Thermoluminescence and optically stimulated luminescence of gamma-irradiated mineral zircon

Thermoluminescence (TL) manifested by gamma-irradiated mineral zircon has shown a strong TL peak at about 165 °C which is due to recombination of electrons and Dy3+ related shallow hole traps. After they have been removed by a short preheat we have observed two TL peaks at 300-320 °C and ≈420 °C, which are mainly due to recombination of electrons and Tb3+ related hole traps centres yielding its characteristic luminescence. The experimental results indicate that optically stimulated luminescence (OSL) is due to luminescent emission of Tb3+ ions and [SiO4]4– groups. The deep traps related to the 420 °C TL peak contribute to the Tb3+ related OSL. The deep traps related to the 300-320 °C TL peak contribute to OSL associated with the luminescent emission of [SiO4]4– groups.

Changing the substrate specificity of arogenate dehydratases (ADTs) from Arabidopsis thaliana.

Phenylalanine (Phe), an essential aromatic amino acid, serves as a precursor for protein synthesis and a variety of secondary metabolites in plants. Two pathways are known for Phe biosynthesis. In the first, prephenate dehydratases (PDTs) convert prephenate to phenylpyruvate, which is transaminated to Phe. In the second, prephenate is transaminated to arogenate, which is converted to Phe by arogenate dehydratases (ADTs). ADTs and PDTs are structurally very similar, as are their substrates. Six ADTs (ADT1-ADT6) have been identified in Arabidopsis thaliana. ADT1 and ADT2 can recognize both prephenate and arogenate as substrates whereas ADT3-ADT6 are solely arogenate-accepting. Twenty ADT domain-swapping chimeras were generated through overlap extension PCR and were tested for PDT function in a pha2 complementation assay. Through targeted mutagenesis it was identified that a single substitution in ADT5 was sufficient to introduce PDT function to this previously solely arogenate-accepting ADT. This research represents the first identification of an amino acid that discriminates an arogenate-only ADT from an ADT that is able to accept prephenate

Imaging of Impact Damage in Composite Materials

Conventional ultrasonic C-scan images are generated from information acquired within “gates” placed at specific temporal locations on low-pass filtered and rectified versions of A-scans. Placing the gates at temporal locations which correspond with interfaces allows the integrity of the interfaces to be examined. However, if the interfaces are closely spaced, as is the case for quasi-isotropic graphite/epoxy composites, the information from upper layers is blurred into the layers below because of the finite time duration of the ultrasonic pulse. This creates a low signal-to-background-level ratio, which causes blurring at and below the first interface

Holistic obstetrics and gynaecology mind maps teaching an easy-to-use tool provides equality of learning, teaching, and assessment

Aim: A pilot study was conducted to evaluate the learning benefits of holistic Obstetrics and Gynaecology mind maps (HOGMMs) in acquiring a range of clinical skills, standardizing assessment, and teaching methods. Methodology: HOGMMs were developed and had been used as a teaching tool for Year 3 medical students (n=113) for 6 months in between January and July 2016 as a tool to assist their learning during their Obstetrics and Gynaecology (OG) rotation. The HOGMMs were taught to all Year 3 medical students and a soft copy of the tool was shared with them as a reference for their use during their clinical placement in OG rotation. After the completion of their OG rotation, students were invited to complete a questionnaire assessing perceived benefits for skill acquisition, and standardizing assessment and teaching methods. Results: The majority of students believed HOGMMs was a useful learning tool across a range of parameters (min = 59%; n = 96). Students who believed HOGMMs to be useful for standardising assessment were more likely to report mutual benefits in terms of student learning (χ2=35.836; P=0.0005) and standardising teaching methods (χ2=20.256; P =0.0005). Conclusion: This study suggests that students’ value our HOGMM’s not only for developing clinical skills but also standardising assessment and teaching methods

Divalent metal inhibition of non-haem iron uptake across the rat duodenal brush border membrane

Duodenal Fe2+ uptake is essential to body Fe2+ homeostasis, but the interaction of metals with the uptake process remains unclear. The present study compared the effects of four essential trace metals (Mn2+, Zn2+, Co2+ and Ni2+) with two toxic metals (Pb2+ and Cd2+) on Fe2+ uptake across the brush border membrane of villus-attached duodenal enterocytes. Everted rat duodenum was exposed to buffer containing 0.2 mm-Fe-59(2+)-ascorbate with or without the competing metal (2 mm) and the tissue was then processed for autoradiography allowing Fe2+ uptake to be determined at specific crypt-villus regions. The quantification method ensured that uptake by cells, rather than Fe2+ binding to the tissue surface, was measured. Fe2+ uptake was significantly inhibited by Cd2+ in upper villus enterocytes only and Pb2+ was without effect on Fe2+ uptake. The inhibition by Cd2+ was not due to general cell damage as judged by the release of lactate dehydrogenase from tissue into incubation fluid. Essential divalent trace metals reduced uptake significantly along the whole length of the crypt-villus axis. Cd2+ uptake, measured separately, took place at all regions of the villus-crypt axis, highest uptake being into crypt enterocytes. The very different uptake profiles for Cd2+ and Fe2+ suggests that the divalent metal transporter 1 is not the principal transporter of Cd2+. The addition of Fe2+ to incubation buffer inhibited Cd2+ uptake by both crypt and villus enterocytes. The possibility that the inhibitory actions of Fe2+ and Cd2+ on the uptakes of Cd2+ and Fe2+ respectively can be explained by a non-competitive action or the involvement of an additional metal transporter is discussed

