933 research outputs found

    Synthesis of Liquid Core−Shell Particles and Solid Patchy Multicomponent Particles by Shearing Liquids Into Complex Particles (SLICE)

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    We report a simple method that uses (i) emulsion shearing with oxidation to make core–shell particles, and (ii) emulsion shearing with surface-tension driven phase segregation to synthesize particles with complex surface compositions and morphologies. Subjecting eutectic gallium–indium, a liquid metal, to shear in an acidic carrier fluid we synthesized smooth liquid core–shell particles 6.4 nm to over 10 ÎŒm in diameter. Aggregates of these liquid particles can be reconfigured into larger structures using a focused ion beam. Using Field’s metal melts we synthesized homogeneous nanoparticles and solid microparticles with different surface roughness and/or composition through shearing and phase separation. This extension of droplet emulsion technique, SLICE, applies fluidic shear to create micro- and nanoparticles in a tunable, green, and low-cost approach

    The calpain system is associated with survival of breast cancer patients with large but operable inflammatory and non-inflammatory tumours treated with neoadjuvant chemotherapy

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    The calpains are a family of intracellular cysteine proteases that function in a variety of important cellular functions, including cell signalling, motility, apoptosis and survival. In early invasive breast cancer expression of calpain-1, calpain-2 and their inhibitor, calpastatin, have been associated with clinical outcome and clinicopathological factors. The expression of calpain-1, calpain-2 and calpastatin was determined using immunohistochemistry on core biopsy samples, in a cohort of large but operable inflammatory and non-inflammatory primary breast cancer patients treated with neoadjuvant chemotherapy. Information on treatment and prognostic variables together with long-term clinical follow-up was available for these patients. Diagnostic pre-chemotherapy core biopsy samples and surgically excised specimens were available for analysis. Expression of calpastatin, calpain-1 or calpain-2 in the core biopsies was not associated with breast cancer specific survival in the total patient cohort; however, in patients with non-inflammatory breast cancer, high calpastatin expression was significantly associated with adverse breast cancer-specific survival (P=0.035), as was low calpain-2 expression (P=0.031). Low calpastatin expression was significantly associated with adverse breast cancer-specific survival of the inflammatory breast cancer patients (P=0.020), as was low calpain-1 expression (P=0.003). In conclusion, high calpain-2 and low calpastatin expression is associated with improved breast cancer-specific survival in non-inflammatory large but operable primary breast cancer treated with neoadjuvant chemotherapy. In inflammatory cases, high calpain-1 and high calpastatin expression is associated with improved breast cancer-specific survival. Determining the expression of these proteins may be of clinical relevance. Further validation, in multi-centre cohorts of breast cancer patients treated with neoadjuvant chemotherapy, is warranted

    Low Temperature Photo-oxidation of Chloroperoxidase Compound II

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    Oxidation of the heme-thiolate enzyme chloroperoxidase (CPO) from Caldariomyces fumago with peroxynitrite (PN) gave the Compound II intermediate, which was photo-oxidized with 365 nm light to give a reactive oxidizing species. Cryo-solvents at pH ≈ 6 were employed, and reactions were conducted at temperatures as low as − 50 °C. The activity of CPO as evaluated by the chlorodimedone assay was unaltered by treatment with PN or by production of the oxidizing transient and subsequent reaction with styrene. EPR spectra at 77 K gave the amount of ferric protein at each stage in the reaction sequence. The PN oxidation step gave a 6:1 mixture of Compound II and ferric CPO, the photolysis step gave an approximate 1:1 mixture of active oxidant and ferric CPO, and the final mixture after reaction with excess styrene contained ferric CPO in 80% yield. In single turnover reactions at − 50 °C, styrene was oxidized to styrene oxide in high yield. Kinetic studies of styrene oxidation at − 50 °C displayed saturation kinetics with an equilibrium constant for formation of the complex of Kbind = 3.8 × 104 M− 1 and an oxidation rate constant of kox = 0.30 s− 1. UV–Visible spectra of mixtures formed in the photo-oxidation sequence at ca. − 50 °C did not contain the signature Q-band absorbance at 690 nm ascribed to CPO Compound I prepared by chemical oxidation of the enzyme, indicating that different species were formed in the chemical oxidation and the photo-oxidation sequence

