Spectral fluctuations of tridiagonal random matrices from the beta-Hermite ensemble

A time series delta(n), the fluctuation of the nth unfolded eigenvalue was recently characterized for the classical Gaussian ensembles of NxN random matrices (GOE, GUE, GSE). It is investigated here for the beta-Hermite ensemble as a function of beta (zero or positive) by Monte Carlo simulations. The fluctuation of delta(n) and the autocorrelation function vary logarithmically with n for any beta>0 (1<<n<<N). The simple logarithmic behavior reported for the higher-order moments of delta(n) for the GOE (beta=1) and the GUE (beta=2) is valid for any positive beta and is accounted for by Gaussian distributions whose variances depend linearly on ln(n). The 1/f noise previously demonstrated for delta(n) series of the three Gaussian ensembles, is characterized by wavelet analysis both as a function of beta and of N. When beta decreases from 1 to 0, for a given and large enough N, the evolution from a 1/f noise at beta=1 to a 1/f^2 noise at beta=0 is heterogeneous with a ~1/f^2 noise at the finest scales and a ~1/f noise at the coarsest ones. The range of scales in which a ~1/f^2 noise predominates grows progressively when beta decreases. Asymptotically, a 1/f^2 noise is found for beta=0 while a 1/f noise is the rule for beta positive.Comment: 35 pages, 10 figures, corresponding author: G. Le Cae

New ophthalmosaurid ichthyosaurs from the European lower cretaceous demonstrate extensive ichthyosaur survival across the Jurassic–Cretaceous boundary

Background Ichthyosauria is a diverse clade of marine amniotes that spanned most of the Mesozoic. Until recently, most authors interpreted the fossil record as showing that three major extinction events affected this group during its history: one during the latest Triassic, one at the Jurassic–Cretaceous boundary (JCB), and one (resulting in total extinction) at the Cenomanian-Turonian boundary. The JCB was believed to eradicate most of the peculiar morphotypes found in the Late Jurassic, in favor of apparently less specialized forms in the Cretaceous. However, the record of ichthyosaurs from the Berriasian–Barremian interval is extremely limited, and the effects of the end-Jurassic extinction event on ichthyosaurs remains poorly understood. Methodology/Principal Findings Based on new material from the Hauterivian of England and Germany and on abundant material from the Cambridge Greensand Formation, we name a new ophthalmosaurid, Acamptonectes densus gen. et sp. nov. This taxon shares numerous features with Ophthalmosaurus, a genus now restricted to the Callovian–Berriasian interval. Our phylogenetic analysis indicates that Ophthalmosauridae diverged early in its history into two markedly distinct clades, Ophthalmosaurinae and Platypterygiinae, both of which cross the JCB and persist to the late Albian at least. To evaluate the effect of the JCB extinction event on ichthyosaurs, we calculated cladogenesis, extinction, and survival rates for each stage of the Oxfordian–Barremian interval, under different scenarios. The extinction rate during the JCB never surpasses the background extinction rate for the Oxfordian–Barremian interval and the JCB records one of the highest survival rates of the interval. Conclusions/Significance There is currently no evidence that ichthyosaurs were affected by the JCB extinction event, in contrast to many other marine groups. Ophthalmosaurid ichthyosaurs remained diverse from their rapid radiation in the Middle Jurassic to their total extinction at the beginning of the Late Cretaceous

Xenodens calminechari gen. et sp. nov., a bizarre mosasaurid (Mosasauridae, Squamata) with shark-like cutting teeth from the upper Maastrichtian of Morocco, North Africa

The mosasaurids (Mosasauridae) were a group of lizards that became highly specialized for marine life in the mid-Cretaceous. By the end of the Cretaceous, they had undergone an adaptive radiation, and showed a wide range of body sizes, locomotor styles, and diets. Their ranks included piscivores, apex predators, and durophages. Here, we report a new taxon, Xenodens calminechari gen. et sp. nov., from the upper Maastrichtian phosphates of Morocco, with dental specializations unlike those of any known reptile. Teeth form a unique dental battery in which short, laterally compressed and hooked teeth formed a saw-like blade. Unique features of tooth structure and implantation suggest affinities with the durophagous Carinodens. The tooth arrangement seen in Xenodens not only expands known disparity of mosasaurids, but is unique among Squamata, or even Tetrapoda. The specialized dentition implies a previously unknown feeding strategy, likely involving a cutting motion used to carve pieces out of large prey, or in scavenging. This novel dental specialization adds to the already considerable disparity and functional diversity of the late Maastrichtian mosasaurids and marine reptiles. This provides further evidence for a diverse marine fauna just prior to the K-Pg extinction

