Strong Trade-off Research Articles

Information Age-Delay Correlation and Optimization With Finite Block Length

Both information age and delay are critical performance metrics of emerging time-sensitive applications. However, their inherent correlation in the finite block length (FBL) regime has remained uninvestigated as it is affected by block length and update rate in a complex manner. In this paper, closed-form expressions for average age of information (AoI), peak AoI (PAoI) and delay are derived for an FBL Last-Come First-Served system with retransmission and non-preemption policies, based on which a comprehensive analysis of the relationship among the three metrics in the FBL regime is presented. It is proved that there exists a strong tradeoff between delay and AoI/PAoI given a block length, and that AoI, PAoI and delay have positive correlation given an update rate, regardless of the weight. With the goal of minimizing delay and AoI simultaneously, the weighted sum of delay and PAoI (upper bound on AoI) is formulated and proved to be convex with respect to block length and update rate. A low-complexity optimization algorithm is developed with a closed-form expression of the optimal update rate, whose performance approaches the Pareto boundaries of the PAoI-delay and the AoI-delay regions, at much lower complexity than exhaustive search.

Evolutionary coexistence in a metacommunity: Competition-colonization trade-off, ownership effects, environmental fluctuations

We study the adaptive dynamics of the colonization rate of species living in a patchy habitat when there is a trade-off with the competitive strength for individual patches. To that end, we formulate a continuous-time competition-colonization model that also includes ownership effects as well as random disturbance affecting the mortality rate. We find that intermediate disturbance (as measured by the fluctuation intensity of the mortality rate), a strong competition-colonization trade-off, and a weak ownership effect are necessary conditions for evolutionary branching and hence for the emergence of polymorphisms (i.e., coexistence) by small evolutionary steps. Specifically, concerning ownership we find that with low-intermediate disturbance, a weak ownership advantage favours evolutionary branching while ownership disadvantage does not. This asymmetry disappears at the higher-intermediate disturbance. Moreover, at a low-intermediate disturbance, the effect of the strength of the competition-colonization trade-off on evolutionary branching is non-monotonic disappears because the possibility of branching disappears again when the trade-off is too strong. We also find that there can be multiple evolutionary attractors for polymorphic populations, each with its own basin of attraction. With small but non-zero random evolutionary steps and depending on the initial polymorphic condition just after branching, a coevolutionary trajectory may come arbitrarily close to the shared boundary of two such basins and may even jump from one side to the other, which can lead to various kinds of long-term evolutionary dynamics, including evolutionary branching-extinction cycles.

Assessing the impact of grassland management on landscape multifunctionality

Land-use intensification has contrasting effects on different ecosystem services, often leading to land-use conflicts. While multiple studies have demonstrated how landscape-scale strategies can minimise the trade-off between agricultural production and biodiversity conservation, little is known about which land-use strategies maximise the landscape-level supply of multiple ecosystem services (landscape multifunctionality), a common goal of stakeholder communities.We combine comprehensive data collected from 150 German grassland sites with a simulation approach to identify landscape compositions, with differing proportions of low-, medium-, and high-intensity grasslands, that minimise trade-offs between the six main grassland ecosystem services prioritised by local stakeholders: biodiversity conservation, aesthetic value, productivity, carbon storage, foraging, and regional identity. Results are made accessible through an online tool that provides information on which compositions best meet any combination of user-defined priorities (https://neyret.shinyapps.io/landscape_composition_for_multifunctionality/).Results show that an optimal landscape composition can be identified for any pattern of ecosystem service priorities. However, multifunctionality was similar and low for all landscape compositions in cases where there are strong trade-offs between services (e.g. aesthetic value and fodder production), where many services were prioritised, and where drivers other than land use played an important role. We also found that if moderate service levels are deemed acceptable, then strategies in which both high and low intensity grasslands are present can deliver landscape multifunctionality. The tool presented can aid informed decision-making by predicting the impact of future changes in landscape composition, and by allowing for the relative roles of stakeholder priorities and biophysical trade-offs to be understood by scientists and practitioners alike.

