Technical Note: Comparison of storage strategies of sea surface microlayer samples

The sea surface microlayer (SML) is an important biogeochemical system whose physico-chemical analysis often necessitates some degree of sample storage. However, many SML components degrade with time so the development of optimal storage protocols is paramount. We here briefly review some commonly used treatment and storage protocols. Using freshwater and saline SML samples from a river estuary, we investigated temporal changes in surfactant activity (SA) and the absorbance and fluorescence of chromophoric dissolved organic matter (CDOM) over four weeks, following selected sample treatment and storage protocols. Some variability in the effectiveness of individual protocols most likely reflects sample provenance. None of the various protocols examined performed any better than dark storage at 4 °C without pre-treatment. We therefore recommend storing samples refrigerated in the dark

The riverine source of CH4 and N2O from the Republic of Congo, western Congo Basin

We discuss concentrations of dissolved CH4, N2O, O2, NO3− and NH4+, and emission fluxes of CH4 and N2O for river sites in the western Congo Basin, Republic of Congo (ROC). Savannah, swamp forest and tropical forest samples were collected from the Congo main stem and seven of its tributaries during November 2010 (41 samples; “wet season”) and August 2011 (25 samples; “dry season”; CH4 and N2O only). Dissolved inorganic nitrogen (DIN: NH4+ + NO3−; wet season) was dominated by NO3- (63 ± 19 % of DIN). Total DIN concentrations (1.5–45.3 µmol L−1) were consistent with the near absence of agricultural, domestic and industrial sources for all three land types. Dissolved O2 (wet season) was mostly undersaturated in swamp forest (36 ± 29%) and tropical forest (77 ± 36%) rivers but predominantly supersaturated in savannah rivers (100 ± 17%). The dissolved concentrations of CH4 and N2O were within the range of values reported earlier for sub-Saharan African rivers. Dissolved CH4 was found to be supersaturated (11.2–9553 nmol L−1; 440–354,444 %), whereas N2O ranged from strong undersaturation to super-saturation (3.2–20.6 nmol L −1 ; 47–205%). Evidently, rivers of the ROC are persistent local sources of CH4 and can be minor sources or sinks for N2O. During the dry season the mean and range of CH4 and N2O concentrations were quite similar for the three land types. Wet and dry season mean concentrations and ranges were not significant for N2O for any land type or for CH4 in savannah rivers. The latter observation is consistent with seasonal buffering of river discharge by an underlying sandstone aquifer. Significantly higher wet season CH4 concentrations in swamp and forest rivers suggest that CH4 can be derived from floating macrophytes during flooding and/or enhanced methanogenesis in adjacent flooded soils. Swamp rivers also exhibited both low (47%) and high (205%) N2O saturation but wet season values were overall significantly lower than in either tropical forest or savannah rivers, which were always supersaturated (103–266%) and for which the overall means and ranges of N2O were not significantly different. In swamp and forest rivers O2 saturation co-varied inversely with CH4 saturation (log %) and positively with % N2O. A significant positive correlation between N2O and O2 saturation in swamp rivers was coincident with strong N2O and O2 undersaturation, indicating N2O consumption during denitrification in the sediments. In savannah rivers persistent N2O supersaturation and a negative correlation between N2O and O2 suggest N2O production mainly by nitrification. This is consistent with a stronger correlation between N2O and NH4+ than between N2O and NO3− . Our ranges of values for CH4 and N2O emission fluxes (33–48 705 µmol CH4 m−2 d−1 ; 1–67 µmol N2O m−2 d−1) are within the ranges previously estimated for sub-Saharan African rivers but they include uncertainties deriving from our use of "basin-wide" values for CH4 and N2O gas transfer velocities. Even so, because we did not account for any contribution from ebullition, which is quite likely for CH4 (at least 20%), we consider our emission fluxes for CH4 to be conservative

Yeast strains and methods of use thereof

The present invention relates to yeast strains and, in particular, to yeast stains for use in fermentation processes. The invention also relates to methods of fermentation using the yeast strains of the invention either alone or in combination with other yeast strains. The invention thither relates to methods for the selection of yeast strains suitable for fermentation cultures by screening for various metabolic products and the use of specific nutrient sources

Rhodium Bis(quinolinyl)benzene Complexes for Methane Activation and Functionalization

A series of rhodium(III) bis(quinolinyl)benzene (bisq^x) complexes was studied as candidates for the homogeneous partial oxidation of methane. Density functional theory (DFT) (M06 with Poisson continuum solvation) was used to investigate a variety of (bisq^x) ligand candidates involving different functional groups to determine the impact on Rh^(III)(bisq^x)-catalyzed methane functionalization. The free energy activation barriers for methane C H activation and Rh–methyl functionalization at 298 K and 498 K were determined. DFT studies predict that the best candidate for catalytic methane functionalization is Rh^(III) coordinated to unsubstituted bis(quinolinyl)benzene (bisq). Support is also found for the prediction that the η^2-benzene coordination mode of (bisq^x) ligands on Rh encourages methyl group functionalization by serving as an effective leaving group for S_N2 and S_R2 attack

