Quantitative enhanced Raman scattering of labeled DNA from gold and silver nanoparticles

Surface-enhanced resonance Raman scattering (SERRS) from silver nanoparticles using 514.5-nm excitation has been shown to offer huge potential for applications in highly sensitive multiplexed DNA assays. If the technique is to be applied to real biological samples and integrated with other methods, then the use of gold nanoparticles and longer wavelengths of excitation are desirable. The data presented here demonstrate that dye-labeled oligonucleotide sequences can be directly detected by SERRS using gold nanoparticles in a quantitative manner for the first time. The performance of gold and silver nanoparticles as SERRS substrates was assessed using 514.5-, 632.8-, and 785-nm excitation and a range of 13 commercially available dye-labeled oligonucleotides. The quantitative response allowed the limit of detection to be determined for each case and demonstrates that the technique is highly effective, sensitive, and versatile. The possibility of excitation at multiple wavelengths further enhances the multiplexing potential of the technique. The importance of effectively combining the optical properties of the nanoparticle and the dye label is demonstrated. For example, at 632.8-nm excitation, the dye BODIPY TR-X and gold nanoparticles make a strong SERRS combination with very little background fluorescence. This study allows the choice of nanoparticle and dye label for particular experimental setups, and significantly expands the applicability of enhanced Raman scattering for use in many disciplines.     

The colour fastness of optionally aftertreated metal complex acid dyes on nylon 6.6 during washing in an activated oxygenbleach containing detergent

Previous studies examining the fading exhibited by optionally aftertreated acid levelling and acid milling dyes on nylon 6.6, during washing in an oxidative-bleach containing detergent, have been extended to metal complex dyes. It has been shown that, in the main, such dyes exhibit low levels of (oxidativebleach) fading in both the single cycle, stressed UK-TO (60 °C) test and after 20 machine washes at 50 °C.     

Stable white light emission from an externally modified organic light-emitting device

A blue organic light-emitting device, based on an iridium phosphorescent dopant in a polyvinylcarbazole host, has been modified by the addition of an external CaS:Eu inorganic phosphor layer. By incorporating a surfactant in the phosphor mixture, a uniform coating could be achieved by drop-casting. The resulting hybrid device exhibited white light emission, with Commission Internationale de l’Eclairage, CIE (x, y) coordinates of x = 0.32, y = 0.35. No significant change in these coordinates was observed for current densities in the range 25–510 A m^?2. The maximum power efficiencies of the white device was 2.3 lm W^?1 at a brightness of 254 cd m^?2.     

The fatty acid composition and intramolecular structure of triglycerides derived from different sites in the body of the sheep

Triglycerides were isolated from a number of different tissues obtained from six adult sheep; the tissues including internal fat depots (perinephric and mesenteric), subcutaneous fat depots (rump and chest) and the subcutaneous region of the metatarsal part of the hind limbs and of the pinnae of the ears. The fatty acid composition of these triglycerides was determined by gas-liquid chromatography and the intramolecular distribution of the acids was studied using pancreatic lipase to remove selectively the fatty acids esterified to the primary alcoholic groups (1- and 3-positions) of the glycerol molecules. Unsaturated fatty acids of the trans configuration were estimated by infra-red absorption analysis. In confirmation of earlier, less detailed, studies it was found that the triglycerides of the internal tissues contained a much higher proportion of saturated fatty acids (particularly stearic acid) than did those of the external tissues. In the most exposed tissues (legs, ears) oleic acid accounted for as much as 60-70% of the total fatty acids present. Trans fatty acid (almost entirely C₁₈ mono-unsaturated) was, like stearic acid, found in greatest concentration in the internal tissue triglycerides. Regardless of their location in the body all the triglycerides examined showed a similar pattern of intramolecular distribution of their major component acids; saturated acids (palmitic acid and stearic acid) were for the most part esterified in the 1- and 3-positions, and oleic acid was found predominantly esterified in the 2-position. Trans unsaturated acid, when present, showed a similar degree of preferential esterification in the 1- and 3-positions to that observed for stearic acid. It was tentatively concluded that long-chain fatty acids absorbed from the intestine influence primarily the composition of the triglycerides of internal adipose tissue.     

Fate of N-nitrosodimethylamine in recycled water after recharge into anaerobic aquifer

Laboratory and field experiments were undertaken to assess the fate of N-nitrosodimethylamine (NDMA) in aerobic recycled water that was recharged into a deep anaerobic pyritic aquifer, as part of a managed aquifer recharge (MAR) strategy. Laboratory studies demonstrated a high mobility of NDMA in the Leederville aquifer system with a retardation coefficient of 1.1. Anaerobic degradation column and ¹⁴C-NDMA microcosm studies showed that anaerobic conditions of the aquifer provided a suitable environment for the biodegradation of NDMA with first-order kinetics. At microgram per litre concentrations, inhibition of biodegradation was observed with degradation half-lives (260 ± 20 days) up to an order of magnitude greater than at nanogram per litre concentrations (25-150 days), which are more typical of environmental concentrations. No threshold effects were observed at the lower ng L⁻¹ concentrations with NDMA concentrations reduced from 560 ng L⁻¹ to <6 ng L⁻¹ over a 42 day ¹⁴C-NDMA aerobic microcosm experiment.Aerobic ¹⁴C-NDMA microcosm studies were also undertaken to assess potential aerobic degradation, likely to occur close to the recharge bore. These microcosm experiments showed a faster degradation rate than anaerobic microcosms, with a degradation half-life of 8 ± 2 days, after a lag period of approximately 10 days.Results from a MAR field trial recharging the Leederville aquifer with aerobic recycled water showed that NDMA concentrations reduced from 2.5 ± 1.0 ng L⁻¹ to 1.3 ± 0.4 ng L⁻¹ between the recharge bore and a monitoring location 20 m down gradient (an estimated aquifer residence time of 10 days), consistent with data from the aerobic microcosm experiment. Further down gradient, in the anaerobic zone of the aquifer, NDMA degradation could not be assessed, as NDMA concentrations were too close to their analytical detection limit (<1 ng L⁻¹).     

