Natural Systems Research Articles

A taxonomy of multiple stable states in complex ecological communities.

Natural systems are built from multiple interconnected units, making their dynamics, functioning and fragility notoriously hard to predict. A fragility scenario of particular relevance concerns so-called regime shifts: abrupt transitions from healthy to degraded ecosystem states. An explanation for these shifts is that they arise as transitions between alternative stable states, a process that is well-understood in few-species models. However, how multistability upscales with system complexity remains a debated question. Here, we identify that four different multistability regimes generically emerge in models of species-rich communities and other archetypical complex biological systems assuming random interactions. Across the studied models, each regime consistently emerges under a specific interaction scheme and leaves a distinct set of fingerprints in terms of the number of observed states, their species richness and their response to perturbations. Our results help clarify the conditions and types of multistability that can be expected to occur in complex ecological communities.

A spectroscopic study of the stability of uranyl-carbonate complexes at 25–150 °C and re-visiting the data available for uranyl-chloride, uranyl-sulfate, and uranyl-hydroxide species

The stabilities of uranyl-carbonate and uranyl-hydroxide aqueous complexes were experimentally determined at temperatures ranging from 25 to 125 °C using in situ UV–vis and Raman spectroscopic techniques. Combined with earlier determinations of the stability of chloride, sulfate, and hydroxide complexes at temperatures up to 250 °C, these data permit to create a consolidated dataset suitable for modeling of U(VI) mobilization in natural systems. The parameters of the Modified Ryzhenko-Bryzgalin and the Helgeson-Kirkham-Flowers (HKF) Equations of State (EoS) were derived based on this dataset and used for thermodynamic modeling different scenarios of U(VI) mobilization. These models suggest that at conditions relevant to natural systems, carbonate-mediated transport of U(VI) is likely suppressed by the high stability of solid UO2(OH)2 and Na2U2O7. In contrast, sulfate-mediated mobilization mechanisms are highly efficient at acidic and near-neutral pH conditions and can lead to effective hydrothermal mobilization of U(VI).

Modeling and analysis method for carbon emission flow in integrated energy systems considering energy quality

AbstractWhile proposing dual carbon strategy goals, research on carbon reduction in integrated energy systems (IESs) has become a focus of attention. Traditional IES carbon emission flow is mostly based on energy flow, without considering the differences in energy quality. Exergy can be used as a reasonable measure of energy quality. Combining the theory of exergy flow and carbon emission flow, a modeling and analysis method for IES carbon emission flow considering energy quality is proposed. First, exergy flow models for electric and natural gas systems, equivalent exergy flow models for heat systems, and exergy hub models are introduced. Afterward, the exergy branch losses are allocated to the nodes at both ends. A networked modeling method for the carbon emission flow of energy stations is proposed. A unified matrix calculation model for IES carbon emission flow considering energy quality is established. On this basis, an IES carbon emission flow calculation method considering energy quality is proposed. Finally, this method is applied to the test IES, and the results show that the carbon emission flow calculation results reflect the distribution of carbon emissions borne by the effective energy supplied by the source and consumed by the load in the system, taking into account both the quantity and quality of energy. The reasonable allocation of new energy is conducive to synchronously improving the energy efficiency, exergy efficiency, and cleanliness of the system.

Fracture behavior of sandstone with partial filling flaw under mixed-mode loading: Three-point bending tests and discrete element method (DEM) numerical approach

