Reactive sputter-deposition of oxygenated amorphous carbon thin films in Ar/O2

Oxygenated amorphous carbon thin films were deposited by DC magnetron sputtering using various argon and oxygen process gas mixtures. The X-ray diffraction data indicated that the predominantly amorphous films had more defined peaks with a higher partial pressure of oxygen. Results indicated that use of oxygen in the working gas enhanced the crystalline nature of the films. Scanning electron and atomic force microscopy revealed that the surface roughness and film topography differed with the oxygen process gas variations. X-ray photoelectron spectroscopy revealed increased surface oxygen content with higher oxygen concentration in the working gas. Raman spectroscopy results suggested that the increased oxygen in the films may have led to a higher percentage of sp³-bonded carbon atoms. The growth rate (deposition rate) of the films decreased as the amount of oxygen increased. This decreased deposition rate was associated with an oxygen etching of the film.     

Dynamic substrate enhancement for the identification of specific, second-site-binding fragments targeting a set of protein tyrosine phosphatases

Protein tyrosine phosphatases (PTPs) are key regulators in living systems and thus are attractive drug targets. The development of potent, selective PTP inhibitors has been a difficult challenge mainly due to the high homology of the phosphotyrosine substrate pockets. Here, a strategy of dynamic substrate enhancement is described targeting the secondary binding sites of PTPs. By screening four different PTPs from bacterial (MptpA) and human origin (PTP1B, HePtp, Shp2) with this assay, specific fragments were identified. One highly specific fragment that binds to the secondary site of Mycobacterium tuberculosis protein tyrosine phosphatase A (MptpA) was characterized in order to validate the assay concept. Finally by covalently linking the secondary fragment to a phosphotyrosine mimetic, a moderately active but highly specific inhibitor of MptpA was obtained.     

Synthesis of an amino coumarin‐based fluorescent reactive dye and its application to wool fibres

The objective of the current study was to introduce the coumarin structure into a conventional reactive dye system. A fluorescent reactive dye was synthesised based upon 7‐amino‐4‐methylcoumarin. The dye was obtained by a multi‐step sequence initiated by displacement of a chlorine group from 2,4,6‐trichloro‐1,3,5‐triazine using H‐acid. Diazo coupling of 3‐aminobenzenesulphato‐ethylsulphone to this adduct, followed by a second chlorine displacement using aminomethylcoumarin completed the sequence. The fluorescent dye and the non‐fluorescent precursor were characterised by mass spectrometry, infrared spectroscopy and capillary electrophoresis. The newly synthesised dye was applied to wool fibres using an exhaust dyeing method. The exhaustion, fixation and total efficiency values were calculated by ultraviolet–visible spectrophotometric analysis of the dyebath. The synthesised red dye presented high values for exhaustion, fixation and total efficiency on the wool fibres. The novel dye, after its application to the wool fibres, exhibited fluorescence under an ultraviolet light. This feature confirmed that the novel dye retained the inherent characteristic feature of fluorescence on the wool fibres. The dyed wool fibres exhibited level 4–5 of light fastness when compared with international wool light fastness standards.     

Differential scanning calorimetry analysis of an enhanced LiNi0.8Co0.2O2 cathode with single wall carbon nanotube conductive additives

The replacement of traditional conductive carbon additives with single wall carbon nanotubes (SWCNTs) in lithium metal oxide cathode composites has been shown to enhance thermal stability as well as power capability and electrode energy density. The dispersion of 1 wt% high purity laser-produced SWCNTs in a LiNi_0.8Co_0.2O₂ electrode created an improved percolation network over an equivalent composite electrode using 4 wt% Super C65 carbon black; evidenced by additive connectivity in SEM images and an order of magnitude increase in electrode electrical conductivity. The cathode with 1 wt% SWCNT additives showed comparable active material capacity (185–188 mAh g⁻¹), at a low rate, and Coulombic efficiency to the cathode composite with 4 wt% Super C65. At increased cycling rates, the cathode with SWCNT additives had higher capacity retention with more than three times the capacity at 10C (16.4 mA cm⁻²). The thermal stability of the electrodes was evaluated by differential scanning calorimetry after charging to 4.3 V and float charging for 12 h. A 40% reduction of the cathode exothermic energy released was measured when using 1 wt% SWCNTs as the additive. Thus, the results demonstrate that replacing traditional conductive carbon additives with a lower weight loading of SWCNTs is a simple way to improve the thermal transport, safety, power, and energy characteristics of cathode composites for lithium ion batteries.     

Investigation of γ-Linolenic Acid and Stearidonic Acid Biosynthesis During a Life Cycle of <Emphasis Type="Italic">Borago officinalis</Emphasis> L.

