Correction: Salazar-Cubillas, K.C.; Dickhoefer, U. Evaluating the Protein Value of Fresh Tropical Forage Grasses and Forage Legumes Using In Vitro and Chemical Fractionation Methods. Animals 2021, 11, 2853

The authors wish to make the following correction to their paper [...]

Tracing the Origins of Refractory Inclusions - the Solar System's Oldest Solids: a Petrographic, Geochemical and 26Al-26Mg Dating Study of CV and CK Refractory Inclusions

<p>Refractory inclusions in carbonaceous chondrite meteorites are of particular interest because both long- and short-lived chronometers have shown that they are the oldest sampled material to have formed in the Solar System. The objective of this study was to establish high-precision petrographic, chemical and isotopic analyses of refractory inclusions and thus offer insights into the chemical and astrophysical environments present during the formation of the Solar System. The former presence of the short-lived isotope 26Al (T1/2 = ca.730 KYr) has been established in a majority of refractory inclusions. Recent studies using both solution-based and in situ methodologies have suggested that the initial 26Al/27Al0 value of refractory inclusions is ca.6 x 10-5, higher than the established "canonical" value of [5.00 +/- 0.05] x 10-5. Knowing the initial concentration of 26Al within the Solar System provides a useful anchor from which ancient materials can be dated. Petrographic and trace element analyses were performed on nine newly-extracted refractory inclusions from CV3 and CK3 chondrites. These analyses revealed all but three refractory inclusions to have experienced multiple episodes of melting and evaporation prior to crystal closure. Mg isotope analyses were performed on eight of the newly extracted refractory inclusions in addition to five inter-laboratory samples. All refractory inclusions shown to have remained unaltered following crystal-closure, regardless of thermal history prior to closure, yielded a model 26Al/27Al0 of [4.89 x 0.265] x 10-5; within error of the canonical value. This result confirms that 26Al was homogenous and at canonical concentrations in the solar nebula. The results also suggest that chemical fractionation and crystal closure for the analysed refractory inclusions was completed within no more than 160 Kyr.</p>

Tracing the Origins of Refractory Inclusions - the Solar System's Oldest Solids: a Petrographic, Geochemical and 26Al-26Mg Dating Study of CV and CK Refractory Inclusions

<p>Refractory inclusions in carbonaceous chondrite meteorites are of particular interest because both long- and short-lived chronometers have shown that they are the oldest sampled material to have formed in the Solar System. The objective of this study was to establish high-precision petrographic, chemical and isotopic analyses of refractory inclusions and thus offer insights into the chemical and astrophysical environments present during the formation of the Solar System. The former presence of the short-lived isotope 26Al (T1/2 = ca.730 KYr) has been established in a majority of refractory inclusions. Recent studies using both solution-based and in situ methodologies have suggested that the initial 26Al/27Al0 value of refractory inclusions is ca.6 x 10-5, higher than the established "canonical" value of [5.00 +/- 0.05] x 10-5. Knowing the initial concentration of 26Al within the Solar System provides a useful anchor from which ancient materials can be dated. Petrographic and trace element analyses were performed on nine newly-extracted refractory inclusions from CV3 and CK3 chondrites. These analyses revealed all but three refractory inclusions to have experienced multiple episodes of melting and evaporation prior to crystal closure. Mg isotope analyses were performed on eight of the newly extracted refractory inclusions in addition to five inter-laboratory samples. All refractory inclusions shown to have remained unaltered following crystal-closure, regardless of thermal history prior to closure, yielded a model 26Al/27Al0 of [4.89 x 0.265] x 10-5; within error of the canonical value. This result confirms that 26Al was homogenous and at canonical concentrations in the solar nebula. The results also suggest that chemical fractionation and crystal closure for the analysed refractory inclusions was completed within no more than 160 Kyr.</p>

From peridotite to fuchsite bearing quartzite via carbonation and weathering: with implications for the Pb budget of continental crust

Extensive carbonation of peridotite results in listvenite, a rock composed of magnesite and quartz. At Gråberget, Røros, SE-Norway, a variably serpentinized peridotite body, surrounded by the Røros schists, a former abyssal sediment displays all stages of transformation of peridotite to quartzite. In this paper we record the sequence of steps in this process by combining the observation of mineral assemblages, textural relationships and geochemistry, and variations in Pb isotopic compositions. Initial serpentinization, a stage that also involved an enrichment in fluid-mobile elements (Pb, Sb and As), was followed by carbonation through CO2 fluids that formed soapstone, and eventually listvenite. The listvenite grades by decreasing amounts of carbonates into fuchsite bearing quartzite. The carbonates dissolved during supergene alteration and formed pores coated with oxides of Fe, Mn and Ni resulting in a brown rock color. The quartzite displays porous stylolites enriched in Pb, As and Sb and fuchsite with porous chromite grains as the only relicts of the original mineralogy in the peridotite. The dissolution of the carbonate occurred at oxidizing conditions at temperatures below 150 °C, where the solubility of magnesite is higher than that of quartz. Formation of quartzite from peridotite is supported by low REE contents and lack of zircons in the two rock types. The transformation involved enrichment of Pb, coupled with the elimination of Mg and enrichment of Si. This chemical fractionation and selective transfer of elements to the continents is an important mechanism and needs to be taken into account in models of continental evolution.

