Safety Is Easy

Development is easy

Kinetochores hold on with a ring complex that links a budding yeast kinetochore to a microtubule (MT) forms a ring around the MT, based on structures from two groups. The ring may help kinetochores to keep hold of an MT, even as the MT shrinks towards the spindle pole during anaphase. Stephen Harrison (Harvard Medical School, Boston, MA) and Peter Sorger (MIT, Cambridge, MA) are hoping to analy...

Is alpha-conversion easy?

λx.S ◦A instead of λx.(A[S]) S ◦ λx.A instead of (λx.A)[S] λx.S2 ◦ S1 ◦ A instead of λx.(A[S1][S2]) S2 ◦ λx.S1 ◦ A instead of (λx.A[S1])[S2] S2 ◦ S1 ◦ λx.A instead of (λx.A)[S1][S2] And so on. Far fewer parentheses. And very close to notation of category theory. If we have composition of substitutions (not in my calculus), then λx.(S2 ◦ S1) ◦ A means λx.(A[S1 ◦ S2]) From the point of view of ca...

Arithmetic Is Easy

Parametric Stabilization Is Easy*

A polynomially parametrized family of continuous-time controllable linear systems is always stabilizable by polynomially parametrized feedback. 1. RESULTS Theorem 1. Let (Aλ,Bλ) be a pair of matrices, all whose entries are real polynomial functions of the parameter λ∈Rr. Assume that Aλ is n×n , Bλ is n×m, and that the pair (Aλ,Bλ) is controllable for each λ∈Rr. Then, there exists an m×n matrix ...

Simple is not easy

I review and challenge the views on simplicity and its role in linguistics put forward by Ludlow (2011). In particular, I criticize the claim that simplicity—in the sense pertinent to science—is nothing more than ease of use or “user-friendliness”, motivated by economy of (cognitive) labor. I argue that Ludlow’s discussion fails to do justice to the diversity of factors that are relevant to sim...