2,519 research outputs found
Safety and Effectiveness of Struvite from Black Water and Urine as a Phosphorus Fertilizer
To ensure food supply, phosphorus must be recycled, for which an appealing method is using struvite fertilizer from human excreta. One struvite from black water and another from urine were assessed for safety under Dutch regulations, and for effectiveness as P fertilizer in a maize field experiment and a literature review. Both struvites contained 12% P, 12% Mg, 6% N, and 0.5-1.5% of several micronutrients. Struvites did not exceed Dutch regulations for heavy metals or pathogens, and based on literature, organic toxins should be far below regulatory limits. In this study and 18 others, struvite appears to have similar effectiveness to soluble fertilizer. Early in the season, 200 kg P2O5 ha-1 of black water struvite and soluble phosphorus improved maize performance (
Size and Causes of the Occupational Gender Wage-gap in the Netherlands
Research from the United States consistently shows that female-dominated occupations generally yield lower wages than male-dominated occupations. Using detailed occupational data, this study analyses the size andcauses of this occupational genderwage-gap in the Dutch labourmarket using multi-levelmodelling techniques.The analyses showthat bothmen andwomen earn lowerwages if they are employed in female-dominated occupations. This especially indicates the signi¢cance of gender inWestern labour markets, since overall levels of wage inequality are relatively small in the Netherlands compared to, for example, the United Kingdom and the United States. Di¡erences in required responsibility are particularly important in accounting for this occupational wage-gap. Nonetheless, we find large wage penalties for working in a female-dominated instead of a maledominated occupation for occupations that require high levels of education, skills, and responsibility.
Mach's Principle and Model for a Broken Symmetric Theory of Gravity
We investigate spontaneous symmetry breaking in a conformally invariant
gravitational model. In particular, we use a conformally invariant scalar
tensor theory as the vacuum sector of a gravitational model to examine the idea
that gravitational coupling may be the result of a spontaneous symmetry
breaking. In this model matter is taken to be coupled with a metric which is
different but conformally related to the metric appearing explicitly in the
vacuum sector. We show that after the spontaneous symmetry breaking the
resulting theory is consistent with Mach's principle in the sense that inertial
masses of particles have variable configurations in a cosmological context.
Moreover, our analysis allows to construct a mechanism in which the resulting
large vacuum energy density relaxes during evolution of the universe.Comment: 9 pages, no figure
Total Synthesis of Aspidosperma and Strychnos Alkaloids through Indole Dearomatization
Monoterpenoid indole alkaloids are the major class of tryptamine-derived alkaloids found in nature. Together with their structural complexity, this has attracted great interest from synthetic organic chemists. In this Review, the syntheses of Aspidosperma and Strychnos alkaloids through dearomatization of indoles are discussed
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