The fracture behavior of natural fracture in the geological reservoir subjected to filling property, affects the crack initiation and propagation under stress perturbation. Partial filling flaws were intermediate between open fractures and filled fractures, the fracture response may be worth exploring. In this work, the effect of the filling property of sandstone with partial filling flaws on the fracture behavior was systematically investigated based on three-point bending tests and the numerical approach of discrete element method (DEM). In the laboratory, semi-circular three-point bending tests were carried out with partial filling flaws of various filling strengths. Based on this, numerical simulations were used to further investigate the effect of the filling ratio and the inclination of the partial filling flaw on the mechanical and fracture responses, and the effect of the partial filling flaw under mixed-mode loading on the fracture mechanism was elucidated coupled with acoustic emission (AE) characteristics. The obtained results showed that the increase in filling strength and filling ratio of partial filling flaw led to a increase in peak strength, with a decreasing trend in peak strength with the inclination of partial filling flaw. In terms of crack propagation pattern, the increasing filling strength of the partial filling flaw induced the transformation of the fracture mechanism toward deflection, with a tortuosity path, while the filling ratio and inclination of partial filling flaw led to fracture mechanism change from deflection to penetration and attraction, accompanied with a larger AE event source in filler. Accordingly, the b-value based on the Gutenberg-Richter equation fluctuated between 5 and 4 at low filling ratio and inclination and remained around 5 at high filling ratio and inclination of partial filling flaw. Related results may provide an application prospective for reservoir stimulation using the natural fracture system.

Decoding degassing modes of magma chamber of arc volcanoes: Insights from CO2/Cl and Cl/H2O ratios of magmatic fluids in groundwater

The H2O-CO2-Cl composition of the fluids released from the magma chambers for arc volcanoes was calculated based on the solubilities of H2O and CO2 in the silicate melt and the partition coefficient of Cl between the aqueous fluid and melt for the stages defined by a simple evolution model of the magma chamber. The degassing modes consisted of mafic bubbling (MB: first boiling) and felsic bubbling (FB: second boiling) releasing fluids as separate bubbles due to the mafic magma supply and felsic magma formation by differentiation, respectively, and felsic solidification (FS) releasing fluid due to felsic pluton formation. The variations in the CO2/Cl and Cl/H2O ratios of the fluids were examined for each degassing mode at pressures ranging from 150 to 400 MPa and were found to have very large variations at 0.00024–845 for CO2/Cl and 0.00043–0.041 for Cl/H2O. The CO2/Cl is concluded to be a good indicator of magma chamber conditions because each mode has a specific ratio distinguished from that of the other modes; i.e., CO2/Cl > 43 for MB, 0.027–23 for FB, and < 0.62 for FS.The alteration of magmatic composition of fluid during ascent was discussed considering the phase separation of fluid, CO2 bubbling in groundwater, dissolution, and deposition of minerals; furthermore, the limitation of the method when applied to natural groundwater systems were outlined. This method was tested for a natural volcanic system, the Kuju volcano in central Kyusyu, Japan, which is an active volcano complex composed of various magma types from rhyolitic to basaltic, replacing the eruption centers from west to east. Groundwater samples from springs and boreholes were collected and analyzed for chemical and isotopic compositions to determine the magmatic H2O, dissolved inorganic carbon (DIC), and Cl concentrations. The new approach to determine the magmatic CO2 concentration in groundwater using 3He concentration proposed herein cancelled the effect of carbonate deposition/dissolution, addition of DIC from organic matter, and bubbling of CO2. The estimated magmatic CO2/Cl ratios were 0.0009–14, which overlapped consistently with the modeled variation in the CO2/Cl ratio. The spatial variation of magmatic CO2/Cl in groundwater showed that higher-CO2/Cl are found near the central part of the volcanic complex which composed of felsic to mafic volcanoes, and low-CO2/Cl are only found around old felsic volcanoes. The CO2 bubbling springs were found to be associated with younger mafic volcanoes. The condition of the magma chambers, as shown by the spatial variation in CO2/Cl, were consistent with the record of the eruptive activities of the Kuju volcano. The CO2/Cl method proposed in this study using groundwater is useful for estimating magmatic conditions in chambers.

Thermal aging performance of soybean insulating oil mixed with glyceryl triacetate

A method of delaying the aging of natural ester oil-paper insulation systems by adding glyceryl triacetate is proposed in this work. A study was conducted on the thermal aging performance of soybean insulating oil mixed with glyceryl triacetate at a volume fraction of 7.5%. Through a 42-day accelerated thermal aging experiment, it was found that the addition of glyceryl triacetate effectively delayed the increase in kinematic viscosity of the insulating oil and reduced the generation of aging products such as moisture and acid. However, the polar compounds in glyceryl triacetate reduced the breakdown voltage of the mixed oil and made the dielectric loss factor higher than that of pure oil. In addition, tests were conducted on the insulating paper immersed in two types of oil, and it was found that the addition of glyceryl triacetate helps to distribute mixed oil molecules on the surface of insulating paper, which effectively helped absorb moisture from the paper, weakening the hydrolysis reaction of cellulose and delaying the aging of insulating paper. In addition, the insulating paper immersed in the mixed oil maintains good power frequency breakdown voltage and dielectric properties throughout the thermal aging experiment.

