Spatial Isolation Research Articles

Gravitational scaling analysis on spatial diffusion of COVID-19 in Hubei Province, China.

The spatial diffusion of epidemic disease follows distance decay law in geography and social physics, but the mathematical models of distance decay depend on concrete spatio-temporal conditions. This paper is devoted to modeling spatial diffusion patterns of COVID-19 stemming from Wuhan city to Hubei province, China. The modeling approach is to integrate analytical method and experimental method. The local gravity model is derived from allometric scaling and global gravity model, and then the parameters of the local gravity model are estimated by observational data and least squares calculation. The main results are as below. The local gravity model based on power law decay can effectively describe the diffusion patterns and process of COVID-19 in Hubei Province, and the goodness of fit of the gravity model based on negative exponential decay to the observational data is not satisfactory. Further, the goodness of fit of the model to data entirely became better and better over time, the size elasticity coefficient increases first and then decreases, and the distance attenuation exponent decreases first and then increases. Moreover, the significance of spatial autoregressive coefficient in the model is low, and the confidence level is less than 80%. The conclusions can be reached as follows. (1) The spatial diffusion of COVID-19 of Hubei bears long range effect, and the size of a city and the distance of the city to Wuhan affect the total number of confirmed cases. (2) Wuhan direct transmission is the main process in the spatial diffusion of COVID-19 in Hubei at the early stage, and the horizontal transmission between regions is not significant. (3) The effect of spatial lockdown and isolation measures taken by Chinese government against the transmission of COVID-19 is obvious. This study suggests that the role of urban gravity (size and distance) should be taken into account to prevent and control epidemic disease.

Liminality, third-culture and hope in a quarantine camp

Through the experience of a quarantine camp in Vietnam, the essay discusses how the experience was a third-culture phenomenon in overdrive because of spatial and social isolation. Through such resemblance, the author points toward a path to understanding and embracing third-culture in the larger context of globalization.

Simulation of Spatiotemporal Relationship between COVID-19 Propagation and Regional Economic Development in China

Coronavirus disease 2019 (COVID-19) propagation in 2019 posed serious threats and challenges to human public health and safety. Currently, COVID-19 is still not effectively controlled in certain countries and regions. This study combines the traditional susceptible-exposed-infectious-recovered (SEIR) model, system dynamics (SD) model, and cellular automata (CA) model to construct a spatiotemporal dynamics pandemic model (SDPM). The SDPM is used to dynamically depict the spatiotemporal diffusion and outbreak of COVID-19 through research on the relationship between epidemic spread and regional development. The results show that: (1) There is a positive correlation between regional development and epidemic spread. The more developed the regional economy, especially in areas with short-range population migration from Hubei Province, the more severe the epidemic spread; and (2) The spatial isolation and control measures adopted by the government can effectively prevent the COVID-19 spread. The results explore the relationship between COVID-19 spread and regional economic development by studying the spatial and temporal transmission characteristics of COVID-19, and provide a scientific reference for the government to formulate reasonable response measures.

Efficient method to identify hidden node collision and improving Quality-of-Service (QoS) in wireless sensor networks

The proposed approach is designed to boost the IEEE 802.15.4 / ZigBee-based WSN streaming efficiency by introducing multipurpose routing. We investigate how those networks can be designed in order to achieve optimum throughput using computational models to explain intra-track and inter-track interference in multipath routing networks. One mode of action in particular – Spatial-TDMA (S-TDMA), Zig Bee dependent WSNs, will greatly reduce the amount of interference, both in one- and multi-track environments. It is also seen that two-way networks can be stronger than their one-way counterparts by means of deliberately selected implementation parameters. Finally, a greater degree of spatial isolation between the routes used indicates improved average efficiency in multi-path scenarios. The simulation is one of our results.

