A microscopic model for spiral ordering along (110) on the MnSi lattice

We study an extended Heisenberg model on the MnSi lattice. In the cubic B20 crystal structure of MnSi, Mn atoms form lattices of of corner-shared equilateral triangles. We find an ubiquitous spiral ordering along (110) for J1 0, where J1, J2, and J3 are 1st, 2nd and 3rd nearest neighbor Heisenberg interactions, respectively. While the ordering direction of (110) is reasonably robust to the presence of the Dzyaloshinskii-Moriya interaction, it can be shifted to the (111) direction with the introduction of a magnetic anisotropy term for small J2/|J1|. We discuss the possible relevance of these results to the partially ordered state recently reported in MnSi.Comment: 5 pages, 4 figure

Patterns of Treatment for Psychiatric Disorders Among Children and Adolesecents in Mississippi Medicaid

The nature of services for psychiatric disorders in public health systems has been understudied, particularly with regard to frequency, duration, and costs. The current study examines patterns of service reception and costs among Medicaid-covered youth newly diagnosed with anxiety, depression, or behavioral disturbance in a large data set of provider billing claims submitted between 2015–2016. Eligibility criteria included: 1) identification of an initial diagnosis of a single anxiety, unipolar mood, or specific behavioral disorder; 2) continuous Medicaid eligibility over the duration of the time period studied; and 3) under 18 years of age on the date of initial psychiatric diagnosis. The final cohort included 7,627 cases with a mean age of 10.65 (±4.36), of which 58.04% were male, 57.09% were Black, 38.97% were White, and 3.95% were of other ethnicities. Data indicated that 65.94% of the cohort received at least some follow-up services within a median 18 days of diagnosis. Of those, 54.27% received a combination of medical and psychosocial services, 32.01% received medical services only, and 13.72% received psychosocial services only. Overall median costs for direct treatment were $576.69, with wide discrepancies between the lowest (anxiety =$308.41) and highest (behavioral disturbance = $653.59) diagnostic categories. Across all categories the frequency and duration of psychosocial services were much lower than would be expected in comparison to data from a well-known effectiveness trial. Overall, follow-up to psychiatric diagnosis could be characterized as highly variable, underutilized, and emphasizing biomedical treatment. Understanding more about these patterns may facilitate systematic improvements and greater cost efficiency in the future

Computational complexity of μ calculation

The structured singular value μ measures the robustness of uncertain systems. Numerous researchers over the last decade have worked on developing efficient methods for computing μ. This paper considers the complexity of calculating μ with general mixed real/complex uncertainty in the framework of combinatorial complexity theory. In particular, it is proved that the μ recognition problem with either pure real or mixed real/complex uncertainty is NP-hard. This strongly suggests that it is futile to pursue exact methods for calculating μ of general systems with pure real or mixed uncertainty for other than small problems

Professional Pilot Studies: Proposed Content

Professional pilot collegiate aviation curricula vary not only in depth of information, but also in topical content area. Although fundamental flight-related skills are clearly important, future graduates must be familiar with advances in automated cockpit technology and human factors. This article combines the observations of industry practitioners, recommendations of educators, guidelines of the Council on Aviation Accreditation, and the authors\u27 opinions into proposed topic areas for four-year professional pilot curricula. Results of a 1993 preliminary study of collegiate professional pilot programs are included for comparison. It is hoped these suggestions will assist collegiate educators in developing, revising, and updating plans of study

Reducing General Aviation Accidents By Utilizing Airline Operational Strategies

The United States maintains one of the largest and most diverse general aviation (GA) industries. However, GA results in hundreds of fatalities each year; thus, increasing safety and preventing accidents are the core values of the GA industry. This research lays the foundation for more work to be completed in order for GA to remain safe, efficient and have their needs met. The findings explain the current trends of GA accidents compared to commercial aviation, the differences in operational strategies between the two types, efforts that have been made by the Federal Aviation Administration (and others) to improve GA, and finally, recommended alternatives for improving GA safety using commercial aviation operational strategies. As a result of this study, recommendations to the stakeholders in the GA community include: (1) embracing in-cockpit technology to not only enable safer operations in crowded skies, but also permit reliable data collection on GA trends for data-driven decision making; (2) offering valuable incentives for pilots to undergo quality recurrent and safety training, while also eliminating loopholes or incentives that compromise safety; and (3) instituting a system of checks and balances to ensure pilots have a sufficient safety net from human error