Meaning and identity of proofs in a bilateralist setting: A two-sorted typed Lambda-calculus for proofs and refutations

Abstract In this paper, I will develop a $\lambda $-term calculus, $\lambda ^{2Int}$, for a bi-intuitionistic logic and discuss its implications for the notions of sense and denotation of derivations in a bilateralist setting. Thus, I will use the Curry–Howard correspondence, which has been well-established between the simply typed $\lambda $-calculus and natural deduction systems for intuitionistic logic, and apply it to a bilateralist proof system displaying two derivability relations, one for proving and one for refuting. The basis will be the natural deduction system of Wansing’s bi-intuitionistic logic 2Int, which I will turn into a term-annotated form. Therefore, we need a type theory that extends to a two-sorted typed $\lambda $-calculus. I will present such a term-annotated proof system for 2Int and prove a Dualization Theorem relating proofs and refutations in this system. On the basis of these formal results, I will argue that this gives us interesting insights into questions about sense and denotation as well as synonymy and identity of proofs from a bilateralist point of view.

A hydrodynamic model of capillary flow in an axially symmetric tube with a non-slowly-varying cross section and a boundary slip

The capillary flow of a Newtonian and incompressible fluid in an axially symmetric horizontal tube with a non-slowly-varying cross section and a boundary slip is considered theoretically under the assumption that the Reynolds number is small enough for the Stokes approximation to be valid. Combining the Stokes equation with the hydrodynamic model assuming the Hagen–Poiseulle flow, a general formula for the capillary flow in a non-slowly-varying tube is derived. Using the newly derived formula, the capillary imbibition and the time evolution of meniscus in tubes with non-uniform cross sections such as a conical tube, a power-law-shaped diverging tube, and a power-law-shaped converging tube are reconsidered. The perturbation parameters and the corrections due to the non-slowly-varying effects are elucidated, and the new scaling formulas for the time evolution of the meniscus of these specific examples are derived. Our study could be useful for understanding various natural fluidic systems and for designing functional fluidic devices such as a diode and a switch.

Effects of conventional and natural management systems on backgrounding and finishing performance of beef steers

Effects of conventional and natural management systems on backgrounding and finishing performance of beef steers

Fast and Slow-Twitch Actuation via Twisted Liquid Crystal Elastomer Fibers.

The performance of robotic systems can benefit from low-density material actuators that emulate muscle typology (e.g., fast and slow twitch) of natural systems. Recent reports detail the thermomechanical, chemical, electrical, and pneumatic response of twisted and coiled fibers. The geometrical constraints imparted on typically commodity materials realize distinguished stimuli-induced actuation including low density, high force, and moderate stroke. Here, actuators are prepared by twisting fibers composed of liquid crystal elastomers (LCEs). The actuators combine the inherent stimuli-response of LCEs with the geometrical constraints of twisted fiber actuators to dramatically increase the deformation rate, specific work, and achievable force output. In some geometries, the thermomechanical response of the LCE exhibits a pseudo-first-order transition.

In vitro digestibility of rice and tapioca starch-based hydrogels produced by high-pressure processing (HPP)

The development of natural systems such as starch-based biopolymers and their applicability present a substantial challenge to the food industry, underscoring the critical need to extend the investigation to their digestibility. This study investigated the in vitro digestibility of rice and tapioca starch-based hydrogels, obtained by High-Pressure Processing (HPP) (600 MPa for 15 min) and by conventional thermal treatment (80 °C for 15 min) to assess the influence of HPP on starch digestibility as well as to identify the critical digestion steps. During in vitro digestion, disintegration, total hydrolysed starch, and starch nutritional fractions were determined. Results demonstrated that rice hydrogels underwent a higher disintegration extent and degree of starch hydrolysis with respect to tapioca hydrogels, being this more evident in HPP hydrogels. Both hydrogels were almost completely digested at the end of the digestion phases, with hydrolysed starch higher than 94% and 88% for rice and tapioca, respectively. HPP could represent a key technology to increase the digestibility of the resistant starch fraction of rice and tapioca starch hydrogels, increasing the potential applicability of these biopolymers.