Disentangling the distinct mechanisms shaping the subsurface oil reservoir bacterial and archaeal communities across northern China

Microbes in surface ecosystem exhibit strong biogeographic patterns, and are less apparent after human management. However, in contrast with the considerable knowledge on the surface ecosystem, the microbial biogeographic patterns in deep subsurface ecosystem under artificial disturbance is poorly understood. Here, we explored the spatial scale-dependence patterns of bacterial and archaeal communities in oil reservoirs under different artificial flooding duration and environmental conditions across northern China. Bacterial and archaeal communities of oil reservoirs exhibited distinct assembly patterns with a stronger distance-decay relationship in archaeal communities than bacterial communities, as different environmental factors linked to the diversity of bacteria and archaea. Specifically, bacterial and archaeal network properties revealed a significant correlation with spatial reservoir isolation by distinct co-occurrence patterns. The co-occurrences of bacterial communities were more complex in high temperature and alkaline pH, while archaeal co-occurrences were more frequent in low temperature and neutral pH. Potential functions in bacterial communities were more connected with chemoheterotrophy, whereas methanogenesis was abundant in archaeal communities, as confirmed by both keystone taxa and main ecological clusters in networks. This revealed that different mechanisms underlain geography and co-occurrence patterns of bacteria and archaea in oil reservoirs, providing a new insight for understanding biogeography and coexistence theory in deep subsurface ecosystem.

A spatial interpretation of Australia's COVID-vulnerability

The school of social vulnerability in disaster sciences offers an alternative perspective on the current COVID-19 (coronavirus) pandemic crisis. Social vulnerability in general can be understood as a risk of exposure to hazard impacts, where vulnerability is embedded in the normal functioning of the society. The COVID-19 pandemic has exposed systemic (political and health care systems), demographic (aging, race) and,based on the results of our approach, spatial (spatial isolation and connectivity) yvulnerabilities as well. In this paper, we develop a risk prediction model based on two composite indicators of social vulnerability. These indicators reflect the two main contrasting risks associated with COVID-19, demographic vulnerability and, as consequences of the lockdowns, economic vulnerability. We conceptualise social vulnerability in the context of the extremely uneven spatial population distribution in Australia. Our approach helps extend understanding about the role of spatiality in the current pandemic disaster.

No pre-zygotic isolation mechanisms between Schistosoma haematobium and Schistosoma bovis parasites: From mating interactions to differential gene expression.

Species usually develop reproductive isolation mechanisms allowing them to avoid interbreeding. These preventive barriers can act before reproduction, "pre-zygotic barriers", or after reproduction, "post-zygotic barriers". Pre-zygotic barriers prevent unfavourable mating, while post-zygotic barriers determine the viability and selective success of the hybrid offspring. Hybridization in parasites and the underlying reproductive isolation mechanisms maintaining their genetic integrity have been overlooked. Using an integrated approach this work aims to quantify the relative importance of pre-zygotic barriers in Schistosoma haematobium x S. bovis crosses. These two co-endemic species cause schistosomiasis, one of the major debilitating parasitic diseases worldwide, and can hybridize naturally. Using mate choice experiments we first tested if a specific mate recognition system exists between both species. Second, using RNA-sequencing we analysed differential gene expression between homo- and hetero-specific pairing in male and female adult parasites. We show that homo- and hetero-specific pairing occurs randomly between these two species, and few genes in both sexes are affected by hetero-specific pairing. This suggests that i) mate choice is not a reproductive isolating factor, and that ii) no pre-zygotic barrier except spatial isolation "by the final vertebrate host" seems to limit interbreeding between these two species. Interestingly, among the few genes affected by the pairing status of the worms, some can be related to pathways affected during male and female interactions and may also present interesting candidates for species isolation mechanisms and hybridization in schistosome parasites.

