Variadic genericity through linguistic reflection : a performance evaluation

This work is partially supported by the EPSRC through Grant GR/L32699 “Compliant System Architecture” and by ESPRIT through Working Group EP22552 “PASTEL”.The use of variadic genericity within schema definitions increases the variety of databases that may be captured by a single specification. For example, a class of databases of engineering part objects, in which each database instance varies in the types of the parts and the number of part types, should lend itself to a single definition. However, precise specification of such a schema is beyond the capability of polymorphic type systems and schema definition languages. It is possible to capture such generality by introducing a level of interpretation, in which the variation in types and in the number of fields is encoded in a general data structure. Queries that interpret the encoded information can be written against this general data structure. An alternative approach to supporting such variadic genericity is to generate a precise database containing tailored data structures and queries for each different instance of the virtual schema.1 This involves source code generation and dynamic compilation, a process known as linguistic reflection. The motivation is that once generated, the specific queries may execute more efficiently than their generic counter-parts, since the generic code is “compiled away”. This paper compares the two approaches and gives performance measurements for an example using the persistent languages Napier88 and PJama.Postprin

Exploring the Synthesis, Structure, and Reactivity of Phosphorus-Chalcogen Heterocycles

In recent years, the field of low-coordinate main group chemistry has seen significant research interest due to their unique structures and unprecedented reactivity. Conversely, the area of phosphinidene chalcogenides, a low-coordinate phosphorus and chalcogen species, have yet to be thoroughly explored. In this context, this dissertation describes the synthesis of a number of phosphorus-chalcogen heterocycles that can be degraded to provide stoichiometric access to low-coordinate phosphorus species. The ability for successful P-Ch transfer relies on using a bulky m-terphenyl group at phosphorus that provides enough steric bulk to kinetically stabilize the phosphorus centre, but also accommodating enough to allow for further reactivity. Previous attempts at this chemistry have utilized more sterically accommodating ligands, however sterically demanding ligands have now been proven to be critical in controlling the fragmentation and transfer of these generated species. In Chapter 2, the synthesis of strained P-Ch heterocycles containing a 4-membered core will be discussed, as well as attempts to use these cyclic structures to gain access to low-coordinate phosphinidene chalcogenides. Chapter 3 continues from the success discussed in the previous chapter, and uses these newly generated rings as P-Ch transfer reagents for their reactions with alkynes. An alternative method of generating phosphinidene chalcogenides that mitigates the synthesis of P-Ch heterocycles will also be discussed. Chapter 4 explores the reactivity of these 4-membered rings using Lewis acids and bases, and again linking these compounds to the monomeric phosphinidene chalcogenides. Chapter 5 introduces the idea of combining two different low-coordinate phosphorus compounds (both generated from their parent dimer heterocycles) to generate a new heterocycle containing elements from Group 13, 15 and 16. The highlight of this thesis is discovering new methods of generating, and trapping phosphinidene chalcogenides. While the sulfur derivatives have been discussed in the literature, the chemistry surround the selenium compounds are unprecedented and include some of the first structural confirmation of such species. All of the compounds discussed in this thesis were characterized to the fullest extent using a range of solution and solid-state techniques, with an emphasis on NMR spectroscopy and single crystal X-ray crystallography

Demonstration of hyper-programming in Java

We demonstrate the use of a hyper-programming system to build persistent Java applications in PJama, an orthogonally persistent version of Java. This allows program representations to contain type-safe links to persistent objects embedded directly within the source code. The potential benefits include greater potential for static program checking, improved efficiency, and reduced programming effort.Postprin

From belonging to being: Engaging with ‘contexts of difference’

This paper seeks to unveil the situated struggle that students experience in comprehending the often tacit rules that govern academic practices in order to engage fully with their academic studies and develop a sense of belonging. I present a critique of the prevailing conception of student belonging, which I suggest does not effectively consider the diversity of contemporary university cohorts due to favouring social groups traditionally dominating the student body. Non-traditional students, especially those from contexts distant from Western higher education, can often struggle with developing confidence and conversance with critical thinking – a central practice of academia – which negatively impacts their experiences of belonging. My research with master’s students in three Scottish universities shows that dialogic active pedagogy can be a means for establishing belonging while also supporting some students\u27 development and demonstration of critical being across multiple domains and to transformatory levels. Such empowering participatory pedagogy, captured in the finding of ‘contexts of difference\u27, can potentially provide the means for students to adapt and establish belonging within the culture, context and subject of their learning while also enabling the development of criticality, to the highest levels, amongst some students

