Stress Distribution in and Deflection Properties of Tri-plate Beams in the Plastic Range

Tri-plate beams combine versatility, economy, and strength in steel design. These beams have many applications which indicate increased efficiency and economy in long-span plate girder construction. Their structural advantages are almost unlimited. Tri-plate beams are fabricated by welding three different types of steel to form an I-section. Each flange and the web of the section is fabricated out a different yield strength steel. Because the flanges of a beam contribute most of its movement resistance, the use of high strength steel of in the flanges is desirable. However, in tri-plate beams, the tension flange consists of a higher strength steel than does the compression flange because of the buckling liability of the compression flange. The utilization of a higher strength steel in the tension flange also makes possible a reduction in the tension flange cross sectional area. Because of its low moment carrying capacity, the web is fabricated out of a lower strength steel. The idea of tri-plate beams is not totally new, having previously been used to a very limited extent in plate girder construction is analogous to composite design, where the reinforced concrete slab is used as a large compression flange, the web is of a low strength steel, and the tension flange is composed of a high-strength steel. High strength steel beams have indicated increased economy in steel design. Tri-plate beams will offer still more economy while, at the same time, provide new possibilities in construction with structural steel. Furthermore, these beams represent savings in material and the availability of lighter sections that can meet the competition presented by prestressed concrete

The Metaphysics of Mental Representation

The representational theory of mind (RTM) explains the phenomenon of intentionality in terms of the existence and nature of mental representations. Despite the typical characterisation of mental representations in terms of their semantics, RTM is best understood as a metaphysical – more specifically formal ontological – theory whose primary defining feature is stipulating the existence of a class of mental particulars called representations. In this regard it is false, since mental representations do not exist. My argument is primarily methodological. Using an extended analysis of mereology and its variants as paradigmatic examples of a formal ontological theory, I argue for a 'synthetic’ approach to ontology which seeks to form a sound descriptive characterisation of the relevant phenomena from empirical data, to which philosophical analysis is applied to produce a rigorous theory. The value and necessity of this method is proved by example in our discussion of mereology which is shown to be defensible given certain assumptions, in particular perdurantism, but still inadequate as an account of parthood without considerable supplementation. We also see that there are viable alternatives which adopt a more synthetic approach and do not require the same assumptions. Having effectively demonstrated the value of a synthetic approach in ontology I critically examine the methodology employed by RTM and find it severely lacking. In the guise of ‘commonsense psychology’ RTM cavalierly imposes a theoretical framework without regard to empirical data, and this results in a severe distortion of the phenomenon of intentionality it purports to explain. RTM is methodologically unsound, and so its commitment to the existence of mental representations is utterly undermined. Furthermore the most attractive aspect of RTM – its semantics – can be separated from any commitment to mental representations existing. Even RTM’s strongest advocates lack motivation to believe that mental representations exist

The use of chronosequences in studies of ecological succession and soil development

1. Chronosequences and associated space-for-time substitutions are an important and often necessary tool for studying temporal dynamics of plant communities and soil development across multiple time-scales. However, they are often used inappropriately, leading to false conclusions about ecological patterns and processes, which has prompted recent strong criticism of the approach. Here, we evaluate when chronosequences may or may not be appropriate for studying community and ecosystem development. 2. Chronosequences are appropriate to study plant succession at decadal to millennial time-scales when there is evidence that sites of different ages are following the same trajectory. They can also be reliably used to study aspects of soil development that occur between temporally linked sites over time-scales of centuries to millennia, sometimes independently of their application to shorter-term plant and soil biological communities. 3. Some characteristics of changing plant and soil biological communities (e.g. species richness, plant cover, vegetation structure, soil organic matter accumulation) are more likely to be related in a predictable and temporally linear manner than are other characteristics (e.g. species composition and abundance) and are therefore more reliably studied using a chronosequence approach. 4. Chronosequences are most appropriate for studying communities that are following convergent successional trajectories and have low biodiversity, rapid species turnover and low frequency and severity of disturbance. Chronosequences are least suitable for studying successional trajectories that are divergent, species-rich, highly disturbed or arrested in time because then there are often major difficulties in determining temporal linkages between stages. 5. Synthesis. We conclude that, when successional trajectories exceed the life span of investigators and the experimental and observational studies that they perform, temporal change can be successfully explored through the judicious use of chronosequences