Photosynthetically stimulated bioerosion in symbiotic sponges: the role of glycerol and oxygen

On coral reefs, some of the most aggressive calcium carbonate eroders are dinoflagellate-hosting sponges of the genus Cliona. Like in other marine taxa, the influence of these symbiotic microorganisms on the metabolism of the host sponge, and thereby on erosion of the surrounding ecosystem, is increasingly acknowledged. Despite elevating pH (and hence carbonate saturation state), dinoflagellate photosynthesis promotes bioerosion by their hosts. This paradox might be solved by a spatial isolation of photosynthesis from carbonate dissolution, but it remains unknown which mechanism connects the dinoflagellates’ photosynthesis with the sponge’s bioerosion. Here, we simulate the outcomes of photosynthesis in two separate ways, namely as production of carbon-rich compounds (in this case glycerol) and as an increase in oxygen content. This allows testing their potential to enhance bioerosion rates of sponge holobionts that were preconditioned under variable photosynthetic regimes. We find that glycerol, a commonly shared photosynthate in marine symbioses, stimulates chemical bioerosion rates in the dark of photosynthetically impaired sponges. Chemical bioerosion was all the more limited by availability of sufficient oxygen, while the combination of added glycerol and oxygen boosted chemical bioerosion rates. We argue that under normal physiological conditions, bioerosion is promoted by both organic carbon and oxygen production, and we provide evidence for the storage of photosynthates for night-time use. We further discuss our findings in the context of the current knowledge of the bioerosion mechanism, which we expand by integrating the effects of carbon-rich compounds and oxygen as drivers for bioerosion by Cliona.

Approaching Charge Separation Efficiency to Unity without Charge Recombination.

Improving the efficiency of charge separation (CS) and charge transport (CT) is essential for almost all optoelectronic applications, yet its maximization remains a big challenge. Here we propose a conceptual strategy to achieve CS efficiency close to unity and simultaneously avoid charge recombination (CR) during CT in a ferroelectric polar-discontinuity (PD) superlattice structure, as demonstrated in (BaTiO_{3})_{m}/(BiFeO_{3})_{n}, which is fundamentally different from the existing mechanisms. The competition of interfacial dipole and ferroelectric PD induces opposite band bending in BiFeO_{3} and BaTiO_{3} sublattices. Consequently, the photoexcited electrons (e) and holes (h) in individual sublattices move forward to the opposite interfaces forming electrically isolated e and h channels, leading to a CS efficiency close to unity. Importantly, the spatial isolation of conduction channels in (BaTiO_{3})_{m}/(BiFeO_{3})_{n} enable suppression of CR during CT, thus realizing a unique band diagram for spatially orthogonal CS and CT. Remarkably, (BaTiO_{3})_{m}/(BiFeO_{3})_{n} can maintain a high photocurrent and large band gap simultaneously. Our results provide a fascinating illumination for designing artificial heterostructures toward ideal CS and CT in optoelectronic applications.

Wet-Etched Microlens Array for 200 nm Spatial Isolation of Epitaxial Single QDs and 80 nm Broadband Enhancement of Their Quantum Light Extraction.

Uniform arrays of three shapes (, , and ) of GaAs microlenses (MLs) by wet-etching are demonstrated, ∼200 nm spatial isolation of epitaxial single QDs embedded (: 890–990 nm) and broadband ( nm) enhancement of their quantum light extraction are obtained, which is also suitable for telecom-band epitaxial QDs. Combined with the bottom distributed Bragg reflector, the -shaped ML forms a cavity and achieves the best enhancement: extraction efficiency of 26%, Purcell factor of 2 and single-photon count rate of counts per second at the first lens; while the -shaped ML shows a broader band (e.g., longer ) enhancement. In the MLs, single QDs with featured exciton emissions are observed, whose time correlations prove single-photon emission with multi-photon probability ; some QDs show both biexciton and exciton X emissions and exhibit a perfect cascade feature. This work could pave a step towards a scalable array of QD single-photon sources and the application of QD photon-pair emission for entanglement experiments.

