Y. Hancock

Long-Term Resilience of Late Holocene Coastal Subsistence System in Southeastern South America

Isotopic and molecular analysis on human, fauna and pottery remains can provide valuable new insights into the diets and subsistence practices of prehistoric populations. These are crucial to elucidate the resilience of social-ecological systems to cultural and environmental change. Bulk collagen carbon and nitrogen isotopic analysis of 82 human individuals from mid to late Holocene Brazilian archaeological sites (∼6,700 to ∼1,000 cal BP) reveal an adequate protein incorporation and, on the coast, the continuation in subsistence strategies based on the exploitation of aquatic resources despite the introduction of pottery and domesticated plant foods. These results are supported by carbon isotope analysis of single amino acid extracted from bone collagen. Chemical and isotopic analysis also shows that pottery technology was used to process marine foods and therefore assimilated into the existing subsistence strategy. Our multidisciplinary results demonstrate the resilient character of the coastal economy to cultural change during the late Holocene in southern Brazil.

Multiparameter Analysis of Human Bone Marrow Stromal Cells Identifies Distinct Immunomodulatory and Differentiation-Competent Subtypes

Summary Bone marrow stromal cells (BMSCs, also called bone-marrow-derived mesenchymal stromal cells) provide hematopoietic support and immunoregulation and contain a stem cell fraction capable of skeletogenic differentiation. We used immortalized human BMSC clonal lines for multi-level analysis of functional markers for BMSC subsets. All clones expressed typical BMSC cell-surface antigens; however, clones with trilineage differentiation capacity exhibited enhanced vascular interaction gene sets, whereas non-differentiating clones were uniquely CD317 positive with significantly enriched immunomodulatory transcriptional networks and high IL-7 production. IL-7 lineage tracing and CD317 immunolocalization confirmed the existence of a rare non-differentiating BMSC subtype, distinct from Cxcl12-DsRed+ perivascular stromal cells in vivo. Colony-forming CD317+ IL-7hi cells, identified at ∼1%–3% frequency in heterogeneous human BMSC fractions, were found to have the same biomolecular profile as non-differentiating BMSC clones using Raman spectroscopy. Distinct functional identities can be assigned to BMSC subpopulations, which are likely to have specific roles in immune control, lymphopoiesis, and bone homeostasis.

Energy losses in interacting fine-particle magnetic composites

The coercivity and energy losses in superparamagnetic (SPM) magnetite and FePt nanoparticle composites subjected to an external, alternating magnetic field have been calculated as a function of the mean particle size and packing density. The effect of interactions has been investigated by fitting the Sharrock law to the coercivity results as a function of the field cycle frequency of the magnetic field. This fitting leads to effective parameters for the anisotropy field and βeff = KV/kBT, which are themselves dependent on the interaction strength. The increase or decrease in the coercivity with interactions depends upon the relative change of and βeff, thus demonstrating the complex effect that interactions have in these nanoparticle composites. The interparticle interactions have a non-trivial effect on the energy loss per cycle. The energy loss is reduced for systems with larger particles since the reduction in coercivity together with a corresponding reduction in the remanence dominates. For small particle sizes, the energy loss is increased. The primary mechanism here seems to be an enhancement of the energy barrier due to interactions, which changes the nature of the particles from SPM to being thermally stable.

An Integrated Approach to the Taxonomic Identification of Prehistoric Shell Ornaments

Shell beads appear to have been one of the earliest examples of personal adornments. Marine shells identified far from the shore evidence long-distance transport and imply networks of exchange and negotiation. However, worked beads lose taxonomic clues to identification, and this may be compounded by taphonomic alteration. Consequently, the significance of this key early artefact may be underestimated. We report the use of bulk amino acid composition of the stable intra-crystalline proteins preserved in shell biominerals and the application of pattern recognition methods to a large dataset (777 samples) to demonstrate that taxonomic identification can be achieved at genus level. Amino acid analyses are fast (<2 hours per sample) and micro-destructive (sample size <2 mg). Their integration with non-destructive techniques provides a valuable and affordable tool, which can be used by archaeologists and museum curators to gain insight into early exploitation of natural resources by humans. Here we combine amino acid analyses, macro- and microstructural observations (by light microscopy and scanning electron microscopy) and Raman spectroscopy to try to identify the raw material used for beads discovered at the Early Bronze Age site of Great Cornard (UK). Our results show that at least two shell taxa were used and we hypothesise that these were sourced locally.

Local and interfacial magnetic properties of inhomogeneous finite linear chains

Abstract The Hubbard Model has been used to study the local and interfacial magnetic properties of finite inhomogeneous cluster systems. These are generally of the type, NMMMMMN , where N and M , respectively, refer to non-magnetic and magnetic atoms, of a 7-site finite chain. The applicability of the Hartree–Fock (HF) approximation is gauged via direct comparison of the ground state magnetization results derived from exact diagonalization methods. The underlying HF and exact mechanisms are compared as a function of the model parameters, with particular attention being paid to the local and interfacial ( N / M interface) magnetic properties. Regimes, which exhibit favourable comparison between HF and exact results are found. Detailed inspection of the HF prediction is made and general trends established as a function of system size and model parameters.

