Drift Flux Distribution Parameter in Three-Phase Air-Lift Reactors

Gas hold-up and liquid circulation velocity data in a three-phase system involving alginate beads in an internal-loop airlift reactor, reported by Lu et al. (1995), have been analyzed to evaluate the distribution parameter in drift flux model. The calculated distribution parameter values were significantly greater than 1.0 (the value used by Lu et al. in their modeling) and also affected by the solid volume fraction. An empirical correlation of this effect has been presented

Zwei Briefe Friedrich Freudenthals aus den Jahren 1909 und 1925 an die Brüder Adolf und Herbert Meyer

Mit dem Kauf von Friedrich Freudenthals 1902 im Verlag von Carl Schünemann in Bremen erschienenen Buch „Der Cambridge-Dragoner und andere Heidegeschichten“ in einem Koblenzer Versandantiquariat wurden im Sommer 2020 zwei handschriftliche Briefe bislang unbekannten Inhalts des in Fintel lebenden Schriftstellers aus den Jahren 1909 und 1925 an die Brüder Adolf und Herbert Meyer erworben. Sie sollen hier vorgestellt werden. Heinrich Kröger berichtete über den Kauf am 19. September 2020 in der Sonntagsbeilage der Böhme-Zeitung "Der Niedersachse"

Sustainable intensification in the production of grass and forage crops in the Low Countries of north-west Europe

Production of grass and fodder crops in areas under intensive production systems in the Low Countries of north-west Europe faces a number of threats related to increased regulations, scarcity of land and restricted freedom of use of the land, and from climate change. Grassland-based farmers are pushed to do more with less, i.e., to improve eco-efficiency, and this requires "more knowledge per ha." This article argues that progress in variety breeding, the application of crop rotation instead of monocultures, a proper use of catch crops, ley-arable farming and overall good management offer realistic opportunities to cope with current threats. A large capacity for mechanization also allows improvement of net yields per ha. This article highlights that progress in plant breeding has compensated for yield declines caused by nutrient-input restrictions in forage maize (Zea mays L.). Both forage maize and grass-clover can take advantages of ley-arable farming, and crop rotation provides an insurance against the effects of low-yielding years and a buffer for reduced nutrient inputs

Magnesium as an intrinsic component of human otoconia

AbstractObjectives: To investigate morphology changes of artificial otoconia (CGC) in the presence of magnesium during growth under in vitro conditions.Methods: Investigating human otoconia by environmental scanning electron microscope and determining their magnesium content by energy-dispersive X-ray microanalysis (EDX). Comparing structural and morphological data of human and artificial otoconia (CGC, Ca1Mg0) without and with magnesium substitution (Ca1-xMgx).Results: EDX- and X-ray data reveals that the inorganic component in human otoconia consists of calcite containing a minor amount of magnesium substitution (Ca1-xMgx). CGC containing magnesium (length 397.0 ± 146.4 µm, diameter 325.6 ± 100.1 µm) are slimmer and significantly smaller (p < .01) than pure CGC (length 548.6 ± 160 µm, diameter 373.0 ± 110.4 µm) and reveal a significant influence on the final morphology. The length/diameter ratio is significantly higher by incorporation of magnesium into CGC (1.84 ± 0.25 µm versus 1.48 ± 0.11 µm in pure CGC, p < .01), which brings the overall shape to a close relationship with human otoconia (1.98 ± 0.08 µm).Conclusions: Magnesium is an intrinsic component of human otoconia by partial substitution of calcium in the calcite crystal structure (Ca1-xMgx) and affects the development of the shape of artificial otoconia (calcite gelatin composites, CGC)

Techno-economic assessment of CO2-containing polyurethane rubbers

Carbon capture and utilization technologies can open up new synthesis routes with economic benefits. Recently, the inclusion of carbon dioxide in polyols was extended by copolymerizing double bond agents. This allows for subsequent chain-extension with diisocyanates to polyurethane rubbers. This paper assesses their economic viability. A preliminary techno-economic assessment based on extended block flow diagrams reveals substantial uncertainty in profitability indicators due to applying a short-cut capital expenditure estimation method. Consequently, a process design for the polyol production was carried out, enabling a refined TEA incorporating an equipment-cost-based approach. Positive net present values are reported for multiple [double bond agent]-[diisocyanate]-[benchmark] combinations. The net present value is most sensitive to the sales and propylene oxide prices. The choice of the double bond moiety has decisive effect; the choice of the diisocyanate has minor effect on the TEA. Finding a favorable market position remains the biggest challenge for CO2-containing synthetic polyurethane rubbers

Ternary amalgams: expanding the structural variety of the Gd14Ag51Gd_{14}Ag_{51} family

In intermetallic chemistry, the Gd$_{14}$Ag$_{51}$ structure type is rather common and has many amalgam representatives. Up to today, binary amalgams of this type have been described for M = Na, Ca, Sr, Eu, Yb, and the structure family still is growing. Yb$_{11}$Hg$_{54}$ is the only representative with a fully ordered crystal structure, and all other representatives exhibit individual disorder phenomena or patterns. The diversity of disorder phenomena in this structural family is unique. In order to shed a light on the underlying reasons for this unexpected structural complexity, we compare the available literature structure models with three new ternary variants, Yb$_{10.7}$Sr$_{0.3}$Hg$_{54}$, Ca$_{4.5}$Eu$_{6.5}$Hg$_{54}$ and Ca$_{6.9}$Na$_{4.1}$Hg$_{54}$ (all in space group type $P\bar{6}$ , a = 13.5379(12), 13.5406(8) and 13.564(5) Å, c = 9.7488(14), 9.7149 and 9.810(7) Å for Yb$_{10.7}$Sr$_{0.3}$Hg$_{54}$, Ca$_{4.5}$Eu$_{6.5}$Hg$_{54}$ and Ca$_{6.9}$Na$_{4.1}$Hg$_{54}$, respectively). Their crystal structures have been examined in detail on the basis of both single crystal and powder X-ray diffraction data. Each of the three new amalgams exhibits its own set of disorder phenomena that is again different from those of the respective binary variants. The synopsis of the crystal structures and their individual disorder phenomena indicates that the reason for the disorder phenomena cannot be found only by analyzing geometric details such as atomic radii quotients or coordination polyhedral volumina, and additional electronic reasons must be assumed

The sense of balance in humans: Structural features of otoconia and their response to linear acceleration

<div><p>We explored the functional role of individual otoconia within the otolith system of mammalians responsible for the detection of linear accelerations and head tilts in relation to the gravity vector. Details of the inner structure and the shape of intact human and artificial otoconia were studied using environmental scanning electron microscopy (ESEM), including decalcification by ethylenediaminetetraacetic acid (EDTA) to discriminate local calcium carbonate density. Considerable differences between the rhombohedral faces of human and artificial otoconia already indicate that the inner architecture of otoconia is not consistent with the point group -3m. This is clearly confirmed by decalcified otoconia specimen which are characterized by a non-centrosymmetric volume distribution of the compact 3+3 branches. This structural evidence for asymmetric mass distribution was further supported by light microscopy in combination with a high speed camera showing the movement of single otoconia specimen (artificial specimen) under gravitational influence within a viscous medium (artificial endolymph). Moreover, the response of otoconia to linear acceleration forces was investigated by particle dynamics simulations. Both, time-resolved microscopy and computer simulations of otoconia acceleration show that the dislocation of otoconia include significant rotational movement stemming from density asymmetry. Based on these findings, we suggest an otolith membrane expansion/stiffening mechanism for enhanced response to linear acceleration transmitted to the vestibular hair cells.</p></div