Measurement of atmospheric HO by a chemical method

The parameters for a chemical technique can be outlined from the following set of desirable goals: (1) sufficient conversion of tracer species A to product B that B can be measured quantitatively in the presence of A and a great excess of air; (2) specificity of reaction such that A is converted to B only by reaction with HO; and (3) sufficient sensitivity for detection that the ambient concentration of HO is not seriously perturbed by the presence of A and B. This proposed study involves finding a chemical reaction specific enough for OH, and a measurement of the product formed. What one wants is a rate constant of about 10 to the -10th power cu cm/s, so that 0.1 percent of the OH will be converted in 100 s. Laboratory studies are needed to find a reaction which will fill this bill, yielding a product in quantity sufficient for precise measurement. This is an extremely fast constant and the search may be difficult. Again there is a question of perturbing the local environment, while still providing a sensitive measurement. Also the temperature and pressure dependence of the reaction rate is a complicated function for many of these species (that is, one must use a RRKM or Troe-based picture), and must be taken into account

Micromechanics of oxides - From complex scales to single crystals

Protective oxide scales shield high temperature materials from corrosion, thus ensuring safety and long material life under adverse operating conditions. Cracking and spallation of such scales can lead to fatigue crack initiation and expose the material to further oxidation. It is therefore imperative to measure the fracture properties of oxides so that they can be incorporated in the life estimation models of high temperature materials. Existing models require inputs on oxide properties such as fracture strain and elastic modulus. The established measurement methods are mainly applied for thick (several microns) scales, but for many materials such as superalloys the oxides are thinner (< 1 \ub5m), and the results would be affected by the influence of substrate and residual stresses. Focused ion beam machining (FIB) enables the preparation of micro sized specimens in the size range of these scales. \ua0In this work, a modified microcantilever geometry with partially removed substrate is proposed for testing of oxide scales. Room temperature microcantilever bending of thermally grown superalloy oxide (complex oxide with an upper layer of spinel and lower layer of Cr2O3) revealed the presence of plasticity, which is attributed to the deformation of the upper cubic spinel layer and low defect density of the volume being probed. Due to difficulties in isolating Cr2O3 from the complex oxide layer, dedicated oxidation exposures are performed on pure chromium to generate Cr2O3 which is tested using the same cantilever geometry at room temperature and 600 \ub0C. Results show lower fracture strain at 600 \ub0C in comparison to room temperature and presence of cleavage type of transgranular fracture in both cases, pointing to a need for studying cleavage fracture of Cr2O3. This was analysed using microcantilever bending of single crystal Cr2O3 to identify the preferential cleavage planes. Finally, fracture toughness was also measured through microcantilever bending and micropillar splitting. \ua0Thus, it is shown that micromechanical testing is an effective tool for measuring fracture properties of oxide scales. The fracture study of Cr2O3 scales show that it is a complex process in which the crystallographic texture also plays a role. Surface energy and fracture toughness criterion was unable to explain the fracture behaviour of single crystal Cr2O3 observed from experiments. Such a comprehensive analysis can contribute towards the development of reliable models for oxidation assisted failure

Radiofrequency Ablation vs Conventional Surgery for Varicose Veins – a Comparison of Treatment Costs in a Randomised Trial

AbstractObjectiveTo compare the costs involved (from procedure to recovery) following radiofrequency ablation and conventional surgery for lower limb varicose veins in a selected population.DesignProspective randomised controlled trial.MethodsPatients with symptomatic great saphenous varicose veins suitable for radiofrequency ablation were randomised to either RF ablation or surgery (sapheno-femoral ligation and stripping). The hospital, general practice and patient costs incurred until full recovery and the indirect cost to society, due to sickness leave after surgery, were calculated to indicate mean cost per patient under each category.ResultsNinety three patients were randomised. Eighty eight patients (47 – RF ablation, 41 – surgery) underwent the allocated intervention. Ablation took longer to perform than surgery (mean 76.8 vs 47.0min, p<.001). Ablation was more expensive (mean hospital cost per patient £1275.90 vs £559.13) but enabled patients to return to work 1week earlier than after surgery (mean 12.2 vs 19.8days, p=0.006). Based on the Annual Survey of Hours and Earnings (Office of National Statistics, UK) for full time employees, the cost per working hour gained after ablation was £6.94 (95% CI 6.26, 7.62).ConclusionThe increased cost of radiofrequency ablation is partly offset by a quicker return to work in the employed group (ISRCTN29015169http://www.controlled-trials.com)

