Supersonic fan blading

Radially extending rotor blades are disposed on a hub to form a supersonic propulsion fan for a turbofan engine. The peripheral spacing of the blades is such as to avoid forming a channel or passageway between adjacent blades. Each has a flat trailing surface extending from the leading edge at least as far to the rear as to cause any pressure waves which might originate on the blade surface to strike the leading surface of the following blade rather than propagate upstream of the blade row. The flat trailing surface of each blade makes an angle with the axis of rotation such that the blade is parallel to a gas inflow into the blades

Aliens in the Garden

This Article examines environmental rhetoric and argues that a nationalist conception of nature has long distorted environmental policies. Environmental discourse frequently seeks to explain the natural world by reference to the world of nations, a phenomenon that can be characterized as the “nationalization of nature.” A contemporary example of the nationalization of nature is the rhetoric of “invasive species,” which depicts harmful foreign plants and animals in ways that bear an uncanny resemblance to the demonization of foreigners by opponents of immigration. A typical newspaper article about invasive species, bearing the headline “Eeeeek! The eels are coming!,” warned about an influx of “Asian swamp eels” and described them as “slimy, beady-eyed immigrants.” The nationalization of nature is a longstanding trope in American environmental discourse, as policies toward native and foreign plants and animals have long served as surrogates for addressing questions of national identity. Conceiving of environmental problems through the lens of nationalism, however, distorts environmental policies by projecting onto nature unrelated anxieties about national security and national identity

Asymptotic parabolicity for strongly damped wave equations

For $S$ a positive selfadjoint operator on a Hilbert space, $$\frac{d^2u}{dt}(t) + 2 F(S)\frac{du}{dt}(t) + S^2u(t)=0$$ describes a class of wave equations with strong friction or damping if $F$ is a positive Borel function. Under suitable hypotheses, it is shown that $$u(t)=v(t)+ w(t)$$ where $v$ satisfies $$2F(S)\frac{dv}{dt}(t)+ S^2v(t)=0$$ and $$\frac{w(t)}{\|v(t)\|} \rightarrow 0, \; \text{as} \; t \rightarrow +\infty.$$ The required initial condition $v(0)$ is given in a canonical way in terms of $u(0)$, $u'(0)$

Uptake of branched-chain alpha-keto acids in \u3ci\u3eBacillus subtilis\u3c/i\u3e

Bacillus subtilis has a constitutive system for the uptake of alpha-keto-beta-methylvalerate, alpha-ketoisovalerate, and (probably) alpha-ketoisocaproate. A mutation, kauA1, which blocks the uptake of alpha-keto-beta-methylvalerate and alpha-ketoisovalerate, is located between metB and citK on the B. subtilis chromosome