Regular Paper

We study the algebraic dimension of twistor spaces of positive type over 4CP². We show that such a twistor space is Moishezon if and only if its anti-canonical class is not nef. More precisely, we show the equivalence of being Moishezon with the existence of a smooth rational curve having negative intersection number with the anticanonical class. Furthermore, we give precise information on the dimension and base locus of the fundamental linear system |-1/2|. This implies, for example, dim|-1/2K| a(Z). We characterize those twistor spaces over 4CP², which contain a pencil of divisors of degree one by the property dim|-1/2K| = 3.     

Retrieving seasonally adjusted quarterly growth rates from annual growth rates that are reported quarterly

Most macroeconomic time series are reported on a quarterly basis. However, in many cases, official statistical agencies report annual (or ‘year-on-year’) growth rates rather than the quarterly data themselves. In this paper, we demonstrate how to recover seasonally adjusted quarterly growth rates from annual growth rates that are reported quarterly. As an illustration, we apply the technique to the highly seasonal UK Retail Sales series. Using only the annual growth rates calculated from the underlying data, we find that our procedure generates estimated seasonally adjusted quarterly growth rates that are almost indistinguishable from the ‘true’ seasonally adjusted quarterly growth rates.     

关于Rhoades文章的评注

本文给出了Ｄ－度量空间中的一个不动点定理,并指出了文献「１」中的错误。     

Paper folding and trigonometric ratios

The purpose of this note is to discuss how paper folding can be used to find the exact trigonometric ratios of the following four angles: 22.5°, 67.5°, 27°, and 63°.