Studies were conducted to determine: 1) if fecal hormone metabolite concentrations correlated with serum estrogen and progesterone concentrations, follicular activity and reproductive behavior in the black rhinoceros (Diceros bicornis) and 2) if threshold values of respective fecal metabolite concentrations correlated with pregnancy. Blood and fecal samples were collected, in conjunction with transrectal ultrasound and behavior observations, for an 18-month period from one black rhinoceros female. Subsequently, serial fecal samples were collected from 13 females in 10 zoos. Quantitative analysis of serum progesterone (P 4 ) and estradiol (E 2 ) was performed by radioimmunoassay (RIA); analysis of fecal estrogen metabolites (E) and fecal progesterone metabolites (P) were performed by enzyme immunoassay (EIA). Serum P 4 concentrations identified two luteal phase patterns and two nadirs which corresponded with behavioral estrus. Fecal E patterns indicated a sharp peak which corresponded with breeding. Concentrations of fecal P illustrated identifiable nadirs and several peaks which corresponded to serum P 4 nadirs and luteal phases. Serum P 4 concentrations were not different between the luteal phase and pregnancy. Fecal P concentrations started to rise above luteal phase concentrations approximately 150 days postbreeding and remained elevated until immediately before parturition. Serum E 2 and fecal E concentrations rose and subsequently declined after parturition. In the fecal samples from seven pregnant females, fecal P concentrations were similarly elevated compared to six nonpregnant females. Results indicated that fecal steroid metabolites accurately reflected serum steroid hormone concentrations and that the measurement of P and E concentrations permitted the characterization of the estrous cycle, the diagnosis of pregnancy, and the onset of parturition.

No abstract

No abstract

synopsisA self-consistent set of chemical thermodynamic values for the polymerization of formaldehyde in the gas phase and in aqueous solution is obtained with the aid of recent experimental thermochemical results and the use of selected methods of calculation of data not otherwise available. Enthalpies, entropies, and Gibbs free energies of formation are derived for the various intermediates and products, including the first six hydroxyl-terminated oligomers. Simple equations for the logarithm of the equilibrium constant as a function of temperature are presented for a number of polymerization reactions, permitting comparison with experimental results. Fkasonable agreement is obtained in almost all cases, even though ideal solutions are assumed.

Part I traces fine structural features of polythene, beginning with the arrangement of carbon atoms disclosed by x‐ray diffraction, and including the incorporation of crystalline segments into crystallites, and finally the combination of crystallites and amorphous regions to form spherulites–the largest structural elements of polythene. Attention is called to the frequent occurrence of side chains in the molecules. The structures of spherulitic and cold‐drawn polythenes are compared. Part II describes an experimental study of the cold‐drawing of polythene which discloses an interesting variant of this process, designated as “redrawing,” in which dimensional changes differ greatly from those of ordinary cold‐drawing. On the basis of these observations and structural considerations presented in Part I, a mechanism of cold‐drawing as a rheological process is outlined.