The energy levels of hydrogen-like atomic systems can be calculated with great precision. Starting from their quantum mechanical solution, they have been refined over the years to include the electron spin, the relativistic and quantum field effects, and tiny energy shifts related to the complex structure of the nucleus. These energy shifts caused by the nuclear structure are vastly magnified in hydrogen-like systems formed by a negative muon and a nucleus, so spectroscopy of these muonic ions can be used to investigate the nuclear structure with high precision. Here we present the measurement of two 2S–2P transitions in the muonic helium-4 ion that yields a precise determination of the root-mean-square charge radius of the $\alpha$ particle of 1.67824(83) femtometres. This determination from atomic spectroscopy is in excellent agreement with the value from electron scattering1, but a factor of 4.8 more precise, providing a benchmark for few-nucleon theories, lattice quantum chromodynamics and electron scattering. This agreement also constrains several beyond-standard-model theories proposed to explain the proton-radius puzzle2–5, in line with recent determinations of the proton charge radius6–9, and establishes spectroscopy of light muonic atoms and ions as a precise tool for studies of nuclear properties. The 2S–2P transitions in muonic helium-4 ions are measured using laser spectroscopy and used to obtain an $\alpha$-particle charge-radius value five times more precise than that from electron scattering.

The growing use of wearable devices has been stimulating research efforts in the development of energy harvesters as more portable and practical energy sources alternatives. The field of piezoelectric nanogenerators (PENGs) and triboelectric nanogenerators (TENGs), especially employing zinc oxide (ZnO) nanowires (NWs), has greatly flourished in recent years. Despite its modest piezoelectric coefficient, ZnO is very attractive due to its sustainable raw materials and the facility to obtain distinct morphologies, which increases its multifunctionality. The integration of ZnO nanostructures into polymeric matrices to overcome their fragility has already been proven to be fruitful, nevertheless, their concentration in the composite should be optimized to maximize the harvesters' output, an aspect that has not been properly addressed. This work studies a composite with variable concentrations of ZnO nanorods (NRs), grown by microwave radiation assisted hydrothermal synthesis, and polydimethylsiloxane (PDMS). With a 25 wt % ZnO NRs concentration in a composite that was further micro-structured through laser engraving for output enhancement, a nanogenerator (NG) was fabricated with an output of 6 V at a pushing force of 2.3 N. The energy generated by the NG could be stored and later employed to power small electronic devices, ultimately illustrating its potential as an energy harvesting device.

Material, Culture, Scientific Culture: Industrial Heritage for the Future

In this article, characterization of fully patterned zinc-tin oxide (ZTO)-based memristive devices with feature sizes as small as 25 µm2 is presented. The devices are patterned via lift-off with a platinum bottom contact and a gold-titanium top contact. An on/off ratio of more than two orders of magnitude is obtained without the need for electroforming processes. Set operation is a current controlled process, whereas the reset is voltage dependent. The temperature dependency of the electrical characteristics reveals a bulk-dominated conduction mechanism for high resistance states. However, the charge transport at low resistance state is consistent with Schottky emission. Synaptic properties such as potentiation and depression cycles, with progressive increases and decreases in the conductance value under 50 successive pulses, are shown. This validates the potential use of ZTO memristive devices for a sustainable and energy-efficient brain-inspired deep neural network computation.

A remarkably well-preserved, almost complete and articulated new specimen (GP/2E 9266) of Tupandactylus navigans is here described for the Early Cretaceous Crato Formation of Brazil. The new specimen comprises an almost complete skeleton, preserving both the skull and post-cranium, associated with remarkable preservation of soft tissues, which makes it the most complete tapejarid known thus far. CT-Scanning was performed to allow the assessment of bones still covered by sediment. The specimen can be assigned to Tupa. navigans due to its vertical supra-premaxillary bony process and short and rounded parietal crest. It also bears the largest dentary crest among tapejarine pterosaurs and a notarium, which is absent in other representatives of the clade. The new specimen is here regarded as an adult individual. This is the first time that postcranial remains of Tupa. navigans are described, being also an unprecedented record of an articulated tapejarid skeleton from the Araripe Basin.

We report a new specimen of the plesiosaur Cardiocorax mukulu that includes the most complete plesiosaur skull from sub-Saharan Africa. The well-preserved three-dimensional nature of the skull offers rare insight into the cranial anatomy of elasmosaurid plesiosaurians. The new specimen of Cardiocorax mukulu was recovered from Bentiaba, Namibe Province in Angola, approximately three meters above the holotype. The new specimen also includes an atlas-axis complex, seventeen postaxial cervical vertebrae, partial ribs, a femur, and limb elements. It is identified as Cardiocorax mukulu based on an apomorphy shared with the holotype where the cervical neural spine is approximately as long anteroposteriorly as the centrum and exhibits a sinusoidal anterior margin. The new specimen is nearly identical to the holotype and previously referred material in all other aspects. Cardiocorax mukulu is returned in an early-branching or intermediate position in Elasmosauridae in four out of the six of our phylogenetic analyses. Cardiocorax mukulu lacks the elongated cervical vertebrae that is characteristic of the extremely long-necked elasmosaurines, and the broad skull with and a high number of maxillary teeth (28–40) which is characteristic of Aristonectinae. Currently, the most parsimonious explanation concerning elasmosaurid evolutionary relationships, is that Cardiocorax mukulu represents an older lineage of elasmosaurids in the Maastrichtian.