Taub-NUT Spacetime in the (A)dS/CFT and M-Theory

In the following thesis, I will conduct a thermodynamic analysis of the Taub-NUT spacetime in various dimensions, as well as show uses for Taub-NUT and other Hyper-Kahler spacetimes. Thermodynamic analysis (by which I mean the calculation of the entropy and other thermodynamic quantities, and the analysis of these quantities) has in the past been done by use of background subtraction. The recent derivation of the (A)dS/CFT correspondences from String theory has allowed for easier and quicker analysis. I will use Taub-NUT space as a template to test these correspondences against the standard thermodynamic calculations (via the Nöether method), with (in the Taub-NUT-dS case especially) some very interesting results. There is also interest in obtaining metrics in eleven dimensions that can be reduced down to ten dimensional string theory metrics. Taub-NUT and other Hyper-Kahler metrics already possess the form to easily facilitate the Kaluza-Klein reduction, and embedding such metrics into eleven dimensional metrics containing M2 or M5 branes produces metrics with interesting Dp-brane results

Basal rot of narcissus : understanding pathogenicity in fusarium oxysporum f. sp. narcissi

Fusarium oxysporum is a globally distributed soilborne fungal pathogen causing root rots, bulb rots, crown rots and vascular wilts on a range of horticultural plants. Pathogenic F. oxysporum isolates are highly host specific and are classified as formae speciales. Narcissus is an important ornamental crop and both the quality and yield of flowers and bulbs can be severely affected by a basal rot caused by F. oxysporum f. sp. narcissi (FON); 154 Fusarium isolates were obtained from different locations and Narcissus cultivars in the United Kingdom, representing a valuable resource. A subset of 30 F. oxysporum isolates were all found to be pathogenic and were therefore identified as FON. Molecular characterisation of isolates through sequencing of three housekeeping genes, suggested a monophyletic origin with little divergence. PCR detection of 14 Secreted in Xylem (SIX) genes, previously shown to be associated with pathogenicity in other F. oxysporum f. spp., revealed different complements of SIX7, SIX9, SIX10, SIX12 and SIX13 within FON isolates which may suggest a race structure. SIX gene sequences were unique to FON and SIX10 was present in all isolates, allowing for molecular identification of FON for the first time. The genome of a highly pathogenic isolate was sequenced and lineage specific (LS) regions identified which harboured putative effectors including the SIX genes. Real-time RT-PCR, showed that SIX genes and selected putative effectors were expressed in planta with many significantly upregulated during infection. This is the first study to characterise molecular variation in FON and provide an analysis of the FON genome. Identification of expressed genes potentially associated with virulence provides the basis for future functional studies and new targets for molecular diagnostics

Opposing roles of Nfkb2 gene products p100 and p52 in the regulation of breast cancer stem cells

Purpose: Nuclear factor-kappa B (NF-κB) signalling has been shown to regulate properties of breast cancer stem cells. However, the specific contribution of the non-canonical NF-κB pathway, components of which are elevated in aggressive breast cancer has not been addressed. Methods: Through shRNA silencing of the Nfkb2 gene, the role of p100/p52 in 4T1 and N202.1A cell lines were assessed by NF-κB reporter, invasion, tumoursphere and orthotopic transplantation assays. The processing of p100 into p52 was also inhibited with a p97 ATPase inhibitor, NMS-873, and its effects on tumoursphere formation was assessed. Results: Knockdown of Nfkb2 led to opposing changes in NF-κB-dependent transcription. NF-κB activity was elevated in 4T1 cells and this resulted in increased motility, cancer stem cell (CSC) activity and tumourigenicity in vivo. Conversely, depletion of Nfkb2 in N202.1a cells decreased NF-κB activity, CSC properties and tumourigenicity in vivo. By selectively overexpressing the p52 subunit in Nfkb2 depleted cells, we found that the increased malignancy in 4T1 cells could not be reverted in the presence of p52, whereas the decreased tumourigenicity of N202.1a cells could be rescued by p52. These results indicate that p100 and its subunit p52 have opposing effects on breast CSC activity. Accordingly, inhibition of an upstream regulator of p100 processing was effective in reducing tumoursphere formation of N202.1A and SKBR3 (ErbB2 HIGH) cells without aggravating that of 4T1 and MDA-MB-231 (ErbB2LOW) cells. Conclusion: These findings indicate that inhibiting the processing of p100 may be a potential therapeutic strategy to suppress CSC activity in a subset of breast tumours. © 2017, Springer Science+Business Media New York

