanying elements (Ag, Cu, Co, Cu, Pb, and Zn) Table No (7 , 8) were subjected to statistical analysis to reveal parameters such as background values (Cb) coefficient of correlation (r), coefficient of variation (c.v), geochemical factors (u), and productivities (q,Q) and coefficient of dispersion (5).
 These parameters can be used as prospecting and exploration criteria.
 The coefficient of correlation of Au with the accompanying elements in rock chip composite samples show values more reliable for prospecting than those of the soil samples.
 Geochemical factors of ratios of contents of epithermal elements to hypothermal elements indicate deeper levels of mineralization and weathering.
 Gold dispersion shows less erratic behavior and this reflects more or less the morphology of the hidden ore bodies.
 The main conclusions are:- Coefficient of corelations when they are reliable can be used to define pathfinders to prospect for the difficult gold.
 Coefficient of mobility can be used to adopt sampling intervals and grid system.
 Geochemical factors can indicate horizon of mineralization and level of weathering.
 Geochemical reserve can be used to indicate priorities for further extensive explorational studies

Uncovering input-sensitive energy bottlenecks in oversubscribed GPU workloads

Graph algorithms are at the core of data-intensive applications in many computational domains. Although accelerator-based implementations have the potential for delivering improved energy efficiency on today’s large-scale graph analytics, there are many challenges to reaching the desired goals. This paper examines the issues of GPU oversubscription and input sensitivity in energy efficient graph processing. We introduce the notion of energy signatures, a collection of runtime events that can determine fluctuations in power consumption as a function of input graph characteristics. The study shows that variations in volume, density, diameter and dispersion in graphs can alter the runtime behavior of GPU applications and these changes in program behavior in turn impact the energy efficiency of the application. Based on the insight gained from our study, we develop three input-aware optimization techniques to mitigate energy bottlenecks. On experiments conducted on a Unified Memory supported GPU, the optimizations yield a 11.97% energy savings on average on Breadth-First Search and Single-Source Shortest Path algorithms.

A Novel Discrete Distribution: Properties and Application Using Nipah Virus Infection Data Set

In this study, the Poisson (PD) distribution was compounded with a continuous distribution to produce the Poisson XLindley distribution (PXLD). Its raw moments and central moments are acquired as a result of a general expression for its rth factorial moment concerning origin being derived. Additionally, the expressions for its coefficient of variation, skewness, kurtosis and index of dispersion have been provided. For the estimate of its parameters, in particular, the methods of maximum likelihood and moments have been addressed. The applicability of the proposed distribution in modeling real data sets on Nipah virus infection, number of Hemocytometer yeast cell count data, and epileptic seizure counts data is examined by analyzing two real-world data sets.

Dispersion management for a 100 PW level laser using a mismatched-grating compressor

Abstract We report dispersion management based on a mismatched-grating compressor for a 100 PW level laser, which utilizes optical parametric chirped pulse amplification and also features large chirped pulse duration and an ultra-broadband spectrum. The numerical calculation indicates that amplified pulses with 4 ns chirped pulse duration and 210 nm spectral bandwidth can be directly compressed to sub-13 fs, which is close to the Fourier-transform limit (FTL). More importantly, the tolerances of the mismatched-grating compressor to the misalignment of the stretcher, the error of the desired grating groove density and the variation of material dispersion are comprehensively analyzed, which is crucially important for its practical application. The results demonstrate that good tolerances and near-FTL compressed pulses can be achieved simultaneously, just by keeping a balance between the residual second-, third- and fourth-order dispersions in the laser system. This work can offer a meaningful guideline for the design and construction of 100 PW level lasers.

New Exact Solutions to a Class of Fractional-Order Modified Unstable Schrödinger Equations

The fractional order modified unstable Schrödinger equation (FMUSE) is studied, which describes the dispersion, nonlinearity, gain or absorption variation of optical pulses propagating in nonuniform fiber systems. First, the generalized fractional wave transform is appropriately used to transform FMUSE into an ordinary differential equation, and the real and imaginary parts are separated and set to zero respectively, and the dispersion relation is obtained. By using the modified (<i>G'</i>/<i>G</i>)-expansion method, a series of new exact analytical solutions with parameters are obtained, including trigonometric solutions, hyperbolic solutions and rational solutions, and the constraints to ensure the existence of solutions are given. Finally, the solutions of dark solitary wave and periodic wave are obtained when the parameters are taken special value.

