Functorial CW-approximation

The usual construction of a CW-approximation is functorial up to homotopy, but it is not functorial. In this note, we construct a functorial CW-approximation. Our construction takes inclusions of subspaces into inclusions of subcomplexes, and commutes with intersections of subspaces of a fixed space.Comment: 10 page

Overcategories and undercategories of model categories

If M is a model category and Z is an object of M, then there are model category structures on the category of objects of M over Z and the category of objects of M under Z under which a map is a cofibration, fibration, or weak equivalence if and only if its image in M under the forgetful functor is, respectively, a cofibration, fibration, or weak equivalence. It is asserted without proof in "Model categories and their localizations" that if M is cofibrantly generated, cellular, or proper, then so is the category of objects of M over Z. The purpose of this note is to fill in the proofs of those assertions and to state and prove the analogous results for undercategories.Comment: 6 page

Feed quality problems and management strategies

Feed is the single most important input in increasing aquaculture production and profits. Success or failure in augmenting yield with feeding depends, to a large extent, on the quality of the diet. Feed quality, generally perceived as the responsibility of the feed manufacturer, is affected by factors outside of the plant such as handling, storage, and use. Thus, the maintenance of feed quality becomes partly the responsibility of the farmer. Every fish farmer must be familiar with the nature and occurrence of major feed quality problems and able to prevent and control them. This paper is based on a farmer's viewpoint. Valuable insights are provided for the feed manufacturer

Uncovered interest parity tests and exchange rate expectations

Empirical studies reject uncovered interest parity. Experimental and survey data studies reject rational expectations and find evidence of adaptive, regressive, bandwagon and distributed lag expectations. In this paper we investigate how these two findings are related. We show that uncovered interest parity test coefficients can be expressed as functions of the parameters of the expectations mechanisms. Negative values for uncovered interest parity test coefficients are explained by adaptive expectations with a high speed of learning and distributed lag expectations, while positive values are caused by adaptive expectations with a low speed of learning, regressive expectations and bandwagon expectations.monetary economics ;