The role of recurrent disturbances for ecosystem multifunctionality

Ecosystem functioning is threatened by an increasing number of anthropogenic stressors, creating a legacy of disturbance that undermines ecosystem resilience. However, few empirical studies have assessed to what extent an ecosystem can tolerate repeated disturbances and sustain its multiple functions. By inducing increasingly recurring hypoxic disturbances to a sedimentary ecosystem, we show that the majority of individual ecosystem functions experience gradual degradation patterns in response to repetitive pulse disturbances. The degradation in overall ecosystem functioning was, however, evident at an earlier stage than for single ecosystem functions and was induced after a short pulse of hypoxia (i.e., three days), which likely reduced ecosystem resistance to further hypoxic perturbations. The increasing number of repeated pulse disturbances gradually moved the system closer to a press response. In addition to the disturbance regime, the changes in benthic trait composition as well as habitat heterogeneity were important for explaining the variability in overall ecosystem functioning. Our results suggest that disturbance-induced responses across multiple ecosystem functions can serve as a warning signal for losses of the adaptive capacity of an ecosystem, and might at an early stage provide information to managers and policy makers when remediation efforts should be initiated.Peer reviewe

Spacecraft design project: High latitude communications satellite

The spacecraft design project was part of AE-4871, Advanced Spacecraft Design. The project was intended to provide experience in the design of all major components of a satellite. Each member of the class was given primary responsibility for a subsystem or design support function. Support was requested from the Naval Research Laboratory to augment the Naval Postgraduate School faculty. Analysis and design of each subsystem was done to the extent possible within the constraints of an eleven week quarter and the design facilities (hardware and software) available. The project team chose to evaluate the design of a high latitude communications satellite as representative of the design issues and tradeoffs necessary for a wide range of satellites. The High-Latitude Communications Satellite (HILACS) will provide a continuous UHF communications link between stations located north of the region covered by geosynchronous communications satellites, i.e., the area above approximately 60 N latitude. HILACS will also provide a communications link to stations below 60 N via a relay Net Control Station (NCS), which is located with access to both the HILACS and geosynchronous communications satellites. The communications payload will operate only for that portion of the orbit necessary to provide specified coverage

Physiological costs of reproduction in female mice

The hypothesis that the large demand of reproduction negatively impacts future reproduction and/or survival has become a major topic in many fields within biology. Although many assume negative linear correlations between characteristics associated with reproduction and those supporting self-maintenance (i.e., costs of reproduction), empirical studies do not always support this assumption. In this dissertation, I investigate the factors that contribute to costs of reproduction in female house mice by using multiple approaches. The overarching goal of this dissertation is to test the assumption that the increased demands of reproduction necessarily incur costs that negatively impact self-maintenance processes, which in turn affect future reproductive performance and/or survival of mothers and their young. To achieve this goal, I used a combination of data exploration and experimental studies to assess costs of reproduction in female wild-derived and laboratory house mice. First, I explored patterns of life-history and metabolic trait co-variation at the intraspecific level across strains of inbred mice with the goal of understanding the genetic architecture that may underlie constraints to reproductive performance. I then investigated how reproductive performance changes with maternal age and protein consumption, finding that performance is not static across age and that protein intake mediates age-specific reproductive strategies without a necessary cost to future reproductive bouts. I then explored the relationship between reproduction and immune defense in my next two chapters by assessing changes in maternal antibody responses as a function of reproductive demand, as well as the developmental effects of that immune challenge on offspring. These two chapters demonstrate that methodologies used to investigate the relationship between female reproduction and immune defense should take a female-centric approach and incorporate responses in both mothers and their offspring. Together, my dissertation work contributes to the current literature by exploring gaps in our understanding and by testing implicit assumptions common among previous investigations

Cross theorems with singularities

We establish extension theorems for separately holomorphic mappings defined on sets of the form W\setminus M with values in a complex analytic space which possesses the Hartogs extension property. Here W is a 2-fold cross of arbitrary complex manifolds and M is a set of singularities which is locally pluripolar (resp. thin) in fibers.Comment: 30 pages. A previous version is available at the ICTP preprints website (ref. IC2007073