Heritability of dispersal in a rapidly spreading invasive spider

Dispersal is an inseparable feature of animal life and a major determinant of species distributions and range dynamics. However, the role of the genetic architecture of dispersal behaviour, and hence the potential for its evolution in range-expanding species, is poorly understood. Here, we aimed to determine the heritability of dispersal behaviour for an invasive dwarf spider, Mermessus trilobatus , which has undergone rapid range expansion in Europe in the last few decades. Our results showed that spider dispersal traits were repeatable for the parental generation and heritable through both dam and sire. Behaviours were similarly heritable for female and male offspring. Interestingly, offspring of highly dispersive dams and sires exhibited almost three times higher dispersal propensity than offspring of at least one low-dispersive parent. The substantially high dispersal behaviour of the offspring of strictly highly vagile dams and sires indicates its recessive inheritance in this species. Recessive inheritance could favour invasiveness by facilitating high dispersal in inbred founder populations at the invasion front and returning to nonexaggerated mobility soon after an increase in genetic diversity. • Dispersal propensity appeared to be recessively inherited in an invasive spider. • Variation in dispersal was present despite a presumably small founder population. • On average dam and sire contributed to 37% of individual variation in dispersal. • Spiders' dispersal traits were consistent at the individual level. • There is a potential to evolve for high dispersal at the invasion front.

Stellar populations in local AGNs: evidence for enhanced star formation in the inner 100 pc

ABSTRACT In modern models and simulations of galactic evolution, the star formation in massive galaxies is regulated by an ad hoc active galactic nuclei (AGN) feedback process. However, the physics and the extension of such effects on the star formation history of galaxies is matter of vivid debate. In order to shed some light in the AGN effects over the star formation, we analysed the inner 500 × 500 pc of a sample of 14 Seyfert galaxies using GMOS and MUSE integral field spectroscopy. We fitted the continuum spectra in order to derive stellar age, metallicity, velocity, and velocity dispersion maps in each source. After stacking our sample and averaging their properties, we found that the contribution of young SP, as well as that of AGN featureless continuum both peak at the nucleus. The fraction of intermediate-age SPs is smaller in the nucleus if compared to outer regions, and the contribution of old SPs vary very little within our field of view (FoV). We also found no variation of velocity dispersion or metallicity within our FoV. Lastly, we detected an increase in the dust reddening towards the center of the galaxies. These results lead us to conclude that AGN phenomenon is usually related to a recent star formation episode in the circumnuclear region.

Post‐fledging spatial dispersion and movement behaviour differs between cavity‐nesting and open‐cup nesting passerines

Spatial dispersion and movement behaviour of siblings vary across animal taxa and can affect fitness. The factors underlying why species differ in movement behaviour of young and why some species form family groups while other species have dispersed young have rarely been addressed. We tested a hypothesis that siblings should be more dispersed in space and move less in species that have offspring with poor locomotor abilities to reduce the chance of the loss of the whole brood. In contrast, siblings should aggregate and move more when their mobility and ability to avoid predators is strong. We tested this hypothesis using songbirds because cavity‐ versus open‐cup‐nesting species strongly contrast in nesting strategy. Offspring of species that nest in cavities leave the nest with well‐developed wings and initially are more mobile and incur lower predation rates than fledglings of species that nest in open‐cups. We used radiotelemetry to track fledglings of three cavity‐ and three open‐cup‐nesting songbird species to test whether young differ in spatial dispersion and movement behaviour between nest types. We found that mobile young of cavity‐nesting species moved farther on a daily basis but remained more aggregated as a family than the less mobile young of open‐cup‐nesting species. Movement distances increased with mobility as young aged, especially in open‐cup‐nesting species, but families of open‐cup‐nesting species remained dispersed throughout the first week after fledging. This variation in spatial dispersion and movement behaviour of young can have important implications for parental care strategies and juvenile survival.

Multiply improved positive matrix factorization for source apportionment of volatile organic compounds during the COVID-19 shutdown in Tianjin, China

