157 research outputs found

    Spatially Resolved Far-Ultraviolet Spectroscopy of the Nuclear Region of NGC 1068

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    We carry out high-resolution FUSE spectroscopy of the nuclear region of NGC 1068. The first set of spectra was obtained with a 30" square aperture that collects all emission from the narrow-line region. The data reveal a strong broad OVI component of FWHM ~3500 kms-1 and two narrow OVI 1031/1037 components of ~350 kms-1. The CIII 977 and NIII 991 emission lines in this spectrum can be fitted with a narrow component of FWHM ~1000 kms-1 and a broad one of ~2500 kms-1. Another set of seven spatially resolved spectra were made using a long slit of 1.25" X 20", at steps of ~1" along the axis of the emission-line cone. We find that (1) Major emission lines in the FUSE wavelength range consist of a broad and a narrow component; (2) There is a gradient in the velocity field for the narrow OVI component of ~200 kms-1 from ~2" southwest of the nucleus to ~4" northeast. A similar pattern is also observed with the broad OVI component, with a gradient of ~3000 kms-1. These are consistent with the HST/STIS findings and suggest a biconical structure in which the velocity field is mainly radial outflow; (3) A major portion of the CIII and NIII line flux is produced in the compact core. They are therefore not effective temperature diagnostics for the conical region; and (4) The best-fitted UV continuum suggests virtually no reddening, and the HeII 1085/1640 ratio suggests a consistently low extinction factor across the cone.Comment: To appear in the Astrophysical Journal. 37 pages with 12 figure

    Anisotropic permeability in deterministic lateral displacement arrays

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    We uncover anisotropic permeability in microfluidic deterministic lateral displacement (DLD) arrays. A DLD array can achieve high-resolution bimodal size-based separation of microparticles, including bioparticles, such as cells. For an application with a given separation size, correct device operation requires that the flow remains at a fixed angle to the obstacle array. We demonstrate via experiments and lattice-Boltzmann simulations that subtle array design features cause anisotropic permeability. Anisotropic permeability indicates the microfluidic array's intrinsic tendency to induce an undesired lateral pressure gradient. This can cause an inclined flow and therefore local changes in the critical separation size. Thus, particle trajectories can become unpredictable and the device useless for the desired separation task. Anisotropy becomes severe for arrays with unequal axial and lateral gaps between obstacle posts and highly asymmetric post shapes. Furthermore, of the two equivalent array layouts employed with the DLD, the rotated-square layout does not display intrinsic anisotropy. We therefore recommend this layout over the easier-to-implement parallelogram layout. We provide additional guidelines for avoiding adverse effects of anisotropy on the DLD.Comment: 13 pages, 10 figures, 1 table, DLD, particle separation, microfluidics, anisotropic permeabilit

    Deterministic Lateral Displacement:Challenges and Perspectives

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    The advent of microfluidics in the 1990s promised a revolution in multiple industries from healthcare to chemical processing. Deterministic lateral displacement (DLD) is a continuous-flow microfluidic particle separation method discovered in 2004 that has been applied successfully and widely to the separation of blood cells, yeast, spores, bacteria, viruses, DNA, droplets, and more. Deterministic lateral displacement is conceptually simple and can deliver consistent performance over a wide range of flow rates and particle concentrations. Despite wide use and in-depth study, DLD has not yet been fully elucidated or optimized, with different approaches to the same problem yielding varying results. We endeavor here to provide up-to-date expert opinion on the state-of-art and current fundamental, practical, and commercial challenges with DLD as well as describe experimental and modeling opportunities. Because these challenges and opportunities arise from constraints on hydrodynamics, fabrication, and operation at the micro- and nanoscale, we expect this Perspective to serve as a guide for the broader micro- and nanofluidic community to identify and to address open questions in the field

    On the possibility of magneto-structural correlations: detailed studies of di-nickel carboxylate complexes

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    A series of water-bridged dinickel complexes of the general formula [Ni<sub>2</sub>(μ<sub>2</sub>-OH<sub>2</sub>)(μ2- O<sub>2</sub>C<sup>t</sup>Bu)<sub>2</sub>(O<sub>2</sub>C<sup>t</sup>Bu)2(L)(L0)] (L = HO<sub>2</sub>C<sup>t</sup>Bu, L0 = HO<sub>2</sub>C<sup>t</sup>Bu (1), pyridine (2), 3-methylpyridine (4); L = L0 = pyridine (3), 3-methylpyridine (5)) has been synthesized and structurally characterized by X-ray crystallography. The magnetic properties have been probed by magnetometry and EPR spectroscopy, and detailed measurements show that the axial zero-field splitting, D, of the nickel(ii) ions is on the same order as the isotropic exchange interaction, J, between the nickel sites. The isotropic exchange interaction can be related to the angle between the nickel centers and the bridging water molecule, while the magnitude of D can be related to the coordination sphere at the nickel sites

    Supermarket Healthy Eating for Life (SHELf): protocol of a randomised controlled trial promoting healthy food and beverage consumption through price reduction and skill-building strategies