A Mossbauer study of some industrial applications of organotin compounds.

The technique of high dilution Mossbauer spectroscopy using the isotope Sn has been employed to study the nuclear environment of several organotin compounds having important industrial applications. For each compound studied structural and co-ordination information has been obtained relating to the mode of action of the organotin compound in its application. Chapters one and two of this thesis describe the theory of the Mossbauer Effect and the instrumentation and computational methods of recording and processing the Mossbauer data. Chapter three provides the main area of study in the thesis and is concerned with the role of organotin compounds in the stabilisation of PVC. Two types of organotin compound, dialkyltin thioglycollates and dialkyltin maleates, have been investigated for their effectiveness in preventing thermal and photochemical degradation of PVC. The resulting changes in the Mossbauer parameters following degradation have led to the identification of the organotin degradation products from which a degradation/stabilisation mechanism has been suggested. In chapter four the observation of a room temperature Mossbauer resonance is used to indicate that dimethylchlorotin acetate has an associated structure. A subsequent X-ray crystallographic determination supports the implications from the Mossbauer data and reveals dimethylchlorotin acetate to be 6 co-ordinate with a polymeric structure.In chapter five Mossbauer data have been obtained for a series of trialkyltin derivatives of L-cysteine and L-homocysteines The tri-alkyltin moiety has been reported to be a biologically active species and the Mossbauer data have revealed the sulphur atom in the cysteine and homocysteine groups to be a specific site for binding to the trialkyl tin moiety.Finally, in chapter six a simple Debye model of the solid has been applied to variable temperature Mossbauer data to suggest possible structures for two bis(triaikyltin)compounds containing two electronically different tin sites

Gene expression profiling of mammary gland development reveals putative roles for death receptors and immune mediators in post-lactational regression

INTRODUCTION: In order to gain a better understanding of the molecular processes that underlie apoptosis and tissue regression in mammary gland, we undertook a large-scale analysis of transcriptional changes during the mouse mammary pregnancy cycle, with emphasis on the transition from lactation to involution. METHOD: Affymetrix microarrays, representing 8618 genes, were used to compare mammary tissue from 12 time points (one virgin, three gestation, three lactation and five involution stages). Six animals were used for each time point. Common patterns of gene expression across all time points were identified and related to biological function. RESULTS: The majority of significantly induced genes in involution were also differentially regulated at earlier stages in the pregnancy cycle. This included a marked increase in inflammatory mediators during involution and at parturition, which correlated with leukaemia inhibitory factor–Stat3 (signal transducer and activator of signalling-3) signalling. Before involution, expected increases in cell proliferation, biosynthesis and metabolism-related genes were observed. During involution, the first 24 hours after weaning was characterized by a transient increase in expression of components of the death receptor pathways of apoptosis, inflammatory cytokines and acute phase response genes. After 24 hours, regulators of intrinsic apoptosis were induced in conjunction with markers of phagocyte activity, matrix proteases, suppressors of neutrophils and soluble components of specific and innate immunity. CONCLUSION: We provide a resource of mouse mammary gene expression data for download or online analysis. Here we highlight the sequential induction of distinct apoptosis pathways in involution and the stimulation of immunomodulatory signals, which probably suppress the potentially damaging effects of a cellular inflammatory response while maintaining an appropriate antimicrobial and phagocytic environment