Stelladens mysteriosus: A Strange New Mosasaurid (Squamata) from the Maastrichtian (Late Cretaceous) of Morocco

Mosasaurids, a clade of specialized marine squamates, saw a major adaptive radiation in the Late Cretaceous, evolving a wide range of body sizes, shapes, and specialized tooth morphologies. The most diverse known mosasaurid faunas come from the late Maastrichtian phosphates of Morocco. Here, we report an unusual new mosasaurid, Stelladens mysteriosus, based on a partial jaw and associated tooth crowns from lower Couche III phosphatic deposits at Sidi Chennane, Oulad Abdoun Basin, Morocco. Stelladens is characterized by short, triangular tooth crowns with a series of strong, elaborate, and serrated ridges on the lingual surface of the tooth, functioning as accessory carinae. Morphology of the teeth and associated jaw fragment suggest affinities with Mosasaurinae. No close analogues to the unique tooth morphology of Stelladens are known, either extant or extinct. It may have had an unusual and highly specialized diet, a specialized prey-capture strategy, or both. The diversity of mosasaurid teeth is much higher than that of plesiosaurs, ichthyosaurs, or extant marine mammals, and likely reflects both the ecological diversity of mosasaurids and complex developmental mechanisms responsible for tooth formation in mosasaurines. Mosasaurid diversity continued to increase up to the Cretaceous–Paleogene boundary.Research of XPS is financed by the Spanish Ministry of Science and Innovation (MCIN) and the European Regional Development Fund (FEDER) (research project PID2021-122612OB-I00), and by the Basque Country Gouvernment (research group IT1485-22). This study is carried out within the framework of the agreement between the universities of Bath and Cadi Ayyad

A Markov Chain based method for generating long-range dependence

This paper describes a model for generating time series which exhibit the statistical phenomenon known as long-range dependence (LRD). A Markov Modulated Process based upon an infinite Markov chain is described. The work described is motivated by applications in telecommunications where LRD is a known property of time-series measured on the internet. The process can generate a time series exhibiting LRD with known parameters and is particularly suitable for modelling internet traffic since the time series is in terms of ones and zeros which can be interpreted as data packets and inter-packet gaps. The method is extremely simple computationally and analytically and could prove more tractable than other methods described in the literatureComment: 8 pages, 2 figure

Development of a Molecular Tagging Velocimetry Technique for Non-Intrusive Velocity Measurements in Low-Speed Gas Flows

N2O molecular tagging velocimetry (N2O-MTV) is developed for use in very-high-temperature reactor environments. Tests were carried out to determine the optimum excitation wavelength, tracer concentration, and timing parameters for the laser system. Using NO tracers obtained from photo-dissociation of N2O, velocity profiles are successfully obtained in air, nitrogen, and helium for a large range of parameters: temperature from 295 to 781 K, pressure from 1 to 3 bars, with a velocity precision of 0.01 m/s. Furthermore, by using two read pulses at adjustable time delays, the velocity dynamic range can be increased. An unprecedented dynamic range of 5,000 has been obtained to successfully resolve the flow during a helium blowdown from 1000 m/s down to 0.2 m/s. This technique is also applied to the high-temperature test facility (HTTF) at Oregon State University (OSU) during a depressurized condition cooldown (DCC) event. Details of these measurements are presented in a companion paper. This technique shows a strong potential for fundamental understanding of gas flows in nuclear reactors and to provide benchmark experimental data to validate numerical simulations

