Factors Controlling the Incubation Period of Birds

The incubation period of birds varies from approximately two to four weeks with three rather well defined periods known; namely, two, three and four weeks. Some of the factors suggested by others responsible for this variation include size of egg, condition of young at the time of hatching, temperature, etc. An evaluation of these factors will be discussed. A study of the histology of the digestive tract of an English Sparrow at the time of hatching (14 days) was carefully compared with the digestive tract of a chick incubated for the same length of time. Likewise, the histology of the tract of an English Sparrow seven days after hatching was compared with that of a chick at the time of hatching (21 days). These comparisons reveal facts of importance to the length of the incubation period

The President’s Report, March 1989

The President’s Report from March 1989

The President’s Report, June 1989

The President’s Report from June 1989

Some Additional Observations on Sphenodon punctatum in Captivity

In the Proceedings of the Iowa Academy of Science, Vol. XXX, 1925, pp. 151-115, appeared an article by Wendell Krull on certain habits of Sphenodon punctatum which be observed about this animal in captivity. Since September, 1924, the writer has been caring for two of the same specimens upon which Mr. Krull made his observations. The reptiles have been kept under exactly the same conditions as those under which Mr. Krull made his observations so that any changes in habits are not due to changes of conditions. While most of my observations and notes coincide very well with Mr. Krull\u27s, perhaps a few additional notes may be of some interest

The Embryology of the English Sparrow (Abstract)

The purpose of this investigation is three-fold: (1) to outline the general embryogeny of the English Sparrow, (2) to determine the relative rates of differentiation of the various external features and (3) to compare the developmental rates of the sparrow with those of the chick and turkey. Two questions arise from the fact that the incubation period of the sparrow is 13 days, while that of the chick is 21 and the turkey 28 days: (1) Is it possible to establish corresponding stages in the three embryos, or do the different organs develop at different times? (2) Are the three at the same stage of development at hatching, or for example, is the sparrow at hatching to be compared to a chick one week before hatching? A series of carefully timed embryos was obtained by incubating fresh sparrow eggs under artificial conditions. Diagnostic features for each day were recorded in chart form so that the age of embryos taken from eggs in nature can be readily determined. An 8 day sparrow embryo is comparable to an 11 day chick or a 14 day turkey embryo in morphological development. However, an adaptive character for hatching, the egg tooth, appears on the 6th day in all three birds

On the relation of standard and helical magnetorotational instability

The magnetorotational instability (MRI) plays a crucial role for cosmic structure formation by enabling turbulence in Keplerian disks which would be otherwise hydrodynamically stable. With particular focus on MRI experiments with liquid metals, which have small magnetic Prandtl numbers, it has been shown that the helical version of this instability (HMRI) has a scaling behaviour that is quite different from that of the standard MRI (SMRI). We discuss the relation of HMRI to SMRI by exploring various parameter dependencies. We identify the mechanism of transfer of instability between modes through a spectral exceptional point that explains both the transition from a stationary instability (SMRI) to an unstable travelling wave (HMRI) and the excitation of HMRI in the inductionless limit. For certain parameter regions we find new islands of the HMRI.Comment: 48 pages, 13 figure

On contractions of classical basic superalgebras

We define a class of orthosymplectic $osp(m;j|2n;\omega)$ and unitary $sl(m;j|n;\epsilon)$ superalgebras which may be obtained from $osp(m|2n)$ and $sl(m|n)$ by contractions and analytic continuations in a similar way as the special linear, orthogonal and the symplectic Cayley-Klein algebras are obtained from the corresponding classical ones. Casimir operators of Cayley-Klein superalgebras are obtained from the corresponding operators of the basic superalgebras. Contractions of $sl(2|1)$ and $osp(3|2)$ are regarded as an examples.Comment: 15 pages, Late

Epidemiological study of canine trypanosomosis in an urban area of Ivory Coast

Following confirmed cases of trypanosomosis in military working dogs, c cross-sectional study was undertaken to evaluate the source of infection and determine the prevalence of canine infection with Trypanosoma congolense in the urban focus of Abidjan, Ivory Coast. Blood from 123 dogs were collected and subjected to PCR using specific primers for Trypanosoma congolense "forest type". In addition, an entomological study was conducted in an urban area near the forest surronding the military camp. The observed prevalence was 30.1% end PCR positivity to Trypanosoma congolense was not significantly associated with sex or age of animals. This study demonstrates the high contamination rate of dogs in enzootic zones, the potential risk of introduction of the disease in free animal populations and the ability of Glossina palpalis to adopt to urban areas and to transmit trypanosomosis in such areas. The factors leading to a possible emergence of canine trypanosomiasis in enzootic zones need further investigations

Unfolding of eigenvalue surfaces near a diabolic point due to a complex perturbation

The paper presents a new theory of unfolding of eigenvalue surfaces of real symmetric and Hermitian matrices due to an arbitrary complex perturbation near a diabolic point. General asymptotic formulae describing deformations of a conical surface for different kinds of perturbing matrices are derived. As a physical application, singularities of the surfaces of refractive indices in crystal optics are studied.Comment: 23 pages, 7 figure