Ambient concentrations of volatile organic compounds (VOCs) vary with emission rates, meteorology, and chemistry. Conventional positive matrix factorization (PMF) loses information because of dilution variations and chemical losses. Multiply improved PMF incorporates the ventilation coefficient, and total solar radiation or oxidants to reduce the effects of dispersion and chemical loss. These methods were applied to hourly speciated VOC data from November 2019 to March 2020 including during the COVID-19 shutdown. Various comparisons were made to assess the influences of these fluctuation drivers by time of day. Dispersion normalized PMF (DN-PMF) reduced the dispersion variations. Dispersion-radiation normalized PMF (DRN-PMF) reduced the impact of chemical loss, especially at night, which was better than Dispersion-Ox normalized PMF (DON-PMF). The conditional bivariate probability function (CBPF) plots of DRN-PMF results were consist with actual source locations. The DN-PMF, DRN-PMF, and DON-PMF results were consistent between 10:00 and 15:00, suggesting dispersion was significantly more influential than photochemical reactions during these times. The DRN-PMF results indicated that the highest VOC contributors during the COVID-19 shutdown were liquefied petroleum gas (LPG) (28.8%), natural gas (25.2%), and pulverized coal boilers emissions (19.6%). Except for petrochemical-related enterprises and LPG, the contribution concentrations of all other sources decreased substantially during the COVID-19 shutdown, by 94.7%, 90.6%, and 86.8% for vehicle emissions, gasoline evaporation, and the mixed source of diesel evaporation and solvent use, respectively. Controlling the use of motor vehicles and related volatilization of diesel fuel and gasoline can be effective in controlling VOCs in the future.

Maintaining chromatic dispersion and signal gain performances in a chalcogenide buffer step-index optical fiber.

Aiming at maintaining the chromatic dispersion properties and fiber optical parametric amplification (FOPA) performance when fiber core fluctuation occurs, we propose a buffer step-index optical fiber. The AsSe2 chalcogenide glass is employed as the core material due to its high nonlinearity and broad transmission spectrum. The calculated results in this study show that the chromatic dispersion variation due to the change of core diameter can be greatly suppressed and a continuous and very broad FOPA signal gain spectrum can be obtained and maintained by carefully controlling the core, buffer and cladding properties such as refractive index and diameters. The calculated results in this study showed that by using the proposed 3-cm-long fiber pumped at 5.02 µm, a broad signal gain bandwidth from 3 to 14 µm at about 15 dB is attainable although the fiber core diameter Dc drastically fluctuated from 2 to 5 µm and the buffer diameter Db varies from 8.9 to 9.3 µm. Moreover, when Dc varies in smaller range from 3 to 4 µm, the FOPA signal gain spectra calculated at different fixed values of Db in the range from 8.9 to 9.3 µm are highly maintained. When Db is kept at 9.0 µm and Dc varies from 3 to 4 µm, the calculated FOPA signal gain spectra at different pump wavelengths from 4.98 to 5.02 µm are also nearly identical in the wavelength range from 3 up to 13 µm.

TO DEVELOP FORENSIC CRITERIA FOR THE DIFFERENTIAL DIAGNOSIS OF INTRACEREBRAL HEMORRHAGE OF TRAUMATIC AND NON-TRAUMATIC ORIGIN USING MUELLER-MATRIX MICROSCOPY OF LINEAR DICHROISM

Differential diagnosis of intracerebral hemorrhage due to traumatic and non-traumatic origin is a challenging issue, especially in the absence of visible body injuries and other signs of violence. For a forensic expert-practitioner, the main thing is objectivity, accuracy, and speed of obtaining the result, which could fully satisfy the methods of laser polarimetry in the case of differential diagnosis of hemorrhages of traumatic and non-traumatic origin in the human brain matter.&#x0D; The purpose: To develop forensic criteria for the differential diagnosis of intracerebral hemorrhage of traumatic and non-traumatic origin using Mueller-matrix microscopy of linear dichroism.&#x0D; Materials and methods: The object of the study was brain matter samples, collected in 115 corpses of both sexes aged 22 to 86 years with accurately known causes of death. The causes of death included coronary artery disease, traumatic brain hemorrhage, ischemic brain infarction, and non-traumatic brain hemorrhages. Brain matter samples have been frozen rapidly, and histological sections have been made using a freezing microtome. The slices have been evaluated using the method of azimuthal-invariant Mueller-matrix microscopy, followed by mathematical and statistical processing of the results. &#x0D; Results: significant topographic heterogeneity of Mueller-matrix invariants of brain matter samples linear dichroism maps among all research groups have been found. Individual and significant variations of dispersion, asymmetry, and kurtosis magnitude have confirmed the heterogeneity of Mueller-matrix invariants. The difference of images and histograms among groups is explained by the presence of necrotic changes in the case of ischemic brain necrosis and blood cells in the brain matter samples. For the set of central statistical moments of the 1st, 3rd, and 4th orders, which characterize the distributions of circular dichroism, the method of MM-microscopy in the differentiation of samples of non-hemorrhage and hemorrhage groups reaches a satisfactory level - 78% - 84%.&#x0D; Conclusions: Brain matter samples Muller-matrix microscopy of linear dichroism is effective for solving diagnostic problems of forensic medicine related to evaluating the cause of death from intracerebral hemorrhage of various origins. Diagnostic efficiency of Mueller-matrix mapping of polarization manifestations of linear dichroism method for intergroup differentiation of samples of deaths from traumatic hemorrhage (Group 2) and ischemic cerebral infarction (Group 3) reaches a satisfactory level of 79 - 84%.