Non-Intrusive Velocity Measurements with MTV During DCC Event in the HTTF

Velocity profiles are measured using molecular tagging velocimetry (MTV) in the high temperature test facility (HTTF) at Oregon State University during a depressurized conduction cooldown (DCC) event. The HTTF is a quarter scale electrically heated nuclear reactor simulator designed to replicate various accident scenarios. During a DCC, a double ended guillotine break results in the reactor pressure vessel (RPV) depressurizing into the reactor cavity and ultimately leading to air ingress in the reactor core (lock-exchange and gas diffusion). It is critical to understand the resulting buoyancy-driven flow to characterize the reactor self-cooling capacity through natural circulation. During tests conducted at ambient pressure and temperature, the RPV containing helium is opened (via the hot and cold legs) to a large vessel filled with nitrogen to simulate the atmosphere. The velocity profile on the hot leg pipe centerline is recorded at 10 Hz with MTV based on NO tracers. The precision of the velocimetry was measured to be 0.02 m/s in quiescent flow prior to the tests. A helium flow from the RPV is initially observed in the top quarter of the pipe. During the first 20 seconds of the event, helium flows out of the RPV with a maximum velocity below 2 m/s. The velocity profile transitions from parabolic to linear in character and decays slowly over the rest of the recording; peak velocities of 0.2 m/s are observed after 30 min. A counter-flow of nitrogen is also observed intermittently, which occurs at lower velocities (>0.1 m/s)

Improving Resulted Hemoglobin A1c Rates: A Feasibility Study for Point-of-Care Hemoglobin A1c Testing at an Urban Family Medicine Office

Study Aims: Our practice’s goal is to increase the number of up to date hemoglobin A1c for diabetic patients seen at JFMA in order to help improve glycemic control The aim of this study is to see if point of care (POC) hemoglobin A1C is a feasible way to increase the number of up to date hemoglobin A1C. We looked at various factors including timing, training, and flow.https://jdc.jefferson.edu/patientsafetyposters/1037/thumbnail.jp

New data on the ichthyosaur Platypterygius hercynicus and its implications for the validity of the genus

The description of a nearly complete skull from the late Albian of northwestern France reveals previously unknown anatomical features of Platypterygius hercynicus (Kuhn 1946), and of European Cretaceous ichthyosaurs in general. These include a wide frontal forming the anteromedial border of the supratemporal fenestra, a parietal excluded from the parietal foramen, and the likely presence of a squamosal, inferred from a very large and deep facet on the quadratojugal. The absence of a squamosal has been considered as an autapomorphy of the genus Platypterygius for more than ten years and has been applied to all known species by default, but the described specimen casts doubt on this putative autapomorphy. Actually, it is shown that all characters that have been proposed previously as autapomorphic for the genus Platypterygius are either not found in all the species currently referred to this genus, or are also present in other Ophthalmosauridae. Consequently, the genus Platypterygius must be completely revised.Peer reviewe

Development of N2O-MTV for Low-Speed Flow and In-Situ Deployment to an Integral Effect Test Facility

A molecular tagging velocity (MTV) technique is developed to non-intrusively measure velocity in an integral effect test (IET) facility simulating a high-temperature helium-cooled nuclear reactor in accident scenarios. In these scenarios, the velocities are expected to be low, on the order of 1 m/s or less, which forces special requirements on the MTV tracer selection. Nitrous oxide (N2O) is identified as a suitable seed gas to generate NO tracers capable of probing the flow over a large range of pressure, temperature, and flow velocity. The performance of N2O-MTV is assessed in the laboratory at temperature and pressure ranging from 295 to 781 K and 1 to 3 atm. MTV signal improves with a temperature increase, but decreases with a pressure increase. Velocity precision down to 0.004 m/s is achieved with a probe time of 40 ms at ambient pressure and temperature. Measurement precision is limited by tracer diffusion, and absorption of the tag laser beam by the seed gas. Processing by cross-correlation of single-shot images with high signal-to-noise ratio reference images improves the precision by about 10% compared to traditional single-shot image correlations. The instrument is then deployed to the IET facility. Challenges associated with heat, vibrations, safety, beam delivery, and imaging are addressed in order to successfully operate this sensitive instrument in-situ. Data are presented for an isothermal depressurized conduction cooldown. Velocity profiles from MTV reveal a complex flow transient driven by buoyancy, diffusion, and instability taking place over short ( 30 min) time scales at sub-meter per second speed. The precision of the in-situ results is estimated at 0.027, 0.0095, and 0.006 m/s for a probe time of 5, 15, and 35 ms, respectively