Circular alternatives to peat in growing media: A microbiome perspective

Peat use in horticulture is associated with a large ecological footprint. Peat is the predominant growing media in Europe. Modern cropping systems rely heavily on dynamic interactions of the crop with the microorganisms in the growing media and yet, in the search for sustainable peat-alternatives, the microbiome of the growing media has often been ignored. In mushroom cultivation, peat is a prime determinant of productivity, in the form of a casing soil which supplies beneficial microbes. In this study we describe the microbial composition, interactions, and activity of four circular substrates used to proportionally replace peat in mushroom growing media. We also evaluate various physico-chemical characteristics of the peat-alternatives. We characterize the impact of sanitary pre-treatments such as steaming and acidification on the microbiome as well as the agronomical performance of the peat-reduced growing media. We found that grass fibres from agricultural residue streams, peat-moss farmed in degraded peatlands, and spent casing soil recycled from previous cultivation cycles can be used to successfully replace peat in mushroom growing media. Peat moss and spent casing were expectedly similar to peat in physical, chemical, and microbiological properties. However, the grass fibres had unique characteristics, such as high organic matter content, low water holding capacity and a diverse and competitive microbiome. Pre-treatment of the substrates by acidification and steaming significantly affected the microbiome, and reduced the presence of pests, pathogens and competitive fungi in the peat-reduced media. Strong trade-offs existed between the productivity and disease pressure in the circular cropping system, which are also governed by the microbial composition of the growing media. Knowledge on the accessibility, sustainability, and economic viability of these peat-alternatives will further determine the transition away from peat use and towards sustainable growing media.

On the resolution, sensitivity and ion transmission efficiency of a planar FAIMS

A detailed experimental characterization and theoretical analysis on the sensitivity, resolution and ion transmission efficiency of a planar FAIMS under different operating conditions including electrospray flow rate, solution concentration, curtain voltage and dispersion voltage are reported in the study based on the direct measurements of the ion current on the FAIMS detector. The sensitivity of FAIMS was shown to increase initially with the increase of electrospray flow rate. At a certain flow rate, which is typically compound dependent, an optimum FAIMS sensitivity was observed. Further increasing the electrospray flow rate would result in the decrease of the FAIMS sensitivity. Interestingly, the ion transmission efficiency of the FAIMS was shown experimentally to monotonically increase with the decrease of the electrospray flow rates. Both the ion transmission efficiency/sensitivity and the resolution of the FAIMS were significantly affected by the dispersion voltage. There is a strong tradeoff between the FAIMS ion transmission efficiency/sensitivity and separation resolution. As the FAIMS dispersion voltage increases, the separation resolution increases while the ion transmission efficiency/sensitivity decreases. The curtain voltage can also dramatically affect the performance of FAIMS, especially in the ion separation mode. The sensitivity of FAIMS at curtain voltage of 1.8 kV is about two-fold higher than the one at 1.0 kV. This study allows one to select the desirable FAIMS operating conditions based on the actual analysis needs.

Evaluating the Performance of 193 nm Ultraviolet Photodissociation for Tandem Mass Tag Labeled Peptides

Despite the successful application of tandem mass tags (TMT) for peptide quantitation, missing reporter ions in higher energy collisional dissociation (HCD) spectra remains a challenge for consistent quantitation, especially for peptides with labile post-translational modifications. Ultraviolet photodissociation (UVPD) is an alternative ion activation method shown to provide superior coverage for sequencing of peptides and intact proteins. Here, we optimized and evaluated 193 nm UVPD for the characterization of TMT-labeled model peptides, HeLa proteome, and N-glycopeptides from model proteins. UVPD yielded the same TMT reporter ions as HCD, at m/z 126–131. Additionally, UVPD produced a wide range of fragments that yielded more complete characterization of glycopeptides and less frequent missing TMT reporter ion channels, whereas HCD yielded a strong tradeoff between characterization and quantitation of TMT-labeled glycopeptides. However, the lower fragmentation efficiency of UVPD yielded fewer peptide identifications than HCD. Overall, 193 nm UVPD is a valuable tool that provides an alternative to HCD for the quantitation of large and highly modified peptides with labile PTMs. Continued development of instrumentation specific to UVPD will yield greater fragmentation efficiency and fulfil the potential of UVPD to be an all-in-one spectrum ion activation method for broad use in the field of proteomics.

