Two sides of the coin. Part 2. Colloid and surface science meets real biointerfaces

Part 1 revisited developments in lipid and surfactant self assembly over the past 40 years [1]. New concepts emerged. Here we explore how these developments can be used to make sense of and bring order to a range of complex biological phenomena. Together with Part 1, this contribution is a fundamental revision of intuition at the boundaries of Colloid Science and Biological interfaces from a perspective of nearly 50 years. We offer new insights on a unified treatment of self assembly of lipids, surfactants and proteins in the light of developments presented in Part 1. These were in the enabling disciplines in molecular forces, hydration, oil and electrolyte specificity; and in the role of non Euclidean geometries-across the whole gammut of physical, colloid and surface chemistry, biophysics and membrane biology and medicine. It is where the early founders of the cell theory of biology and the physiologists expected advances to occur as D'Arcy Thompson predicted us 100 years ago

Quantum key distribution with "dual detectors"

To improve the performance of a quantum key distribution (QKD) system, high speed, low dark count single photon detectors (or low noise homodyne detectors) are required. However, in practice, a fast detector is usually noisy. Here, we propose a "dual detectors" method to improve the performance of a practical QKD system with realistic detectors: the legitimate receiver randomly uses either a fast (but noisy) detector or a quiet (but slow) detector to measure the incoming quantum signals. The measurement results from the quiet detector can be used to bound eavesdropper's information, while the measurement results from the fast detector are used to generate secure key. We apply this idea to various QKD protocols. Simulation results demonstrate significant improvements in both BB84 protocol with ideal single photon source and Gaussian-modulated coherent states (GMCS) protocol; while for decoy-state BB84 protocol with weak coherent source, the improvement is moderate. We also discuss various practical issues in implementing the "dual detectors" scheme.Comment: 22 pages, 9 figure

Strong reinforcement effects in 2D cellulose nanofibril-graphene oxide (CNF-GO) nanocomposites due to GO-induced CNF ordering

Nanocomposites from native cellulose with low 2D nanoplatelet content are of interest as sustainable materials combining functional and structural performance. Cellulose nanofibril-graphene oxide (CNF-GO) nanocomposite films are prepared by a physical mixing-drying method, with a focus on low GO content, the use of very large GO platelets (2-45 μm) and nanostructural characterization using synchrotron X-ray source for WAXS and SAXS. These nanocomposites can be used as transparent coatings, strong films or membranes, as gas barriers or in laminated form. CNF nanofibrils with random in-plane orientation, form a continuous non-porous matrix with GO platelets oriented in-plane. GO reinforcement mechanisms in CNF are investigated, and relationships between nanostructure and suspension rheology, mechanical properties, optical transmittance and oxygen barrier properties are investigated as a function of GO content. A much higher modulus reinforcement efficiency is observed than in previous polymer-GO studies. The absolute values for modulus and ultimate strength are as high as 17 GPa and 250 MPa at a GO content as small as 0.07 vol%. The remarkable reinforcement efficiency is due to improved organization of the CNF matrix; and this GO-induced mechanism is of general interest for nanostructural tailoring of CNF-2D nanoplatelet composites

Ordered and ushered; the assembly and translocation of the adhesive Type I and P Pili

Type I and P pili are chaperone-usher pili of uropathogenic Escherichia coli, which allow bacteria to adhere to host cell receptors. Pilus formation and secretion are orchestrated by two accessory proteins, a chaperone, which catalyses pilus subunit folding and maintains them in a polymerization-competent state, and an outer membrane-spanning nanomachine, the usher, which choreographs their assembly into a pilus and drives their secretion through the membrane. In this review, recent structures and kinetic studies are combined to examine the mechanism of type I and P pili assembly, as it is currently known. We also investigate how the knowledge of pilus biogenesis mechanisms has been exploited to design selective inhibitors of the process

Melt processable cellulose fibres engineered for replacing oil-based thermoplastics