Global reference seismological data sets: multimode surface wave dispersion

SUMMARYGlobal variations in the propagation of fundamental-mode and overtone surface waves provide unique constraints on the low-frequency source properties and structure of the Earth’s upper mantle, transition zone and mid mantle. We construct a reference data set of multimode dispersion measurements by reconciling large and diverse catalogues of Love-wave (49.65 million) and Rayleigh-wave dispersion (177.66 million) from eight groups worldwide. The reference data set summarizes measurements of dispersion of fundamental-mode surface waves and up to six overtone branches from 44 871 earthquakes recorded on 12 222 globally distributed seismographic stations. Dispersion curves are specified at a set of reference periods between 25 and 250 s to determine propagation-phase anomalies with respect to a reference Earth model. Our procedures for reconciling data sets include: (1) controlling quality and salvaging missing metadata; (2) identifying discrepant measurements and reasons for discrepancies; (3) equalizing geographic coverage by constructing summary rays for travel-time observations and (4) constructing phase velocity maps at various wavelengths with combination of data types to evaluate inter-dataset consistency. We retrieved missing station and earthquake metadata in several legacy compilations and codified scalable formats to facilitate reproducibility, easy storage and fast input/output on high-performance-computing systems. Outliers can be attributed to cycle skipping, station polarity issues or overtone interference at specific epicentral distances. By assessing inter-dataset consistency across similar paths, we empirically quantified uncertainties in traveltime measurements. More than 95 per cent measurements of fundamental-mode dispersion are internally consistent, but agreement deteriorates for overtones especially branches 5 and 6. Systematic discrepancies between raw phase anomalies from various techniques can be attributed to discrepant theoretical approximations, reference Earth models and processing schemes. Phase-velocity variations yielded by the inversion of the summary data set are highly correlated (R ≥ 0.8) with those from the quality-controlled contributing data sets. Long-wavelength variations in fundamental-mode dispersion (50–100 s) are largely independent of the measurement technique with high correlations extending up to degree ∼25. Agreement degrades with increasing branch number and period; highly correlated structure is found only up to degree ∼10 at longer periods (T &amp;gt; 150 s) and up to degree ∼8 for overtones. Only 2ζ azimuthal variations in phase velocity of fundamental-mode Rayleigh waves were required by the reference data set; maps of 2ζ azimuthal variations are highly consistent between catalogues ( R = 0.6–0.8). Reference data with uncertainties are useful for improving existing measurement techniques, validating models of interior structure, calculating teleseismic data corrections in local or multiscale investigations and developing a 3-D reference Earth model.

Tan's adiabatic sweep theorem from the variational theorem for the scattering length

It is shown that variation of the one-particle dispersion in a universal many-body system enables us to obtain Tan's adiabatic sweep theorem and its generalization. The derivation is based on the Hellmann-Feynman theorem and the variational theorem for the scattering length suggested in our previous paper [Cherny and Shanenko, Phys. Rev. E 62, 1646 (2000)]. As an example, the universal effects in the system of spinless bosons are considered. With the help of the variational theorem, we obtain the mean kinetic and interaction energies and derive the virial theorem for the homogeneous and trapped bosons. The results can easily be generalized to the two-component fermions with interactions between opposite spins.

Measurements of the Expansion Velocities of Ionized-Gas Superbubbles in Nearby Galaxies Based on Integral Field Spectroscopy Data

The study of the dynamic properties of bubbles in the interstellar medium is important for understanding the feedback mechanisms from star-formation processes in galaxies. The ongoing integral field spectroscopy of nearby star-forming galaxies reveals many expanding bubbles and superbubbles identified by the local increase in gas velocity dispersion. The limited angular resolution often prevents bona fide measures of the expansion velocities in galaxies outside the Local Group, even despite sufficient spectroscopic resolution. We present a method that makes it possible to measure the expansion velocity of bubbles surrounding massive stars and clusters based on the data about local variations in gas velocity dispersion. We adapt the method for the Fabry-Perot interferometers used with the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences, as well as for any integral field spectrograph with a Gaussian line spread function. We apply the method described to analyze the kinematics of ionized superbubbles gas and the only known supernova remnant in the IC 1613 galaxy. The estimate of the kinematic age of the supernova remnant (on the order of 3100 years) agrees well with the previously obtained independent estimate based on X-ray data.