Multiobjective Dynamic Optimization for Optimal Load-Following of Natural Gas Combined Cycle Power Plants under Stress Constraints

With the increasing penetration of intermittent renewable energy sources into the electric grid, there is an associated need for conventional thermal power plants that are designed to operate at base-load conditions to cycle their load rapidly and frequently and operate under low-load conditions. Fast load-following operations lead to plant efficiency loss and the reduction of equipment life. A high-fidelity dynamic model of a natural gas combined cycle power plant, with rigorous equipment level submodels, is developed to capture the plant transient performance and the thermomechanical stress evolution at the high-pressure drum is computed to assess the drum life consumption. Stress evolution is modeled for the location of the edge at the drum/downcomer junction that experiences high circumferential stress amplitude during the fast load-following operation, leading to higher fatigue damage than locations considered under existing design standards. A dynamic optimization problem is solved for optimal load-following operation. Depending on the value of the stress constraint and the desired ramp rate, satisfying the desired stress constraint may be infeasible without relaxing the ramp rate. A multiobjective dynamic optimization problem is solved using a lexicographic approach that minimizes ramp rate relaxation and maximizes efficiency while satisfying stress constraints, avoiding spraying to saturation, and maintaining main steam and reheat steam temperature within bounds. It was observed that the optimal ramp rate can be highly nonlinear as opposed to the industry-standard linear ramp rate. Nonlinear optimal ramp-rate profiles not only help to avoid stress constraints that may be unavoidable by using the linear profile but also result in higher efficiency than the linear profile. The study shows that there is a strong tradeoff between the relaxation in the plant ramp rate and the time-average thermal efficiency.

Fading opportunities for mitigating agriculture-environment trade-offs in a south American deforestation hotspot

Strong trade-offs between agriculture and the environment occur in deforestation frontiers, particularly in the world's rapidly disappearing tropical and subtropical dry forests. Pathways to mitigate these trade-offs are often unclear, as well as how deforestation or different policies alter the option space of available pathways. Using a spatial optimization framework based on linear programming, we develop a landscape-scale possibility frontier describing trade-offs between agricultural profit, biodiversity, and carbon stock for the Argentinean Dry Chaco, a global deforestation hotspot. We use this framework to assess how current land-use zoning, as well as past and future land-use-trajectories, alter the option space to minimize trade-offs between biodiversity, carbon, and agriculture. Our analyses yield four major insights. First, we found substantial co-benefits between biodiversity and carbon, yet strong trade-offs of both with agriculture. Second, development according to the current zoning could lead to highly suboptimal socio-ecological outcomes; our analysis pinpoints how this zoning could be improved. Third, high landscape-scale multifunctionality can be achieved using different land-use strategies, but maintaining >40% of forest is essential in all of them, and silvopasture systems appear to be central for achieving high overall multifunctionality. Finally, our results suggest the window of opportunity is closing rapidly: recent land-use changes since 2000 have rapidly moved the Chaco within the option space, with forest extent declining towards critical thresholds for maintaining balanced, multifunctional landscapes. Our results emphasize that the time for sustainability planning in the Chaco is now. More broadly, we show how multi-criteria optimization can describe dynamic trade-offs between agriculture and the environment at landscape and regional scales. This can help to identify land-system tipping points that, once crossed, would inhibit more sustainable futures, and policies to avoid such potential traps.

Investor sentiment and mean-variance relation: Evidence from emerging futures markets

We examine the role of news sentiment in determining the mean-variance relation in the emerging futures market. The relation is significantly negative for the Kuala Lumpur Composite Index Futures (KLCIF) in high and low sentiment regimes, while weakly negative in high sentiment and strongly positive in low sentiment regimes for Hang Seng Index Futures (HSIF) and the MSCI Singapore Free Index (SiMSCIF). The negative trade-off is contributed by extremely high sentiment, especially in the KLCIF. A strong negative trade-off during the Asian financial crisis is found for KLCIF. The macroeconomic variables do not show any consistent regime patterns. We do not find any significant impact from U.S. sentiment.