Size matters: Natural experiments suggest the dear enemy effect is moderated by pack size in African wild dogs.

Remote monitoring of communal marking sites, or latrines, provides a unique opportunity to observe undisturbed scent marking behaviour of African wild dogs (Lycaon pictus). We used remote camera trap observations in a natural experiment to test behavioural scent mark responses to rivals (either familiar neighbours or unfamiliar strangers), to determine whether wild dogs exhibit the "dear enemy" or "nasty neighbour" response. Given that larger groups of wild dogs represent a greater threat to smaller groups, including for established residents, we predicted that the overarching categories "dear enemy" vs. "nasty neighbour" may be confounded by varying social statuses that exists between individual dyads interacting. Using the number of overmarks as a metric, results revealed an interaction between sender and receiver group size irrespective of familiarity consistent with this prediction: in general, individuals from large resident packs overmarked large groups more than they overmarked smaller groups, whereas individuals from smaller packs avoided overmarking larger groups, possibly to avoid detection. Monitoring a natural system highlights variables such as pack size that may be either overlooked or controlled during scent presentation experiments, influencing our ability to gain insights into the factors determining territorial responses to rivals.

Prototype Development of Modified Roof Turbine Ventilator for Thermal Comfort Enhancement

A mechanical ventilator known as a turbine ventilator harnesses the wind to supply natural ventilation. Due to their high performance and cheap running costs, these devices are increasingly being used to ventilate areas. This study evaluated the impact of a modified turbine ventilator system on thermal comfort and airflow inside a room. The results showed that the natural ventilation system failed to meet the ASHRAE Standard 55-2020 for thermal comfort. The installation of a turbine ventilator decreases the temperature by 1.3°C but still did not meet the standards. The modified turbine ventilator system consisted of a 305 mm diameter inner 12V, 12W exhaust fan installed in a 500 mm diameter ventilator and connected to a 50W, 12V Monocrystalline Solar Panel showed the greatest improvement with a decrease in room temperature of 4.4°C, an increase in airflow, and full compliance with the ASHRAE Standard 55-2020. The study concludes that modifications to the natural ventilation system can significantly improve thermal comfort and airflow, with the modified ventilator system being the most effective solution.

Enhancing MANET Performance: A Novel Approach Through Nature-Inspired Scheduling Algorithms

In the rapidly evolving landscape of Mobile Ad Hoc Networks (MANETs), the quest for optimal performance through efficient scheduling remains paramount. This paper, titled "Enhancing MANET Performance: A Novel Approach Through Nature-Inspired Scheduling Algorithms," introduces an innovative methodology that leverages the intricate mechanisms of nature to address the complex challenges inherent in MANET scheduling. Drawing inspiration from the adaptive behaviors observed in natural systems, we have developed a suite of nature-inspired algorithms—encompassing the genetic algorithm, particle swarm optimization, and ant colony optimization—tailored specifically to enhance the scheduling efficiency within the dynamic and decentralized context of MANETs.&#x0D; Our research undertakes a comprehensive evaluation of these algorithms against traditional scheduling methods, showcasing a notable improvement in key performance metrics such as network throughput, latency, and energy consumption. The novel contribution of this study lies in the adaptation and optimization of these bio-inspired algorithms for the unique demands of MANET scheduling, culminating in the development of a proprietary analytical model that significantly outperforms existing strategies. Through a rigorous comparative analysis, our results illuminate the superiority of our approach, demonstrating not only enhanced network efficiency but also improved scalability and reliability under varying conditions.&#x0D; The implications of this research extend beyond the immediate enhancements to MANET performance, proposing a paradigm shift in how scheduling challenges are approached within ad hoc networks. By bridging the gap between biological principles and technological applications, this study paves the way for future innovations in network management, offering a blueprint for the development of more adaptive, robust, and efficient networking solutions.