Steering spatially separated dual sites on nano-TiO2 through SMSI and lattice matching for robust photocatalytic hydrogen evolution

Spatial isolation of different functional sites at the nanoscale in multifunctional catalysts for steering reaction sequence and paths remains a major challenge. Herein, we reported the spatial separation of dual-site Au and RuO2 on the nanosurface of TiO2 (Au/TiO2/RuO2) through the strong metal-support interaction (SMSI) and the lattice matching (LM) for robust photocatalytic hydrogen evolution. The SMSI between Au and TiO2 induced the encapsulation of Au nanoparticles by an impermeable TiOx overlayer, which can function as a physical separation barrier to the permeation of the second precursor. The LM between RuO2 and rutile-TiO2 can increase the stability of RuO2/TiO2 interface and thus prevent the aggregation of dual-site Au and RuO2 in the calcination process of removing TiOx overlayer of Au. The photocatalytic hydrogen production is used as a model reaction to evaluate the performance of spatially separated dual-site Au/TiO2/RuO2 catalysts. The rate of hydrogen production of the Au/TiO2/RuO2 is as high as 84 μmol h−1 g−1 under solar light irradiation without sacrificial agents, which is 2.5 times higher than the reference Au/TiO2 and non-separated Au/RuO2/TiO2 samples. Systematic characterizations verify that the spatially separated dual-site Au and RuO2 on the nanosurface of TiO2 can effectively separate the photo-generated carriers and lower the height of the Schottky barrier, respectively, under UV and visible light irradiation. This study provides new inspiration for the precise construction of different sites in multifunctional catalysts.

Numerical and Species Composition of Insects Transmitting Viral Infection in North Ossetia

One of the major tasks in the production of original and elite potato seeds is to prevent the rapid re-infection of the healthy material with viruses in the open field. The high rate of infection with each subsequent reproduction reduces seed productivity and worsens the tuber varietal quality. Currently, about two dozen viruses that infect potatoes have been identified. In the field, most of the harmful viruses of potatoes are transmitted by insects such as aphids, cicadas and bedbugs. The purpose of our research was to study the species composition of transmitters and the intensity of their flight in North Ossetia. Studying the activity of the winged aphid vector is a prerequisite for the implementation of protective measures against re-infection of the sanitized material with viruses. The most important criteria characterizing aphids in transferring potato viruses during the growing season were as follows: the species composition, the dynamics of the potato planting periods, the timing of the critical threshold with regards to the number of aphids, and the total vector intensity during the growing season. There are very few aphid vectors in the mountain zone of the Republic of North Ossetia, which is at and above an altitude of 1,650 meters above sea level. Therefore, mountain regions of this height are a natural insulator against viral infection. In the foothill zone, the most numerous aphid vectors are bean, buckthorn, and alder buckthorn-willowherb aphids, whose number varies from 35 to 280 individuals per year on a Merike trap.
 Keywords: potatoes, insect vectors, a Merike trap, mountain zone, spatial isolation

Processes of change in the Hungarian and Ukrainian Community in Izsnyéte, Transcarpathia

I started my research in Izsnyéte, Transcarpathia, in 2012 with an anthropological research group. Initially, we were curious about the coexistence mechanisms of the local settlement, the cultural peculiarities of the ethnic groups living there, but due to the war situation, we had to stop our empirical research sooner before 2015. In 2017, as a doctoral student, I continued my empirical research in Izsnyéte, where Hungarians represent an absolute majority against the state-forming Ukrainian ethnic group. The basic research concept was to choose a local settlement close to the border where two or three different ethnicities have lived together for decades. In my study, I examine the process of ethnicity production and the processes of image and change of the living ethnicities of the settlement and their applicability to each other in comparison with the data of previous research, reflecting on the changes, mainly in the light of assimilation. Already the results of the 2012 research showed spatial isolation, in many cases dissimilation was experienced among coexisting ethnicities, but with many other factors and aspects several years later, it caused diverse processes.

Assembly of abundant and rare bacterial and fungal sub-communities in different soil aggregate sizes in an apple orchard treated with cover crop and fertilizer