Ecological footprint and human well-being nexus: accounting for broad-based financial development, globalization, and natural resources in the Next-11 countries

The Next-11 (N11) countries have witnessed great advancements in economic activities in the past few years. However, the simultaneous attainment of environmental sustainability and improved human well-being has remained elusive. This study probes into ecological footprint (EF) and human well-being nexus in N11 countries by applying advanced estimation techniques compatible with heterogeneity, endogeneity, and cross-sectional dependence across country groups. From the findings, human well-being, captured by the human development index, increases the EF, and EF also increases human well-being which suggests a strong trade-off between both indicators. This shows that policies that are channeled toward promoting human well-being are not in consonance with environmental wellness. Financial development and biocapacity increase the EF, while natural resources and globalization reduce it. Human well-being increases the EF in all the countries except in Egypt. This study argues that strong institutions could help mitigate the trade-offs and ease the simultaneous attainment of both environmental preservation and improved human well-being. The limitations of the study, as well as, possible directions for future research are discussed.

First Data of Reproductive Biology of Metlapilcoatlus indomitus (Serpentes: Viperidae) in Captivity

The Jumping Viper genus Metlapilcoatlus is composed of five species distributed throughout the Mesoamerican region, with M. indomitus being endemic to Honduras. While there have been numerous publications about its distribution, basic data concerning the species natural history (reproduction, diet, and behavior) remain poorly known. Here we expand on the knowledge of M. indomitus through an ex-situ study of two captive individuals inside a herpetarium. Over the course of three years from October 11, 2017, we monitored reproductive patterns of courtship, copulation, and reproductive potential. We register two events of courtship and copulation, and three deliveries with a total of 61 neonates (26, 14, and 21 respectively). We found significant differences in the total length of the neonates between broods (p = 3.557e-12). Our data mark a strong correlation and linear trade-off between the number of offspring per delivery and their length, with neonates of broods containing fewer offspring being of greater length, whereas those neonates from larger broods were shorter in average.

Computational Fluid Dynamics Study of Cerebral Thromboembolism Risk in Ventricular Assist Device Patients: Effects of Pulsatility and Thrombus Origin.

This study investigates the hypothesis that by surgically manipulating the outflow graft (OG) implantation during ventricle assist device placement, it may be possible to reduce the risk of cerebral embolism. We investigate this hypothesis using a computational approach on a patient-specific basis under fully pulsatile hemodynamics with a multiscale computational fluid dynamics model incorporating a coupled Eulerian-Lagrangian scheme that effectively tracks emboli in the fluid domain. Blood is modeled as a non-Newtonian fluid based on the hematocrit level. Preliminary flow analysis shows that depending on the anastomosis angle the left ventricular assist device (LVAD) can enhance the flow to the cerebral circulation by nearly 31%. Z-test results suggest that unsteady-flow modeling ought to be an integral part of any cardiovascular simulation with residual ventricular function. Assuming unsteady-flow conditions, a shallow LVAD outflow graft anastomosis angle is the most optimal if thrombi are released from the aortic-root reducing cerebral embolization incidence to 15.5% and from the ventricle to 17%, while a more pronounced anastomosis angle becomes advantageous when particles originate from the LVAD with an embolization rate of 16.9%. Overall, computations suggest that a pronounced LVAD anastomosis angle is the better implementation. Unsteady modeling is shown to be necessary for the presence of significant antegrade aortic-root flow which induces cyclical flow patterns due to residual pulsatility. On the other hand, depending on thrombus origin and ventricular assist devices (VAD) anastomosis angle there is a strong tradeoff in embolization rates.

Dense time-course gene expression profiling of the Drosophila melanogaster innate immune response

BackgroundImmune responses need to be initiated rapidly, and maintained as needed, to prevent establishment and growth of infections. At the same time, resources need to be balanced with other physiological processes. On the level of transcription, studies have shown that this balancing act is reflected in tight control of the initiation kinetics and shutdown dynamics of specific immune genes.ResultsTo investigate genome-wide expression dynamics and trade-offs after infection at a high temporal resolution, we performed an RNA-seq time course on D. melanogaster with 20 time points post Imd stimulation. A combination of methods, including spline fitting, cluster analysis, and Granger causality inference, allowed detailed dissection of expression profiles, lead-lag interactions, and functional annotation of genes through guilt-by-association. We identified Imd-responsive genes and co-expressed, less well characterized genes, with an immediate-early response and sustained up-regulation up to 5 days after stimulation. In contrast, stress response and Toll-responsive genes, among which were Bomanins, demonstrated early and transient responses. We further observed a strong trade-off with metabolic genes, which strikingly recovered to pre-infection levels before the immune response was fully resolved.ConclusionsThis high-dimensional dataset enabled the comprehensive study of immune response dynamics through the parallel application of multiple temporal data analysis methods. The well annotated data set should also serve as a useful resource for further investigation of the D. melanogaster innate immune response, and for the development of methods for analysis of a post-stress transcriptional response time-series at whole-genome scale.

