Phase-ordering dynamics of the Gay-Berne nematic liquid crystal

Phase-ordering dynamics in nematic liquid crystals has been the subject of much active investigation in recent years in theory, experiments and simulations. With a rapid quench from the isotropic to nematic phase a large number of topological defects are formed and dominate the subsequent equilibration process. We present here the results of a molecular dynamics simulation of the Gay-Berne model of liquid crystals after such a quench in a system with 65536 molecules. Twist disclination lines as well as type-1 lines and monopoles were observed. Evidence of dynamical scaling was found in the behavior of the spatial correlation function and the density of disclination lines. However, the behavior of the structure factor provides a more sensitive measure of scaling, and we observed a crossover from a defect dominated regime at small values of the wavevector to a thermal fluctuation dominated regime at large wavevector.Comment: 18 pages, 16 figures, animations available at http://www.physics.brown.edu/Users/faculty/pelcovits/lc/coarsening.htm

Ethylene receptor ETR2 controls trichome branching by regulating microtubule assembly in Arabidopsis thaliana

The single-celled trichome of Arabidopsis thaliana is a widely used model system for studying cell development. While the pathways that control the later stages of trichome development are well characterized, the early signalling events that co-ordinate these pathways are less well understood. Hormones such as gibberellic acid, salicylic acid, cytokinins, and ethylene are known to affect trichome initiation and development. To understand the role of the plant hormone ethylene in trichome development, an Arabidopsis loss-of-function ethylene receptor mutant, etr2-3, which has completely unbranched trichomes, is analysed in this study. It was hypothesized that ETR2 might affect the assembly of the microtubule cytoskeleton based on analysis of the cytoskeleton in developing trichomes, and exposures to paclitaxol and oryzalin, which respectively act either to stabilize or depolymerize the cytoskeleton. Through epistatic and gene expression analyses it is shown that ETR2 is positioned upstream of CHROMATIN ASSEMBLY FACTOR1 and TRYPTICHON and is independent of the GLABRA2 and GLABRA3 pathways. These results help extend understanding of the early events that control trichome development and identify a signalling pathway through which ethylene affects trichome branching

Multivariate analysis of mineral constituents of edible Parasol Mushroom (Macrolepiota procera) and soils beneath fruiting bodies collected from Northern Poland

Caps and stipes of 141 fruiting bodies of Parasol Mushroom (Macrolepiota procera) and surface layer of soils collected from 11 spatially distant and background (pristine) areas in Northern Poland were analyzed for Ag, Al, Ba, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Mg, Mn, Na, Ni, P, Pb, Rb, Sr, and Zn by inductively coupled plasma optical emission spectroscopy and cold vapor atomic absorption spectroscopy. In terms of bioconcentration and bioexclusion concept, K, Ag, Cu, Rb, and P were highly bioconcentrated in caps, and their bioconcentration factor values varied for the 11 sites between 120 and 500—67–420, 70–220, 10–170, and 45–100, respectively. Cd, Zn, Mg, and Na showed bioconcentration factors (BCFs) between 3.3 and 36, 3.7–15, 0.92–6.3, and 1.4–44 while Al, Ba, Ca, Co, Cr, Mn, Ni, Pb, and Sr were excluded (BCF < 1). The Parasol Mushroom is a species harvested in the wild, and its caps are of unique taste and can contain a spectrum of essential and hazardous mineral compounds accumulated at elevated concentrations, even if collected at the background (pristine) areas. These elevated mineral concentrations of the caps are due to the efficient bioconcentration potential of the species (K, Ag, Cu, Rb, P, Cd, Zn, Mg, and Na) and abundance in the soil substrates (Al, Ca, Fe, Mn). The estimated intake rates of Cd, Hg, and Pb contained in Parasol Mushroom’s caps show a cause for concern associated with these metals resulting from the consumption of between 300- and 500-g caps daily, on a frequent basis in the mushrooming season