If cellulosic materials are to replace materials derived from non-renewable resources, it is necessary to overcome intrinsic limitations such as fragility, permeability to gases, susceptibility to water vapour and poor three-dimensional shaping. Novel properties or the enhancement of existing properties are required to expand the applications of cellulosic materials and will create new market opportunities. Here we have overcome the well-known restrictions that impede melt-processing of high cellulose content composites. Cellulose fibres, partially derivatised to dialcohol cellulose, have been used to manufacture three-dimensional high-density materials by conventional melt processing techniques, with or without the addition of a thermoplastic polymer. This work demonstrates the use of melt processable chemically modified cellulose fibres in the preparation of a new generation of highly sustainable materials with tuneable properties that can be tailored for specific applications requiring complex three-dimensional parts

Local-scale feedbacks influencing cold-water coral growth and subsequent reef formation

Despite cold-water coral (CWC) reefs being considered biodiversity hotspots, very little is known about the main processes driving their morphological development. Indeed, there is a considerable knowledge gap in quantitative experimental studies that help understand the interaction between reef morphology, near-bed hydrodynamics, coral growth, and (food) particle transport processes. In the present study, we performed a 2-month long flume experiment in which living coral nubbins were placed on a reef patch to determine the effect of a unidirectional flow on the growth and physiological condition of Lophelia pertusa. Measurements revealed how the presence of coral framework increased current speed and turbulence above the frontal part of the reef patch, while conditions immediately behind it were characterised by an almost stagnant flow and reduced turbulence. Owing to the higher current speeds that likely promoted a higher food encounter rate and intake of ions involved in the calcification process, the coral nubbins located on the upstream part of the reef presented a significantly enhanced average growth and a lower expression of stress-related enzymes than the downstream ones. Yet, further experiments would be needed to fully quantify how the variations in water hydrodynamics modify particle encounter and ion intake rates by coral nubbins located in different parts of a reef, and how such discrepancies may ultimately affect coral growth. Nonetheless, the results acquired here denote that a reef influenced by a unidirectional water flow would grow into the current: a pattern of reef development that coincides with that of actual coral reefs located in similar water flow settings. Ultimately, the results of this study suggest that at the local scale coral reef morphology has a direct effect on coral growth thus, indicating that the spatial patterns of living CWC colonies in reef patches are the result of spatial self-organisation

A three-objective user equilibrium model:Time surplus maximisation under uncertainty

In this paper, we propose a user equilibrium model considering the three most important factors influencing route choice behaviour in a road network, namely, travel time, travel time reliability and monetary cost. We further develop the time surplus maximisation bi-objective user equilibrium (TSmaxBUE) model and incorporate the concept of travel time budget to model how users might react to uncertainty induced by day-to-day variability in travel time caused by traffic incidents. This results in a three-objective user equilibrium model, which has a possibly infinite set of equilibrium flows. To compute equilibrium flows, we introduce time budget surplus (TBS) defined as the maximum travel time a user is willing to spend minus the actual time budget required for a desired level of travel time reliability. At equilibrium, for each origin-destination (O-D) pair, all individuals are travelling on the path with the highest TBS value among all the efficient paths between this O-D pair. This becomes a time budget surplus maximisation three-objective user equilibrium model (TBSmaxTUE). We show that the TBSmaxTUE model is a special case of three-objective user equilibrium considering minimisation of expected travel time, travel time variance and toll (monetary cost) as objectives. We illustrate the model and our results on a small network

Investigation of low-dissipation monotonicity-preserving scheme for direct numerical simulation of compressible turbulent flows

