\u3ci\u3eEnallagma Anna,\u3c/i\u3e A Damselfly New to the Great Lakes Region (Odonata: Coenagrionidae)

Enallagma anna, a predominantly western North America damselfly, is now recorded from southwestern Michigan and southwestern Ontario for the first time

\u3ci\u3eEnallagma Anna,\u3c/i\u3e A Damselfly New to the Great Lakes Region (Odonata: Coenagrionidae)

Enallagma anna, a predominantly western North America damselfly, is now recorded from southwestern Michigan and southwestern Ontario for the first time

Anisotropic transport and magnetic properties, and magnetic-field tuned states of CeZn11 single crystals

We present detailed temperature and field dependent data obtained from magnetization, resistivity, heat capacity, Hall resistivity and thermoelectric power measurements performed on single crystals of CeZn11. The compounds orders antiferromagnetically at $\sim$ 2 K. The zero-field resistivity and TEP data show features characteristic of a Ce-based intermetallic with crystal electric field splitting and possible correlated, Kondo lattice effects. We constructed the T-H phase diagram for the magnetic field applied along the easy, [110], direction which shows that the magnetic field required to suppress T_N below 0.4 K is in the range of 45-47.5 kOe. A linear behavior of the rho(T) data, H||[110], was observed only for H=45 kOe for 0.46 K<T<1.96 K followed by the Landau-Fermi-liquid regime for a limited range of fields, 47.5 kOe< H<60 kOe. From the analysis of our data, it appears that CeZn11 is a weakly to moderately correlated local moment compound with rather small Kondo temperature. The thermoelectric and transport properties of CeZn11 are mostly governed by the CEF effects. Given the very high quality of our single crystals, quantum oscillations are found for both CeZn11 and its non-magnetic analogue, LaZn11

Fragile antiferromagnetism in the heavy-fermion compound YbBiPt

We report results from neutron scattering experiments on single crystals of YbBiPt that demonstrate antiferromagnetic order characterized by a propagation vector, $\tau_{\rm{AFM}}$ = ($\frac{1}{2} \frac{1}{2} \frac{1}{2}$), and ordered moments that align along the [1 1 1] direction of the cubic unit cell. We describe the scattering in terms of a two-Gaussian peak fit, which consists of a narrower component that appears below $T_{\rm{N}}~\approx 0.4$ K and corresponds to a magnetic correlation length of $\xi_{\rm{n}} \approx$ 80 $\rm{\AA}$, and a broad component that persists up to $T^*\approx$ 0.7 K and corresponds to antiferromagnetic correlations extending over $\xi_{\rm{b}} \approx$ 20 $\rm{\AA}$. Our results illustrate the fragile magnetic order present in YbBiPt and provide a path forward for microscopic investigations of the ground states and fluctuations associated with the purported quantum critical point in this heavy-fermion compound.Comment: 5 pages, 3 figure

Commensurate antiferromagnetic ordering in Ba(Fe{1-x}Co{x})2As2 determined by x-ray resonant magnetic scattering at the Fe K-edge

We describe x-ray resonant magnetic diffraction measurements at the Fe K-edge of both the parent BaFe2As2 and superconducting Ba(Fe0.953Co0.047)2As2 compounds. From these high-resolution measurements we conclude that the magnetic structure is commensurate for both compositions. The energy spectrum of the resonant scattering is in reasonable agreement with theoretical calculations using the full-potential linear augmented plane wave method with a local density functional.Comment: 5 pages, 3 figures; accepted for publication in Phys. Rev. B Rapid Com

Evidence from neutron diffraction for superconductivity in the stabilized tetragonal phase of CaFe2As2 under uniaxial pressure

CaFe2As2 single crystals under uniaxial pressure applied along the c axis exhibit the coexistence of several structural phases at low temperatures. We show that the room-temperature tetragonal phase is stabilized at low temperatures for pressures above 0.06 GPa, and its weight fraction attains a maximum in the region where superconductivity is observed under applied uniaxial pressure. Simultaneous resistivity measurements strongly suggest that this phase is responsible for the superconductivity in CaFe2As2 found below 10 K in samples subjected to nonhydrostatic pressure conditions.Comment: 5 pages, 3 figures

