Locally nilpotent derivations of affine domains
Any locally nilpotent derivation of an affine domain is equivalent to a restriction of a Jacobian type derivation of a polynomial ring.
On weighted projective planes and their affine rulings
(Here, and throughout this paper, all algebraic varieties are over an algebraically closed field k of characteristic zero.) As we will see in Section 1, the weighted projective planes P(a; b; ) satisfy (‡). Paper [2] investigates the problem of finding all affine rulings of a given surface X satisfying (†). In particular, it shows that if X satisfies (†) then the problem reduces to that of describing a certain set T0(X) of triples (m; T1; T2), where m is a positive integer and each Ti is a 2 hi matrix with entries in N (0 hi 2). The aim of the present paper is to give an explicit description of the set T0(X) in the case where X is a weighted projective plane; this is achieved by Corollary 7.1 and Propositions 7.3, 7.4 and 7.7. Thus [2] and this paper solve the above mentioned problem for weighted projective planes. Let us also point out the following characterization of weighted projective planes, which we prove in the form of Corollary 6.12, below (see 1.19 for the notion of resolution graph of a normal surface):
The colonial ethnological line: Timor and the racial geography of the Malay Archipelago
This article examines the connected histories of racial science and colonial geography in Island Southeast Asia. By focusing on the island of Timor, it explores colonial boundaries as modes of arranging racial classifications, and racial typologies as forms of articulating political geography. Portuguese physical anthropologist António Mendes Correia's work on the ethnology of East Timor is examined as expressive of these productive connections. Correia's classificatory work ingeniously blended political geography and racial taxonomy. Between 1916 and 1945, mainly based on data from the Portuguese enclave of Oecussi and Ambeno, he claimed a distinct Malayan racial type for the whole colony of ‘Portuguese Timor’. Over the years he developed an anthropogeographical theory that simultaneously aimed to reclassify East Timor and to revise the racial cartography of the Malay Archipelago, including Wallace's famous ethnological line.