Trading off retained daily catch for longer seasons to maximize angler benefits in recreational fisheries management

Abstract Recreational fishing benefits associated with angling opportunity, such as fishing season duration and certainty of season duration, may outweigh trip-based benefits, such as retained catch, in measures of angler utility. We developed an age-structured population dynamics model to predict how these three beneficial attributes are affected by four recreational management parameters: minimum size limit; bag limit; inter-season quota transfer limits; and in-season adjustment of season duration. We incorporated results of stated-preference angler surveys to produce a bioeconomic model for two case studies: Atlantic Florida red snapper, and central Oregon Pacific halibut. In maximizing long-term total utility, a strong trade-off between season length and retained daily catch was observed in both fisheries, arising from increased minimum size limits which lengthened fishing seasons but reduced daily retained catch. The optimal management policy across the combination of beneficial attributes was sensitive to assumptions of the curvature of utility functions, i.e. to the degree to which anglers value those attributes with diminishing marginal returns, but generally involved satisfying the strong stated preferences for increased angling opportunity.

Unravelling resilience mechanisms in forests: role of non-structural carbohydrates in responding to extreme weather events.

Extreme weather events are increasing in frequency and intensity due to global climate change. We hypothesized that tree carbon reserves are crucial for resilience of beech, buffering the source-sink imbalance due to late frosts and summer droughts, and that different components of non-structural carbohydrates (NSCs) play specific roles in coping with stressful situations. To assess the compound effects on mature trees of two extreme weather events, first a late frost in spring 2016 and then a drought in summer 2017, we monitored the phenology, radial growth and the dynamics of starch and soluble sugars in a Mediterranean beech forest. A growth reduction of 85% was observed after the spring late frost, yet not after the drought event. We observed a strong impact of late frost on starch, which also affected its dynamic at the beginning of the subsequent vegetative season. In 2017, the increase of soluble sugars, associated with starch hydrolysis, played a crucial role in coping with the severe summer drought. Non-structural carbohydrates helped to counteract the negative effects of both events, supporting plant survival and buffering source-sink imbalances under stressful conditions. Our findings indicate a strong trade-off between growth and NSC storage in trees. Overall, our results highlight the key role of NSCs on beech trees, response to extreme weather events, confirming the resilience of this species to highly stressful events. These insights are useful for assessing how forests may respond to the potential impacts of climate change on ecosystem processes in the Mediterranean area.

Synergistic effects of Al and Ti on the oxidation behaviour and mechanical properties of L12-strengthened FeCoCrNi high-entropy alloys

Synergistic effects of Al and Ti on the oxidation behaviour and mechanical properties of FeCoCrNi high-entropy alloys were systematically investigated. Our results reveal that increasing the Al/Ti ratio slows down the oxidation kinetics at 700−900 °C and changes the oxide scale from TiO2 and spinel oxides to Cr2O3 and Al2O3, leading to a substantial improvement of oxidation resistance. From a mechanical aspect, however, increasing the Al/Ti ratio decreases the mechanical strength, demonstrating a strong trade-off between oxidation resistance and mechanical properties. The underlying mechanisms for the Al and Ti effects on the oxidation resistance and mechanical properties were discussed.