Cement stabilisation of crude-oil-contaminated soil

© 2016, Thomas Telford Services Ltd. All rights reserved. Crude-oil-contaminated soils are usually considered unsuitable construction materials for earthworks. This paper presents an experimental investigation of the effects of applying Portland cement on the plasticity, strength and permeability of a crude-oil-contaminated soil in order to ascertain its suitability for use as an earthworks construction material. Series of specific gravity, Atterberg limits, compaction, strength and permeability characteristics were determined for a natural soil, the soil after being artificially contaminated with crude oil and the contaminated soil with varying proportions of added cement. It was found that the geotechnical properties of the soil became less desirable after contamination with crude oil, but the application of cement to the contaminated soil improved its properties by way of cation exchange, agglomeration and cementation. Cement stabilisation of crude-oil-contaminated soil provides a stable supporting structure, as well as a capping layer, that prevents the crude oil from interacting with the construction materials above. Thus, instead of disposing of contaminated soils, creating unnecessary waste and incurring costs, stabilisation with cement – which is practically feasible to undertake on site – makes such soils useful for supporting structural foundations or road pavement structures

Global and local sea level during the Last Interglacial: A probabilistic assessment

The Last Interglacial (LIG) stage, with polar temperatures likely 3-5 C warmer than today, serves as a partial analogue for low-end future warming scenarios. Based upon a small set of local sea level indicators, the Intergovernmental Panel on Climate Change (IPCC) inferred that LIG global sea level (GSL) was about 4-6 m higher than today. However, because local sea levels differ from GSL, accurately reconstructing past GSL requires an integrated analysis of globally distributed data sets. Here we compile an extensive database of sea level indicators and apply a novel statistical approach that couples Gaussian process regression of sea level to Markov Chain Monte Carlo modeling of geochronological errors. Our analysis strongly supports the hypothesis that LIG GSL was higher than today, probably peaking at 6-9 m. Our results highlight the sea level hazard associated with even relatively low levels of sustained global warming.Comment: Preprint version of what has since been published in Natur

Evaluation of a gelatin-based adhesive for historic paintings that incorporates citronella oil as an eco-friendly biocide

[EN] The presented study focuses on evaluating the efficiency of a gelatin-based product that incorporates a plasticizer (glycerol) and a biocide (citronella oil), proposed as an eco-friendly adhesive for polychrome decoration applied in different parts of the architectural complex of the Longshan Temple in Lukang (eighteenth century, Taiwan). Seven laboratory physico-chemical tests were performed: (a) viscosity measurement; (b) drying curves; (c) moisture content determination; (d) water vapor permeability test; (e) mechanical test; (f) adhesion test; (g) susceptibility to fungi colonization test, which provide information on the workability, water content and water barrier properties, as well as mechanical, adhesion, and the biocide properties of the proposed product. The obtained results indicate that the workability, mechanical and adhesive properties of the new adhesive are adequate. Permeability in polychromies is slightly reduced due to the additional barrier effect of the adhesive incorporated into the paint film. The efficiency of citronella oil for preventing the growth of fungus Aspergillus niger on paintings consolidated with the adhesive was also probed. In parallel to these laboratory trials, the micro-invasive tests carried out, using nanoindentation combined with atomic force microscopy (NI-AFM), provided direct evidence for the improvement in the mechanical properties induced by applying the new adhesive to the original polychromies.This work was supported by the Spanish Ministerio de Economia, Industria y Competitividad (MINECO), the Fondo Europeo de Desarrollo Regional (ERDF), and the Agencia Estatal de Investigacion (AEI).Lee, Y.; Martín Rey, S.; Osete Cortina, L.; Martín-Sánchez, I.; Domenech Carbo, MT.; Bolivar-Galiano, F. (2018). Evaluation of a gelatin-based adhesive for historic paintings that incorporates citronella oil as an eco-friendly biocide. Journal of Adhesion Science and Technology. 32(21):2320-2349. https://doi.org/10.1080/01694243.2018.1477411S23202349322

A Gene Regulatory Network for Root Epidermis Cell Differentiation in Arabidopsis

The root epidermis of Arabidopsis provides an exceptional model for studying the molecular basis of cell fate and differentiation. To obtain a systems-level view of root epidermal cell differentiation, we used a genome-wide transcriptome approach to define and organize a large set of genes into a transcriptional regulatory network. Using cell fate mutants that produce only one of the two epidermal cell types, together with fluorescence-activated cell-sorting to preferentially analyze the root epidermis transcriptome, we identified 1,582 genes differentially expressed in the root-hair or non-hair cell types, including a set of 208 “core” root epidermal genes. The organization of the core genes into a network was accomplished by using 17 distinct root epidermis mutants and 2 hormone treatments to perturb the system and assess the effects on each gene's transcript accumulation. In addition, temporal gene expression information from a developmental time series dataset and predicted gene associations derived from a Bayesian modeling approach were used to aid the positioning of genes within the network. Further, a detailed functional analysis of likely bHLH regulatory genes within the network, including MYC1, bHLH54, bHLH66, and bHLH82, showed that three distinct subfamilies of bHLH proteins participate in root epidermis development in a stage-specific manner. The integration of genetic, genomic, and computational analyses provides a new view of the composition, architecture, and logic of the root epidermal transcriptional network, and it demonstrates the utility of a comprehensive systems approach for dissecting a complex regulatory network