Gradient flux measurements of sea–air DMS transfer during the Surface Ocean Aerosol Production (SOAP) experiment

Direct measurements of marine dimethylsulfide (DMS) fluxes are sparse, particularly in the Southern Ocean. The Surface Ocean Aerosol Production (SOAP) voyage in February–March 2012 examined the distribution and flux of DMS in a biologically active frontal system in the southwest Pacific Ocean. Three distinct phytoplankton blooms were studied with oceanic DMS concentrations as high as 25 nmol L−1. Measurements of DMS fluxes were made using two independent methods: the eddy covariance (EC) technique using atmospheric pressure chemical ionization–mass spectrometry (API-CIMS) and the gradient flux (GF) technique from an autonomous catamaran platform. Catamaran flux measurements are relatively unaffected by airflow distortion and are made close to the water surface, where gas gradients are largest. Flux measurements were complemented by near-surface hydrographic measurements to elucidate physical factors influencing DMS emission. Individual DMS fluxes derived by EC showed significant scatter and, at times, consistent departures from the Coupled Ocean–Atmosphere Response Experiment gas transfer algorithm (COAREG). A direct comparison between the two flux methods was carried out to separate instrumental effects from environmental effects and showed good agreement with a regression slope of 0.96 (r2 = 0.89). A period of abnormal downward atmospheric heat flux enhanced near-surface ocean stratification and reduced turbulent exchange, during which GF and EC transfer velocities showed good agreement but modelled COAREG values were significantly higher. The transfer velocity derived from near-surface ocean turbulence measurements on a spar buoy compared well with the COAREG model in general but showed less variation. This first direct comparison between EC and GF fluxes of DMS provides confidence in compilation of flux estimates from both techniques, as well as in the stable periods when the observations are not well predicted by the COAREG model

On the Effectiveness of Dry Film Lubricant Coatings in Reducing Automotive Valve Train Wear

The effect of three dry lubricants on automotive valve train wear resistance was studied experimentally. Scuffing wear occurs as the cam slides across the lifter face where the rotating motion of the camshaft is converted into the linear motion necessary to drive the cylinder head valves. This scuffing is caused by localized microscopic bonding between the skidding surfaces. It can be minimized by using dry film lubricant coatings to increase the boundary lubrication depth adjacent to the contact area. To compare valve train wear resistance in the laboratory, rotating cam lobes coated with dry lubricants--parkerization, spray-applied graphite coating, and brush-applied molybdenum disulfide coating-were pressed against valve lifters that were constrained in a fixture. The brush-applied molybdenum disulfide coating was the most effective of the three tested lubricants in reducing scuffing wear

Using eddy covariance to measure the dependence of air–sea CO2 exchange rate on friction velocity

Parameterisation of the air–sea gas transfer velocity of CO2 and other trace gases under open-ocean conditions has been a focus of air–sea interaction research and is required for accurately determining ocean carbon uptake. Ships are the most widely used platform for air–sea flux measurements but the quality of the data can be compromised by airflow distortion and sensor cross-sensitivity effects. Recent improvements in the understanding of these effects have led to enhanced corrections to the shipboard eddy covariance (EC) measurements. Here, we present a revised analysis of eddy covariance measurements of air–sea CO2 and momentum fluxes from the Southern Ocean Surface Ocean Aerosol Production (SOAP) study. We show that it is possible to significantly reduce the scatter in the EC data and achieve consistency between measurements taken on station and with the ship underway. The gas transfer velocities from the EC measurements correlate better with the EC friction velocity (u*) than with mean wind speeds derived from shipboard measurements corrected with an airflow distortion model. For the observed range of wind speeds (u10 N = 3–23 m s−1), the transfer velocities can be parameterised with a linear fit to u*. The SOAP data are compared to previous gas transfer parameterisations using u10 N computed from the EC friction velocity with the drag coefficient from the Coupled Ocean–Atmosphere Response Experiment (COARE) model version 3.5. The SOAP results are consistent with previous gas transfer studies, but at high wind speeds they do not support the sharp increase in gas transfer associated with bubble-mediated transfer predicted by physically based models

Dialkyldithiophosphate Acids (HDDPs) as Effective Lubricants of Sol–Gel Titania Coatings in Technical Dry Friction Conditions

The goal of this study was the investigation of the effectiveness of dialkyldithiophosphate acids (HDDPs) films in improving the tribological properties of thin, sol– gel derived titania coatings. Amorphous, anatase, and rutile titania coatings were obtained using sol–gel dip–coating deposition after treatment at 100, 500, and 1,000 C, respectively. Titania coatings were then modified from the liquid phase by HDDPs acids having dodecyl-(C12), tetradecyl-(C14), and hexadecyl-(C16) alkyl chains deposited by dip–coating (DC) and Langmuir–Blodgett (LB) methods. The influence of the deposition procedure, the length of the HDDPs alkyl chain and the type of titania substrate on the surface morphology and tribological properties were studied. It was found, using wetting contact angle measurements, that these modifications of titania coatings decrease the surface free energy and increase its hydrophobicity. The surface topography imaged by Atomic force microscopy (AFM), exhibit island-like or agglomerate features for the DC deposition method, while smooth topographies were observed for LB depositions. Tribological tests were conducted by means of a microtribometer operating in the normal load range 30–100 mN. An enhancement of tribological properties was observed upon modification, as compared to unmodified titania