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Electrons bound in highly charged heavy ions such as hydrogen-like bismuth 209 Bi 82+ experience electromagnetic fields that are a million times stronger than in light atoms. Measuring the wavelength of light emitted and absorbed by these ions is therefore a sensitive testing ground for quantum electrodynamical (QED) effects and especially the electron–nucleus interaction under such extreme conditions. However, insufficient knowledge of the nuclear structure has prevented a rigorous test of strong-field QED. Here we present a measurement of the so-called specific difference between the hyperfine splittings in hydrogen-like and lithium-like bismuth 209 Bi 82+,80+ with a precision that is improved by more than an order of magnitude. Even though this quantity is believed to be largely insensitive to nuclear structure and therefore the most decisive test of QED in the strong magnetic field regime, we find a 7- σ discrepancy compared with the theoretical prediction. Precision measurements provide a sensitive test of fundamental constants and their uncertainties. Here the authors precisely measure the hyperfine structure splitting in bismuth ions, and report significant discrepancy with the theoretical prediction of quantum electrodynamics.

The number of precaudal vertebrae in all extant crocodylians is remarkably conservative, with nine cervicals, 15 dorsals and two sacrals, a pattern present also in their closest extinct relatives. The consistent vertebral count indicates a tight control of axial patterning by Hox genes during development. Here we report on a deviation from this pattern based on an associated skeleton of the giant caimanine Purussaurus, a member of crown Crocodylia, and several other specimens from the Neogene of the northern neotropics. P. mirandai is the first crown-crocodylian to have three sacrals, two true sacral vertebrae and one non-pathological and functional dorsosacral, to articulate with the ilium (pelvis). The giant body size of this caiman relates to locomotory and postural changes. The iliosacral configuration, a more vertically oriented pectoral girdle, and low torsion of the femoral head relative to the condyles are hypothesized specializations for more upright limb orientation or weight support. All living crocodiles, alligators, caimans and gharials – collectively called crocodylians – have a similar body plan that suits their lifestyles as aquatic ambush predators. This similarity extends throughout their bodies, including the skeleton. Their backbones, for example, always have nine vertebrae in the neck, 15 in the trunk, and two in the pelvis. Closely related extinct crocodylians also organize their spines in the same way. Scheyer et al., however, now report that one extinct caiman called Purussaurus mirandai had a spine that was structured unlike any other known crocodylian. Weighing almost three tons (~2,600 kg), the 10-meter-long Purussaurus was more than twice as heavy as the largest living crocodylian, the saltwater crocodile. When Scheyer et al. examined fossilized remains from Venezuela that are estimated to be between 7–5 million years old, they found an extra vertebra in the creature's pelvic area and one less in its trunk. Scheyer et al. speculate that this unusual arrangement may have helped the extinct creature to support its massive weight and compensate for the strain imposed on its skeleton. Within the animal kingdom, so-called homeobox genes dictate how different body structures, including the spine, develop in embryos. Shifts in where these genes are active in the embryo can result in an extra pelvic vertebra in humans and other animals. Scheyer et al. conclude that changes in the boundaries of the activity of homeobox genes may also explain the extra pelvic vertebra in this ancient caiman. It is not yet clear if other extinct crocodylians had extra pelvic vertebrae as well. But these new findings are likely to lead to more research on related giant crocodylian fossils to find out. Such research could help scientists to better understand the biomechanics of crocodylians and may lead to new insights on caimans, which have thrived in the tropics of northern South America for the past seven million years. Further research in this area may also help explain how these reptiles have adapted to their environment and the role they play in their ecosystems, which is currently threatened by human activity.

