Marine oxygen production and open water supported an active nitrogen cycle during the Marinoan Snowball Earth

The Neoproterozoic Earth was punctuated by two low-latitude Snowball Earth glaciations. Models permit oceans with either total ice cover or substantial areas of open water. Total ice cover would make an anoxic ocean likely, and would be a formidable barrier to biologic survival. However, there are no direct data constraining either the redox state of the ocean or marine biological productivity during the glacials. Here we present iron-speciation, redox-sensitive trace element, and nitrogen isotope data from a Neoproterozoic (Marinoan) glacial episode. Iron-speciation indicates deeper waters were anoxic and Fe-rich, while trace element concentrations indicate surface waters were in contact with an oxygenated atmosphere. Furthermore, synglacial sedimentary nitrogen is isotopically heavier than the modern atmosphere, requiring a biologic cycle with nitrogen fixation, nitrification and denitrification. Our results indicate significant regions of open marine water and active biologic productivity throughout one of the harshest glaciations in Earth history

A study on the constitutive equation effects in the fracture initiation of AA5450 sheets

© Springer Nature Singapore Pte Ltd. 2019.Determination of the fracture initiation in the sheet metal forming applications can be achieved successfully using ductile fracture criteria (DFCs) and finite element codes together. In this study three different uncoupled, energy based ductile fracture criteria have been employed to predict the onset of the fracture in the AA5450 aluminum alloy sheets. Also, two different constitutive models namely, isotropic von-Mises and anisotropic Hill, have been implemented to the finite element code ABAQUS through VUMAT subroutine to investigate the effect of constitutive equations on the applicability of the utilized DFCs. It was shown that the constitutive model has significant influence on the estimation of the time and place of the fracture initiation in the sheets

A quiet NICU for improved infants' health, development and well-being:a systems approach to reducing noise and auditory alarms

<p>Noise is a direct cause of health problems, long-lasting auditory problems and development problems. Preterm infants are, especially, at risk for auditory and neurocognitive development. Sound levels are very high at the neonatal intensive care unit (NICU) and may contribute to the frequently observed detrimental outcomes of prematurely born infants. Despite efforts to reduce noise level at the NICU, these have not changed over the past years. Although many authors indicate that a systems approach could solve such interrelated problems, methods to do so are generally lacking for the complicated situation in a critical care setting. A new approach was developed, that is, combining Fuzzy Front End earliest stage product development and human factors methods, with a focus on all Human-tech levels and on their interaction. A concept built up from several emerging technologies was developed, including tactile alarms, artificial intelligence for medicine, multimodal alarm system and mobile communication in critical care. Current and envisioned nursing work was modelled. Outcome of the study is an overview of investigations to develop the measures.</p>

Of stocks and barter: John Holt and the Kongo rubber trade, 1906–1910

Not long after the Atlantic slave trade was phased out in the Kongo region south of the river Zaire in the 1860s, rubber came to dominate the regional export economy.1 Vegetable oils, which had defined the economic transition from capturing slaves to producing commodities in many West African regions earlier in the century, were also exported from Kongo, as was cultivated coffee, but none of these commodities characterised the new economic era as much as extracted wild rubber. During the West-Central African rubber boom, which lasted from 1879 to 1913, Kongo formed the core of British commercial interests in this part of Africa, especially since Portuguese protectionist measures kept foreign traders out of the Angolan ports of Luanda and Benguela to the south. Of several British companies operating in Kongo since the mid-nineteenth century, however, only two firms from Liverpool managed to endure the competitive environment of the trade in commodities. One was the house of Hatton &#38; Cookson, pioneers of ‘legitimate’ commerce in the wider Congo region. The other was a company managed by John Holt, who had built his fortune in the produce trade of the Bight of Biafra but had relatively little experience in West-Central Africa. Historians have neglected Holt’s presence on the coast of West-Central Africa, although the Holt company archives are unique in the detail they provide on the rubber trade in this region