    Insect olfaction and the evolution of receptor tuning

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    Insects detect odorants primarily using odorant receptors (OR) housed in the dendritic membrane of olfactory sensory neurons (OSN). Pioneering studies indicated that insects, like mammals, detect odorants in a combinatorial fashion with a specific odor ligand activating several broadly tuned ORs, and each OR being activated by several ligands. Several recent studies, however, challenge this view by providing examples where ecologically relevant odorants are detected by high-specificity ORs activating dedicated neuronal circuits. Here we review these contrasting findings on the ligand selectivity of insect ORs and their neuronal wiring, and outline scenarios describing how adaptive and neutral evolution might shape both narrow and broad receptor tuning. The fact that not all ORs display narrow tuning might partly be due to key ligands having been missed from screens or too high stimuli concentrations being used. However, the birth-and-death model of OR evolution, involving both adaptive and neutral events, could also explain the evolution of broad tuning in certain receptors due to positive selection or relaxed constraint. If the insect olfactory system indeed contains both narrowly and broadly tuned ORs, this suggests that it is a hybrid between dedicated channels and combinatorial coding. The relative extent of the two coding modes is then likely to differ between species, depending on requirements of perceived chemical space and the size of the OR repertoire. We address this by outlining scenarios where certain insect groups may be more likely to have evolved combinatorial coding as their dominant coding strategy. Combinatorial coding may have evolved predominantly in insects that benefit from the ability to discriminate between a larger number of odorants and odor objects, such as polyphagous or social species. Alternatively, combinatorial coding may have evolved simply as a mechanism to increase perceived odor space in species with small OR repertoires

    Assembled Monolayers Depends upon the Roughness of the Substrate and the Orientation of the Terminal Moiety

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    The origin of the odd even effect in properties of self-assembled monolayers (SAMs) and/or technologies derived from them is poorly understood. We report that hydrophobicity and, hence, surface wetting of SAMs are dominated by the nature of the substrate (surface roughness and identity) and SAM tilt angle, which influences surface dipoles/orientation of the terminal moiety. We measured static contact angles (theta(s)) made by water droplets on n-alkanethiolate SAMs with an odd (SAM(O)) or even (SAM(E)) number of carbons (average theta(s) range of 105.8-112.1 degrees). When SAMs were fabricated on smooth template-stripped metal (M-TS) surfaces [root-mean-square (rms) roughness = 0.36 +/- 0.01 nm for Au-TS and 0.60 +/- 0.04 nm for Ag-TS], the odd-even effect, characterized by a zigzag oscillation in values of theta(s), was observed. We, however, did not observe the same effect with rougher as-deposited (M-AD) surfaces (rms roughness = 2.27 +/- 0.16 nm for Au-AD and 5.13 +/- 0.22 nm for Ag-AD). The odd-even effect in hydrophobicity inverts when the substrate changes from Au-TS (higher theta(s) for SAM(E) than SAM(O), with average Delta theta(s) (vertical bar n - (n + 1)vertical bar) approximate to 3 degrees) to Ag-TS (higher theta(s) for SAM(O) than SAM(E), with average Delta theta(s) (vertical bar n - (n + 1)vertical bar) approximate to 2 degrees). A comparison of hydrophobicity across Ag-TS and Au-TS showed a statistically significant difference (Student\u27s t test) between SAM(E) (Delta theta(s) (vertical bar Ag evens - Au evens vertical bar) approximate to 5 degrees; P \u3c 0.01) but failed to show statistically significant differences on SAM(O) (Delta theta(s) (vertical bar Ag odds) (- Au odds vertical bar) approximate to 1 degrees; p \u3e 0.1). From these results, we deduce that the roughness of the metal substrate (from comparison of M-AD versus M-TS) and orientation of the terminal -CH2CH3 (by comparing SAM(E) and SAM(O) on Au-TS versus Ag-TS) play major roles in the hydrophobicity and, by extension, general wetting properties of n-alkanethiolate SAMs

    Microscopic origins of the surface exciton photoluminescence in ZnO nanostructures

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    Photoluminescence (PL) studies of the surface exciton peak in ZnO nanostructures at ∌3.367 eV are reported to elucidate the nature and origin of the emission and its relationship to nanostructure morphology. Localised voltage application in high vacuum and different gas atmospheres show a consistent PL variation (and recovery), allowing an association of the PL to a bound excitonic transition at the ZnO surface modified by an adsorbate. Studies of samples treated by plasma and of samples exposed to UV light under high vacuum conditions show no consistent effects on the surface exciton peak indicating no involvement of oxygen species. X-ray photoelectron spectroscopy data indicate involvement of adsorbed OH species. The relationship of the surface exciton peak to the nanostructure morphology is discussed in light of x-ray diffraction, scanning and transmission electron microscopy data

    American scientists and their fictions: professional authorship and intellectual identity, 1870-1900

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    Writers and critics in the Gilded Age United States frequently debated the relations between literature and science. A common contemporary interpretation of this relationship held that these two ways of knowing and writing were fundamentally opposed and that the advancement of science in American culture came at the expense of literary sensibilities. Nevertheless, and often as an effort to challenge this supposed opposition, many scientists also cultivated reputations as literary figures, and produced or planned diverse works ranging from travel-writing and novels to verse drama. Such authors as Clarence King, J. Peter Lesley, Simon Newcomb and Nathaniel Southgate Shaler sustained a hybrid literary-scientific culture in the late nineteenth-century. This interdisciplinary cultural zone was fragile and increasingly fractured by around 1900, as the emergence and consolidation of new categories of intellectual labour became increasingly wedded to the images of the “professional author” and the “scientist” as mutually exclusive identities. This article seeks to contribute to recurrent debates about the “two cultures” of literature and science by foregrounding the differentiation of these new forms of professional and intellectual identity as a decisive factor which constrained the possibility of a shared literary-scientific culture by the turn of the twentieth century
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