Seed germination and early seedling development represent critical stages for turfgrass establishment under increasingly frequent drought and salinity constraints. This study evaluated the germination performance of three cultivars of Lolium perenne L. and three cultivars of Poa pratensis L. exposed to iso-osmotic drought stress simulated with polyethylene glycol (PEG) and salt stress induced by NaCl. Germination percentage, mean germination time, germination index, seedling vigor index, and radicle and plumule elongation were quantified, and post-stress recovery tests assessed the reversibility of stress effects. Osmotic restriction imposed by PEG caused stronger inhibition of germination and seedling growth than NaCl at equivalent water potentials. L. perenne showed higher overall tolerance, maintaining faster emergence and greater seedling vigor across treatments, while P. pratensis was more sensitive but exhibited substantial germination recovery after stress removal. Cultivar-dependent variation was evident in both species, and multivariate analyses consistently differentiated tolerant and sensitive genotypes. The contrasting germination strategies, with rapid activation in L. perenne and delayed, recovery-oriented germination in P. pratensis, highlight species-specific adaptive responses to water and salt stress. These findings provide a physiological basis for selecting resilient turfgrass cultivars suited to drought- and salinity-prone environments, contributing to sustainable turfgrass establishment and management.

The Urumaco stratigraphic sequence, western Venezuela, preserves a variety of paleoenvironments that include terrestrial, riverine, lacustrine and marine facies. A wide range of fossil vertebrates associated with these facies supports the hypothesis of an estuary in that geographic area connected with a hydrographic system that flowed from western Amazonia up to the Proto-Caribbean Sea during the Miocene. Here the elasmobranch assemblages of the middle Miocene to middle Pliocene section of the Urumaco sequence (Socorro, Urumaco and Codore formations) are described. Based on new findings, we document at least 21 taxa of the Lamniformes, Carcharhiniformes, Myliobatiformes and Rajiformes, and describe a new carcharhiniform species (†Carcharhinus caquetius sp. nov.). Moreover, the Urumaco Formation has a high number of well-preserved fossil Pristis rostra, for which we provide a detailed taxonomic revision, and referral in the context of the global Miocene record of Pristis as well as extant species. Using the habitat preference of the living representatives, we hypothesize that the fossil chondrichthyan assemblages from the Urumaco sequence are evidence for marine shallow waters and estuarine habitats.

CB1 and GPR55 receptors form heteromers in striatal neurons; however, the effects of these heteromers on GABA release at their terminals and their impact on motor behavior remain unknown. In this study, we investigate the presence of CB1-GPR55 heteromers on striatonigral neurons and their axon terminals, and also assess their impact on cAMP accumulation, GABA release, and motor behavior. Furthermore, we explore the effects of sequential receptor activation to examine the phenomenon of increased dimerization induced by receptor activation. A PLA assay combined with Substance P immunofluorescence demonstrated the presence of CB1-GPR55 heteromers in the dorsal striatum and substantia nigra of rats. The kainic acid lesion in the striatum leads to a decrease in PLA dots in both regions. Sequential activation of CB1R, followed by GPR55 activation (CB1→GPR55), increased cAMP accumulation and GABA release at the nigral terminals more compared to GPR55 alone activation. In contrast, simultaneous activation (CB1 + GPR55) or the reverse (GPR55→CB1) did not affect the stimulation effects of GPR55 on cAMP accumulation or GABA release. Additionally, CB1/GPR55 immunoprecipitation in synaptosomes revealed an increase during the sequential activation of CB1→GPR55. Treatments with PTx or ChTx did not alter the effects of CB1→GPR55 sequential activation on GABA release. Finally, intranigral injections of a CB1→GPR55 agonist induced more contralateral turns than GPR55 activation alone. These findings indicate that the sequential activation of CB1→GPR55 within CB1/GPR55 heteromers in striatonigral neurons enhances cAMP accumulation, GABA release, and motor behavior by increasing heteromerization via CB1 activation.

Most works related to the identification of mathematical nonlinear systems suggest that such approaches can always be directly applied to any nonlinear system. This misconception is greatly discouraging when the obtained results are not expected. Thus, the current work hypothesizes that the more information one has about the mathematical structure of the model, the most precise the identification result. Therefore, a variant of the Sparse Identification of Nonlinear Dynamics (SINDY) approach is presented to obtain the full mathematical nonlinear model of a high-order system with coupled dynamics, namely, a commercial quadcopter. Furthermore, due to its high sensitivity to inputs, a control system is devised using the identified model to stabilize the quadcopter. This illustrates the effectiveness of the proposed identification method.