Human adaptation to heat in the context of climate change: A conceptual framework

Climate change is causing serious damage to natural and social systems, as well as having an impact on human health. Among the direct effects of climate change is the rise in global surface temperatures and the increase in the frequency, duration, intensity and severity of heat waves. In addition, understanding of the adaptation process of the exposed population remains limited, posing a challenge in accurately estimating heat-related morbidity and mortality. In this context, this study seeks to establish a conceptual framework that would make it easier to understand and organise knowledge about human adaptation to heat and the factors that may influence this process. An inductive approach based on grounded theory was used, through the analysis of case studies connecting concepts. The proposed conceptual framework is made up of five components (climate change, vulnerability, health risks of heat, axes of inequality and health outcomes), three heat-adaptation domains (physiological, cultural and political), two levels (individual and social), and the pre-existing before a heat event. The application of this conceptual framework facilitates the assistance of decision-makers in planning and implementing effective adaptation measures. Recognizing the importance of addressing heat adaptation as a health problem that calls for political solutions and social changes. Accordingly, this requires a multidisciplinary approach that would foster the participation and collaboration of multiple actors for the purpose of proposing effective measures to address the health impact of the rise in temperature.

Vivianite oxidation is not photocatalyzed

Vivianite is a hydrous Fe(II) phosphate mineral found in anoxic environments that plays an integral role in P cycling and environmental biogeochemistry. Imbued in the vivianite literature dating as far back as 1918 is the notion that vivianite is light-sensitive and susceptible to rapid photooxidation induced entirely by solar light. However, despite an exhaustive search, to our knowledge this conventionally accepted assumption has never been directly tested, nor has the band gap ever been measured. Resolving this question of photochemical control of vivianite redox chemistry is important for performing and interpreting experiments involving vivianite reactivity with contaminants, and potentially iron and phosphate cycling in the photic zone of aquatic systems. The present study was specifically designed to address this question. Pure synthetic vivianite samples were irradiated in aqueous suspensions with a Xe lamp at conditions mimicking the solar spectrum and compared to dark controls. Particles stirred in anoxic suspensions for up to 66 days showed no detectable oxidation irrespective of light exposure, according to colorimetric Fe(II)/Fe(III) assays, micro X-ray diffraction, and Raman spectroscopy. In contrast, the same experiment performed using air-equilibrated suspensions showed systematic oxidation of up to ∼80 mol% Fe(II) at 66 days, but again with no detectable light exposure effect. To test for UV reactivity, further experiments on vivianite powders under air versus N2 atmosphere were performed using a Hg lamp with a longpass filter. In contrast to oxidation in air where no effect of light was detected, after 24 h irradiation anoxically, an additional 0.8 % Fe was oxidized compared to dark controls, and after 13 days only an additional 0.3 % Fe was oxidized. The band gap of pure vivianite was measured by the Tauc method to be 3.5 eV. Contrary to previous reports, solar light has minimal impact on the oxidation of pure vivianite; any such effect would be insignificant when compared to its relatively fast oxidation by oxygen exposure. As such, light does not need to be excluded when running typical vivianite laboratory experiments. Long-term storage of natural vivianite in museums or private collections should continue protective measures given that a possible photocatalytic role of impurities cannot yet be ruled out.Nonetheless, at all depths in natural aquatic systems, including the photic zone, it appears that the primary abiotic control on the reactivity and half-life of vivianite particles would be the dissolved oxygen concentration, not light exposure.

Educators unplugged: working and thinking in natural environments

ABSTRACT This study investigates the cultural experiences of higher education educators/academics while working outdoors in natural environments, ‘unplugged’ from technological and institutional systems. a) That disconnection from institutional/technological systems would catalyse re/connection with natural systems—the natural environment, our colleagues and ourselves; and (b) That disconnecting from institutional/technological systems would generate psychological, emotional and social margin in our work and invigorate our teaching. Collective autoethnography with structured methods – problematising, data assemblage, data analysis and reporting. By deliberately disconnecting from institutional and technological systems for two days we hoped to find social and emotional margin in our work. However, what we did not anticipate, but was a very welcome outcome of this project, was the development of a way of knowing, an epistemology, of being unplugged in nature. This epistemology prompted us to wild our pedagogies and reconsider sustainable ways of learning and working.