Standardisation of specification for different trolling lures

Fishing experiments were conducted with buffalo horn, wooden and galvanised iron jigs of different lengths and weights rigged in troll lines. It was observed that jigs with 12 cm length and 60 g weight were superior to others in luring seer fish. Fish head jigs of 60 g weight showed a higher efficiency index than those of 50 and 70 g tried in these studies

Cyclic Deformation of Microcantilevers Using In-Situ Micromanipulation

Background: The trend in miniaturisation of structural components and continuous development of more advanced crystal plasticity models point towards the need for understanding cyclic properties of engineering materials at the microscale. Though the technology of focused ion beam milling enables the preparation of micron-sized samples for mechanical testing using nanoindenters, much of the focus has been on monotonic testing since the limited 1D motion of nanoindenters imposes restrictions on both sample preparation and cyclic testing.Objective/Methods: In this work, we present an approach for cyclic microcantilever bending using a micromanipulator setup having three degrees of freedom, thereby offering more flexibility.Results: The method has been demonstrated and validated by cyclic bending of Alloy 718plus microcantilevers prepared on a bulk specimen. The experiments reveal that this method is reliable and produces results that are comparable to a nanoindenter setup.Conclusions: Due to the flexibility of the method, it offers straightforward testing of cantilevers manufactured at arbitrary position on bulk samples with fully reversed plastic deformation. Specific microstructural features, e.g., selected orientations, grain boundaries, phase boundaries etc., can therefore be easily targeted

Effect of weight of otter boards on the horizontal opening of trawl nets

The paper gives briefly the experiments carried out to determine the optimum weight of otter board that should be used for a trawl gear for better efficiency

On the troll line investigations off Cochin during five fishing seasons. Pt. 3. Investigations during 1965-66 and 1966-67 seasons

During these two seasons investigations were carried out with a view to exploring the possibility of this operation on commercial basis and to study the effect of certain meteorological factors on catch

Evolution of suitable trawl nets for medium size trawlers - 1: Comparative fishing efficiency between 32 m bulged belly, long wing and four panel trawls

Comparative studies of the efficiency of 32 m bulged belly, long wing and four panel trawls have shown that the bulged belly trawl to be superior to the other nets in catching bottom fishes and column fishes. 40% of the bottom fishes and 48% of the column fishes were caught by the bulged belly trawl. However, for prawn catch, the long wing trawl appears to be better as it landed 52% of the total prawn catch of the three nets. Bulged belly trawl was found to be next only to long wing trawl in this respect

Effect of sailkite in improving trawl gear performance

Effectiveness of sailkite has been evaluated in two trawl designs, namely, a 25m high opening trawl and a 32m large mesh demersal trawl, rigged with sailkite through full scale comparative field trials. A 25m high opening trawl showed significant increase in total catch by 54.4% ribbon fish (Trichiurus spp.) alone by 138.3% with a reduction in miscellaneous catch, comprising mostly small sciaenids and juvenile fish, by 13.2% while 32m large mesh demersal trawl showed an improvement in total catch by 9%, ribbon fish by 17.2% and miscellaneous catch by 7.7%. The difference in fishing performance between the two gear arrangements has been attributed to changed net mouth configuration because of higher head line lift and also the possible herding effect on the fish in the vicinity of trawl mouth, due to addition of sailkite

Relationship between suspicious coincidence in natural images and contour-salience in oriented filter responses

Salient contour detection is an important lowlevel visual process in the human visual system, and has significance towards understanding higher visual and cognitive processes. Salience detection can be investigated by examining the visual cortical response to visual input. Visual response activity in the early stages of visual processing can be approximated by a sequence of convolutions of the input scene with the difference-of-Gaussian (DoG) and the oriented Gabor filters. The filtered responses are unusually high for prominent edge locations in the image, and are uniformly similar across different natural image inputs. Furthermore, such a response follows a power law distribution. The aim of this thesis is to examine how these response properties could be utilized to the problem of salience detection. First, I identify a method to find the best threshold on the response activity (orientation energy) toward the detection of salient contours: compare the response distribution to a Gaussian distribution of equal variance. Second, I justify this comparison by providing an explanation under the framework of Suspicious Coincidence proposed by Barlow [1]. A connection is provided between perceived salience of contours and the neuronal goal of detecting suspiciousness, where salient contours are seen as affording suspicious coincidences by the visual system. Finally, the neural plausibility of such a salience detection mechanism is investigated, and the representational effciency is shown which could potentially explain why the human visual system can effortlessly detect salience