The rho proteins, p21 ~ , are ubiquitously expressed guanine nucleotide binding proteins with ,'o30% amino acid homology to p21'% but their biochemical function is unknown. We show here that microinjection of constitutively activated recombinant rho protein (Vall4rho) into subconfluent cells induces dramatic changes in cell morphology: 15-30 min after injection cells adopt a distinct and novel ...

S OF SOME OF MY PAPERS GROUPED BY TOPIC 1. Regularity. Let k be an algebraically closed field. We will work over a standard graded polynomial ring U over k. Projective dimension and regularity are the main numerical invariants that measure the complexity of a minimal free resolution. Let L be a homogeneous ideal in U , and let b ij (L) be its graded Betti numbers. The projective dimension pd(L)...

The history of the living world can be summarised as an elaboration of ever more perfect eyes within a Cosmos in which there is always something new to be seen (Teilhard du Chardin, 1955). Today, the bottleneck in the atomic resolution imaging of biological systems is a fundamental need for crystals. This limits the scope of detailed structural analysis to macromolecules and macromolecular asse...

In these notes, we present a general framework to compute the codimension one part of the elimination ideal of a system of homogeneous polynomials. It is based on the computation of the so-called MacRae’s invariants that we will obtain by means of determinants of complexes. Our approach mostly uses tools from commutative algebra. We begin with some basics on elimination theory and then introduc...

The theoretical problem of integrating evolution, heredity, development, and cognition has a long pedigree with a complicated history. Many of these fields were considered the subjects of one science in the 19th century (Maienschein 1987). Leading theoretical biologists of the age wrote large, expansive treatises that biologists now can read only with equal measures of wonder and incredulity: w...

A portion of the Fly's Eye II has been recording Cherenkov flashes since November, 1987, in a declination band which includes these three x-ray sources. The data have been analyzed on a nightly basis in a search for evidence of ultra-high energy (UHE) gamma ray emissions. Introduction. Cyg X-3, Her X-1, and the Crab nebula or pulsar have all been reported to be sources of UHE ã-rays. Reviews on...

Lawrence Weed noted that while we think in the abstract, we live in the concrete [1]. In their paper “Combining Health Data Uses to Ignite Health System Learning”, Ainsworth and Buchan report optimistically on an approach to a very complex sociotechnical domain, health and healthcare systems [2]. This work moves us forward to making operational our abstract aspiration of a learning healthcare s...

Dans les muséums d'histoire naturelle et autres institutions à vocation de conservation, collections fossiles sont trésors des paléontologues. Elles conservatoires du monde vivant temps géologiques. Il importe aux paléontologues connaître l'histoire qu'ils consultent pour diverses raisons, que ce soit comparer nouvelles découvertes avec déjà connus ou réviser la systématique d'un groupe d'organ...

Low molecularweight GTP-binding proteins are molecular switches that control a diverse array of biological processes (Bourne et al., 1991). When bound to GTP, these proteins transduce signals to effector proteins. When bound to GDP, these proteins are in an inactive state. The cycling between the active, GTP-bound state and the inactive, GDP-bound state is controlled by positive and negative mo...