전통가옥을 활용한 카페 인테리어의 내부 구성요소에 관한 연구

The main purpose of this study is to understand the versatility by analyzing the colors of the interior components of the cafe interior using modern traditional houses from three countries in East Asia. To this end, the concept and category of traditional houses were redefined and the characteristics of representative traditional houses in each country were described. Based on this, we sampled four cafes for analysis from cities in each country with clear characteristics of traditional houses. Each cafe sample has something in common: a modern remodel of the traditional architectural style. As a result of quantitative extraction and comparative analysis of the colors from the cafe sample image to the interior components (walls, ceilings, floors, and windows) using the Natural Color System (NCS), the interior components as a whole adhered to the traditional form and structure. The YR series showed medium brightness and chromaticity below medium saturation. This is a similar result to traditional colors. However, in the case of China, the use of color was significantly reduced, and in the case of Japan, it was confirmed that the use of color was higher in terms of brightness and saturation than traditional colors, confirming that the three kingdoms were largely evolving similarly in their use of color. This is analyzed to be in line with the globalization trend of universal standards and individualization of application.

Correlation between microbial communities and volatile flavor compounds in the fermentation of Semen Sojae Praeparatum

SSP (Sojae Semen Praeparatum, SSP), a traditional medicinal and edible product, undergoes natural fermentation resulting in a unique flavor. However, the complexity of the natural fermentation system results in inconsistent quality. This study utilized E-nose, headspace solid-phase microextraction combined with full two-dimensional gas chromatography-mass spectrometry, and high-throughput sequencing techniques to reveal the correlation between key volatile flavor compounds and dominant microbial communities during SSP fermentation. The results showed that total organic acids increased from 50.61 mg/g to 72.29 mg/g during SSP fermentation, and levels of umami and sweet amino acids significantly increased. Alcohols, esters, and acids were the main flavor compounds during SSP fermentation, with 52 being identified as key volatile flavor compounds. In the microbial community, bacterial communities dominated by Proteobacteria, Cyanobacteria, and Firmicutes exhibited dynamic solid changes, while fungal communities dominated by Ascomycota, Basidiomycota, unclassified_Fungi, and Mortierellomycota showed relatively stable abundance. Spearman correlation analysis showed that 9 dominant microbial genera were significantly correlated with 27 key volatile flavor compounds, among which Cladosporium, Leuconostoc, Weissella, and Lactiplantibacillus may be the core functional microbial community for SSP characteristic flavors. This study provided theoretical references for the targeted control of SSP quality and the screening of starter fermentation cultures.

Rain gardens enhance the taxonomic richness but not the abundance of soil invertebrates in urban ecosystems

Natural treatment systems such as rain gardens aim to overcome the negative effects of urban stormwater, preventing harm to human population and infrastructure. Rain gardens house an abundance of soil fauna comprising a functionally important group of organisms. However, the responses of different groups of soil fauna to rain gardens remain poorly explored. In this study, we investigated the abundance, taxonomic richness, taxonomic diversity, and community composition of ground-dwelling and belowground invertebrates in rain gardens and nearby lawns in Nanjing and Zhenjiang cities, China. In Nanjing, we found that the taxonomic richness of ground-dwelling and belowground invertebrates was significantly higher in rain gardens than in lawns. We also discovered that the community composition of ground-dwelling invertebrates differed significantly between rain gardens and lawns, a distinction primarily explained by gravel coverage. However, in Zhenjiang, there were no significant differences in the abundance, taxonomic richness, taxonomic diversity, or community composition of ground-dwelling and belowground invertebrates between rain gardens and lawns. These results indicate that the effects of rain gardens on soil faunal community structure varied with soil fauna groups and cities. Considering that soil fauna have positive effects on the function of rain gardens such as water infiltration and decomposition, we suggest that the addition of ground surface mulch such as gravel may enhance soil biodiversity.