Dynamic and mass transfer phenomena of spherical capped bubbles

Imperial Users onl

Causally Symmetric Bohm Model

The aim of this paper is to construct a version of Bohm’s model that also includes the existence of backwards-in-time influences in addition to the usual forwards causation. The motivation for this extension is to remove the need in the existing model for a preferred reference frame. As is well known, Bohm’s explanation for the nonlocality of Bell’s theorem necessarily involves instantaneous changes being produced at space-like separations, in conflict with the “spirit” of special relativity even though these changes are not directly observable. While this mechanism is quite adequate from a purely empirical perspective, the overwhelming experimental success of special relativity (together with the theory’s natural attractiveness), makes one reluctant to abandon it even at a “hidden” level. There are, of course, trade-offs to be made in formulating an alternative model and it is ultimately a matter of taste as to which is preferred. However, constructing an explicit example of a causally symmetric formalism allows the pros and cons of each version to be compared and highlights the consequences of imposing such symmetry. In particular, in addition to providing a natural explanation for Bell nonlocality, the new model allows us to define and work with a mathematical description in 3-dimensional space, rather than configuration space, even in the correlated many-particle case

Autonomous Underwater Vehicles as Tools for Deep-Submergence Archaeology

Marine archaeology beyond the capabilities of scuba divers is a technologically enabled field. The tool suite includes ship-based systems such as towed side-scan sonars and remotely operated vehicles, and more recently free-swimming autonomous underwater vehicles (AUVs). Each of these platforms has various imaging and mapping capabilities appropriate for specific scales and tasks. Broadly speaking, AUVs are becoming effective tools for locating, identifying, and surveying archaeological sites. This paper discusses the role of AUVs in this suite of tools, outlines some specific design criteria necessary to maximize their utility in the field, and presents directions for future developments. Results are presented for a recent joint AUV–towed system survey and a demonstration of current mine-hunting technologies applied to archaeology

Mathematics Disability vs. Learning Disability: A 360 Degree Analysis

A fundamental issue for research in mathematics disability (MD) and reading disability (RD) is: If these disabilities are clearly distinct, why is there so high a level of comorbidity, together with the converse; if these disabilities are so similar, why are there clear differences in underlying causes and aetiology? In order to address this puzzle, we introduce the “360 degree analysis” (360DA) framework and apply it to the overlap between RD and MD. The 360DA process starts by analyzing the issue from four perspectives: theoretical, developmental, affective, and pedagogical. Under 360DA, these analyses are then integrated to provide insights for theory, and for individual assessment and support, together with directions for future progress. The analyses confirm extensive similarities between arithmetic and reading development in terms of rote learning, executive function (EF), and affective trauma, but also major differences in terms of the conceptual needs, the motor coordination needs, and the methods of scaffolding. In terms of theory, commonalities are interpreted naturally in terms of initial general developmental delay followed by domain-independent affective trauma following school failure. Dissociations are interpreted in terms of cerebellar vs. hippocampal learning networks, sequential vs. spatial processing, and language vs. spatial scaffolding, with a further dimension of the need for accurate fixation for reading. The framework has significant theoretical and applied implications

Post-Harvest to Consumer Driver Review of the Aquatic Supply Chain

This paper provides an overview of the key current features of the international markets for aquatic food and appraises how the future drivers of the post-harvest/consumption aspects of the value chain will interact. This encompasses product from both wild capture fisheries and aquaculture. Here, ‘post-harvest’ covers all those activities involved in delivering aquatic products from the water to the plate, in particular those concerned with their processing and trading. The system is highly diverse, and a wide range of aquatic species and products, changing patterns of demand and supply, in a spectrum of cultural, economic and political contexts give rise to a variety of post-harvest configurations and future directions. The only constant across the sector is product perishability, at higher rates than for most terrestrial foods, and a critical element to be managed if values are to be delivered without loss and if the potential for adding value can be realised

The Physical Meaning of Time-Delayed Collection Field Transients from Disordered Devices

Charge carrier mobility and recombination determine the performance of many opto-electronic devices such as solar cells, sensors and light-emitting diodes. Understanding how these parameters change as a function of material choice, charge carrier density and device geometry is essential for developing the next generation of devices. The Time-Delayed-Collection-Field technique (TDCF) is becoming a widely used method to measure both recombination and carrier transport with values derived from this method being widely reported for many material systems. However, most novel materials are highly disordered with a high density of trap states and standard TDCF-theory neglects the influence of these states. In this work we examine how reliable TDCF can be as a measurement technique when the device contains significant energetic disorder. We identify regimes where the results can be relied upon and where the results should be taken with more caution. Finally, we provide simple and easy to use experimental tests to help the experimentalist decide if the physical processes are dominated by trap states

The ruminal metabolism of lactic acid.

Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1977.Abstract available in PDF file

Immunology of the protein toxin of bacterial insect pathogens

The toxicity for certain insect larvae of the parasporal protein crystal of the bacterium Bacillus thuringiensis is well documented. There is evidence that the crystal is a protoxin which is activated to form a toxin by digestion in the insect gut. It is believed that difference in host-specificity and toxicity of strains of B. thuringiensis may be reflected by differences in the composition of the crystal toxins. A method was developed for the isolation of pure crystals from mature cultures of B. thuringiensis consisting of 50% spores and 50% crystals. The method is essentially a 2-stage process; in the first stage a flotation technique removes.60% of the spores from the mixture and in the second stage a phase separation technique completes the purification. 60-65% of the crystals were recovered from the culture at a purity of 99%. Preparations of crystals from 23 strains of B. thuringiensis were used to prepare antisera. A selection from these antisera enabled an antigenic analysis of solutions of the crystals from 94 strains of B. thuringiensis to be carried out using the Ouchterlony gel diffusion technique. Although crystals stimulated production of only one antibody, solutions of many of the crystals contained several antigens. The 94 strains were divisible into 32 groups on the basis of the antigens of crystal solutions. Altogether 11 different crystal antigens were distinguished in the strains of B. thuringiensis investigated. Crystals from 93 strains of B. thuringiensis were digested by the gut juice of larvae of Pieris brassicae. Ouchterlony gel diffusion indicated that digestion of the crystals resulted in loss of 4 out of the 11 antigens detected in crystal solutions; other antigens were more resistant to digestion. Some antigens not detectable in the crystal solutions appeared in the digests. The antigenic composition of crystal digests was less varied than that of crystal solutions. 2 The soluble products of digestion of crystals of the Berliner strain of B. thuringiensis were investigated by gel filtration. Two fractions were separated: fraction C1 was composed of material of molecular weight 200,000 and fraction C2 was composed of material of molecular weight 5,000-10,000. Fraction C1 was not toxic on injection into the haemocoel of larvae of P. brassicae although fraction C2 was toxic by this route and so is believed to contain the activated toxin. Digestion experiments also indicated that fraction C1 was the precursor of fraction C2 in the digestion process. 3 antigens were detected in fraction C2 of the crystal digest. A gel filtration technique was designed to investigate the association of the antigens present in fraction C2 with particular molecules. Gel filtration of mixtures of monospecific antisera and fraction C2 indicated that the 3 antigens in fraction C2 were present as different antigenic sites on one peptide molecule. These mixtures were fed to larvae of P. brassicae. The results indicated that one of the 3 antigens was necessary for the toxic function of fraction 02. Neutralisation of the other 2 antigens individually had no apparent effect on toxicity; neutralisation of both of these antigens together reduced toxicity. Evidence is presented to suggest that the protoxin crystal is activated by insect gut juices by digestion to yield a single toxic fraction of comparatively low Molecular weight

Aftermath of Munich: Strategic priorities in British rearmament October 1938 - August 1939.

Slessor, Douglas, Spaight et al justified the Munich Agreement as providing a 'breathing space' to accelerate British rearmament. Whilst Chamberlain realised Britain's military weakness, feared a German 'knock-out blow', and underestimated the Czech Army, his prime motive was to prevent, not postpone, a war which he abhorred. Nevertheless he realised the need to accelerate defensive measures such as fighter aircraft, anti-aircraft guns and civil defence. Anxieties that Germany would invade Holland, seizing strategic airfields and the Channel Ports, over ruled the policy of 'limited Liability'. French pressure, and Lord Halifax's support enabled Hore-Belisha to raise equipment for an enlarged field force. Chamberlain opposed conscription for fear of alienating the trade unions; whilst he believed a Ministry of Supply would lose industrialists' co-operation with rearmament and undermine economic recovery. Hitler's Czechoslovakian coup, French requests for an appropriately enlarged British field force and the Premier's desire for a permanent couverture of anti-aircraft guns, combined to beget conscription. Disclosure of 50-60 week delays for deliveries of machine tools finally ended opposition to a Ministry of Supply. Extensions of subcontracting and the shadow factory system enabled British aircraft production to match Germany's by September 1939. By then both Fighter and Bomber Command enjoyed improvements in number and quality. Radar now covered most of Britain. However Germany gained considerably by annexing Czechoslovakia. She seized equipment for 15 infantry divisions. Czech tanks provided three additional armoured divisions in 1940. Greater Germany was the second largest Industrial power and less vunerable to blockade. Mismanagement denied her the heavy bombers and submarines necessary to defeat Britain. Had Britain acted with greater urgency to establish a Ministry of Supply and provide a substantial field force, the Battle of France might have been extended or even won, thus postponing or avoiding the Battle of Britain