Geographic variation in dispersal of western burrowing owl (Athene cunicularia hypugaea) populations across North America

Abstract Dispersal is one of the key elements of species’ metapopulation dynamics and, hence, influences global conservation status. Furthermore, determining the geographic variation in magnitude and direction of dispersal throughout a species’ distribution may expand our understanding of the causes of population declines in species of conservation concern. For instance, western burrowing owl (Athene cunicularia hypugaea) populations have declined at the northern and eastern edge of their breeding distribution during the 20th century. In the same period, large areas of thornscrub that did not support breeding owls were converted to irrigated agriculture in the southern edge of the subspecies’ breeding distribution in northwestern Mexico. These farmlands now support some of the highest breeding densities of owls. We tested the hypothesis that owls that colonized this recently created habitat originated from declining migratory populations from the northern portion of the subspecies’ range. We used stable isotopes 2H, 13C, and 15N in owl feathers to infer breeding dispersal patterns throughout the subspecies’ breeding range. Populations near the northern edge of the subspecies’ breeding range had immigrants that dispersed over larger distances than immigrants at low and mid latitude populations. However, agricultural populations in northwestern Mexico disrupted this latitudinal pattern, attracting owls from more distant locations. We also found immigrants originated from further distances in declining populations than increasing populations. Stable isotopes provided no evidence of contemporaneous breeding dispersal from Canadian populations to northwestern Mexico but suggest that agricultural areas in the southern edge of the subspecies’ distribution have altered the continental dispersal pattern.

Top predator introduction changes the effects of spatial isolation on freshwater community structure.

Current conceptual metacommunity models predict that the consequences of local selective pressures on community structure increase with spatial isolation when species favored by local conditions also have higher dispersal rates. This appears to be the case of freshwater insects in the presence of fish. The introduction of predatory fish can produce trophic cascades in freshwater habitats because fish tend to prey upon intermediate predatory taxa, such as predatory insects, indirectly benefiting herbivores and detritivores. Similarly, spatial isolation can limit dispersal and colonization rates of predatory insects more strongly than of herbivores and detritivores, thus generating similar cascading effects. Here we tested the hypothesis that the effect of introduced predatory fish on insect community structure increases with spatial isolation by conducting a field experiment in artificial ponds that manipulated the presence/absence of fish (the redbreast tilapia) at three different distances from a source wetland. Our results showed that fish have direct negative effects on the abundance of predatory insects but probably have variable net effects on the abundance of herbivores and detritivores because the direct negative effects of predation by fish may offset indirect positive ones. Spatial isolation also resulted in indirect positive effects on the abundance of herbivores and detritivores but this effect was stronger in the absence rather than in the presence of fish so that insect communities diverged more strongly between fish and fishless ponds at higher spatial isolation. We argue that an important additional mechanism, ignored in our initial hypothesis, was that as spatial isolation increases fish predation pressure upon herbivores and detritivores increases due to the relative scarcity of predatory insects, thus dampening the positive effect that spatial isolation confers to lower trophic levels. Our results highlight the importance of considering interspecific variation in dispersal and multiple trophic levels to better understand the processes generating community and metacommunity patterns.

Variations of Movement, Dispersal, and Morphometrics among Subpopulations of Javan Endemic Damselfly, &lt;i&gt;Drepanosticta spatulifera&lt;/i&gt; (Odonata: Platystictidae) in Petungkriyono Forest

Drepanosticta spatulifera is a Javan endemic damselfly. The population is spread unevenly in the Petungkriyono Forest and is threatened due to environmental pressure. The aims of this research are to know the variation of the movement, dispersal, and morphometric among subpopulations of D. spatulifera. Movement and dispersal variation data collection was done using Mark Release Recapture (MRR) for six weeks from early August until mid-September 2020. The collection of morphometric samples was done during the last week of the MRR survey and 46 individuals were measured with 12 continuous characters. During the MRR survey, 596 males of D. spatulifera were marked and 302 were recaptured. D. spatulifera had short movement and dispersal thus no individuals were found across the subpopulations. The distance moved of successive capture and net lifetime movement were dominantly less or equal to five meters. The duration of the MRRsurvey had a low correlation with the dispersal distance of D. spatulifera. In themorphometric variations, closer subpopulations tended to have a similar cluster ofmorphometric characters. Variation of distance moved between successive captureand wing size from Mangli Stream was significantly different from other sites. Thesubpopulation of Mangli, the farthest and higher altitude of the sites, had thehighest distance move, more disperse, and the largest wing size. Our study showedthat D. spatulifera was extremely sedentary damselfly. It will enhance inbreeding andvulnerability to extinction. Therefore, the interaction between the subpopulationsof D. spatulifera in the Petungkriyono Forest needs to be done more.

