Velocities of compressional and shear waves in limestones

Carbonate rocks are important hydrocarbon reservoir rocks with complex textures and petrophysical properties (porosity and permeability) mainly resulting from various diagenetic processes (compaction, dissolution, precipitation, cementation, etc.). These complexities make prediction of reservoir characteristics (e.g. porosity and permeability) from their seismic properties very difficult. To explore the relationship between the seismic, petrophysical and geological properties, ultrasonic compressional- and shear-wave velocity measurements were made under a simulated in situ condition of pressure (50 MPa hydrostatic effective pressure) at frequencies of approximately 0.85 MHz and 0.7 MHz, respectively, using a pulse-echo method. The measurements were made both in vacuum-dry and fully saturated conditions in oolitic limestones of the Great Oolite Formation of southern England. Some of the rocks were fully saturated with oil. The acoustic measurements were supplemented by porosity and permeability measurements, petrological and pore geometry studies of resin-impregnated polished thin sections, X-ray diffraction analyses and scanning electron microscope studies to investigate submicroscopic textures and micropores. It is shown that the compressional- and shear-wave velocities (V-p and V-s, respectively) decrease with increasing porosity and that V-p decreases approximately twice as fast as V-s. The systematic differences in pore structures (e.g. the aspect ratio) of the limestones produce large residuals in the velocity versus porosity relationship. It is demonstrated that the velocity versus porosity relationship can be improved by removing the pore-structure-dependent variations from the residuals. The introduction of water into the pore space decreases the shear moduli of the rocks by about 2 GPa, suggesting that there exists a fluid/matrix interaction at grain contacts, which reduces the rigidity. The predicted Biot-Gassmann velocity values are greater than the measured velocity values due to the rock-fluid interaction. This is not accounted for in the Biot-Gassmann velocity models and velocity dispersion due to a local flow mechanism. The velocities predicted by the Raymer and time-average relationships overestimated the measured velocities even more than the Biot model.

Annular variability and eddy-zonal flow interactions in a simplified atmospheric GCM. Part 1: Characterization of high and low frequency behaviour

Experiments have been performed using a simplified, Newtonian forced, global circulation model to investigate how variability of the tropospheric jet can be characterized by examining the combined fluctuations of the two leading modes of annular variability. Eddy forcing of this variability is analyzed in the phase space of the leading modes using the vertically integrated momentum budget. The nature of the annular variability and eddy forcing depends on the time scale. At low frequencies the zonal flow and baroclinic eddies are in quasi equilibrium and anomalies propagate poleward. The eddies are shown primarily to reinforce the anomalous state and are closely balanced by the linear damping, leaving slow evolution as a residual. At high frequencies the flow is strongly evolving and anomalies are initiated on the poleward side of the tropospheric jet and propagate equatorward. The eddies are shown to drive this evolution strongly: eddy location and amplitude reflect the past baroclinicity, while eddy feedback on the zonal flow may be interpreted in terms of wave breaking associated with baroclinic life cycles in lateral shear.

An observing system simulation experiment to evaluate the scientific merit of wind and ozone measurements from the future SWIFT instrument

(from author) One of the first papers in the peer-review literature to discuss an OSSE to evaluate future wind observations in the stratosphere. Provides key evidence to justify the construction of the SWIFT instrument (currently planned to be built by the Canadian Space Agency for launch on ~ 2010).

Evolution of micromorphological and chemical characters in the lichen-forming fungal family Pertusariaceae

Micromorphological characters of the fruiting bodies, such as ascus-type and hymenial amyloidity, and secondary chemistry have been widely employed as key characters in Ascomycota classification. However, the evolution of these characters has yet not been studied using molecular phylogenies. We have used a combined Bayesian and maximum likelihood based approach to trace character evolution on a tree inferred from a combined analysis of nuclear and mitochondrial ribosomal DNA sequences. The maximum likelihood aspect overcomes simplifications inherent in maximum parsimony methods, whereas the Markov chain Monte Carlo aspect renders results independent of any particular phylogenetic tree. The results indicate that the evolution of the two chemical characters is quite different, being stable once developed for the medullary lecanoric acid, whereas the cortical chlorinated xanthones appear to have been lost several times. The current ascus-types and the amyloidity of the hymenial gel in Pertusariaceae appear to have been developed within the family. The basal ascus-type of pertusarialean fungi remains unknown. (c) 2006 The Linnean Society of London, Biological Journal of the Linnean Society, 2006, 89, 615-626.

Architect and user interaction: The spoken representation of form and functional meaning

The paper is an investigation of the exchange of ideas and information between an architect and building users in the early stages of the building design process before the design brief or any drawings have been produced. The purpose of the research is to gain insight into the type of information users exchange with architects in early design conversations and to better understand the influence the format of design interactions and interactional behaviours have on the exchange of information. We report an empirical study of pre-briefing conversations in which the overwhelming majority of the exchanges were about the functional or structural attributes of space, discussion that touched on the phenomenological, perceptual and the symbolic meanings of space were rare. We explore the contextual features of meetings and the conversational strategies taken by the architect to prompt the users for information and the influence these had on the information provided. Recommendations are made on the format and structure of pre-briefing conversations and on designers' strategies for raising the level of information provided by the user beyond the functional or structural attributes of space.

