Convergence of human age-sex distributions to an equilibrium-state age-sex distribution

The main concern of the paper is to investigate the effects of introducing migration into the process of population growth using an overall net migration rate and an age-sex composition of net migrants (i.e., the net number of migrants) as compared with the case in which there is no migration. It is shown that the convergence to an equilibrium state occurs in the presence of a constant stream of migration with fixed age-sex structure and constant vital rates. The duration of convergence (i.e., the time required for convergence) is less when there is net immigration than when there is no migration but more when there is net emigration, provided the age-sex composition of net migrants contains nonnegative values at all ages for both sexes or at least, for the sex which is assumed to be dominant. If the age-sex composition of net migrants contains positive, negative, and/or zero values, the duration may be less than, or equal to, or greater than that in the case with no migration depending on the actual age-sex composition of the net migrants and the mignitude of the net migration rate. The instrinsic growth rate follows a trend which is opposite to that of the duration of convergence, except when the age-sex composition of net migrants contains zero values at all ages below the oldest age at which reproduction takes place. In the case of this exception, the intrinsic growth rate will remain the same as in the absence of migration provided the net migration rate is not greater than one which is true in demographic applications.     

Instant success for Instant Pharmacology

Instant Pharmacology (1999). Saeb-Parsy K, Assomull RG, Kahn FZ, Saeb-Parsy K, and Kelly E. John Wiley and Sons 349 pp. £19.99 pbk; ISBN 0471976393 © 1999 John Wiley & Sons, Inc.     

Social play in wild brown bears of varying age-sex class

Social play behaviour is a well-described phenomenon, almost ubiquitous among mammals. Despite its prevalence, social play takes several forms and may vary in function across species. For solitary species, the function of play outside of the family group remains unclear. Here, we describe the motor patterns of play among non-littermate wild brown bears Ursus arctos of different age-sex class. Play was documented during a time of abundant food availability in three different scenarios: play among non-littermate subadults, play among non-littermate cubs, and play among a ‘group’ of bears of different age and sex class. We used a previously described behavioural ethogram to recognise play. Play followed typical motor patterns and postures expressed by bears during play-fighting: relaxed face, puckered-lip, ears partially flattened to crescent, wrestling, jaw gaping, play-biting, paw-swatting, and lunging. No vocalisations were conducted during play bouts. Older bears displayed ‘self-handicapping’ and ‘role-reversal’ in the play postures they selected when playing with younger bears, suggesting that tactics vary according to age class and dominance ranking. Playing likely allows for the evaluation of conspecifics in a non-aggressive way during times of reduced competition and could also relieve stress in complex social situations.     

Establishing a twin register in Sri Lanka.

Nearly all twin registers are based in developed countries and there is no twin register in the developing world. Our objectives were to initiate the process of establishing a nationwide twin register in Sri Lanka by starting a volunteer register first and working towards a population-based register. Regular newspaper advertisements, feature articles, radio talks, and television programmes were used to publicise a competition for twins, their parents/relatives and friends requesting them to participate by sending in details of twins. The competition ran from 28 March 1997 for a period of 3 months. It offered prizes for three winners selected by drawing lots. Advertisements highlighted the objective of the competition as establishing a twin register for future research and emphasised that informed consent would be obtained for individual research projects. Those who registered comprise 4602 twin pairs (same sex: male--1564, female--1885; different sex--1153), 80 sets of triplets (same sex: male--17, female--31; different sex--42) and two sets of quadruplets (different sex). The oldest twins, triplets, quadruplets are 85, 46, and 5 years old, respectively; 88.0% of twins are less than 30 years old. Although others have previously used media publicity to enrol twins in twin registers, we believe this to be the first time that twins have been enrolled through competition. We have more young twins, and our gender and zygosity proportions after applying Weinburg's rule do not match the proportions expected from a volunteer twin sample. Establishing a twin register for research purposes has proved possible in a developing country.     

Estimating list inflation in a practice register.

The reason why patients were incorrectly registered in an age-sex register was studied. Whereas underregistration was caused by patient delay in registering with a doctor, the much greater number of overregistered patients were thought to be there largely because of administrative delays in removing their names from the register. It is suggested that it would be possible for the software of a computer system in general practice to correct the population size and structure for estimated list inflation.     

Rabbit skeletal alpha-tropomyosin chains are in register.

2-Acetamido-2-deoxy-3-O-(D-2-propionyl-L-alanine)-D-glucopyranose ($\text{5}$) and 2-acetamido-2-deoxy-3-O-(D-2-propionyl-L-alanyl-D-isoglutamine)-D-glucopyranose ($\text{10}$) have been synthesized by condensation of benzyl 2-acetamido-4,6-O-benzylidene-3-O-(D-1-carboxyethyl)-2-deoxy-β-D-glucopyranoside ($\text{1}$) respectively with the L-alanine derivative $\text{2}$ and the dipeptide $\text{7}$, followed by debenzylidenation and hydrogenolysis. Compound $\text{10}$ is adjuvant active, whereas $\text{5}$ is inactive, so that $\text{10}$ is the smallest adjuvant active structure for the time being.