Pressure-Induced Superconductivity in Sc to 74 GPa

Using a diamond anvil cell with nearly hydrostatic helium pressure medium we have significantly extended the superconducting phase diagram Tc(P) of Sc, the lightest of all transition metals. We find that superconductivity is induced in Sc under pressure, Tc increasing monotonically to 8.2 K at 74.2 GPa. The Tc(P) dependences of the trivalent d-electron metals Sc, Y, La, and Lu are compared and discussed within a simple s-d charge transfer framework.Comment: to be published in Phys. Rev. B (Brief Reports

Social rank overrides environmental and community fluctuations in determining meat access by female chimpanzees in the Taï National Park, Côte d’Ivoire

Meat, long hypothesized as an important food source in human evolution, is still a substantial component of the modern human diet, with some humans relying entirely on meat during certain times of the year. Understanding the socio-ecological context leading to the successful acquisition and consumption of meat by chimpanzees (Pan troglodytes), our closest living relative, can provide insight into the emergence of this trait because humans and chimpanzees are unusual among primates in that they both (i) hunt mammalian prey, (ii) share meat with community members, and (iii) form long-term relationships and complex social hierarchies within their communities. However, females in both human hunter-gatherer societies as well as chimpanzee groups rarely hunt, instead typically accessing meat via males that share meat with group members. In general, female chimpanzee dominance rank affects feeding competition, but so far, the effect of female dominance rank on meat access found different results within and across studied chimpanzee groups. Here we contribute to the debate on how female rank influences meat access while controlling for several socio-ecological variables. Multivariate analyses of 773 separate meat-eating events collected over more than 25 years from two chimpanzee communities located in the Taï National Park, Côte d’Ivoire, were used to test the importance of female dominance rank for being present at, and for acquiring meat, during meat-eating events. We found that high-ranking females were more likely to be present during a meat-eating event and, in addition, were more likely to eat meat compared to the subordinates. These findings were robust to both large demographic changes (decrease of community size) and seasonal ecological changes (fruit abundance dynamics). In addition to social rank, we found that other female properties had a positive influence on presence to meat-eating events and access to meat given presence, including oestrus status, nursing of a small infant, and age. Similar to findings in other chimpanzee populations, our results suggest that females reliably acquire meat over their lifetime despite rarely being active hunters. The implication of this study supports the hypothesis that dominance rank is an important female chimpanzee property conferring benefits for the high-ranking females

Pirates For Academic Success

ECU reported in 2019 that the school had an overall retention rate of 83%. Although this percentage seems high, it is nothing compared to UNC Chapel Hill’s overall retention rate of 97.2% or Duke’s rate of 97.6%, (both reported from 2013-2017.) Because of this our group decided to research why ECU’s retention rate was so much lower than surrounding universities and provide resources and information to take a step forward in solving these problems. After spending our first year conducting interviews among students, it was clear that most students were not aware of the resources offered to them on campus. Some were not even aware of their style of learning and how to effectively study for upcoming exams or quizzes. From this we created Pirates for Academic Success. Our goal was to make videos explaining not only what resources were available on campus that you may not know about but also explain different studying techniques and how discovering your style of learning can lead to a more effective study pattern. Doing this allows students who don’t know ECU campus that well or who don’t know many other students a way to find resources in a less intimidating way. This can lead to higher grades, more confidence in coursework and classes, and a higher chance of students staying at ECU for a second year. “Confident students develop relationships with faculty that can lead to participation in research and other developmental activities...this leads further to possible future connections, letters of recommendation, internships, future work, or graduate school� (Croskey, 2021). Our group has set up a vimeo containing videos ranging from how to use different online homework platforms such as cengage to resources at the library students may not be aware of and how to effectively use them. Through this we have established a relationship with the library, marketing our videos and receiving special access to the library to make more videos using their equipment

Nanoscale austenite reversion through partitioning, segregation, and kinetic freezing: Example of a ductile 2 GPa Fe-Cr-C steel

Austenite reversion during tempering of a Fe-13.6Cr-0.44C (wt.%) martensite results in an ultrahigh strength ferritic stainless steel with excellent ductility. The austenite reversion mechanism is coupled to the kinetic freezing of carbon during low-temperature partitioning at the interfaces between martensite and retained austenite and to carbon segregation at martensite-martensite grain boundaries. An advantage of austenite reversion is its scalability, i.e., changing tempering time and temperature tailors the desired strength-ductility profiles (e.g. tempering at 400{\deg}C for 1 min. produces a 2 GPa ultimate tensile strength (UTS) and 14% elongation while 30 min. at 400{\deg}C results in a UTS of ~ 1.75 GPa with an elongation of 23%). The austenite reversion process, carbide precipitation, and carbon segregation have been characterized by XRD, EBSD, TEM, and atom probe tomography (APT) in order to develop the structure-property relationships that control the material's strength and ductility.Comment: in press Acta Materialia 201

Weak low-energy couplings from topological zero-mode wavefunctions

We discuss a new method to determine the low-energy couplings of the $\Delta S=1$ weak Hamiltonian in the $\epsilon$-regime. It relies on a matching of the topological poles in $1/m^2$ of three-point functions of two pseudoscalar densities and a four-fermion operator computed in lattice QCD, to the same observables in the Chiral Effective Theory. We present the results of a NLO computation in chiral perturbation theory of these correlation functions together with some preliminary numerical results.Comment: 7 pages. Contribution to Lattice 200