Soil bacterial and fungal communities often comprise the “abundant biosphere” and “rare biosphere”, which co-exist in soil aggregates to form a complex system of inter-species interactions. However, the different assembly processes exhibited by abundant and rare bacterial and fungal communities due to the spatial isolation of aggregates are still unclear. In this study, the stochastic and deterministic processes associated with the assembly of abundant and rare sub-communities of bacteria and fungi were quantified in different sized soil aggregates in apple orchards treated with a cover crop and fertilizer. The importance of variable selection in the assembly of the abundant bacterial community increased from macroaggregates to small microaggregates. The assembly of the rare bacterial community followed a transition from homogeneous selection to weak homogeneous selection with decreases in the soil organic carbon and total nitrogen contents. Both the abundant and rare bacterial community assemblies in soil aggregates were not limited in terms of their dispersal. The assembly of the abundant fungal community was dominated by stochastic processes, whereas the assembly of the rare fungal community was dominated by homogeneous selection and limited dispersal in different sized soil aggregates. The compositions of the abundant and rare bacterial and fungal communities were also affected by soil aggregates and agricultural practices. Most of the top 20 operational taxonomic units (OTUs) with high abundances among bacteria and fungi were related to the macroaggregate amounts compared with rare bacteria and fungi, and some OTUs among abundant fungi were related to the microaggregate and small microaggregate amounts. This study provides a priori hypotheses for testing in future experiments, thereby facilitating a systematic approach to understand the mechanisms responsible for the changes in the fungal and bacterial community compositions in different sized soil aggregates.

Detection of Serratia marcescens in neonatal intensive care units requires a rapid and comprehensive infection control response starting with the very first case.

Background: Serratia marcescens is a well-known and challenging pathogen in neonatal intensive care units. It is responsible for severe infections and can cause nosocomial outbreaks. Methods: We present the infection control response to a Serratia marcescens cluster which occurred in a tertiary neonatal intensive care unit. Results and conclusions: The presented comprehensive and decisive hygiene management response starting with the very first case aims especially at early detection and immediate interruption of nosocomial transmission. Frequent and sensitive microbiological screening, rigorous spatial isolation of colonized infants, and reinforcing adherence to hand hygiene are essential in this response, which comprises eight measures. It prevented a full-blown outbreak.

Ultrabright Fluorescent Organic Nanoparticles Based on Small-Molecule Ionic Isolation Lattices*.

Ultrabright fluorescent nanoparticles (NPs) hold great promise for demanding bioimaging applications. Recently, extremely bright molecular crystals of cationic fluorophores were obtained by hierarchical coassembly with cyanostar anion-receptor complexes. These small-molecule ionic isolation lattices (SMILES) ensure spatial and electronic isolation to prohibit aggregation quenching of dyes. We report a simple, one-step supramolecular approach to formulate SMILES materials into NPs. Rhodamine-based SMILES NPs stabilized by glycol amphiphiles show high fluorescence quantum yield (30 %) and brightness per volume (5000 M-1 cm-1 /nm3 ) with 400 dye molecules packed into 16-nm particles, corresponding to a particle absorption coefficient of 4×107 M-1 cm-1 . UV excitation of the cyanostar component leads to higher brightness (>6000 M-1 cm-1 / nm3 ) by energy transfer to rhodamine emitters. Coated NPs stain cells and are thus promising for bioimaging.

Ultrabright Fluorescent Organic Nanoparticles Based on Small‐Molecule Ionic Isolation Lattices**

AbstractUltrabright fluorescent nanoparticles (NPs) hold great promise for demanding bioimaging applications. Recently, extremely bright molecular crystals of cationic fluorophores were obtained by hierarchical coassembly with cyanostar anion‐receptor complexes. These small‐molecule ionic isolation lattices (SMILES) ensure spatial and electronic isolation to prohibit aggregation quenching of dyes. We report a simple, one‐step supramolecular approach to formulate SMILES materials into NPs. Rhodamine‐based SMILES NPs stabilized by glycol amphiphiles show high fluorescence quantum yield (30 %) and brightness per volume (5000 M−1 cm−1/nm3) with 400 dye molecules packed into 16‐nm particles, corresponding to a particle absorption coefficient of 4×107 M−1 cm−1. UV excitation of the cyanostar component leads to higher brightness (>6000 M−1 cm−1/ nm3) by energy transfer to rhodamine emitters. Coated NPs stain cells and are thus promising for bioimaging.

