Magnetoelastic Effects in Iron Telluride

Iron telluride doped lightly with selenium is known to undergo a first order magneto-structural transition before turning superconducting at higher doping. We study the effects of magneto-elastic couplings on this transition using symmetry considerations. We find that the magnetic order parameters are coupled to the uniform monoclinic strain of the unit cell with one iron per cell, as well as to the phonons at high symmetry points of the Brillouin zone. In the magnetic phase the former gives rise to monoclinic distortion while the latter induces dimerization of the ferromagnetic iron chains due to alternate lengthening and shortening of the nearest-neighbour iron-iron bonds. We compare this system with the iron arsenides and propose a microscopic magneto-elastic Hamiltonian which is relevant for all the iron based superconductors. We argue that this describes electron-lattice coupling in a system where electron-electron interaction is crucial.Comment: 5 pages, 2 figure

Magneto-elastic quantum fluctuations and phase transitions in the iron superconductors

We examine the relevance of magneto-elastic coupling to describe the complex magnetic and structural behaviour of the different classes of the iron superconductors. We model the system as a two-dimensional metal whose magnetic excitations interact with the distortions of the underlying square lattice. Going beyond mean field we find that quantum fluctuation effects can explain two unusual features of these materials that have attracted considerable attention. First, why iron telluride orders magnetically at a non-nesting wave-vector $(\pi/2, \pi/2)$ and not at the nesting wave-vector $(\pi, 0)$ as in the iron arsenides, even though the nominal band structures of both these systems are similar. And second, why the $(\pi, 0)$ magnetic transition in the iron arsenides is often preceded by an orthorhombic structural transition. These are robust properties of the model, independent of microscopic details, and they emphasize the importance of the magneto-elastic interaction.Comment: 4 pages, 3 figures; minor change

Ultra high bypass Nacelle aerodynamics inlet flow-through high angle of attack distortion test

A flow-through inlet test program was conducted to evaluate inlet test methods and determine the impact of the fan on inlet separation when operating at large angles of attack. A total of 16 model configurations of approximately 1/6 scale were tested. A comparison of these flow-through results with powered data indicates the presence of the fan increased separation operation 3 degrees to 4 degrees over the flow through inlet. Rods and screens located at the fan face station, that redistribute the flow, achieved simulation of the powered-fan results for separation angle of attack. Concepts to reduce inlet distortion and increase angle of attack capability were also evaluated. Vortex generators located on the inlet surface increased inlet angle of attack capability up to 2 degrees and reduced inlet distortion in the separated region. Finally, a method of simulating the fan/inlet aerodynamic interaction using blockage sizing method has been defined. With this method, a static blockage device used with a flow-through model will approximate the same inlet onset of separation angle of attack and distortion pattern that would be obtained with an inlet model containing a powered fan

Christian civilization in Ireland

Thesis (M.A.)--Boston University This item was digitized by the Internet Archive

America’s Two Pastimes: Baseball and Constitutional Law; Review of Adrian Vermeule, \u3ci\u3eCommon Good Constitutionalism\u3ci\u3e

For the last 50 years, the two prevailing constitutional interpretation methodologies have been Originalism and Living Constitutionalism. The former treats the Constitution almost like a contract and demands that interpreters focus on the ordinary contemporary understanding its terms would have received when they became law. The latter treats the Constitution as a charter for the structure of a new government that would survive and mature as needed to protect both the nation and its people as new threats to government and civil liberties arise. Professor Adrian Vermeule’s book Common Good Constitutionalism offers a new approach to constitutional interpretation, one that gives far greater prominence to the need to protect and advance the good of the nation as a whole than either of the other two theories would require. His theoretical justification for the new approach stems from the classical or natural law principle that a nation may demand that its interests outweigh those of any individual or group. He criticizes Originalism as a morally sterile, positivistic approach to legal interpretation, and Living Constitutionalism as concerned only with the interests of individuals and groups without regard for those of the polity. Professor Vermeule, however, does not give sufficient weight to what the Constitution did—viz., create a democratic republic whose elected representatives would make moral judgments—than what a court may do when reviewing their work. He also fails to address a goodly number of issues that any new theory of constitutional interpretation must address to serve the role that he posits for Common Good Constitutionalism. He does not give adequate weight to the rationale endorsed in Marbury v. Madison that it is the text that governs, not background principles, however weighty they might be. He does not address how his theory affects antidiscrimination law, the application of the Bill of Rights to the states, or principles of stare decisis. In sum, Common Good Constitutionalism, while valuable, is better seen as a codicil to Originalism (to which it is closer than Living Constitutionalism) than as an entirely new, different will

COVID-19 and the Provisional Licensing of Qualified Medical School Graduates as Physicians

Each level of government has its own peculiar responsibilities to address the COVID-19 pandemic. The states are responsible for licensing physicians who can treat the affected people. Each year, a large number of American and foreign medical school graduates do not find a residency position in the United States. Medical school graduates who have passed the qualifying examination have acquired a considerable amount of education and training during their medical studies, far more than physician assistants, nurses, military corpsmen and medics, and civilian paramedics or emergency medical technicians. They comprise a pool of talent that could be immensely useful in ameliorating the shortage of physician care throughout the country during the pandemic. State lawmakers should allow those graduates to receive a provisional license so that they can provide emergency medical care under the supervision of a licensed physician to help treat the ever-increasing number of COVID-19 patients we will see throughout the near future, or those patients who suffer from more common illness and injuries