The present study demonstrates that the phenomenon of non-thickness limited (NTL) growth of anodic films in a phosphate/glycerol electrolyte at 453 K on tantalum and aluminium is due to the formation ...of porous films. For both tantala and alumina films, the resultant morphology comprises cells of material orientated approximately normal to the metal/film interface, with each cell containing a central pore of typical diameter in the range 3–15 nm and a barrier layer of film material at the base of the pore. The total porosity is about 5%. The hardness of NTL tantala films, determined by nanoindentation, was 5.1 GPa, reasonably similar to that of conventional anodic tantala.
Light from a monolithic Nd:YAG non-planar ring oscillator laser was phase modulated using a low-phase-noise 12 MHz crystal oscillator driving a LiNbO3 electro-optic modulator. An upper limit to the ...additional amplitude spectral density of the phase noise arising from the modulation process was measured to be 4 x 10 exp -8 rad/sq rt Hz over an 800-Hz bandwidth around the modulation frequency. This noise is in addition to the intrinsic phase noise of the oscillator. This is significantly less than that required by the GEO 600 gravitational wave detector. (Author)
Strikingly different morphologies of amorphous anodic films on a Mg/40 at.%Ta alloy are shown to result from single-stage and sequential anodizing procedures. The alloy, prepared by magnetron ...sputtering, was anodized galvanostatically in ammonium pentaborate (pH 8.3) and sodium silicate (pH 12.6) electrolytes at 293 K and studied by transmission electron microscopy, Rutherford backscattering spectroscopy, glow discharge optical emission spectroscopy and X-ray photoelectron spectroscopy. For one-step anodizing in the pentaborate electrolyte, a single-layered film, of approximate composition Ta
2O
5
·
MgO, forms at a ratio of ∼1.8 nm
V
−1. In the silicate electrolyte, an outer, magnesium-rich layer, containing silicon species, also forms, with a ratio of 0.8 nm
V
−1. The outer layer can develop due to relatively fast migration of magnesium ions in the inner layer and the stabilization of the pH at the film surface, probably linked to generation of a silica gel that also limits loss of magnesium species to the electrolyte. Further thickening of the anodic film, in ammonium pentaborate electrolyte, produces fingers of low resistivity, inner oxide that penetrate the pre-existing, high resistivity outer layer, with a bi-modal distribution of finger sizes. When fingers reach the film surface, magnesium ions are ejected to the electrolyte. The absence of fingers in films grown in sodium silicate electrolyte is possibly due to prevention, by the silica gel, of their initiation.
The Laboratory for Laser Energetics (LLE) experimental program supports the US inertial confinement fusion (ICF) effort by investigating the requirements for attaining ignition using direct drive ...targets. The primary tool for this research is OMEGA, a 60-beam, 351-nm, Nd:glass laser with an on-target energy capability in excess of 30 kJ. The laser is designed to ultimately achieve an irradiation uniformity of ∼1% on direct-drive capsules with shaped laser pulses (dynamic range>400:1). In addition, OMEGA provides unique capabilities for irradiating indirect-drive targets. This paper reports on a number of recent laser enhancements, including a new design for distributed phase plates (DPPs), two-dimensional smoothing by spectral dispersion (2-D SSD), distributed polarization rotators (DPRs) and laser pulse shaping. A variety of spherical-implosion, planar-target, and indirect-drive experiments attest to the versatility of the OMEGA laser. A key result is the highest thermonuclear yield (10
14 neutrons) and yield efficiency (1% of scientific breakeven) ever attained in laser fusion experiments.
We report on experiments performed to investigate the quality of supermirrors for ring-laser-gyroscopes. The principal measurement techniques employ an interferometric profilometer to probe surface ...roughness and a laser scatter meter to measure total scatter loss of supermirror coatings. Measured scatter losses are compared with those expected, given typical roughness measurements both of pre-coated substrates as well as the coated mirrors. The measurements offer insight into the general usefulness of profilometer data for the efficient qualification of substrates before cleaning and coating procedures. (Author)
The present study examines the behaviour of hydrogen impurity in an Al–6.5 at.% W alloy during anodizing, using elastic recoil detection and nuclear reaction analyses. Increased concentrations of ...hydrogen are found near the alloy/anodic film interface, amounting to ∼2×10
15 H atoms
cm
−2 for the particular alloy, containing 0.1–0.3 at.% hydrogen in the bulk regions, and conditions of anodizing. The enrichment arises from hydrogen in the alloy (i) diffusing to the interface, which acts as a trap, or (ii) accumulating at the interface, due to the growth of the anodic film, or a combination of both processes. Diffusion is consistent with the known mobility of hydrogen in aluminium near ambient temperature. Further, accumulation, and subsequent oxidation, of hydrogen are expected based on the general behaviour of alloying elements in anodized aluminium. The anodic films contained ∼0.1–0.3 at.% hydrogen, originating from either the electrolyte or the alloy.
In order to elucidate the factors controlling enrichment of alloying elements during anodic oxidation of alloys, and anodic oxidation behaviour of alloys generally, the influence of anodic film ...growth on a Ta–1.5 at.% Cu alloy has been examined by transmission electron microscopy, Rutherford backscattering spectroscopy and glow discharge optical emission spectroscopy. Contrasting with the behaviour of Al–Cu alloys, film growth proceeds without significant enrichment of copper in the tantalum alloy substrate, although a thermodynamic driving force for enrichment exists. Factors controlling the development of enriched alloy layers are considered, including influences of distributions of alloying element in the substrate, film structure and ionic transport in the anodic film. Comparisons of alloy systems suggest kinetic factors may be important, in particular the influence of film formation at the alloy/oxide interface on concentrations of vacancies and diffusion rates in the alloy layer immediately beneath the growing oxide film.
Breath analysis applied to biomedical applications has gained much momentum is recent years due to the growing research demonstrating that breath gas can provide clinically useful data. Particularly ...exciting is the area of real-time breath analysis which, when coupled with appropriately chosen target species, can offer a novel method for non-invasive patient monitoring. Here we describe the role of ethane, a breath gas of universal appeal in assessing in vivo oxidative stress (cell damage). We first present a review of emerging applications where real-time ethane monitoring could yield original new results for healthcare. We then report on results from a portable ethane spectroscopy system (accuracy better then 100 parts per trillion (1 part in 1010) over a 1 s time response) that we have developed to exploit some of these applications. By presenting some initial results from pilot studies in the life sciences, we comment on the requirements that the next stage of optical spectroscopy technology has to meet in order to benefit clinical end-users.
The aim of this study was to assess the effects of changes to the stable environment on exhaled markers of respiratory inflammation in six horses with clinical histories of recurrent airway ...obstruction. The horses were maintained for two weeks under conventional stable management (straw bedding and hay) and for two weeks on a reduced-dust regimen (paper bedding and ensiled grass), in a crossover study design. Exhaled ethane and carbon monoxide (CO) and exhaled breath condensate hydrogen peroxide (H2O2) were measured every three days under each regimen. The presence of clinical signs of airway inflammation (nasal discharge and cough) was monitored daily. The reduced-dust regimen was associated with fewer clinical signs of airway inflammation than the conventional regimen. Exhaled ethane and CO were significantly lower on the reduced-dust regimen and these markers were correlated with clinical signs of respiratory inflammation, but exhaled H2O2 was not affected by the management regimen.