Control of the exchange coupling in granular CoPt/Co recording media

In order to control the exchange coupling between the grains in a perpendicular recording media, a simple method is to totally decouple the grains using a thick oxide and apply a continuous magnetic capping layer to improve the uniformity of the coupling. In this paper, a system of CoPt grains coupled with a Co layer is investigated using an atomistic spin model. We show that the exchange coupling between the CoPt grains and the Co layer has an impact on the reversal process of the grains, as well as causing a reduction in the coercivity of the whole system. Further, we have studied the coercivity of the whole system as a function of the exchange coupling parameter between the grains and the exchange layer, and have found a sharp decrease in the coercivity. The coercivity as a function of the exchange layer thickness is also studied for different exchange coupling parameters.

Streptomyces coelicolor strains lacking polyprenol phosphate mannose synthase and protein O-mannosyl transferase are hyper-susceptible to multiple antibiotics

Polyprenol phosphate mannose (PPM) is a lipid-linked sugar donor used by extra-cytoplasmic glycosyl tranferases in bacteria. PPM is synthesiszed by polyprenol phosphate mannose synthase, Ppm1, and in most Actinobacteria is used as the sugar donor for protein O-mannosyl transferase, Pmt, in protein glycosylation. Ppm1 and Pmt have homologues in yeasts and humans, where they are required for protein O-mannosylation. Actinobacteria also use PPM for lipoglycan biosynthesis. Here we show that ppm1 mutants of Streptomyces coelicolor have increased susceptibility to a number of antibiotics that target cell wall biosynthesis. The pmt mutants also have mildly increased antibiotic susceptibilities, in particular to β-lactams and vancomycin. Despite normal induction of the vancomycin gene cluster, vanSRJKHAX, the pmt and ppm1 mutants remained highly vancomycin sensitive indicating that the mechanism of resistance is blocked post-transcriptionally. Differential RNA expression analysis indicated that catabolic pathways were downregulated and anabolic ones upregulated in the ppm1 mutant compared to the parent or complemented strains. Of note was the increase in expression of fatty acid biosynthetic genes in the ppm1- mutant. A change in lipid composition was confirmed using Raman spectroscopy, which showed that the ppm1- mutant had a greater relative proportion of unsaturated fatty acids compared to the parent or the complemented mutant. Taken together, these data suggest that an inability to synthesize PPM (ppm1) and loss of the glycoproteome (pmt- mutant) can detrimentally affect membrane or cell envelope functions leading to loss of intrinsic and, in the case of vancomycin, acquired antibiotic resistance.

Role of random edge-disorder on the transport properties of ultra-thin zig-zag graphene nanoribbons

We report on an introductory study used to gauge the significance of random weakedge disorder on the coherent transport properties of ultra-thin zig-zag nanoribbons (ZGNRs) beyond the simple (i.e., first nearest-neighbour) tight-binding approximation. Such extensions include up to third nearest-neighbour hopping in an extended tight-binding model, as well as a mean-field Hubbard-U . The effect of the random weak-edge disorder causes charge-carrier localization that reduces the conductance about the Fermi energy in all of the systems studied. In the non-interacting systems, the extended tight-binding model is found to be more robust against disorder due to the increased kinetic degrees of freedom. Localization effects from the random weak-edge disorder are found to compete with the mean-field Hubbard-U resulting in spin-dependent conductance properties.

A proposed simulation method for directed self-assembly of nanographene

Abstract A methodology for predictive kinetic self-assembly modeling of bottom-up chemical synthesis of nanographene is proposed. The method maintains physical transparency in using a novel array format to efficiently store molecule information and by using array operations to determine reaction possibilities. Within a minimal model approach, the parameter space for the bond activation energies (i.e. molecule functionalization) at fixed reaction temperature and initial molecule concentrations is explored. Directed self-assembly of nanographene from functionalized tetrabenzanthracene and benzene is studied with regions in the activation energy phase-space showing length-to-width ratio tunability. The degree of defects and reaction reproducibility in the simulations is also determined, with the rate of functionalized benzene addition providing additional control of the dimension and quality of the nanographene. Comparison of the reaction energetics to available density functional theory data suggests the synthesis may be experimentally tenable using aryl-halide cross-coupling and noble metal surface-assisted catalysis. With full access to the intermediate reaction network and with dynamic coupling to density functional theory-informed tight-binding simulation, the method is proposed as a computationally efficient means towards detailed simulation-driven design of new nanographene systems.

Thermal expansion of magnetite (4.2―300 K)

The thermal expansion of a synthetic single-crystal sample of magnetite (Fe3O4) in the [111] direction has been investigated for the temperature range of 4.2–300 K using three-terminal capacitance dilatometry. The strain results and corresponding thermal expansion curve show the Verwey transition to be first-order with T v = 120 ± 2 K. At T = 4.2–70 K, the sample shows Invar-like behaviour.