© 2014 Elsevier Ltd. The influence of numerical dissipation on direct numerical simulation (DNS) of decaying isotropic turbulence and turbulent channel flow is investigated respectively by using the seventh-order low-dissipation monotonicity-preserving (MP7-LD) scheme with different levels of bandwidth dissipation. It is found that for both benchmark test cases, small-scale turbulence fluctuations can be largely suppressed by high level of scheme dissipation, while the appearance of numerical errors in terms of high-frequency oscillations could destabilize the computation if the dissipation is reduced to a very low level. Numerical studies show that reducing the bandwidth dissipation to 70% of the conventional seventh-order upwind scheme can maximize the efficiency of the MP7-LD scheme in resolving small-scale turbulence fluctuations and, in the meantime preventing the accumulation of non-physical numerical errors. By using the optimized MP7-LD scheme, DNS of an impinging oblique shock-wave interacting with a spatially-developing turbulent boundary layer is conducted at an incoming free-stream Mach number of 2.25 and the shock angle of 33.2°. Simulation results of mean velocity profiles, wall surface pressure, skin friction and Reynolds stresses are validated against available experimental data and other DNS predictions in both the undisturbed equilibrium boundary layer region and the interaction zone, and good agreements are achieved. The turbulence kinetic energy transport equation is also analyzed and the balance of the equation is well preserved in the interaction region. This study demonstrates the capability of the optimized MP7-LD scheme for DNS of complex flow problems of wall-bounded turbulent flow interacting with shock-waves

Allelic imbalance in gene expression as a guide to cis-acting regulatory single nucleotide polymorphisms in cancer cells

Using the relative expression levels of two SNP alleles of a gene in the same sample is an effective approach for identifying cis-acting regulatory SNPs (rSNPs). In the current study, we established a process for systematic screening for cis-acting rSNPs using experimental detection of AI as an initial approach. We selected 160 expressed candidate genes that are involved in cancer and anticancer drug resistance for analysis of AI in a panel of cell lines that represent different types of cancers and have been well characterized for their response patterns against anticancer drugs. Of these genes, 60 contained heterozygous SNPs in their coding regions, and 41 of the genes displayed imbalanced expression of the two cSNP alleles. Genes that displayed AI were subjected to bioinformatics-assisted identification of rSNPs that alter the strength of transcription factor binding. rSNPs in 15 genes were subjected to electrophoretic mobility shift assay, and in eight of these genes (APC, BCL2, CCND2, MLH1, PARP1, SLIT2, YES1, XRCC1) we identified differential protein binding from a nuclear extract between the SNP alleles. The screening process allowed us to zoom in from 160 candidate genes to eight genes that may contain functional rSNPs in their promoter regions

Tuberculosis contact investigation with a new, specific blood test in a low-incidence population containing a high proportion of BCG-vaccinated persons

BACKGROUND: BCG-vaccination can confound tuberculin skin test (TST) reactions in the diagnosis of latent tuberculosis infection. METHODS: We compared the TST with a Mycobacterium tuberculosis specific whole blood interferon-gamma assay (QuantiFERON(®)-TB-Gold In Tube; QFT-G) during ongoing investigations among close contacts of sputum smear positive source cases in Hamburg, Germany. RESULTS: During a 6-month period, 309 contacts (mean age 28.5 ± 10.5 years) from a total of 15 source cases underwent both TST and QFT-G testing. Of those, 157 (50.8%) had received BCG vaccination and 84 (27.2%) had migrated to Germany from a total of 25 different high prevalence countries (i.e. >20 cases/100,000). For the TST, the positive response rate was 44.3% (137/309), whilst only 31 (10%) showed a positive QFT-G result. The overall agreement between the TST and the QFT-G was low (κ = 0.2, with 95% CI 0.14.-0.23), and positive TST reactions were closely associated with prior BCG vaccination (OR 24.7; 95% CI 11.7–52.5). In contrast, there was good agreement between TST and QFT-G in non-vaccinated persons (κ = 0.58, with 95% CI 0.4–0.68), increasing to 0.68 (95% CI 0.46–0.81), if a 10-mm cut off for the TST was used instead of the standard 5 mm recommended in Germany. CONCLUSION: The QFT-G assay was unaffected by BCG vaccination status, unlike the TST. In close contacts who were BCG-vaccinated, the QFT-G assay appeared to be a more specific indicator of latent tuberculosis infection than the TST, and similarly sensitive in unvaccinated contacts. In BCG-vaccinated close contacts, measurement of IFN-gamma responses of lymphocytes stimulated with M. tuberculosis-specific antigen should be recommended as a basis for the decision on whether to perform subsequent chest X-ray examinations or to start treatment for latent tuberculosis infection