Variation of structure and optical material dispersion in lead borate glass containing multi valence chromium and germanium cations

In pursuit of manufacturing glass having a high refractive index and low dispersion, a series of lead and borate glasses containing germanium and chromium oxide by composition 25B2O3-73.8PbO-xGeO2-(1.2 − x)Cr2O3, with 0 ≤ x ≤ 1.2 mol.%, are prepared. IR measurements are carried out to explore the structure of as-prepared samples. The deconvoluted IR peaks revealed presence of bridging oxygen up to x = 0.6 mol%. At x > 0.6 mol% none bridging oxygen is the dominant. The dependence of the measured hydrostatic density and corresponding molar volume for the studied compositions are analyzed and discussed. The dispersion curves of refractive index (n) and absorption index (k) are calculated in the spectral range 300–2500 nm. The effect of increasing the ratio GeO2/[GeO2 + Cr2O3] on the calculated dispersion energy, lattice energy, oscillator energy and material dispersion are deduced. For photonic applications, the wavelength at zero material dispersion for the investigated samples is calculated and compared with other systems based on Borates, silicates and Germinate fiber. The results recommend that the present glass could be used in different modern optoelectronics devices.

Dispersal evolution in temporally variable environments: implications for plant range dynamics.

Dispersal-the movement of an individual from the site of birth to a different site for reproduction-is an ecological and evolutionary driver of species ranges that shapes patterns of colonization, connectivity, gene flow, and adaptation. In plants, the traits that influence dispersal often vary within and among species, are heritable, and evolve in response to the fitness consequences of moving through heterogeneous landscapes. Spatial and temporal variation in the quality and quantity of habitat are important sources of selection on dispersal strategies across species ranges. While recent reviews have evaluated the interactions between spatial variation in habitat and dispersal dynamics, the extent to which geographic variation in temporal variability can also shape range-wide patterns in dispersal traits has not been synthesized. In this paper, we summarize key predictions from metapopulation models that evaluate how dispersal evolves in response to spatial and temporal habitat variability. Next, we compile empirical data that quantify temporal variability in plant demography and patterns of dispersal trait variation across species ranges to evaluate the hypothesis that higher temporal variability favors increased dispersal at plant range limits. We found some suggestive evidence supporting this hypothesis while more generally identifying a major gap in empirical work evaluating plant metapopulation dynamics across species ranges and geographic variation in dispersal traits. To address this gap, we propose several future research directions that would advance our understanding of the interplay between spatiotemporal variability and dispersal trait variation in shaping the dynamics of current and future species ranges.

Distributed Sensing with Low-Cost Mobile Sensors Toward a Sustainable IoT

Cities are monitored by sparsely positioned high-cost reference stations that fail to capture local variations. Although these stations must be ubiquitous to achieve high spatio-temporal resolutions, the required capital expenditure makes that infeasible. Here, low-cost IoT devices come into prominence; however, non-disposable and often non-rechargeable batteries they have pose a huge risk for the environment. The projected numbers of required IoT devices will also yield to heavy network traffic, thereby crippling the RF spectrum. To tackle these problems and ensure a more sustainable IoT, cities must be monitored with fewer devices extracting highly granular data in a self-sufficient manner. Hence, this paper introduces a network architecture with energy harvesting low-cost mobile sensors mounted on bikes and unmanned aerial vehicles, underpinned by key enabling technologies. Based on the experience gained through real-world trials, a detailed overview of the technical challenges encountered when using low-cost sensors and the requirements for achieving high spatio-temporal resolutions in the 3D space are highlighted. Finally, to show the capability of the envisioned architecture in distributed sensing, a case study on air quality monitoring investigating the variations in particulate and gaseous pollutant dispersion during the first lockdown of the COVID.19 pandemic is presented. The results showed that using mobile sensors is as accurate as using stationary ones with the potential of reducing device numbers, leading to a more sustainable IoT.