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    Background: In the context of rising food prices, there is a need for evidence on the most effective approaches for promoting healthy eating. Individually-targeted behavioural interventions for increasing food-related skills show promise, but are unlikely to be effective in the absence of structural supports. Fiscal policies have been advocated as a means of promoting healthy eating and reducing obesity and nutrition-related disease, but there is little empirical evidence of their effectiveness. This paper describes the Supermarket Healthy Eating for LiFe (SHELf) study, a randomised controlled trial to investigate effectiveness and cost-effectiveness of a tailored skill-building intervention and a price reduction intervention, separately and in combination, against a control condition for promoting purchase and consumption of healthy foods and beverages in women from high and low socioeconomic groups.Methods/design: SHELf comprises a randomised controlled trial design, with participants randomised to receive either (1) a skill-building intervention; (2) price reductions on fruits, vegetables and low-joule soft drink beverages and water; (3) a combination of skill-building and price reductions; or (4) a control condition. Five hundred women from high and low socioeconomic areas will be recruited through a store loyalty card program and local media. Randomisation will occur on receipt of informed consent and baseline questionnaire. An economic evaluation from a societal perspective using a cost-consequences approach will compare the costs and outcomes between intervention and control groups.Discussion: This study will build on a pivotal partnership with a major national supermarket chain and the Heart Foundation to investigate the effectiveness of intervention strategies aimed at increasing women&rsquo;s purchasing and consumption of fruits and vegetables and decreased purchasing and consumption of sugar-sweetened beverages. It will be among the first internationally to examine the effects of two promising approaches - skill-building and price reductions - on diet amongst women.<br /

    Cysteamine Inhibits Glycine Utilisation and Disrupts Virulence in Pseudomonas aeruginosa.

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    Pseudomonas aeruginosa is a major opportunistic human pathogen which employs a myriad of virulence factors. In people with cystic fibrosis (CF) P. aeruginosa frequently colonises the lungs and becomes a chronic infection that evolves to become less virulent over time, but often adapts to favour persistence in the host with alginate-producing mucoid, slow-growing, and antibiotic resistant phenotypes emerging. Cysteamine is an endogenous aminothiol which has been shown to prevent biofilm formation, reduce phenazine production, and potentiate antibiotic activity against P. aeruginosa, and has been investigated in clinical trials as an adjunct therapy for pulmonary exacerbations of CF. Here we demonstrate (for the first time in a prokaryote) that cysteamine prevents glycine utilisation by P. aeruginosa in common with previously reported activity blocking the glycine cleavage system in human cells. Despite the clear inhibition of glycine metabolism, cysteamine also inhibits hydrogen cyanide (HCN) production by P. aeruginosa, suggesting a direct interference in the regulation of virulence factor synthesis. Cysteamine impaired chemotaxis, lowered pyocyanin, pyoverdine and exopolysaccharide production, and reduced the toxicity of P. aeruginosa secreted factors in a Galleria mellonella infection model. Thus, cysteamine has additional potent anti-virulence properties targeting P. aeruginosa, further supporting its therapeutic potential in CF and other infections

    Characterisation of proteins in excretory/secretory products collected from salmon lice, Lepeophtheirus salmonis

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    Background  The salmon louse, Lepeophtheirus salmonis, is an ectoparasitic copepod which feeds on the mucus, skin and blood of salmonid fish species. The parasite can persist on the surface of the fish without any effective control being exerted by the host immune system. Other ectoparasitic invertebrates produce compounds in their saliva, excretions and/or secretions which modulate the host immune responses allowing them to remain on or in the host during development. Similarly, compounds are produced in secretions of L. salmonis which are thought to be responsible for immunomodulation of the host responses as well as other aspects of crucial host-parasite interactions.  Methods  In this study we have identified and characterised the proteins in the excretory/secretory (E/S) products of L. salmonis using LC-ESI-MS/MS.  Results  In total 187 individual proteins were identified in the E/S collected from adult lice and pre-adult sea lice. Fifty-three proteins, including 13 serine-type endopeptidases, 1 peroxidase and 5 vitellogenin-like proteins were common to both adult and pre-adult E/S products. One hundred and seven proteins were identified in the adult E/S but not in the pre-adult E/S and these included serine and cysteine-type endopeptidases, vitellogenins, sphingomyelinase and calreticulin. A total of 27 proteins were identified in pre-adult E/S products but not in adult E/S.  Conclusions  The assigned functions of these E/S products and the potential roles they play in host-parasite interaction is discussed

    DHA Supplemented in Peptamen Diet Offers No Advantage in Pathways to Amyloidosis: Is It Time to Evaluate Composite Lipid Diet?

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    Numerous reports have documented the beneficial effects of dietary docosahexaenoic acid (DHA) on beta-amyloid production and Alzheimer's disease (AD). However, none of these studies have examined and compared DHA, in combination with other dietary nutrients, for its effects on plaque pathogenesis. Potential interactions of DHA with other dietary nutrients and fatty acids are conventionally ignored. Here we investigated DHA with two dietary regimes; peptamen (pep+DHA) and low fat diet (low fat+DHA). Peptamen base liquid diet is a standard sole-source nutrition for patients with gastrointestinal dysfunction. Here we demonstrate that a robust AD transgenic mouse model shows an increased tendency to produce beta-amyloid peptides and amyloid plaques when fed a pep+DHA diet. The increase in beta-amyloid peptides was due to an elevated trend in the levels of beta-secretase amyloid precursor protein (APP) cleaving enzyme (BACE), the proteolytic C-terminal fragment beta of APP and reduced levels of insulin degrading enzyme that endoproteolyse beta-amyloid. On the contrary, TgCRND8 mice on low fat+DHA diet (based on an approximately 18% reduction of fat intake) ameliorate the production of abeta peptides and consequently amyloid plaques. Our work not only demonstrates that DHA when taken with peptamen may have a tendency to confer a detrimental affect on the amyloid plaque build up but also reinforces the importance of studying composite lipids or nutrients rather than single lipids or nutrients for their effects on pathways important to plaque development
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