Two recent papers in Nature show that human blastocyst-like structures (or blastoids) can be generated from human pluripotent stem cells (Yu et al 2021) or through reprogramming of fibroblasts (Liu et al 2021), respectively. Both papers perform extensive single cell transcriptional analysis and compare blastoid cells with the cells in preimplantation human embryos, leading to a conclusion that the blastoids contain cell lineages corresponding to the epiblast, primitive endoderm and trophectoderm in preimplantation human embryos. Transcriptional analysis is, however, critically dependent on having relevant reference samples, not only of targeted cell types but also of potential alternative cell lineages. For this reason, we have reevaluated the blastoid data with a more comprehensive cellular reference, including extended cultures of blastocysts, several stem cell-based embryo models and a gastrulation stage human specimen. From this reanalysis we resolve that reprogrammed blastoids by Liu et al. fail to generate cells with trophectoderm profiles. Instead, cells identified as trophectoderm lineages in reprogrammed blastoids possess a transcriptional profile more representative of amniotic cells in post-implantation human embryos. Our reanalysis also shows that stem cell-derived blastoids did contain trophectoderm-like cells, highlighting the potential of human blastoids to model blastocyst development.

We employ l39 La NMR spectroscopy as a structural probe of metallic La2Cu04+a. We find a distribution of lateral displacements of the oxygen atoms which form the apices of the oxygen octahedra. We directly observe a wide distribution of structures of the La-O layer; this distribution is strongly temperature dependent. We present copper NQR spectra which reveal a second, unexplained, copper site in the Cu02 planes. We show that these features are not manifestations of disturbances of the lattice by interstitial dopants, but are the intrinsic response of La2CuC>4+a to doped holes.

In contrast with the simultaneous structural and magnetic first order phase transition T0 previously reported, our detailed investigation on an underdoped Ba(0.84)K(0.16)Fe2As2 single crystal unambiguously revealed that the transitions are not concomitant. The tetragonal (τ: I4/mmm)-orthorhombic (ϑ: Fmmm) structural transition occurs at T(S)≃110 K, followed by an adjacent long-range antiferromagnetic (AFM) transition at T(N)≃102 K. Hysteresis and coexistence of the τ and ϑ phases over a finite temperature range observed by NMR experiments confirm the first order character of the τ-ϑ transition and provide evidence that both T(S) and T(N) are strongly correlated. Our data also show that superconductivity develops in the ϑ phase below T(c)=20 K and coexists with AFM. This new observation, T(S)≠T(N), firmly establishes another similarity between the hole-doped BaFe2As2 and the electron-doped iron-arsenide superconductors.