This study investigated the levels of γ-linolenic (GLA, 18:3n-6) and stearidonic acid (SDA, 18:4n-3) in various parts of the borage plant (Borago officinalis L.) to elucidate Δ6-desaturase activity. Lipid class and fatty acid (FA) composition during germination of the seeds and FA composition of various borage parts were determined as well as FA compositions of neutral lipids (NL), polar lipids (PL), glycolipids (GL) and monogalactosyl diacylglycerols (MGDG) of borage leaves. When seeds were germinated for 12 days in the dark then exposed to light for 8 h, an overall decrease in oil content was seen with a significant increase in PL from 0.2 to 39.1%. An increase in SDA (from 0.2 to 0.6 g/100 g oil) indicated minor FA synthesis during germination and therefore, Δ6-desaturase activity with the most marked increase after light exposure. The FA compositions of developing and mature seeds were similar, suggesting oil/FA synthesis takes place at the initial stage of seed development. Among all the borage parts, the leaves had the highest amounts of α-linolenic acid (ALA, 18:3n-3) (36.2%), indicating Δ15-desaturase activity, and SDA (25.2%), indicating Δ6-desaturase activity. In leaves, the GL and especially, MGDG fractions had the highest amounts of SDA (31.8 and 39.8%, respectively), indicating that Δ6-desaturase is most active in chloroplasts. Leaves and developing seeds appear to be the major sources of Δ6-desaturase in borage, associated with different organelles in the different tissues.     

An investigation into the conversion of In<Subscript>2</Subscript>O<Subscript>3</Subscript> into InN nanowires

Straight In₂O₃ nanowires (NWs) with diameters of 50 nm and lengths ≥2 μm have been grown on Si(001) via the wet oxidation of In at 850°C using Au as a catalyst. These exhibited clear peaks in the X-ray diffraction corresponding to the body centred cubic crystal structure of In₂O₃ while the photoluminescence (PL) spectrum at 300 K consisted of two broad peaks, centred around 400 and 550 nm. The post-growth nitridation of In₂O₃ NWs was systematically investigated by varying the nitridation temperature between 500 and 900°C, flow of NH₃ and nitridation times between 1 and 6 h. The NWs are eliminated above 600°C while long nitridation times at 500 and 600°C did not result into the efficient conversion of In₂O₃ to InN. We find that the nitridation of In₂O₃ is effective by using NH₃ and H₂ or a two-step temperature nitridation process using just NH₃ and slower ramp rates. We discuss the nitridation mechanism and its effect on the PL.     

Covalent immobilization of nisin on multi-walled carbon nanotubes: superior antimicrobial and anti-biofilm properties

Despite unique and useful properties of multi-walled carbon nanotubes (MWNTs) such as high strength and a low synthesis cost, their weak antimicrobial property hampers their use as an antimicrobial material. Herein, we demonstrate that the immobilization of nisin, a natural and inexpensive antimicrobial peptide, with poly(ethylene glycol) (PEG(1000)) as a linker significantly enhanced the antimicrobial and anti-biofilm properties of MWNTs. The MWNT-nisin composite showed up to 7-fold higher antimicrobial property than pristine MWNTs against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Bacillus subtilis. Moreover, the MWNT-nisin composite had a dramatically improved capability to prevent biofilm formation both on a deposited film and in suspension. In particular, the MWNT-nisin deposit film exhibited a 100-fold higher anti-biofilm property than the MWNT deposit film. Further, it has been shown that PEG and nisin are covalently attached to MWNTs with excellent stability against leaching. We envision that our novel MWNT-nisin composite can serve as an effective and economical antimicrobial material.     

Minimizing profile error when estimating the sieve-size distribution of iron ore pellets using ordinal logistic regression

Size measurement of pellets in industry is usually performed by manual sampling and sieving techniques. Automatic on-line analysis of pellet size based on image analysis techniques would allow non-invasive, frequent and consistent measurement. We evaluate the statistical significance of the ability of commonly used size and shape measurement methods to discriminate among different sieve-size classes using multivariate techniques. Literature review indicates that earlier works did not perform this analysis and selected a sizing method without evaluating its statistical significance. Backward elimination and forward selection of features are used to select two feature sets that are statistically significant for discriminating among different sieve-size classes of pellets. The diameter of a circle of equivalent area is shown to be the most effective feature based on the forward selection strategy, but an unexpected five-feature classifier is the result using the backward elimination strategy. The discrepancy between the two selected feature sets can be explained by how the selection procedures calculate a feature's significance and that the property of the 3D data provides an orientational bias that favours combination of Feret-box measurements. Size estimates of the surface of a pellet pile using the two feature sets show that the estimated sieve-size distribution follows the known sieve-size distribution.