Training Levels and Methodologies for Glass Cockpit Training in Collegiate Aviation

Modern commercial aircraft use extremely complex and sophisticated flight instrumentation systems that present training concerns for the aviation industry and collegiate aviation programs. The authors sampled 42 four-year collegiate flight-training programs to determine their current program emphasis on glass cockpit training and plans for curriculum enhancements in that area. Although nearly fifty percent of sampled program administrators believe instruction in flight automation is critical to the success of their graduates, most cite cost of materials and competing curriculum priorities as reasons to defer such instruction to future employers. The authors suggest that program enhancements are within the reach of modern college aviation programs and offer suggestions for three different levels of glass cockpit training

Exploring the origins of the Dzyalloshinski-Moria interaction in MnSi

By using magnetization and small-angle neutron scattering (SANS) measurements, we have investigated the magnetic behavior of Mn_{1-x}Ir_{x}Si system to explore the effect of increased carrier density and spin-orbit interaction on the magnetic properties of MnSi. We determine estimates of the spin wave stiffness and the Dzyalloshinski-Moria, DM, interaction strength and compare with Mn_{1-x}Co_{x}Si and Mn_{1-x}Fe_{x}Si. Despite the large differences in atomic mass and size of the substituted elements, Mn_{1-x}Co_{x}Si and Mn_{1-x}Ir_{x}Si show nearly identical variations in their magnetic properties with substitution. We find a systematic dependence of the transition temperature, the ordered moment, the helix period and the DM interaction strength with electron count for Mn{1-x}Ir{x}Si, Mn_{1-x}Co_{x}Si, and Mn_{1-x}Fe_{x}Si indicating that the magnetic behavior is primarily dependent upon the additional carrier density rather than on the mass or size of the substituting species. This indicates that the variation in magnetic properties, including the DM interaction strength, are primarily controlled by the electronic structure as Co and Ir are isovalent. Our work suggests that although the rigid band model of electronic structure along with Moira's model of weak itinerant magnetism describe this system surprisingly well, phenomenological models for the DM interaction strength are not adequate to describe this system.Comment: 17 pages, 7 Figure

Fermi surface, possible unconventional fermions, and unusually robust resistive critical fields in the chiral-structured superconductor AuBe

The noncentrosymmetric superconductor (NCS) AuBe is investigated using a variety of thermodynamic and resistive probes in magnetic fields of up to 65~T and temperatures down to 0.3~K. Despite the polycrystalline nature of the samples, the observation of a complex series of de Haas-van Alphen (dHvA) oscillations has allowed the calculated bandstructure for AuBe to be validated. This permits a variety of BCS parameters describing the superconductivity to be estimated, despite the complexity of the measured Fermi surface. In addition, AuBe displays a nonstandard field dependence of the phase of dHvA oscillations associated with a band thought to host unconventional fermions in this chiral lattice. This result demonstrates the power of the dHvA effect to establish the properties of a single band despite the presence of other electronic bands with a larger density of states, even in polycrystalline samples. In common with several other NCSs, we find that the resistive upper critical field exceeds that measured by heat capacity and magnetization by a considerable factor. We suggest that our data exclude mechanisms for such an effect associated with disorder, implying that topologically protected superconducting surface states may be involved

The Principal Axis of the Virgo Cluster

Using accurate distances to individual Virgo cluster galaxies obtained by the method of Surface Brightness Fluctuations, we show that Virgo's brightest ellipticals have a remarkably collinear arrangement in three dimensions. This axis, which is inclined by 10 to 15 degrees from the line of sight, can be traced to even larger scales where it appears to join a filamentary bridge of galaxies connecting Virgo to the rich cluster Abell 1367. The orientations of individual Virgo ellipticals also show some tendency to be aligned with the cluster axis, as does the jet of the supergiant elliptical M87. These results suggest that the formation of the Virgo cluster, and its brightest member galaxies, have been driven by infall of material along the Virgo-A1367 filament.Comment: 8 pages, 4 figures, accepted for publication in ApJ Letter