Manipulation of carbon media, temperature and hydraulic efficiency to increase nitrate removal rate in denitrification beds

The accumulation of reactive nitrogen (Nr) in terrestrial and aquatic environments is a global environmental issue that causes or contributes to climate change, stratospheric ozone depletion, and deterioration of coastal and terrestrial waters. Point source discharges of Nr from municipal and septic treatment systems, agricultural tile drainage, and industrial discharges contribute to these issues. Practical, low-cost methods are needed to reduce the Nr load into the environment from small-volume point source discharges. Denitrification beds are one such method. Improving the nitrate removal rate of denitrification beds will lead to reduced bed volumes, lower construction costs that likely facilitate greater uptake of the technology and reduced accumulation of Nr in the environment. The main objective of this thesis was to test a number of approaches that might increase the rate of nitrate removal rate in a denitrification bed under non-nitrate limiting conditions, including: manipulation of carbon source, temperature and hydraulic flow. To date, operational denitrification beds have used wood media as the carbon source which sustains nitrate removal rates of between 2–10 g N m-3 of media d-1 and relatively high permeability. While previous laboratory experiments have investigated the potential of alternative carbon sources, these studies were typically of short duration and small scale and did not necessarily provide reliable information for denitrification bed design purposes. To address this issue, nitrate removal, hydraulic and nutrient leaching characteristics of nine different carbon substrates were compared in 0.2 m3 barrels, at 14oC and 23.5oC over a 23 month period. The relationship between hydraulic efficiency and nitrate removal of the different media was also investigated. Findings from the barrel trial were field tested in pilot scale (2.9 m3) denitrification beds receiving municipal effluent dosed with KNO3, over a 15 month period. The pilot scale trial tested whether nitrate removal could be improved by using an alternative carbon media (maize cobs) and increasing bed temperature through passive solar heating. The influence of bed flow regime (horizontal-point, horizontal-diffuse, downflow and upflow) on hydraulic efficiency and nitrate removal was also investigated. This thesis demonstrated that more labile carbon sources, such as maize cobs, had significantly higher nitrate removal rates (15.0 to 21.8 g N m-3 d-1) than wood media (3.0 to 4.9 g N m-3 d-1) over the duration of the barrel trial. Nitrate removal rates increased with increasing temperature with mean Q10 of 1.6 for all media. The hydraulic efficiency of fragmented wood media decreased with increasing grain-size. However, nitrate removal rate was not dependent on hydraulic efficiency of the media, which was attributed to the significant secondary porosity of the media allowing denitrification to occur both on the surface and within the media particle. In the pilot scale trial, bed temperature increased by 3.4oC due to passive solar heating, but did not cause a measureable increase in nitrate removal rate due to variability in removal rates and possibly low temperature responsiveness of maize cobs for removing nitrate. Flow regime affected the hydraulic efficiency of denitrification beds and nitrate removal rates were lower in flow regimes with poor hydraulic efficiency. This was attributed to short-circuit flow reducing the bed volume that contributed to nitrate removal. The results indicate that a four-fold reduction in denitrification bed size could potentially be achieved by using maize cobs as the carbon substrate, as opposed to wood fragments, and increasing bed temperature by incorporating passive solar heating techniques. The findings of this thesis indicate that future research on improving the nitrate removal rate of denitrification beds under non-nitrate limiting conditions should focus on carbon substrates, increasing bed temperature, and hydraulic design of beds rather than on hydraulic efficiency of media. For example, research on coupling improved solar heating design with an appropriate inlet/outlet structure and location

Rich man, poor man, beggar man, thief : accounting and the stigma of poverty

In this paper, we examine the roles of accounting in two institutions dealing with poverty in Toronto during the 1920s. We draw on Georg Simmel’s influential insights on poverty to explore how accounting for poverty alleviation programs helps structure the relationship between rich and poor in society. We argue that accounting serves to bridge the social distance between rich and poor while insulating the rich from the stigma of the poor. This enables the rich to benefit from their efforts to assist the poor, ensuring the legitimation of wealth and the continued existence of poverty. Our analysis of these two historical institutions helps us comprehend some of the roles of accounting in poverty alleviation today