Long-Range C–H Bond Activation by Rh^(III)-Carboxylates

Traditional C–H bond activation by a concerted metalation–deprotonation (CMD) mechanism involves precoordination of the C–H bond followed by deprotonation from an internal base. Reported herein is a “through-arene” activation of an uncoordinated benzylic C–H bond that is 6 bonds away from a Rh^(III) ion. The mechanism, which was investigated by experimental and DFT studies, proceeds through a dearomatized xylene intermediate. This intermediate was observed spectroscopically upon addition of a pyridine base to provide a thermodynamic trap

Transition-Metal-Mediated Nucleophilic Aromatic Substitution with Acids

Transition-metal-mediated nucleophilic aromatic substitution (S_NAr) reactions prefer that a suitably strong nucleophile be in an aprotic medium. Usually, using protic nucleophile/medium requires high reaction temperatures (>180 °C) to overcome the attenuated nucleophilicity for attack on the arene π system. Surprisingly, we demonstrate herein a Rh^(III)-mediated S_NAr reaction of a fluoroarene moiety with RCO_2H (R = CH_3, CF_3) in acid media that proceeds at moderate temperatures (<100 °C). We show both by experimental and with DFT calculations that the mechanism proceeds through an internal nucleophilic aromatic substitution (I-S_NAr), where the nucleophile coordinates to the metal ion prior to substitution, thereby mitigating the acid influence

A DNA-barcode biodiversity standard analysis method (DNA-BSAM) reveals a large variance in the effect of a range of biological, chemical and physical soil management interventions at different sites, but location is one of the most important aspects determining the nature of agricultural soil microbiology

There are significant knowledge gaps in our understanding of how to sustainably manage agricultural soils to preserve soil biodiversity. Here we evaluate and quantify the effects of agricultural management and location on soil microbiology using nine field trials that have consistently applied different soil management practices in the United Kingdom using DNA barcode sequence data. We tested the basic hypothesis that various agricultural management interventions have a significant and greater effect on soil bacterial and fungal diversity than geographic location. The analyses of soil microbial DNA sequence data to date has lacked standardisation which prevents meaningful comparisons across sites and studies. Therefore, to analyse these data and crucially compare and quantify the size of any effects on soil bacterial and fungal biodiversity between sites, we developed and employed a post-sequencing DNA-barcode biodiversity standard analysis method (DNA-BSAM). The DNA-BSAM comprises a series of standardised bioinformatic steps for processing sequences but more importantly defines a standardised set of ecological indices and statistical tests. Use of the DNA-BSAM reveals the hypothesis was not strongly supported, and this was primarily because: 1) there was a large variance in the effects of various management interventions at different sites, and 2) that location had an equivalent or greater effect size than most management interventions for most metrics. Some dispersed sites imposed the same organic amendments interventions but showed different responses, and this combined with observations of strong differences in soil microbiomes by location tentatively suggests that any effect of management may be contingent on location. This means it could be unreliable to extrapolate the findings of individual trials to others. The widespread use of a standard approach will allow meaningful cross-comparisons between soil microbiome studies and thus a substantial evidence-base of the effects of land-use on soil microbiology to accumulate and inform soil management decisions.Agriculture and Horticulture Development Board (AHDB); British Beet Research Organisation (BBRO

The Fourteenth Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the extended Baryon Oscillation Spectroscopic Survey and from the second phase of the Apache Point Observatory Galactic Evolution Experiment

The fourth generation of the Sloan Digital Sky Survey (SDSS-IV) has been in operation since July 2014. This paper describes the second data release from this phase, and the fourteenth from SDSS overall (making this, Data Release Fourteen or DR14). This release makes public data taken by SDSS-IV in its first two years of operation (July 2014-2016). Like all previous SDSS releases, DR14 is cumulative, including the most recent reductions and calibrations of all data taken by SDSS since the first phase began operations in 2000. New in DR14 is the first public release of data from the extended Baryon Oscillation Spectroscopic Survey (eBOSS); the first data from the second phase of the Apache Point Observatory (APO) Galactic Evolution Experiment (APOGEE-2), including stellar parameter estimates from an innovative data driven machine learning algorithm known as "The Cannon"; and almost twice as many data cubes from the Mapping Nearby Galaxies at APO (MaNGA) survey as were in the previous release (N = 2812 in total). This paper describes the location and format of the publicly available data from SDSS-IV surveys. We provide references to the important technical papers describing how these data have been taken (both targeting and observation details) and processed for scientific use. The SDSS website (www.sdss.org) has been updated for this release, and provides links to data downloads, as well as tutorials and examples of data use. SDSS-IV is planning to continue to collect astronomical data until 2020, and will be followed by SDSS-V.Comment: SDSS-IV collaboration alphabetical author data release paper. DR14 happened on 31st July 2017. 19 pages, 5 figures. Accepted by ApJS on 28th Nov 2017 (this is the "post-print" and "post-proofs" version; minor corrections only from v1, and most of errors found in proofs corrected