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Review of<i> Picturing Frederick Douglass: An illustrated biography of the nineteenth century's most photographed American</i>, by John Stauffer, Zoe Trodd and Celeste-Marie Bernier
No full textEffect of a meandering channel on wetland performance
No full textVegetation plays an important role in controlling mixing and contaminant removal in wetlands. Recent studies have shown that the hydraulic performance of a wetland can be significantly affected by the presence of a main flow channel (MFC) where vegetation density is much lower than the average vegetation density in the wetland. The existence of a main flow channel induces short-circuiting, which reduces hydraulic and treatment efficiency. A numerical study was carried out to analyze the effect of channel sinuosity and vegetation density on the hydraulic performance of a channelized wetland. A rectangular wetland characterized by a meandering channel and later vegetated zones (LVZs) was considered, and numerical simulations were carried out using a 2-D depth-average hydrodynamic and solute transport model. The hydraulic performance was analyzed as a function of the average vegetation density, channel sinuosity and the ratio of vegetation densities in the LVZs and the MFC. Results show that increasing sinuosity of the main flow channel can promote mixing and improve hydraulic efficiency. Different performance metrics also indicate negligible impact of the average vegetation density on the hydraulic performance, especially when the width of the MFC is relatively large
Complications in the study of ancient tuberculosis:Presence of environmental bacteria in human archaeological remains
No full textThere are many reports of ancient DNA from bacteria of the Mycobacterium tuberculosis complex (MTBC) being present in skeletons with and without osteological indications of tuberculosis. A possible complication in these studies is that extracts might also contain DNA from the microbiome of the individual whose remains are being analysed and/or from environmental bacteria that have colonised the skeleton after death. These contaminants might include ‘mycobacteria other than tuberculosis’ (MOTT), which are common in the environment, but which are not normally associated with clinical cases of tuberculosis. In this paper we show that MOTT of various types, as well as bacteria of related genera, are present in most if not all archaeological remains. Our results emphasise the complications inherent in the biomolecular study of archaeological human tuberculosis. The specificity of any polymerase chain reaction directed at the MTBC cannot be assumed and, to confirm that an amplification is authentic, a sequencing strategy must be applied that allows characterisation of the PCR product. Any variations from the reference MTBC sequence must then be checked against sequence data for MOTT and other species to ensure that the product does actually derive from MTBC. Our results also illustrate the challenges faced when assembling MTBC genome sequences from ancient DNA samples, as misidentification of MOTT sequence reads as MTBC would lead to errors in the assembly. Identifying such errors would be particularly difficult, if not impossible, if the MOTT DNA content is greater than that of the authentic MTBC. The difficulty in identifying and excluding MOTT sequences is exacerbated by the fact that many MOTT are still uncharacterized and hence their sequence features are unknown
Origin of artificial radionuclides in soil and sediment from North Wales
No full textDuring the operations at the Sellafield nuclear fuel reprocessing complex, artificial radionuclides are discharged to the Irish Sea under authorisation, where they are dispersed. In this study, the southern distribution and transport of Sellafield derived radionuclides have been investigated. Both natural and artificial radionuclides have been studied in a soil core from the riverbank of the Afon Goch in Anglesey, North Wales. Particulate input is dominant for all artificial radionuclides (including the more soluble 137Cs and 236U) with an estimated lag time of about a decade. The preferential northward seawater movement in the NE Irish Sea limits solution input of 137Cs and 236U to the areas south of Sellafield. The relatively long lag time reflects both the water circulation pattern and distance between the study site in north Wales and the source point in Cumbria. Two redox active zones are observed in the top and the bottom of this core, although there is no evidence for any redistribution of Pu and natural uranium by these redox processes. However, 236U, derived from irradiated uranium, showed variable distribution in the core. This could be a potential response to the geochemical conditions, showing that 236U may be a promising tracer for the environmental processes and a signature of the Sellafield historical discharges of irradiated uranium. ?? 2015
Phase transition observations and discrimination of small cloud particles by light polarization in expansion chamber experiments
No full textCloud microphysical processes involving the ice phase in tropospheric clouds are among the major uncertainties in cloud formation, weather, and general circulation models. The detection of aerosol particles, liquid droplets, and ice crystals, especially in the small cloud particle-size range below 50 μm, remains challenging in mixed phase, often unstable environments. The Cloud Aerosol Spectrometer with Polarization (CASPOL) is an airborne instrument that has the ability to detect such small cloud particles and measure the variability in polarization state of their backscattered light. Here we operate the versatile Cosmics Leaving OUtdoor Droplets (CLOUD) chamber facility at the European Organization for Nuclear Research (CERN) to produce controlled mixed phase and other clouds by adiabatic expansions in an ultraclean environment, and use the CASPOL to discriminate between different aerosols, water, and ice particles. In this paper, optical property measurements of mixed-phase clouds and viscous secondary organic aerosol (SOA) are presented. We report observations of significant liquid–viscous SOA particle polarization transitions under dry conditions using CASPOL. Cluster analysis techniques were subsequently used to classify different types of particles according to their polarization ratios during phase transition. A classification map is presented for water droplets, organic aerosol (e.g., SOA and oxalic acid), crystalline substances such as ammonium sulfate, and volcanic ash. Finally, we discuss the benefits and limitations of this classification approach for atmospherically relevant concentrations and mixtures with respect to the CLOUD 8–9 campaigns and its potential contribution to tropical troposphere layer analysis
Recent advances in engineering nonribosomal peptide assembly lines.
No full textCovering: up to July 2015Nonribosomal peptides are amongst the most widespread and structurally diverse secondary metabolites in nature with many possessing bioactivity that can be exploited for therapeutic applications. Due to the major challenges associated with total- and semi-synthesis, bioengineering approaches have been developed to increase yields and generate modified peptides with improved physicochemical properties or altered bioactivity. Here we review the major advances that have been made over the last decade in engineering the biosynthesis of nonribosomal peptides. Structural diversity has been introduced by the modification of enzymes required for the supply of precursors or by heterologous expression of tailoring enzymes. The modularity of nonribosomal peptide synthetase (NRPS) assembly lines further supports module or domain swapping methodologies to achieve changes in the amino acid sequence of nonribosomal peptides. We also review the new synthetic biology technologies promising to speed up the process, enabling the creation and optimisation of many more assembly lines for heterologous expression, offering new opportunities for engineering the biosynthesis of novel nonribosomal peptides
Near-infrared reflectance in neotropical salamanders
No full textVariations in near infrared reflectance are highlighted between 3 species of Neotropical salamander. Salamanders Bolitoglossa striatula and Bolitoglossa colonnea display an increased optical reflectance in the near infrared region, in contrast with the moss salamander Nototriton. picadoi which display limited reflectance in this region. Near-infrared reflectance was identified in a non-invasive manner using a modified consumer camera and confirmed with reflection spectrometry
The retail-banking expansion in Chile and the "democratisation" of credit practices: juggling with threats, opportunities, and the unavoidable
No full textThis paper tries to address how Chilean households are dealing with the retailled“democratisation” of credit that the neoliberal Chilean society hasexperienced from 20 years ago. The social place of credit use and indebtednesshas been researched in the context of austerity measures, sovereign debtissues, and the subprime crisis; fewer accounts have drawn attention in placeswhere the credit expansion had happened in times of economic growth, andmoreover has been considered an essential feature of modernisation and theestablishment of a consumer culture. Using theory of practices as a syntheticapproach, contradictory elements in everyday lives of families emergesattached to credit practices