Doctoral supervision of colleagues: peeling off the veneer of satisfaction and competence

The nexus of teaching, administration and research activities engaged in by academic staff in higher education means that each individual plays a multitude of roles in relation to colleagues, producing inevitable tensions. One role relationship that epitomizes this extraordinary juggling task is that of doctoral supervisor/supervisee, when both are academic staff in the same institution. The last 10 years has seen an upsurge of research interest in doctoral research students, and government and funding bodies have imposed ever more stringent requirements on supervisors. However, staff pairings have been ignored in this literature and research. This article reports on an exploration that seeks to redress this omission by giving voice to the participants (colleague supervisor or research student), allowing them to articulate constructs about what may be unique in the interaction, thus highlighting factors that support or impede success in the enterprise.

Doctoral supervision of colleagues: peeling off the veneer of satisfaction and competence

The nexus of teaching, administration and research activities engaged in by academic staff in higher education means that each individual plays a multitude of roles in relation to colleagues, producing inevitable tensions. One role relationship that epitomizes this extraordinary juggling task is that of doctoral supervisor/supervisee, when both are academic staff in the same institution. The last 10 years has seen an upsurge of research interest in doctoral research students, and government and funding bodies have imposed ever more stringent requirements on supervisors. However, staff pairings have been ignored in this literature and research. This article reports on an exploration that seeks to redress this omission by giving voice to the participants (colleague supervisor or research student), allowing them to articulate constructs about what may be unique in the interaction, thus highlighting factors that support or impede success in the enterprise.

Comparison of subspace and ARX models of a waveguide's terahertz transient response after optimal wavelet filtering

A quasi-optical deembedding technique for characterizing waveguides is demonstrated using wide-band time-resolved terahertz spectroscopy. A transfer function representation is adopted for the description of the signal in the input and output port of the waveguides. The time-domain responses were discretized and the waveguide transfer function was obtained through a parametric approach in the z-domain after describing the system with an AutoRegressive with eXogenous input (ARX), as well as with a state-space model. Prior to the identification procedure, filtering was performed in the wavelet domain to minimize both signal distortion, as well as the noise propagating in the ARX and subspace models. The optimal filtering procedure used in the wavelet domain for the recorded time-domain signatures is described in detail. The effect of filtering prior to the identification procedures is elucidated with the aid of pole-zero diagrams. Models derived from measurements of terahertz transients in a precision WR-8 waveguide adjustable short are presented.

The language of poverty: an exploration of the narratives of the poor

Within the development discourse, the narratives of the poor are a well utilized rhetorical tool to describe poverty and its causes. However, narratives can also reveal the beliefs and ‘world-view’ of the narrators. To explore this influence, the authors applied a discursive approach, to deconstruct the narratives of 101 slum dwellers in Kibera, Nairobi. The results revealed that poverty was largely attributed to external constraints, beyond an individual's control. Despite wanting a better life, participants held low expectations for the future. Hopes and dreams were placed on their children. While risk and uncertainty was a constant theme, large differences were found between genders as to the aspirations for the future. Copyright © 2009 John Wiley & Sons, Ltd and ERP Environment.

Commercial property loan valuations in the UK : the changing landscape of practice and liability

This paper is the first of two which aim to examine the major legal liability implications of changes to the commercial property loan valuation process caused by the recession in the UK property market and to make recommendations to valuers and their professional institutions to improve the quality of the process and the result. This paper identifies the market background to commercial property lending and discusses the implications of the falls in value for lenders and valuers. These include two major strands; first, the outcome of discussions between the representative bodies of these two groups and, second, the increasing litigation caused by lenders suing valuers for professional negligence. The discussions between representative groups have driven a debate on the valuation process leading to a number of reports and guidance notes. This paper discusses the outcomes paying particular attention to the basis of valuation for loan purposes and the provision of additional information in valuation reports. This paper also reviews the legal framework which influences the relationship between the lenders and valuers and discusses the duty of care. The role of instructions in the valuation process, the significance of the identity of the person to be advised and the possibility of a conflict of interest arising are all considered. The paper also addresses the issue of the standards required of a commercial loan valuer, including how this is interpreted by the courts and the legal status of professional guidance notes. The paper concludes by identifying potential areas for dispute within the loan valuation process and raising a number of research questions concerning the operation of this process which are addressed in a following paper.

Post-frying oil drainage from potato chips and french fries: a comparative study of atmospheric and vacuum drainage

This paper represents a study of the transient changes occurring in temperature, and moisture and oil contents during the so called “post-frying drainage”—which is the duration for which a product is held in the head space of the fryer after it is removed from the oil. Since most of the oil adhering to the product penetrates into the structure during this period, this paper examines the effects of applying vacuum during drainage (1.33 kPa) to maintain the product temperature consistently above the water saturation temperature corresponding to the prevailing pressure (11 °C), which potentially eliminates water condensation and prevents the occluded surface oil from penetrating into the product structure. Draining under vacuum significantly lowers the oil content of potato chips by 38% compared to atmospheric drainage. This phenomenon can be further confirmed by confocal laser scanning microscopy (CLSM) images, which show that the boundary between the core and the crust regions is clearly visible in the case of vacuum drainage, whereas in the case of atmospheric drainage, the oil is distributed throughout the structure. Unfortunately, the same approach did not reduce the oil content of French fries—the oil content of vacuum-drained product was found similar to the product obtained by draining under atmospheric pressure. This is because the reduction in oil content only occurs when there is net moisture evaporation from the product and the evaporation rate is sufficient to force out the oil from the product; this was clearly not the case with French fries. The CLSM images show that the oil distribution in the products drained under atmospheric pressure and vacuum was similar.