Earth’s inner core is changing in shape as well as in rotation rate
Related Articles
Twist–torsion coupling in beating axonemes
Motile cilia and flagella produce regular bending waves that enable single-cell navigation due to non-planar waveforms with characteristic torsion. However, it is not known how torsion, a geometric property of the three-dimensional waveform, relates to mechanical twist deformations of the axoneme, the conserved cytoskeletal core of cilia and flagella. Here we show that axoneme twisting and torsion are coupled and that twist waves propagate along the beating axoneme of Chlamydomonas reinhardtii algae. We resolve the three-dimensional shapes of the axonemal waveform with nanometre precision at millisecond timescales using defocused dark-field microscopy and beat-cycle averaging, observing regular hetero-chiral torsion waves propagating base to tip. To investigate whether the observed torsion results from axonemal twist, we attach gold nanoparticles to axonemes and measure their cross-section rotation during beating. We find that, locally, the axonemal cross-section co-rotates with the bending plane, evidencing twist–torsion coupling. Our results demonstrate the link between shape and mechanical deformation in beating axonemes and can inform models of the dynamics of motor proteins inside the axoneme responsible for shaping the beat of motile cilia.
Conceptualizing space environmental sustainability
Recent advancements have significantly enhanced the capabilities for in-space servicing, assembly, and manufacturing (ISAM), to develop infrastructure in orbit and on the surface of celestial bodies. This progress is a departure from the traditional sustainability paradigm focused solely on Earth, highlighting the urgent need to define and operationalize the concept of “space sustainability” along with the development of an evaluation framework. The expansion of human activity into space, particularly in low-earth orbit, cis-lunar space, and beyond, underscores the critical importance of considering sustainability implications. Leveraging space resources offers economic growth and sustainable development opportunities, while reducing pressure on Earth’s ecosystems. This paradigm shift requires responsible and ethical utilization of space resources. A space sustainability assessment framework is essential for guiding ISAM capabilities, operations, missions, standards, and policies. This paper introduces an initial framework encompassing (1) pollution, (2) resource depletion, (3) landscape alteration, and (4) space environmental justice, with potential metrics (resources use and emissions, midpoint, and endpoint indicators) to measure impacts in the four domains.
MADS31 supports female germline development by repressing the post-fertilization programme in cereal ovules
The female germline of flowering plants develops within a niche of sporophytic (somatic) ovule cells, also referred to as the nucellus. How niche cells maintain their own somatic developmental programme, yet support the development of adjoining germline cells, remains largely unknown. Here we report that MADS31, a conserved MADS-box transcription factor from the B-sister subclass, is a potent regulator of niche cell identity. In barley, MADS31 is preferentially expressed in nucellar cells directly adjoining the germline, and loss-of-function mads31 mutants exhibit deformed and disorganized nucellar cells, leading to impaired germline development and partial female sterility. Remarkably similar phenotypes are observed in mads31 mutants in wheat, suggesting functional conservation within the Triticeae tribe. Molecular assays indicate that MADS31 encodes a potent transcriptional repressor, targeting genes in the ovule that are normally active in the seed. One prominent target of MADS31 is NRPD4b, a seed-expressed component of RNA polymerase IV/V that is involved in epigenetic regulation. NRPD4b is directly repressed by MADS31 in vivo and is derepressed in mads31 ovules, while overexpression of NRPD4b recapitulates the mads31 ovule phenotype. Thus, repression of NRPD4b by MADS31 is required to maintain ovule niche functionality. Our findings reveal a new mechanism by which somatic ovule tissues maintain their identity and support germline development before transitioning to the post-fertilization programme.
Flexible, multimodal device for measurement of body temperature, core temperature, thermal conductivity and water content
Body core temperature is an important physiological indicator for self-health management and medical diagnosis. However, existing devices always fails to achieve continuous monitoring of core body temperature due to their invasive or motion-restricted measurement principles. Here, a wearable flexible device which can continuously monitor the core body temperature was developed. The flexible device integrated with fourteen temperature sensors and one thermal conductivity sensor on the polydimethylsiloxane substrate can be conformally attached to the human skin. With the wearable data processing module and wireless communication module, the continuous monitoring of the core body temperature for 24 h and the portable monitoring of the skin thermal conductivity were realized using this device. Owing to the annular distribution design of the temperature sensor and the directional heat transfer design of the thermal conductivity sensor, this device is comparable in accuracy and stability compared to standard instruments that require invasive or motion-restricted measurements.
Crop rotation increases Tibetan barley yield and soil quality on the Tibetan Plateau
Tibetan barley (Hordeum vulgare) accounts for over 70% of the total food production in the Tibetan Plateau. However, continuous cropping of Tibetan barley causes soil degradation, reduces soil quality and causes yield decline. Here we explore the benefits of crop rotation with wheat and rape to improve crop yield and soil quality. We conducted 39 field experiments on the Tibetan Plateau, comparing short-term (≤5 years), 5–10 years and long-term (≥10 years) continuous cropping with rotation of Tibetan barley with wheat or rape. Results showed that Tibetan barley–wheat and Tibetan barley–rape rotations increased yields by 17% and 12%, respectively, while improving the soil quality index by 11% and 21%, compared with long-term continuous cropping. Both Tibetan barley rotations with wheat and rape improved soil quality and consequently yield, mainly by increasing soil microbial biomass nitrogen and microbial biomass carbon and decreasing pH. By contrast, long-term continuous cropping led to decreased soil organic matter, lower microbial biomass nitrogen and increased pH, contributing to yield decline. The benefits of rotations on crop yield and soil quality increased over time. Implementing crop rotation with wheat or rape thus offers a sustainable agricultural strategy for improving food security on the Tibetan Plateau.
Responses