Determination of the ΔS=1\Delta S = 1 weak Hamiltonian in the SU(4) chiral limit through topological zero-mode wave functions

A new method to determine the low-energy couplings of the $\Delta S=1$ weak Hamiltonian is presented. It relies on a matching of the topological poles in $1/m^2$ of three-point correlators of two pseudoscalar densities and a four-fermion operator, measured in lattice QCD, to the same observables computed in the $\epsilon$-regime of chiral perturbation theory. We test this method in a theory with a light charm quark, i.e. with an SU(4) flavour symmetry. Quenched numerical measurements are performed in a 2 fm box, and chiral perturbation theory predictions are worked out up to next-to-leading order. The matching of the two sides allows to determine the weak low-energy couplings in the SU(4) limit. We compare the results with a previous determination, based on three-point correlators containing two left-handed currents, and discuss the merits and drawbacks of the two procedures.Comment: 38 pages, 9 figure

Superconductivity at 17 K in Yttrium Metal under Nearly Hydrostatic Pressures to 89 GPa

In an experiment in a diamond anvil cell utilizing helium pressure medium, yttrium metal displays a superconducting transition temperature which increases monotonically from Tc ? 3.5 K at 30 GPa to 17 K at 89.3 GPa, one of the highest transition temperatures for any elemental superconductor. The pressure dependence of Tc differs substantially from that observed in previous studies under quasihydrostatic pressure to 30 GPa. Remarkably, the dependence of Tc on relative volume V/Vo is linear over the entire pressure range above 33 GPa, implying that higher values of Tc are likely at higher pressures. For the trivalent metals Sc, Y, La, Lu there appears to be some correlation between Tc and the ratio of the Wigner-Seitz radius to the ion core radius.Comment: submitted for publicatio

A precise determination of the charm quark's mass in quenched QCD

We present a lattice determination of the charm quark's mass, using the mass of the D_s meson as experimental input. All errors are under control with the exception of the quenched approximation. Setting the scale with F_K=160 MeV, our final result for the renormalization group invariant (RGI) quark mass is M_c = 1.654(45) GeV, which translates to m_c(m_c) =1.301(34) GeV for the running mass in the MSbar scheme. A 6 percent increase of the RGI quark mass is observed when the scale is set by the nucleon mass. This is a typical quenched scale ambiguity, which is reduced to about 3 percent for m_c(m_c), and to 4 percent for the mass ratio M_c/M_s. In contrast, the mass splitting m(Dstar_s)-m(D_s) changes from 117(11) MeV to 94(11) MeV, which is significantly smaller than the experimental value of 144 MeV.Comment: 27 pages, 5 figure

Characterization of new hybrid pixel module concepts for the ATLAS Insertable B-Layer upgrade

The ATLAS Insertable B-Layer (IBL) collaboration plans to insert a fourth pixel layer inside the present Pixel Detector to recover from eventual failures in the current pixel system, especially the b-layer. Additionally the IBL will ensure excellent tracking, vertexing and b-tagging performance during the LHC phase I and add robustness in tracking with high luminosity pile-up. The expected peak luminosity for IBL is 2 to 3centerdot1034 cm-2s-1 and IBL is designed for an integrated luminosity of 700 fb-1. This corresponds to an expected fluence of 5centerdot1015 1 MeV neqcm-2 and a total ionizing dose of 250 MRad. In order to cope with these requirements, two new module concepts are under investigation, both based on a new front end IC, called FE-I4. This IC was designed as readout chip for future ATLAS Pixel Detectors and its first application will be the IBL. The planar pixel sensor (PPS) based module concept benefits from its well understood design, which is kept as similar as possible to the design of the current ATLAS Pixel Detector sensor. The second approach of the new three dimensional (3D) silicon sensor technology benefits from the shorter charge carrier drift distance to the electrodes, which completely penetrate the sensor bulk. Prototype modules of both sensor concepts have been build and tested in laboratory and test beam environment before and after irradiation. Both concepts show very high performance even after irradiation to 5centerdot1015 1 MeV neqcm-2 and meet the IBL specifications in terms of hit efficiency being larger than 97%. Lowest operational threshold studies have been effected and prove independent of the used sensor concept the excellent performance of FE-I4 based module concepts in terms of noise hit occupancy at low thresholds.Comment: Part of 9th International Conference on Position Sensitive Detectors (PSD9

Mechanical properties of three-dimensional interconnected alumina/steel metal matrix composites

Three-dimensional interconnected alumina/steel metal matrix composites (MMCs) were produced by pressureless Ti-activated melt infiltration method using three types of Al2O3 powder with different sizes and shapes. By partial sintering during infiltration an interpenetrating ceramic network was realised. The effect of the ceramic particle size and shape on the resulting ceramic network, volume % fraction and the MMC properties is presented. The MMCs were characterised for mechanical properties at room temperature and elevated temperature. An increase in flexural strength and Young's modulus with decreasing particle size has been observed. In addition, the effect of the volume of ceramic content and the surface finish of the MMCs on the wear behaviour is show