A Simple Approach to Isolate Slow and Fast Cycling Organic Carbon Fractions in Central European Soils—Importance of Dispersion Method

Numerous approaches have been developed to isolate fast and slow cycling soil organic carbon (SOC) pools using physical and chemical fractionation. Most of these methods are complex, expensive, and time consuming and unsuited for high-throughput application, such as for regional scale assessments. For simpler and faster fractionation via particle size the key issue is the dispersion of soil. It is unclear how the initial dispersion of soil affects the turnover rates of isolated fractions. We investigated five commonly used dispersion methods using different intensities: shaking in water, shaking in water with glass beads, ultrasonication at 100 and 450 J ml−1 and sodium hexametaphosphate (Na-HMP). We used soils from long-term field experiments that included a change from C3 to C4 vegetation and adjacent control sites using δ13C isotope ratio mass spectrometry. We evaluated the degree of C3/C4 moieties of the fractions, mass and carbon recovery and reproducibility as well as the time expenditures of the dispersions, sieving and drying techniques to develop an efficient and cheap fractionation method. Our results indicate that ultrasonication as well as H2O treatment with and without glass beads resulted in fractions with different turnover. Moreover, isolation performances depended on soil texture. While the isolation of the fractions using water with and without glass beads was equivalent to ultrasonication in soils with low clay contents, these methods had limited potential for soils with high clay contents. Furthermore, treatment with water alone had less reproducible results than other tested methods. The SOC recovery was comparable and satisfactory amongst non-chemical dispersion methods and reached over 95% for each of these methods. The use of Na-HMP was unsuccessful due to high time expenditures and strong SOC leaching. We propose particle size fractionation combined with ultrasonic dispersion as a fast and highly reliable method to quantify slow and fast cycling SOC pools for a wide range of soil types and textures from agricultural sites in central Europe.

Evaluating the Protein Value of Fresh Tropical Forage Grasses and Forage Legumes Using In Vitro and Chemical Fractionation Methods

The objectives of the present study were (1) to assess the adequacy of the in vitro and chemical methods to predict post-ruminal crude protein supply (PRCP) from fresh tropical forage, and (2) to identify PRCP supply predictors. Twenty-three fresh forage grasses and 15 forage legumes commonly used in domestic cattle feeding in the tropics and subtropics were incubated in the rumen of cows to determine ruminal crude protein (CP) degradation. The PRCP supply was calculated from in situ rumen-undegraded CP and in vitro organic matter digestibility (i.e., reference method), from ammonia-nitrogen release during in vitro incubation (i.e., in vitro method), and from the concentrations of chemical CP fractions (i.e., chemical method). The adequacy was evaluated using error-index and dimensionless parameters, and stepwise regression was used to select PRCP predictors. Adequacy ranged from poor to moderate (0.53 to 0.74) for the in vitro method being lower for forage legumes at a slow rumen passage rate (0.20), and even poorer (0.02 to 0.13) for the chemical method. Hence, the in vitro method can estimate PRCP supply in tropical forages with moderate to high but not with slow passage rates. Equations developed in the present study appear to predict PRCP supply with reasonable adequacy.

Marine dissolved organic matter: a vast and unexplored molecular space

Marine dissolved organic matter (DOM) comprises a vast and unexplored molecular space. Most of it resided in the oceans for thousands of years. It is among the most diverse molecular mixtures known, consisting of millions of individual compounds. More than 1 Eg of this material exists on the planet. As such, it comprises a formidable source of natural products promising significant potential for new biotechnological purposes. Great emphasis has been placed on understanding the role of DOM in biogeochemical cycles and climate attenuation, its lifespan, interaction with microorganisms, as well as its molecular composition. Yet, probing DOM bioactivities is in its infancy, largely because it is technically challenging due to the chemical complexity of the material. It is of considerable interest to develop technologies capable to better discern DOM bioactivities. Modern screening technologies are opening new avenues allowing accelerated identification of bioactivities for small molecules from natural products. These methods diminish a priori the need for laborious chemical fractionation. We examine here the application of untargeted metabolomics and multiplexed high-throughput molecular-phenotypic screening techniques that are providing first insights on previously undetectable DOM bioactivities. Key points • Marine DOM is a vast, unexplored biotechnological resource. • Untargeted bioscreening approaches are emerging for natural product screening. • Perspectives for developing bioscreening platforms for marine DOM are discussed.