A Mitosis Block Links Active Cell Cycle with Human Epidermal Differentiation and Results in Endoreplication

How human self-renewal tissues co-ordinate proliferation with differentiation is unclear. Human epidermis undergoes continuous cell growth and differentiation and is permanently exposed to mutagenic hazard. Keratinocytes are thought to arrest cell growth and cell cycle prior to terminal differentiation. However, a growing body of evidence does not satisfy this model. For instance, it does not explain how skin maintains tissue structure in hyperproliferative benign lesions. We have developed and applied novel cell cycle techniques to human skin in situ and determined the dynamics of key cell cycle regulators of DNA replication or mitosis, such as cyclins E, A and B, or members of the anaphase promoting complex pathway: cdc14A, Ndc80/Hec1 and Aurora kinase B. The results show that actively cycling keratinocytes initiate terminal differentiation, arrest in mitosis, continue DNA replication in a special G2/M state, and become polyploid by mitotic slippage. They unambiguously demonstrate that cell cycle progression coexists with terminal differentiation, thus explaining how differentiating cells increase in size. Epidermal differentiating cells arrest in mitosis and a genotoxic-induced mitosis block rapidly pushes epidermal basal cells into differentiation and polyploidy. These observations unravel a novel mitosis-differentiation link that provides new insight into skin homeostasis and cancer. It might constitute a self-defence mechanism against oncogenic alterations such as Myc deregulation

Sea level and climate changes during OIS 5e in the Western Mediterranean

Palaeontological, geomorphological and sedimentological data supported by isotopic dating on Oxygen Isotopic Stage (OIS) 5e deposits from the Spanish Mediterranean coast, are interpreted with the aim of reconstructing climatic instability in the Northern Hemisphere. Data point to marked climatic instability during the Last Interglacial (OIS 5e), with a change in meteorological conditions and, consequently, in the sedimentary environment. The oolitic facies generated during the first part of OIS 5e (ca. 135 kyr) shift into reddish conglomeratic facies during the second part (ca. 117 kyr). Sea surface Temperature (SST) and salinity are interpreted mainly on the basis of warm Senegalese fauna, which show chronological and spatial differential distribution throughout the Western Mediterranean. Present hydrological and meteorological conditions are used also as modern analogues to reconstruct climatic variability throughout the Last Interglacial, and this variability is interpreted within the wider framework of the North Atlantic record. All the available data indicate an increase in storminess induced by an increase in the influence of northwesterlies, a slight drop of SST in the northern Western Mediterranean, and an important change in meteorological conditions at the end of OIS 5e (117 kyr). These changes correlate well with the decrease in summer insolation and with the climatic instability recorded in North Atlantic high latitudes

ENHANCER of TRY and CPC 2 ( ETC2 ) reveals redundancy in the region-specific control of trichome development of Arabidopsis

>An evolutionarily conserved set of proteins consisting of MYB and bHLH transcription factors and a WD40 domain protein is known to act in concert to control various developmental processes including trichome and root hair development. Their function is difficult to assess because most of them belong to multigene families and appear to act in a redundant fashion. In this study we identified an enhancer of the two root hair and trichome patterning mutants triptychon ( try ) and caprice ( cpc ), enhancer of try and cpc2 ( etc2 ). The ETC2 gene shows high sequence similarity to the single-repeat MYB genes CPC and TRY. Overexpression results in the suppression of trichomes and overproduction of root hairs similarly as observed for TRY and CPC suggesting that ETC2 has similar biochemical properties. The etc2 single mutant shows an increase in trichome number on leaves and petiols. Double and triple mutant analysis indicates that the ETC2 gene acts redundant with TRY and CPC in trichome patterning.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43456/1/11103_2004_Article_DO00000893.pd