Development and Testing of a High Stability Engine Control (HISTEC) System

Flight tests were recently completed to demonstrate an inlet-distortion-tolerant engine control system. These flight tests were part of NASA's High Stability Engine Control (HISTEC) program. The objective of the HISTEC program was to design, develop, and flight demonstrate an advanced integrated engine control system that uses measurement-based, real-time estimates of inlet airflow distortion to enhance engine stability. With improved stability and tolerance of inlet airflow distortion, future engine designs may benefit from a reduction in design stall-margin requirements and enhanced reliability, with a corresponding increase in performance and decrease in fuel consumption. This paper describes the HISTEC methodology, presents an aircraft test bed description (including HISTEC-specific modifications) and verification and validation ground tests. Additionally, flight test safety considerations, test plan and technique design and approach, and flight operations are addressed. Some illustrative results are presented to demonstrate the type of analysis and results produced from the flight test program

An NSTA Position Statement: Science-Technology-Society: Science Education for the 1980s

Science and technology influence every aspect of our lives. They are central to our welfare as individuals and to the welfare of our society. All around us are examples of the importance of science and technology for production of food, shelter, clothing, medicines, transportation, and various sources of energy. There are an increasing number of science- and technology-related societal problems as well as increasing societal benefits. Science and technology are central to our personal and cultural welfare and to many societal problems. We must insure appropriate science education for all citizens

Stabilization of an ambient-pressure collapsed tetragonal phase in CaFe2As2 and tuning of the orthorhombic-antiferromagnetic transition temperature by over 70 K via control of nanoscale precipitates

We have found a remarkably large response of the transition temperature of CaFe2As2 single crystals grown from excess FeAs to annealing and quenching temperature. Whereas crystals that are annealed at 400ˆC exhibit a first-order phase transition from a high-temperature tetragonal to a low-temperature orthorhombic and antiferromagnetic state near 170 K, crystals that have been quenched from 960ˆC exhibit a transition from a high-temperature tetragonal phase to a low-temperature, nonmagnetic, collapsed tetragonal phase below 100 K. By use of temperature-dependent electrical resistivity, magnetic susceptibility, x-ray diffraction, Mössbauer spectroscopy, and nuclear magnetic resonance measurements we have been able to demonstrate that the transition temperature can be reduced in a monotonic fashion by varying the annealing or quenching temperature from 400ˆ to 850ˆC with the low-temperature state remaining antiferromagnetic for transition temperatures larger than 100 K and becoming collapsed tetragonal, nonmagnetic for transition temperatures below 90 K. This suppression of the orthorhombic-antiferromagnetic phase transition and its ultimate replacement with the collapsed tetragonal, nonmagnetic phase is similar to what has been observed for CaFe2As2 under hydrostatic pressure. Transmission electron microscopy studies indicate that there is a temperature-dependent width of formation of CaFe2As2 with a decreasing amount of excess Fe and As being soluble in the single crystal at lower annealing temperatures. For samples quenched from 960ˆC there is a fine (of order 10 nm) semiuniform distribution of precipitate that can be associated with an average strain field, whereas for samples annealed at 400ˆC the excess Fe and As form mesoscopic grains that induce little strain throughout the CaFe2As2 lattice

Magnetic ordering and structural distortion in Ru-doped BaFe2As2 single crystals studied by neutron and x-ray diffraction

We present a systematic investigation of the antiferromagnetic ordering and structural distortion for the series of Ba(Fe1−xRux)2As2 compounds (0⩽x⩽0.246). Neutron and x-ray diffraction measurements demonstrate that, unlike for the electron-doped compounds, the structural and magnetic transitions remain coincident in temperature. Both the magnetic and structural transitions are gradually suppressed with increased Ru concentration and coexist with superconductivity. For samples that are superconducting, we find strong competition between superconductivity, the antiferromagnetic ordering, and the structural distortion