445 research outputs found

    Sponges of the family Esperiopsidae (Demospongiae, Poecilosclerida) from Northwest Africa, with the descriptions of four new species

    Get PDF
    Sponges belonging to the genera Amphilectus Vosmaer, Esperiopsis Carter and Ulosa de Laubenfels of the family Esperiopsidae were collected during 1986 and 1988 expeditions of the Netherlands Centre for Biodiversity Naturalis (at that time the National Museum of Natural History at Leiden and the Zoological Museum of Amsterdam) in waters off the coasts of Mauritania and the Cape Verde Islands. Four new species, Amphilectus utriculus sp. nov., Amphilectus strepsichelifer sp. nov., Esperiopsis cimensis sp. nov., Ulosa capblancensis sp. nov., and two already known species, Amphilectus cf. fucorum (Esper) and Ulosa stuposa (Esper) are described and discussed

    Spin-mediated dissipation and frequency shifts of a cantilever at milliKelvin temperatures

    Get PDF
    We measure the dissipation and frequency shift of a magnetically coupled cantilever in the vicinity of a silicon chip, down to 2525 mK. The dissipation and frequency shift originates from the interaction with the unpaired electrons, associated with the dangling bonds in the native oxide layer of the silicon, which form a two dimensional system of electron spins. We approach the sample with a 3.433.43 μ\mum-diameter magnetic particle attached to an ultrasoft cantilever, and measure the frequency shift and quality factor as a function of temperature and the distance. Using a recent theoretical analysis [J. M. de Voogd et al., arXiv:1508.07972 (2015)] of the dynamics of a system consisting of a spin and a magnetic resonator, we are able to fit the data and extract the relaxation time T1=0.39±0.08T_1=0.39\pm0.08 ms and spin density σ=0.14±0.01\sigma=0.14\pm0.01 spins per nm2^2. Our analysis shows that at temperatures 500\leq500 mK magnetic dissipation is an important source of non-contact friction.Comment: 5 pages, 3 figure

    Cerebellar Zones: A Personal History

    Get PDF
    Cerebellar zones were there, of course, before anyone noticed them. Their history is that of young people, unhindered by preconceived ideas, who followed up their observations with available or new techniques. In the 1960s of the last century, the circumstances were fortunate because three groups, in Leiden, Lund, and Bristol, using different approaches, stumbled on the same zonal pattern in the cerebellum of the cat. In Leiden, the Häggqvist myelin stain divulged the compartments in the cerebellar white matter that channel the afferent and efferent connections of the zones. In Lund, the spino-olivocerebellar pathways activated from individual spinal funiculi revealed the zonal pattern. In Bristol, charting the axon reflex of olivocerebellar climbing fibers on the surface of the cerebellum resulted in a very similar zonal map. The history of the zones is one of accidents and purposeful pursuit. The technicians, librarians, animal caretakers, students, secretaries, and medical illustrators who made it possible remain unnamed, but their contributions certainly should be acknowledged

    Preliminary Assessment of Sponge Biodiversity on Saba Bank, Netherlands Antilles

    Get PDF
    Background Saba Bank Atoll, Netherlands Antilles, is one of the three largest atolls on Earth and provides habitat for an extensive coral reef community. To improve our knowledge of this vast marine resource, a survey of biodiversity at Saba Bank included a multi-disciplinary team that sampled fishes, mollusks, crustaceans, macroalgae, and sponges. Methodology/Principal Findings A single member of the dive team conducted surveys of sponge biodiversity during eight dives at six locations, at depths ranging from 15 to 30 m. This preliminary assessment documented the presence of 45 species pooled across multiple locations. Rarefaction analysis estimated that only 48 to 84% of species diversity was sampled by this limited effort, clearly indicating a need for additional surveys. An analysis of historical collections from Saba and Saba Bank revealed an additional 36 species, yielding a total of 81 sponge species recorded from this area. Conclusions/Significance This observed species composition is similar to that found on widespread Caribbean reefs, indicating that the sponge fauna of Saba Bank is broadly representative of the Caribbean as a whole. A robust population of the giant barrel sponge, Xestospongia muta, appeared healthy with none of the signs of disease or bleaching reported from other Caribbean reefs; however, more recent reports of anchor chain damage to these sponges suggests that human activities can have dramatic impacts on these communities. Opportunities to protect this extremely large habitat should be pursued, as Saba Bank may serve as a significant reservoir of sponge species diversity

    The impact of loco-regional recurrences on metastatic progression in early-stage breast cancer: a multistate model

    Get PDF
    To study whether the effects of prognostic factors associated with the occurrence of distant metastases (DM) at primary diagnosis change after the incidence of loco-regional recurrences (LRR) among women treated for invasive stage I or II breast cancer. The study population consisted of 3,601 women, enrolled in EORTC trials 10801, 10854, or 10902 treated for early-stage breast cancer. Data were analysed in a multivariate, multistate model by using multivariate Cox regression models, including a state-dependent covariate. The presence of a LRR in itself is a significant prognostic risk factor (HR: 3.64; 95%-CI: 2.02-6.5) for the occurrence of DM. Main prognostic risk factors for a DM are young age at diagnosis (</=40: HR: 1.79; 95%-CI: 1.28-2.51), larger tumour size (HR: 1.58; 95%-CI: 1.35-1.84) and node positivity (HR: 2.00; 95%-CI: 1.74-2.30). Adjuvant chemotherapy is protective for a DM (HR: 0.66; 95%-CI: 0.55-0.80). After the occurrence of a LRR the latter protective effect has disappeared (P = 0.009). The presence of LRR in itself is a significant risk factor for DM. For patients who are at risk of developing LRR, effective local control should be the main target of therapy

    Nothing in (sponge) biology makes sense - except when based on holotypes

    Get PDF
    Sponge species are infamously difficult to identify for non-experts due to their high morphological plasticity and the paucity of informative morphological characters. The use of molecular techniques certainly helps with species identification, but unfortunately it requires prior reference sequences. Holotypes constitute the best reference material for species identification, however their usage in molecular systematics and taxonomy is scarce and frequently not even attempted, mostly due to their antiquity and preservation history. Here we provide case studies in which we demonstrate the importance of using holo-type material to answer phylogenetic and taxonomic questions. We also demonstrate the possibility of sequencing DNA fragments out of century-old holotypes. Furthermore we propose the deposition of DNA sequences in conjunction with new species descriptions