Features of reproduction and assisted reproduction in the white (Ceratotherium simum) and black (Diceros bicornis) rhinoceros

Despite the worldwide increase of rhinoceros calf numbers, the growth of the population of white and black rhinoceros is slowing down mainly due to anthropogenic causes, such as poaching and habitat loss. Assisted reproduction is one of the methods of preserving the valuable genomes of these animals from being lost, and assists in breeding them in captivity to maintain the specie(s) numbers and provide an option for possible reintroduction into the wild. Since wild rhinoceros are difficult to handle and examine clinically, most of the current information available on their reproductive characteristics has been gained from captive rhinoceros populations. Nevertheless, very little is known about rhinoceros reproduction. Since the rhinoceros belongs to the odd-toed ungulates (Perissodactyls) group, like the horse and the tapir, the horse has been proposed as a suitable model to study reproduction and artificial reproductive techniques in the rhinoceros. In this review, the current knowledge of the reproduction of the rhinoceros is summarized

Straightforward Synthesis of α,β-Unsaturated Thioesters via Ruthenium-Catalyzed Olefin Cross-Metathesis with Thioacrylate

The cross-metathesis reaction of S-ethyl thioacrylate with a variety of olefins is effectively catalyzed by using a ruthenium benzylidene olefin metathesis catalyst. This reaction provides a convenient and versatile route to substituted α,β-unsaturated thioesters, key building blocks in organic synthesis.

Stepping-stones for the unemployed: The effect of temporary jobs on the duration until regular work

Individual labour market transitions from unemployment into temporary work are often succeeded by a transition from temporary into regular work. We investigate whether temporary work increases the transition rate to regular work. In that case, temporary work may enhance labour market efficiency. We use longitudinal survey data of individuals to estimate a multi-state duration model, applying the “timing of events” approach. To deal with selectivity, the model incorporates transitions from unemployment to temporary jobs and unobserved determinants of the transition rates. The data contain multiple spells in labour market states at the individual level. We analyse the results using novel graphical representations. The results unambiguously show that temporary jobs serve as stepping-stones towards regular employment. They shorten the duration of unemployment and they substantially increase the fraction of unemployed workers who have regular work within a few years after entry into unemployment, as compared to a situation without temporary jobs.Unemployment; fixed term contracts; temporary work; job search; duration model; treatment effect