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The planets’ gravitational interaction causes rhythmic changes in Earth’s orbital parameters (also called Milanković cycles), which have powerful applications in geology and astrochronology. For instance, the primary astronomical eccentricity cycle due to the secular frequency term (g₂−g₅) (∼405 kyr in the recent past) utilized in deep-time analyses is dominated by the orbits of Venus and Jupiter, i.e., long eccentricity cycle. The widely accepted and long-held view is that (g₂−g₅) was practically stable in the past and may hence be used as a “metronome” to reconstruct accurate geologic ages and chronologies. However, using state-of-the-art integrations of the solar system, we show here that (g₂−g₅) can become unstable over long timescales, without major changes in, or destabilization of, planetary orbits. The (g₂−g₅) disruption is due to the secular resonanceσ₁₂= (g₁−g₂) + (s₁−s₂), a major contributor to solar system chaos. We demonstrate that entering/exiting theσ₁₂resonance is a common phenomenon on long timescales, occurring in ∼40% of our solutions. Duringσ₁₂-resonance episodes, (g₂−g₅) is very weak or absent and Earth’s orbital eccentricity and climate-forcing spectrum are unrecognizable compared to the recent past. Our results have fundamental implications for geology and astrochronology, as well as climate forcing, because the paradigm that the long eccentricity cycle is stable, dominates Earth's orbital eccentricity spectrum, and has a period of ∼405 kyr requires revision.

 

Abstract Each year, bovine respiratory disease (BRD) results in significant economic loss in the cattle sector, and novel metabolic profiling for early diagnosis represents a promising tool for developing effective measures for disease management. Here, 1 H-nuclear magnetic resonance ( 1 H-NMR) spectra were used to characterize metabolites from blood plasma collected from male dairy calves (n = 10) intentionally infected with two of the main BRD causal agents, bovine respiratory syncytial virus (BRSV) and Mannheimia haemolytica (MH), to generate a well-defined metabolomic profile under controlled conditions. In response to infection, 46 metabolites (BRSV = 32, MH = 33) changed in concentration compared to the uninfected state. Fuel substrates and products exhibited a particularly strong effect, reflecting imbalances that occur during the immune response. Furthermore, 1 H-NMR spectra from samples from the uninfected and infected stages were discriminated with an accuracy, sensitivity, and specificity ≥ 95% using chemometrics to model the changes associated with disease, suggesting that metabolic profiles can be used for further development, understanding, and validation of novel diagnostic tools. 

Teacher education has begun to embrace the use of 360 videos to improve preservice teachers' (PSTs) engagement and immersion. While recent research on such use is promising overall, there are specific questions that have been left unanswered about the construct of presence in 360 videos. More specifically, research has yet to fully explore how video delivery devices and PST characteristics may impact presence. The purpose of this study was to respond to this gap in the literature by examining PST major, delivery device (ie, head mounted display vs. flat screen), and the interaction between the two in informing presence. A total of 93 PSTs watched 360 videos and then completed a questionnaire. Findings indicated that presence in head‐mounted displays was related to emotions and agency. Conversely, presence with flat screens meant familiarity and control. Moreover, PST major was a predictor of presence, suggesting that 360 videos should be personalized according to PST career and professional goals. Finally, the interaction effect of preparing to teach K‐12 mathematics and wearing a head‐mounted display had a negative and statistically significant effect on participants' perceived presence, thus indicating a non‐cumulative effect.

What is already known about this topic

360 videos are increasingly used to support preservice teacher training.

360 videos for teacher education foster immersion, presence, and noticing skills.

What this paper adds

Empirical evidence that 360 videos experienced with head‐mounted display facilitate agency and emotional involvement.

Empirical evidence that 360 videos experienced with flat screens facilitate feelings of control.

Data showed that preservice teachers' content area (math) was a positive predictor of presence in 360 videos.

Implications for practice and/or policy

Head‐mounted displays show promise as a delivery mode for 360 videos in teacher education.

360 videos should be personalized according to PST career and professional goals.

The eXtended Reality Presence Scale is confirmed as a robust instrument to measure presence in immersive environments.

More research is needed to evaluate the scalability of this approach in other contexts.

 

Reliable studies of the long-term dynamics of planetary systems require numerical integrators that are accurate and fast. The challenge is often formidable because the chaotic nature of many systems requires relative numerical error bounds at or close to machine precision (∼10⁻¹⁶, double-precision arithmetic); otherwise, numerical chaos may dominate over physical chaos. Currently, the speed/accuracy demands are usually only met by symplectic integrators. For example, the most up-to-date long-term astronomical solutions for the solar system in the past (widely used in, e.g., astrochronology and high-precision geological dating) have been obtained using symplectic integrators. However, the source codes of these integrators are unavailable. Here I present the symplectic integratororbitN(lean version 1.0) with the primary goal of generating accurate and reproducible long-term orbital solutions for near-Keplerian planetary systems (here the solar system) with a dominant massM₀. Among other features,orbitN-1.0includesM₀’s quadrupole moment, a lunar contribution, and post-Newtonian corrections (1PN) due toM₀(fast symplectic implementation). To reduce numerical round-off errors, Kahan compensated summation was implemented. I useorbitNto provide insight into the effect of various processes on the long-term chaos in the solar system. Notably, 1PN corrections have the opposite effect on chaoticity/stability on a 100 Myr versus Gyr timescale. For the current application,orbitNis about as fast as or faster (factor 1.15–2.6) than comparable integrators, depending on hardware.¹¹

The orbitN source code (C) is available athttp://github.com/rezeebe/orbitN.

 

Climate change is leading to substantial global thermal changes, which are particularly pronounced in polar regions. Few studies have examined the impact of heat stress on reproduction in Antarctic terrestrial arthropods, specifically how brief, extreme events may alter survival. We observed that sublethal heat stress reduces male fecundity in an Antarctic mite, yielding females that produced fewer viable eggs. Females and males collected from microhabitats with high temperatures showed a similar reduction in fertility. This impact is temporary, as indicated by recovery of male fecundity following return to cooler, stable conditions. The diminished fecundity is likely due to a drastic reduction in the expression of male-associated factors that occur in tandem with a substantial increase in the expression of heat shock proteins. Cross mating between mites from different sites confirmed that heat-exposed populations have impaired male fertility. However, the impact on fertility declines with time when the mites are allowed to recover under less stressful conditions, suggesting that the negative effects are transient. Modeling indicated that heat stress is likely to reduce population growth and that short bouts of non-lethal heat stress could have substantial effects on local populations of Antarctic arthropods.