This research introduces a physics-based identification technique utilizing genetic algorithms. The primary objective is to derive a parametric matrix, denoted as A, describing the time-invariant linear model governing the longitudinal dynamics of an aircraft. This is achieved by proposing a fitness function based on the properties of the transition matrix and taking advantage of some of the capabilities of the genetic algorithm, mainly those of restricting the search ranges of the unknowns. In this case, such unknowns are related to the type of aircraft and flight conditions that are considered during the identification process. The proposed identification method is validated with a reliable nonlinear model that can be found in the literature, as well as with the calculation of the trim condition and linearization generally used in aircraft dynamics. In summary, this study suggests that the genetic algorithm provided with the adequate fitness function could be an appealing alternative for aircraft model identification, even when limited data are available. Furthermore, in some cases, linearization using a genetic algorithm can be more efficient than classical methods.

Premise of research. Plants cope with complex environments throughout their life cycles. The perception and integration of information acquired from different environmental parameters are key to responding appropriately and securing plant survival. In Arabidopsis thaliana, SALT OVERLY SENSITIVE 2 (SOS2) and SOS3, its protein-interacting partner, have been described as central players in salt-stress responses, while another SOS2-interacting partner, ABSCISIC ACID (ABA)–INSENSITIVE 2 (ABI2), is involved in ABA signaling. SOS2 was also suggested to be involved in the photocontrol of seed germination, although its function in photomorphogenesis is not fully understood. Here we studied the role played by SOS2, SOS3, and ABI2 in light-dependent responses in Arabidopsis mutants. We assessed whether SOS2, SOS3, and ABI2 modulate light- and hormone-regulated seed germination and seedling deetiolation. Methodology. We examined physiological responses in wild-type and SOS2, SOS3, and ABI2 knockout mutants of A. thaliana exposed to red light and explored whether these proteins modulate germination (by changing hormone sensitivity) and seedling deetiolation. In addition, we analyzed the presence of cis-regulatory elements (CREs) in their promoters and expression profiles from public microarrays to confirm their function in photomorphogenesis. Pivotal results. Germination experiments demonstrate that SOS2, SOS3, and ABI2 are positive regulators of germination induced by red light. Differences in germination between the wild type and mutants are explained by changes in gibberellin sensitivity. Analysis of hypocotyl growth inhibition and cotyledon opening suggest that these components are also required for full seedling deetiolation under red light. Furthermore, identification of CREs in gene promoters and expression analysis matched the proposed role for these genes in both processes. Conclusions. SOS2, SOS3, and ABI2 are known components of salt signaling, and here we demonstrate that they are also positive elements of light signaling by regulating seedling deetiolation and altering gibberellic acid sensitivity during germination. These results suggest that they act as integrators of different signaling pathways.

Escaramujo is a project with the goal of promote scientific development and integration regarding science for Latin America. It consists of a series of Laboratories and Workshops for High Energy Physics, astroparticle and instrumentation, given by Federico Izraelevitch. Escaramujo has been conduced at several institutions in Latin America. In this work, the moun mean lifetime measurements performed during the workshop held in Chiapas are presented. The results are compared with the corresponding value reported by the Particle Data Group (PDG).

An iniid fossil (Cetacea, Odontoceti) is reported based on a periotic found in the Codore Formation (late Miocene to middle Pliocene) of northwestern Venezuela. The marine sediments where the Codore dolphin was collected have yielded another cetacean and a diverse elasmobranch fauna. Cladistic analysis indicates a close relationship between the Codore dolphin and the extant Amazon River dolphin (Inia geoffrensis); key characteristics include a large cochlear portion that is dorsoventrally compressed and the extremely small size of the posterior process. High-resolution micro-computed tomography scans were used for the description and analysis of the bony labyrinth endocast. Geometric morphometric analysis of the bony labyrinth endocast places the Codore dolphin as intermediate between the La Plata dolphin (Pontoporia blainvillei) and Inia geoffrensis (principal component 1), but distinctive from both extant species (principal component 2). Comparisons of the depositional environment with cladistically informed reconstructions and inferences based on cochlear and vestibular anatomy suggest that the Codore dolphin had the flexibility to enter marine, brackish, and fluvial environments as some extant cetaceans do today (e.g., Pontoporia blainvillei).