Ottoia prolifica Walcott, 1911 is a 500 million years old fossil cycloneuralian worm from the Burgess Shale, Canada, British Columbia. We report newly observed details of the morphology and ontogeny of this species. Previously unknown details could be observed by applying crossedpolarized light. This approach revealed that the tail end is equipped with six hook-shaped spines and that the scalid...

A 16-year-old male patient was admitted to our hospital with traumatic luxation of right testis due to self-mutilation with a retractable knife on Apr. 20, 2004. He had been followed as temporal lobe epilepsy and suspicions of gender identify disorder by a pediatrician. He was fully oriented with a clear sensory and normal perception, but had no memory of what he had done. His parents were free...

An R-module is called semi-endosimple if it has no proper fully invariant essential submodules. For a quasi-projective retractable module MR we show that M is finitely generated semi-endosimple if and only if the endomorphism ring of M is a finite direct sum of simple rings. For an arbitrary module M , conditions equivalent to the semi-endosimplicity of its quasi-injective hull are found. As co...

Structural-functional roles of microtubules in cells and cell appendages are becoming well established . A "static" supportive function could be assigned to the microtubular arrays in the axonemes of Heliozoa (Actinophrys, 7 ; Echinosphaerium, 18) and Radiolaria (Nassellaria, 5), in the tentacles of Suctoria (Acineta, 3 ; Tokophrya, 12), and in the endosprits of the ciliate Cyathodinium (9) . M...

We report the discovery of sipunculan worms from the Lower Cambrian Maotianshan Shale, near Kunming (southwest China). Their sipunculan identity is evidenced by the general morphology of the animals (sausage-shaped body with a slender retractable introvert and a wider trunk) and by other features, both external (e.g. perioral crown of tentacles, and hooks, papillae and wrinkle rings on the body...

A ring R is called right strong stably finite (r.ssf) if for all n ≥ 1, injective endomorphisms of R (n) R are essential. If R is an r.ssf ring and e is an idempotent of R such that eR is a retractable R-module, then eRe is an r.ssf ring. A direct product of rings is an r.ssf ring if and only if each factor is so. The R.ssf condition is investigated for formal triangular matrix rings. In partic...

It is shown that square free set theoretic involutive non-degenerate solutions of the Yang-Baxter equation whose associated permutation group (referred to as an involutive Yang-Baxter group) is abelian are retractable in the sense of Etingof, Schedler and Soloviev. This solves a problem of Gateva-Ivanova in the case of abelian IYB groups. It also implies that the corresponding finitely presente...

A series of experiments was performed to determine whether sign-tracking would occur in rats with intravenous (i.v.) cocaine as the unconditioned stimulus. In Experiment 1, a retractable lever paired with food produced strong sign-tracking, but a lever paired with one of three doses of i.v. cocaine did not elicit any approach or contact behavior. Experiment 2 demonstrated that doses of cocaine ...

Abstract In recent years, as a new type of gob-side entry retaining method, roadway automatically formed by roof cutting and pressure releasing (RAFRCPR) has been widely used in China. Under the condition deep mining, deformation gangue rib is difficult to control, it for traditional I-shaped steel provide needed support. To effectively control rib, U-shaped retractable prevention structure (UR...