Evaluation of the operationally defined soluble, insoluble, and complexing copper consumed through drinking water in human saliva

Previous studies suggest that different copper species formed in saliva have different reactivity in chemical reactions that may be associated with perception of metallic sensation occurring in the oral cavity. This study was performed to understand copper speciation in human saliva, which will help to understand the perception mechanism of metallic taste. Saliva samples were treated with CuSO₄·5H₂O at the levels of 0, 2.5, 10, 20, or 40 mg/L as Cu in vitro. Also saliva is collected before and after drinking 20 mL of 0, 2.5, and 5 mg/L copper in water (in vivo treatment). Copper speciation was operationally determined based on apparent molecular size using ultrafiltration coupled with inductively coupled plasma mass spectrometry. For in vitro copper treatment, 50–70% of copper was soluble at Cu ≤ 10 mg/L, whereas 60–70% of copper was in complex or insoluble form at Cu > 20 mg/L. For in vivo copper treatment, 90–95% of copper was soluble in saliva. These results suggest that copper is in the soluble unbound form in saliva at low concentrations. At higher concentrations, copper either becomes insoluble or binds with salivary components.     

ROTATING TOOL POINT FREQUENCY RESPONSE PREDICTION USING RCSA

This article describes the prediction of rotating tool point frequency response functions using receptance coupling substructure analysis (RCSA). In this approach, the at-speed spindle-machine dynamics are identified by impact tests of a rotating cylindrical standard artifact. After removing the portion of the artifact beyond the holder flange in simulation, models of arbitrary tool-holder combinations are coupled to the spindle response to predict the speed-dependent tool point frequency response. Given this information, process dynamics predictions for spindles that exhibit dynamic changes with rotating speed are made possible without detailed knowledge of the spindle geometry, assembly tolerances, etc. Experimental results and comparisons with prediction are provided.     

Prediction of recrystallization in investment cast single-crystal superalloys

Modelling and targeted experimentation are used to quantify the processing conditions which cause recrystallization in a single-crystal superalloy. The plasticity needed is traced to the differential thermal contractions of the metal and its ceramic mould during processing. For typical cooling rates, the plasticity causing recrystallization is induced above 1000 °C, thus over a temperature interval of approximately 300 °C after solidification is complete. The total accumulated plastic strain needed for recrystallization is estimated to be in the range of 2–3%. Modelling is used to rationalize the influence of mould thickness, stress concentration factor and geometry on the induced plasticity. Negligible plastic strains were predicted in a solid casting with no stress concentration features, as found experimentally. However, recrystallization occurred in thin-walled sections, particularly beneath shroud-like features due to the plasticity induced there. The model provides the foundation for a systems-based approach which enables recrystallization to be predicted and thus avoided in new designs of turbine blade aerofoil.     

Characterisation of phenolic acids,flavonoids, proanthocyanidins and antioxidant activity of water extracts from seed coats of marama bean [Tylosema esculentum] – an underutilised food legume

Freeze‐dried aqueous phenolic extracts with possible application as natural antioxidant functional food ingredients were prepared from marama bean seed coats by extracting with water. Phenolic acids, flavonoids and proanthocyanidins in the extracts were characterised by HPLC/MS. The major flavonoids were the flavanols methyl (epi)afzelechin‐3‐O‐gallate (40%) and methyl (epi)catechin‐3‐O‐gallate (28%), and the major phenolic acid was gallic acid (10%). Proanthocyanidins in the extracts were predominantly prodelphinidins composed of epicatechin‐3‐O‐gallate and epigallocatechin present as major terminal and extension units and epigallocatechin‐3‐O‐gallate and epicatechin present as minor extension unit constituents. The polymer structure was found to be unique compared with other legumes because of the high percentage of galloylated units. Extracts showed a high DPPH free radical scavenging activity (707 μmol TE g^?1), protective effect against AAPH‐induced human red blood cell haemolysis and copper‐catalysed human LDL oxidation suggesting that the extracts may have potential health benefits.     

Characterisation of biaxial orientation gradients in poly(ethylene terephthalate) films and bottles using polarised attenuated total reflection FTIR spectroscopy

Polarised attenuated total reflection (ATR) infrared spectroscopy has been used to quantify biaxial orientation in commercially manufactured poly(ethylene terephthalate) (PET) films and stretch-blow moulded bottles. Using a single-bounce accessory with a high refractive index element, and applying appropriate data normalisation prior to measuring band intensities, measurement of the average square direction cosines that describe the orientation is simple. Using this technique it was shown that uniaxially drawn PET films were actually biaxially oriented, and there were significant gradients in orientation through the film thickness. Bulk measurements, or methods that assume uniaxial orientation, would give incorrect results from these materials. The bottles exhibited complex orientation patterns that depended on preform and mould design, and again there were strong orientation gradients through the bottle walls. Kratky's model (pseudo-affine) was used in an attempt to predict the biaxial orientation gradients as a function of preform and bottle dimensions.