Source-to-sink magnetic properties of NE Saharan dust in Eastern Mediterranean marine sediments: review and paleoenvironmental implications

We present a review of the magnetic properties of NE Saharan dust that was conducted, following a source-to-sink approach, to unravel the paleoclimatic significance of environmental magnetic records from Eastern Mediterranean marine sediments. Our synthesis indicates that pedogenic hematite, which formed during past wetter Green Sahara periods (GSPs), is the most common magnetic mineral in Eastern Mediterranean marine sediments as a result of its eolian transportation, along with smaller amounts of lithogenic hematite, from the NE Sahara. Coupled with the limited impact of reductive sedimentary diagenesis on hematite abundances in Eastern Mediterranean Sea sediments, this indicates that hematite concentrations provide reliable quantitative estimates of NE Saharan dust supply. Our results indicate that variations in NE Saharan dust supply record an on-off mechanism in which a key control on eolian input is provided by the monsoon-driven spread and retreat of savannah vegetation through the Sahara. Magnetite/maghemite is also a common magnetic mineral in NE Saharan dust, and also formed mainly pedogenically during GSPs but in much smaller amounts compared to hematite. Limited production of magnetite/maghemite in the source area during GSPs, along with the later imprint of diagenetic processes, indicates that magnetite/maghemite abundances cannot be used to estimate dust inputs from the NE Sahara. Goethite cannot be used either to estimate variations in NE Saharan dust supply, because its occurrence in Eastern Mediterranean marine sediments also appears to be linked to fluvial inputs. Our results reinforce the view that a source-to-sink approach should be routinely conducted in environmental magnetic studies to understand the complex combination of processes involved in the production, transportation, sedimentation, and diagenetic evolution of magnetic minerals in sedimentary environments. © 2015 Larrasoaña, Roberts, Liu, Lyons, Oldfield, Rohling and Heslop.A Rand D H gratefully acknowledge support from Australian Research Council grant DP110105419 , and ER acknowledges support from 2012 Australia Laureate Fellowship FL120100050.Peer reviewe

Acyl-chain elongation drives ketosynthase substrate selectivity in trans-acyltransferase polyketide synthases

Type I modular polyketide synthases (PKSs), responsible for the biosynthesis of many biologically active agents, possess a ketosynthase (KS) domain within each module to catalyze chain elongation. Acylation of the KS active site Cys residue is followed by transfer to malonyl-acyl carrier protein, yielding an extended β-ketoacyl chain. To date, the precise contribution of KS selectivity in controlling product fidelity has been unclear. We submitted six KS domains from the trans-acyl transferase PKSs to a mass spectrometry-basedelongation assay, and identified higher substrat selectivity in the elongating step than in preceding acylation. A close correspondence between observed KS selectivity and that predicted by phylogenetic analysis was seen. Our findings provide insights into the mechanism of KS selectivity in this important group of PKSs, can serve as guidance for engineering, and show that targeted mutagenesis can be used to expand the repertoire of acceptable substrates

Civic republican social justice and the case of state grammar schools in England

The aim of this paper is to consider the ways in which civic republican theory can provide a meaningful and useful account of social justice, one that is which holds resonance for educational debates. Recognising the need for educationalists interested in civic republicanism to pay greater attention to ideas of justice – and in particular social justice as it concerns relationships between citizens (citizen to citizen, group to group or citizen to group) – it is argued that a form of civic republicanism committed to freedom as non-domination is capable of providing a substantive model for analysing social (in)justice within educational arenas. After positioning the contribution offered here within existing educational literature on civic republicanism, salient elements of social justice as freedom as non-domination are identified. On this basis, debates concerning the existence and potential expansion of state (public) grammar schools in England are considered in relation to the account of republican social justice as non-domination. It is argued that from this republican position grammar schools (1) represent an arbitrary domination of the interests of those less well off by those with greater material and cultural capital and (2) in doing so lead to advantages for some at the expense of others. Though the focus of the paper is on grammar schools in England, it is suggested that republican justice may be a useful frame for considering similar educational cases in England and elsewhere

phenix.mr_rosetta: molecular replacement and model rebuilding with Phenix and Rosetta.

The combination of algorithms from the structure-modeling field with those of crystallographic structure determination can broaden the range of templates that are useful for structure determination by the method of molecular replacement. Automated tools in phenix.mr_rosetta simplify the application of these combined approaches by integrating Phenix crystallographic algorithms and Rosetta structure-modeling algorithms and by systematically generating and evaluating models with a combination of these methods. The phenix.mr_rosetta algorithms can be used to automatically determine challenging structures. The approaches used in phenix.mr_rosetta are described along with examples that show roles that structure-modeling can play in molecular replacement

Time Course of the Neural Activity Related to Behavioral Decision-Making as Revealed by Event-Related Potentials

Objective: To study the time course of the electrocortical activity evoked by gains and losses in the Iowa Gambling Task (IGT), the brain sources of this electrical activity, and its association with behavioral parameters of task performance in order to achieve a better knowledge of decision-making processes. Method: Event-related potentials (ERPs) were obtained from a 64-channel EEG in 25 participants when performing the IGT. Brain source localization analyses of the ERP components were also assessed. Results: ERP amplitudes were sensitive to gains and losses. An early fronto-central negativity was elicited when feedback was provided for both gains and losses, and correlated with the number of gains at FCz and with the number of both gains and losses at Cz. The P200 component had larger amplitudes to losses and correlated positively with the number of losses. Feedback related negativity (FRN) was higher at frontal, temporal and occipital electrodes in trials with monetary losses. In addition, trials with monetary losses elicited larger P300 magnitudes than trials with monetary gains at all electrode localizations. Conclusions: All ERP components (except P300) were related to participants’ performance in the IGT. Amplitudes of P200 and P300 were associated with the conscious recognition of the error during the decision-making. Performance data and source analysis underline the importance of the medial prefrontal cortex when processing feedback about monetary losses in the IGT.This research was supported by grants from the Spanish Ministry of Science and Innovation (Ministerio de Ciencia y Tecnología), European Regional Development Funds (ERDF) and Ministry of Economy, Industry and Competitiveness (Ministerio de Economía, Industria y Competitividad, Gobierno de España). References: PSI2008-04394, PSI2017-88388-C4-1-R and PSI2017-88388-C4-3-R