Genome-wide shifts in climate-related variation underpin responses to selective breeding in a widespread conifer

Locally adapted temperate tree populations exhibit genetic trade-offs among climate-related traits that can be exacerbated by selective breeding and are challenging to manage under climate change. To inform climatically adaptive forest management, we investigated the genetic architecture and impacts of selective breeding on four climate-related traits in 105 natural and 20 selectively bred lodgepole pine populations from western Canada. Growth, cold injury, growth initiation, and growth cessation phenotypes were tested for associations with 18,600 single-nucleotide polymorphisms (SNPs) in natural populations to identify "positive effect alleles" (PEAs). The effects of artificial selection for faster growth on the frequency of PEAs associated with each trait were quantified in breeding populations from different climates. Substantial shifts in PEA proportions and frequencies were observed across many loci after two generations of selective breeding for height, and responses of phenology-associated PEAs differed strongly among climatic regions. Extensive genetic overlap was evident among traits. Alleles most strongly associated with greater height were often associated with greater cold injury and delayed phenology, although it is unclear whether potential trade-offs arose directly from pleiotropy or indirectly via genetic linkage. Modest variation in multilocus PEA frequencies among populations was associated with large phenotypic differences and strong climatic gradients, providing support for assisted gene flow polices. Relationships among genotypes, phenotypes, and climate in natural populations were maintained or strengthened by selective breeding. However, future adaptive phenotypes and assisted gene flow may be compromised if selective breeding further increases the PEA frequencies of SNPs involved in adaptive trade-offs among climate-related traits.

Trait correlations and landscape fragmentation jointly alter expansion speed via evolution at the leading edge in simulated range expansions

Rapid evolution during range expansion is a key mechanism influencing species’ ability to colonize new habitat. Understanding how selective processes alter expansion speed is thus critical to predicting both the spread of invasive species and responses to climate change. Theory predicts evolution of increased dispersal and fecundity at the leading edge of expansions. However, these traits are often negatively correlated, and what conditions might lead to one trait being favoured over the other are unclear. Further, while most theory assumes populations spread through homogeneously favourable environments, how selective processes acting on dispersal and fecundity alter expansion dynamics in patchy landscapes is not well understood. We investigated the role of landscape fragmentation and trait correlations in determining evolutionary trajectories at the leading edge of range expansions, and how these in turn alter expansion speed. We simulated populations with heritable trade-offs between dispersal and fecundity spreading through one-dimensional landscapes with varying degrees of fragmentation. We found that, in populations with a weak trade-off, the strongest dispersers were selected for at the leading edge. However, in highly fragmented landscapes and with a strong trade-off, fecundity was instead favoured. Expansion speed was strongly correlated with dispersal ability at the leading edge at all levels of patchiness, and variation in expansion speed across replicates increased with fragmentation and trade-off strength. Our findings demonstrate that evolution induced by both landscape structure and trait correlations can alter spread dynamics, and that selective processes imposed by spread per se may not always be dominant in influencing expansion speed.

Nullstellensatz Size-Degree Trade-offs from Reversible Pebbling

We establish an exactly tight relation between reversible pebblings of graphs and Nullstellensatz refutations of pebbling formulas, showing that a graph G can be reversibly pebbled in time t and space s if and only if there is a Nullstellensatz refutation of the pebbling formula over G in size t + 1 and degree s (independently of the field in which the Nullstellensatz refutation is made). We use this correspondence to prove a number of strong size-degree trade-offs for Nullstellensatz, which to the best of our knowledge are the first such results for this proof system.

Performance Analysis of Silicon Carrier Selective Contact Solar Cells With ALD MoOx as Hole Selective Layer

Carrier selective contact (CSC) architecture is one of several promising candidates for high-efficiency silicon solar cells operating close to the thermodynamic limit. However, an industrially feasible process is lacking for manufacturable CSC cells. Specifically, although evaporated molybdenum oxide (MoOx) has been actively researched as a hole selective layer, a more industry-compatible deposition process is critically needed. Atomic layer deposition (ALD) has been widely employed in the industry for material stacks requiring precise thickness control and uniformity. In this paper, we present a performance analysis of CSC solar cells fabricated using ALD MoOx as the hole selective layer. As a first step, the standard ALD recipe was modified to obtain sub-stoichiometric MoOx with a higher work function due to increased oxygen vacancy concentration. The modified MoOx recipe resulted in low open-circuit voltage values in fabricated not-passivated CSC solar cells. A 4 nm thick amorphous silicon layer inserted in the hole selective stack showed significant improvement in minority lifetime but worse solar cell performance due to increased series resistance. Besides indicating a strong trade-off between passivation and series resistance, the solar cell data highlights series resistance as a key performance limiter in CSC solar cells.