Universal allometry from empirical parameters

Allometric settings of population dynamics models are appealing due to their parsimonious nature and broad utility when studying system level effects. Here, we parameterise the size-scaled Rosenzweig-Macarthur ODEs to eliminate prey-mass dependency. We define the functional response term to match experiments, and examine situations where metabolic theory derivations and observation diverge. We produce dynamics consistent with observation. Our parameterisation of the Rosenzweig-Macarthur system is an accurate minimal model across 15+ orders of mass magnitude.

Modelling the sedimentary response to orbital variations.

<div> <p>Carbonate-rich middle Eocene sedimentary sequences are relatively scarce, hampering the reconstruction of paleoclimate dynamics within this high-CO<sub>2</sub> world. Nevertheless, the Newfoundland Ridge (North-Atlantic Ocean) hosts a unique sedimentary archive of middle Eocene paleoceanographic change at astronomical 10<sup>4</sup>-year resolution. International Ocean Discovery Program (IODP) Sites U1408 and U1410 exhibit well-defined lithologic alternations between calcareous ooze and clay-rich intervals, occurring at the obliquity beat and associated with changing intensities of Northern Component Water (NCW) formation (Vahlenkamp et al., 2018). These lithological variations are captured by the calcium-iron ratio (Ca/Fe) proxy as a measure of carbonate content. Yet, the asymmetric shape of the Ca/Fe cycles immediately reflects a strong non-linear response to the sinusoidal obliquity forcing. To explore the causes of this non-linearity, we built a simple physically-motivated and time-dependent model that simulates the sedimentary response at IODP Sites U1408 and U1410 between 46 and 42 million years ago.  </p> </div><div> <p>dy/dt = 1/T (b<sup>x</sup> – y)</p> </div><div> <p>The orbital input x constitutes of an insolation gradient during boreal winter (more specifically at winter solstice), as NCW formation is a high northern latitude winter process that depends on the Atlantic interhemispheric temperature gradient<span> </span>(Karas et al., 2017; Vahlenkamp et al., 2018). The latitudes between which the insolation gradient x is calculated is not user-prescribed but part of the parametrization of the model. Two further parameters define the model. The characteristic time constant T accelerates (T < 1) or slows the response to the forcing (T > 1), whereas the base of the exponential-response term b determines the degree of non-linearity in the system. We explored this four-space first with a coarse and then with a finer mesh, and found that the optimum model lies in the neighbourhood of the following values: latitudinal gradient between 63°N and 31°S, T = 4.94 kyr, b = 2.13. The corresponding system reproduces the asymmetric shape of the Ca/Fe cycles, while also exhibiting precession-obliquity interference patterns that occur in the proxy series. These kind of simple modelling efforts hold the potential to refine our mechanistic understanding of the Earth System response to astronomical forcing in the deep and warmer-than-present geologic past.</p> </div><div> <p>Karas et al. (2017) Pliocene oceanic seaways and global climate. Scientific Reports 7: 39842</p> <p>Vahlenkamp et al. (2018) Astronomically paced changes in deep-water circulation in the western North Atlantic during the middle Eocene. Earth and Planetary Science Letter 484: 329 – 340.</p> </div><p> </p><p> </p>

Predicting On-axis Rotorcraft Dynamic Responses Using Machine Learning Techniques

Physical-law-based models are widely utilized in the aerospace industry. One such use is to provide flight dynamics models for use in flight simulators. For human-in-the-loop use, such simulators must run in real-time. Owing to the complex physics of rotorcraft flight, to meet this real-time requirement, simplifications to the underlying physics sometimes have to be applied to the model, leading to errors in the model's predictions of the real vehicle's response. This study investigated whether a machine-learning technique could be employed to provide rotorcraft dynamic response predictions. Machine learning was facilitated using a Gaussian process (GP) nonlinear autoregressive model, which predicted the on-axis pitch rate, roll rate, yaw rate, and heave responses of a Bo105 rotorcraft. A variational sparse GP model was then developed to reduce the computational cost of implementing the approach on large datasets. It was found that both of the GP models were able to provide accurate on-axis response predictions, particularly when the model input contained all four control inceptors and one lagged on-axis response term. The predictions made showed improvement compared to a corresponding physics-based model. The reduction of training data to one-third (rotational axes) or one-half (heave axis) resulted in only minor degradation of the sparse GP model predictions.

Identification of circularRNAs and their targets in Gossypium under Verticillium wilt stress based on RNA-seq

Circular RNAs (circRNAs), a class of recently discovered non-coding RNAs, play a role in biological and developmental processes. A recent study showed that circRNAs exist in plants and play a role in their environmental stress responses. However, cotton circRNAs and their role in Verticillium wilt response have not been identified up to now. In this study, two CSSLs (chromosome segment substitution lines) of G.barbadense introgressed into G. hirsutum, CSSL-1 and CSSL-4 (a resistant line and a susceptible line to Verticillium wilt, respectively), were inoculated with V. dahliae for RNA-seq library construction and circRNA analysis. A total of 686 novel circRNAs were identified. CSSL-1 and CSSL-4 had similar numbers of circRNAs and shared many circRNAs in common. However, CSSL-4 differentially expressed approximately twice as many circRNAs as CSSL-1, and the differential expression levels of the common circRNAs were generally higher in CSSL-1 than in CSSL-4. Moreover, two C-RRI comparisons, C-RRI-vs-C-RRM and C-RRI-vs-C-RSI, possessed a large proportion (approximately 50%) of the commonly and differentially expressed circRNAs. These results indicate that the differentially expressed circRNAs may play roles in the Verticillium wilt response in cotton. A total of 280 differentially expressed circRNAs were identified. A Gene Ontology analysis showed that most of the ‘stimulus response’ term source genes were NBS family genes, of which most were the source genes from the differentially expressed circRNAs, indicating that NBS genes may play a role in Verticillium wilt resistance and might be regulated by circRNAs in the disease-resistance process in cotton.

A fractional-order delay differential model for Ebola infection and CD8+ T-cells response: Stability analysis and Hopf bifurcation

In this paper, we study a fractional-order model with time-delay to describe the dynamics of Ebola virus infection with cytotoxic T-lymphocyte (CTL) response in vivo. The time-delay is introduced in the CTL response term to represent time required to stimulate the immune system. Based on fractional Laplace transform, some conditions on stability and Hopf bifurcation are derived for the model. The analysis shows that the fractional-order with time-delay can effectively enrich the dynamics and strengthen the stability condition of fractional-order infection model. Finally, the derived theoretical results are justified by some numerical simulations.

Effects of Type of Recall Test and Spaced Presentations of Stimulus Terms, Response Terms and Stimulus-Response Terms on Retention in Paired-Associate Learning

The present experiment tested the effects of reinforcement type (stimulus term, response term, and stimulus-response pairs) and type of recall-retention test (stimulus type or response type) as between- S variables and delay-of-reinforcement interval as a within- S variable on retention in paired-associate learning. The analysis showed that type of reinforcement and delay-of-reinforcement interval resulted in significant effects. Type of recall-retention test was not significant and interactions were nonsignificant.

Inter-Item Associative Strength and Proactive Inhibition in Paired-Associate Learning

The experimental design was 2 × 2 factorial, with 2 levels of prior list (one or none), 2 of response term inter-item associative strength (high or low), and a 15-min. retention interval. The expectation was that high inter-item associative strength would reduce proactive inhibition. The hypothesis failed; the proportion of function words per list had no effect on recall.