Hierarchical microcavity topography for enhancement of water vapor condensation heat transfer by regulating droplet dynamics and droplet size distribution

Manipulating droplet dynamics is of great importance in condensation heat transfer enhancement. Cavity topography was believed to be able to regulate droplet merging and self-removal via Laplace force imbalance by the cavity wall and the effect of spatial confinement and isolation. However, the size effect of the microcavity on the droplet dynamics behavior, droplet size distribution and condensation heat transfer performance are not sufficiently understood. In this paper, hierarchical microcavity-arrayed superhydrophobic surfaces with a nominal cavity diameter of 20, 35, 50 and 70 μm were fabricated. Condensation experiments were first carried out in the atmosphere under an optical microscope, and then in pure steam in a self-designed environmental chamber at 4000 Pa. Local dynamic behaviors and time-lapsed evolutions of droplets during condensation were observed. Droplet size distribution and jumping rate were statistically analyzed using ImageJ software. It was proved the smaller cavity size of 20 μm is beneficial to facilitate condensate droplet jumping and increase the density of small droplets. The surface coverage ratio on the microcavity-arrayed superhydrophobic surfaces was only half of that on the hydrophobic surface at steady state. Enhancement of pure steam condensation heat transfer can be realized by effectively regulating droplet dynamics using microcavity topographies at limited subcooling degrees.

A geographical perspective on the relationship between Impatiens spur lengths and bill lengths of sunbirds in Afrotropical mountains.

Trait matching—a correlation between the morphology of plants and their pollinators—has been frequently observed in pollination interactions. Different intensities of natural selection in individual regions should cause such correlations to be observable across different local assemblages. In this study, we focused on matching between spur lengths of the genus Impatiens and bill lengths of sunbirds in tropical Africa. For 25 mountain and island locations, we compiled information about the composition and traits of local Impatiens and sunbird assemblages. We found that assemblage mean and maximum values of bill lengths were positively correlated with mean and maximum spur lengths across locations. Moreover, our results suggest that the positive correlations hold only for forest sunbird assemblages sharing the same habitat with Impatiens species. We further show that long‐billed sunbirds seem to locally match the morphology of multiple Impatiens plant species, not vice versa. Our observation implies that trait matching significantly contributes to structuring of Impatiens–sunbird pollination systems. We suggest that special habitat preferences together with spatial isolation of mountain environment might play a role in this case.

Comparative Phylogeography of Veronica spicata and V. longifolia (Plantaginaceae) Across Europe: Integrating Hybridization and Polyploidy in Phylogeography.

Climatic fluctuations in the Pleistocene caused glacial expansion-contraction cycles in Eurasia and other parts of the world. Consequences of these cycles, such as population expansion and subsequent subdivision, have been studied in many taxa at intraspecific population level across much of the Northern Hemisphere. However, the consequences for the potential of hybridization and polyploidization are poorly understood. Here, we investigated the phylogeographic structure of two widespread, closely related species, Veronica spicata and Veronica longifolia, across their European distribution ranges. We assessed the extent and the geographic pattern of polyploidization in both species and hybridization between them. We used genome-scale SNP data to clarify phylogenetic relationships and detect possible hybridization/introgression events. In addition, crossing experiments were performed in different combination between V. spicata and V. longifolia individuals of two ploidy levels and of different geographic origins. Finally, we employed ecological niche modeling to infer macroclimatic differences between both species and both ploidy levels. We found a clear genetic structure reflecting the geographical distribution patterns in both species, with V. spicata showing higher genetic differentiation than V. longifolia. We retrieved significant signals of hybridization and introgression in natural populations from the genetic data and corroborated this with crossing experiments. However, there were no clear phylogeographic patterns and unequivocal macroclimatic niche differences between diploid and tetraploid lineages. This favors the hypothesis, that autopolyploidization has happened frequently and in different regions. The crossing experiments produced viable hybrids when the crosses were made between plants of the same ploidy levels but not in the interploidy crosses. The results suggest that hybridization occurs across the overlapping areas of natural distribution ranges of both species, with apparently directional introgression from V. spicata to V. longifolia. Nevertheless, the two species maintain their species-level separation due to their adaptation to different habitats and spatial isolation rather than reproductive isolation.