A bioturbation classification of European marine infaunal invertebrates

Bioturbation, the biogenic modification of sediments through particle reworking and burrow ventilation, is a key mediator of many important geochemical processes in marine systems. In situ quantification of bioturbation can be achieved in a myriad of ways, requiring expert knowledge, technology, and resources not always available, and not feasible in some settings. Where dedicated research programmes do not exist, a practical alternative is the adoption of a trait-based approach to estimate community bioturbation potential (BPc). This index can be calculated from inventories of species, abundance and biomass data (routinely available for many systems), and a functional classification of organism traits associated with sediment mixing (less available). Presently, however, there is no agreed standard categorization for the reworking mode and mobility of benthic species. Based on information from the literature and expert opinion, we provide a functional classification for 1033 benthic invertebrate species from the northwest European continental shelf, as a tool to enable the standardized calculation of BPc in the region. Future uses of this classification table will increase the comparability and utility of large-scale assessments of ecosystem processes and functioning influenced by bioturbation (e.g., to support legislation). The key strengths, assumptions, and limitations of BPc as a metric are critically reviewed, offering guidelines for its calculation and application

Participant characteristics in the prevention of gestational diabetes as evidence for precision medicine:a systematic review and meta-analysis

BackgroundPrecision prevention involves using the unique characteristics of a particular group to determine their responses to preventive interventions. This study aimed to systematically evaluate the participant characteristics associated with responses to interventions in gestational diabetes mellitus (GDM) prevention. MethodsWe searched MEDLINE, EMBASE, and Pubmed to identify lifestyle (diet, physical activity, or both), metformin, myoinositol/inositol and probiotics interventions of GDM prevention published up to May 24, 2022. ResultsFrom 10347 studies, 116 studies (n = 40940 women) are included. Physical activity results in greater GDM reduction in participants with a normal body mass index (BMI) at baseline compared to obese BMI (risk ratio, 95% confidence interval: 0.06 [0.03, 0.14] vs 0.68 [0.26, 1.60]). Combined diet and physical activity interventions result in greater GDM reduction in participants without polycystic ovary syndrome (PCOS) than those with PCOS (0.62 [0.47, 0.82] vs 1.12 [0.78–1.61]) and in those without a history of GDM than those with unspecified GDM history (0.62 [0.47, 0.81] vs 0.85 [0.76, 0.95]). Metformin interventions are more effective in participants with PCOS than those with unspecified status (0.38 [0.19, 0.74] vs 0.59 [0.25, 1.43]), or when commenced preconception than during pregnancy (0.21 [0.11, 0.40] vs 1.15 [0.86–1.55]). Parity, history of having a large-for-gestational-age infant or family history of diabetes have no effect on intervention responses.ConclusionsGDM prevention through metformin or lifestyle differs according to some individual characteristics. Future research should include trials commencing preconception and provide results disaggregated by a priori defined participant characteristics including social and environmental factors, clinical traits, and other novel risk factors to predict GDM prevention through interventions.</p

Completely Bare Swedish Superlatives

This paper shows that Swedish differs from both German and English with respect to the distribution and interpretation of definiteness-marking on superlatives: Bare degree and amount superlatives unambiguously receive a relative interpretation, definite-marked amount superlatives are unambiguously ‘proportional’ (although they do not always carry a ‘more than half’ interpretation), and definite-marked degree superlatives can have an absolute or a relative reading. We show that an analysis based on movement of the superlative morpheme accounts well for the Swedish pattern but does not provide the tools for a cross-linguistically valid framework, failing in particular to account well for relative readings in conjunction with definiteness-marking. We therefore propose an alternative, non-movement approach building on a very recent treatment of the superlative morpheme, giving it access to a contrast set and an association relation. The crucial difference between Swedish on the one hand and English and German on the other hand is proposed to lie in whether the association relation is saturated through semantic composition or by context

Active Learning for Surrogate Models to Augment AI-Driven Molecular Design

This project investigated whether an active learning (AL) framework can help mitigate computational costs for AI-driven molecular design, without negatively impacting accuracy. The surrogate models Random Forest (RF) and Support Vector Regression (SVR) were tested together with the acquisition functions (AF) Random, Thompson Sampling (TS), Tanimoto Similarity, Expected Improvement (EI), Probability of Improvement (PI), Upper Confidence Bound (UCB) and ε−Greedy. Of these, the combination RF and Random acquisition were concluded to perform the best with regards to error rate, measured as root mean square error, and time consumption, measured in runtime per epoch. SVR had slightly lower error, but took substantially longer time. Depending on the choice of AF, one run using RF took approximately 2-17.5 hours, while one run using SVR took approximately 100-175 hours. Four tuning parameters were introduced to see if they could further optimize the framework. It was discovered that a longer retrain interval and a smaller acquisition batch did not significantly impact accuracy while shortening the time consumption. To summarise, an RF model with the Random AF with a 5 epoch initial pooling, no warm-up phase, a retrain interval of 20 and an acquisition batch size of 20 was selected to mitigate computational costs while simultaneously keeping the error stable