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An axiomatization of the general theory of relativity is proposed. The assumed philosophical background is critical realism. None of the “principles” commonly considered as founding the theory, such as (a) the equality of inertial and gravitational mass, (b) the principle of equivalence, (c) the principle of general covariance, (d) the geodesic postulate, and (e) Mach's principle, are taken as axioms in our system.

AbstractIñguez-Covarrubias, G., Franco-Gómez, Ma. de J. and McCaskey, T. A. 1995. Use of acidulants to control volatile nitrogen loss and nitrogen insolubility of broiler litter. J. Appl. Anim. Res., 7: 129–135.Loss of crude protein and bioavailability of nitrogen due to heat and heat plus acid treatment of broiler litter was evaluated. Broiler litter held 2 days at 60C lost 9.1% crude protein (P<0.05), whereas, litter treated with acid to pH 6 lost 2.6% (P<0.05). Thus acid treatment was beneficial to reduce nitrogen loss by 71.4%. Heat treatment of broiler litter also adversely affected the bioavailability of dietary nitrogen since litter acid detergent fiber-nitrogen (ADF-N) increased 17.3%. Whereas, the ADF-N of litter acidified to pH 6 prior to heating was reduced almost to 100% (P<0.05). Nitrogen fractions that are lost during the heating of litter were also analyzed.

We present a generalization of a class of Szekeres space-times. The new solutions satisfy Einstein's equations with a cosmological constant and have the same geometrical properties as the corresponding class found by Szekeres. Particular cases leading to known solutions are considered.

AbstractIñiguez-Covarrubias, G., Franco-Gómez, Ma. de J. and Castañeda- Huizar, P. 1995. An economic analysis of swine waste silage as sheep feed ingredient. J. Appl. Anim. Res., 9: 61–71.The characterization and evaluation of the nutrient composition of swine waste silage as a feedstuff and its comparison with a conventional sheep diet, have established a basis for estimating the monetary value of the silage. It was concluded that $85.60 was the maximum supportable cost that could be paid per ton of swine waste silage for an expected growth rate of 44.7 g/day when a conventional sheep diet that allows a daily gain of 218 g/day costs $181.5. Considering the monthly production and operation costs, to produce 286 tons/month of swine waste silage, it was shown that the cost per produced ton (dry basis), equals to the maximum supportable cost that could be paid per ton of swine waste silage. Therefore, the pig producers must consider the initial investment required for manure processing as a necessary investment for manure handling and disposal and not necessarily as a business. With proper attention in the economical balance, swine waste silage can be incorporated in sheep gestation and growing-finishing rations contributing to alleviate pollution problems, decrease feed costs, increase supplies of available nitrogen and essential mineral sources and create new employment opportunities.

AbstractIñiguez-Covarrubias, G., Franco-Gómez, Ma, de J. and Andrade- Maldonado, Gpe. del R. 1994. Biodegradation of swine waste by house fly larvae and evaluation of their protein quality in rats. J. Appl. Anim. Res., 6: 65–74.Swine waste was converted into a high-protein product by upgrading with housefly larvae. Fresh manure was seeded with housefly eggs. The eggs were allowed to hatch and the larvae to tunnel and aerate the manure. This process deodorized the manure by the 6th or 7th day. The larvae migrated out of the manure to a dry box. The larvae were dried, ground and used in rat feeding tests for the evaluation of the protein quality in terms of protein efficiency ratio (PER), the in vitrodigestibility value of larvae meal protein was also determined. The larvae meal contained 52.5% C.P. of 90.6% digestibility with very high (29.1) percent of ether extract. It supported growth in rats as good as casein with PER 3.3as against 3.1 for casein. If found economically viable on large scale, the process will render the swine excreta pollution free and producing a protein energy rich feed for livestock as a by product.

A method based on the invariace under a continuous Lie group of transformations is worked out to reduce the problem of finding solutions to the cosmological equations of Jordan and Brans-Dicke theory of gravitation for the Robertson-Walker metrics and the cases of the dust universe and the vacuum universe. The reduction consists in a first-order differential equation and a quadrature for each case. Previously known cosmological solutions are re-obtained. In particular, it becomes apparent during the development of this scheme that the flat-space solutions are indeed the general solution.