资源环境科技发展态势分析平台

Skeletal inclusions in approximately 99-million-year-old amber from northern Myanmar provide unprecedented insights into the soft tissue and skeletal anatomy of minute fauna, which are not typically preserved in other depositional environments(1-3). Among a diversity of vertebrates, seven specimens that preserve the skeletal remains of enantiornithine birds have previously been described(1,4-8), all of which (including at least one seemingly mature specimen) are smaller than specimens recovered from lithic materials. Here we describe an exceptionally well-preserved and diminutive bird-like skull that documents a new species, which we name Oculudentavis khaungraae gen. et sp. nov. The find appears to represent the smallest known dinosaur of the Mesozoic era, rivalling the bee hummingbird (Mellisuga helenae)-the smallest living bird-in size. The O. khaungraae specimen preserves features that hint at miniaturization constraints, including a unique pattern of cranial fusion and an autapomorphic ocular morphology(9) that resembles the eyes of lizards. The conically arranged scleral ossicles define a small pupil, indicative of diurnal activity. Miniaturization most commonly arises in isolated environments, and the diminutive size of Oculudentavis is therefore consistent with previous suggestions that this amber formed on an island within the Trans-Tethyan arc(10). The size and morphology of this species suggest a previously unknown bauplan, and a previously undetected ecology. This discovery highlights the potential of amber deposits to reveal the lowest limits of vertebrate body size.

A quantum dot device designed to host four electrons is used to demonstrate Nagaoka ferromagnetism-a model of itinerant magnetism that has so far been limited to theoretical investigation.

Engineered, highly controllable quantum systems are promising simulators of emergent physics beyond the simulation capabilities of classical computers(1). An important problem in many-body physics is itinerant magnetism, which originates purely from long-range interactions of free electrons and whose existence in real systems has been debated for decades(2,3). Here we use a quantum simulator consisting of a four-electron-site square plaquette of quantum dots(4) to demonstrate Nagaoka ferromagnetism(5). This form of itinerant magnetism has been rigorously studied theoretically(6-9) but has remained unattainable in experiments. We load the plaquette with three electrons and demonstrate the predicted emergence of spontaneous ferromagnetic correlations through pairwise measurements of spin. We find that the ferromagnetic ground state is remarkably robust to engineered disorder in the on-site potentials and we can induce a transition to the low-spin state by changing the plaquette topology to an open chain. This demonstration of Nagaoka ferromagnetism highlights that quantum simulators can be used to study physical phenomena that have not yet been observed in any experimental system. The work also constitutes an important step towards large-scale quantum dot simulators of correlated electron systems.

Multiomic profiling of several cohorts of patients treated with immune checkpoint blockade highlights the presence and potential role of B cells and tertiary lymphoid structures in promoting therapy response.

Treatment with immune checkpoint blockade (ICB) has revolutionized cancer therapy. Until now, predictive biomarkers(1-10) and strategies to augment clinical response have largely focused on the T cell compartment. However, other immune subsets may also contribute to anti-tumour immunity(11-15), although these have been less well-studied in ICB treatment(16). A previously conducted neoadjuvant ICB trial in patients with melanoma showed via targeted expression profiling(17) that B cell signatures were enriched in the tumours of patients who respond to treatment versus non-responding patients. To build on this, here we performed bulk RNA sequencing and found that B cell markers were the most differentially expressed genes in the tumours of responders versus non-responders. Our findings were corroborated using a computational method (MCP-counter(18)) to estimate the immune and stromal composition in this and two other ICB-treated cohorts (patients with melanoma and renal cell carcinoma). Histological evaluation highlighted the localization of B cells within tertiary lymphoid structures. We assessed the potential functional contributions of B cells via bulk and single-cell RNA sequencing, which demonstrate clonal expansion and unique functional states of B cells in responders. Mass cytometry showed that switched memory B cells were enriched in the tumours of responders. Together, these data provide insights into the potential role of B cells and tertiary lymphoid structures in the response to ICB treatment, with implications for the development of biomarkers and therapeutic targets.