884 resultados para Antony Downs


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Knowledge of the plan competes with self-consciousness of experience. The less we are able to understand our spatio-visual experience by the abstract coordinates of the plan, the more we are thrust back into a lived experience of the building in duration. This formula, frequently unacknowledged, has been one of the main precepts of the experientialist modernism which arises out of the picturesque and which stands in critique of classical idealism. One of the paths to critique this formula is by showing that the attention to the experience of the spaces in duration is predicated on obscuring, complicating and weakening the apprehension of the plan as a figure. Another development in the practice of modern planning has been architects using a kind of over-drawing where human circulation diagrams or 'movement lines' are drawn expressively across the orthographic plane; thus representing the lived experience of buildings. We will show that these two issues are linked; the plan's weak figure and the privilege this supposes for durational experience has a corollary - experience itself demands to be visible in the plan, and this is one origin of the present fascination with 'diagramming'. In this paper we explore the practice of architectural planning and its theoretical underpinnings in an attempt to show the viability of a history of architectural planning methods.

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Foreign Exchange trading has emerged in recent times as a significant activity in many countries. As with most forms of trading, the activity is influenced by many random parameters so that the creation of a system that effectively emulates the trading process will be very helpful. In this paper we try to create such a system using Machine learning approach to emulate trader behaviour on the Foreign Exchange market and to find the most profitable trading strategy.

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Foreign exchange trading has emerged in recent times as a significant activity in many countries. As with most forms of trading, the activity is influenced by many random parameters so that the creation of a system that effectively emulates the trading process is very helpful. In this paper, we try to create such a system with a genetic algorithm engine to emulate trader behaviour on the foreign exchange market and to find the most profitable trading strategy.

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Support vector machines (SVMs) have recently emerged as a powerful technique for solving problems in pattern classification and regression. Best performance is obtained from the SVM its parameters have their values optimally set. In practice, good parameter settings are usually obtained by a lengthy process of trial and error. This paper describes the use of genetic algorithm to evolve these parameter settings for an application in mobile robotics.

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Phosphonoformate and phosphonoacetate are effective antiviral agents, however they are charged at physiological pH and as such penetration into cells and diffusion across the blood-brain bamer is limited. In an attempt to increase the lipophilicity and improve the transport properties of these molecules, prodrugs were synthesised and their stabilities and reconversion to the parent compound subsequently investigated by the techniques of 31P nuclear magnetic resonance spectroscopy and high performance liquid Chromatography. A series of 4-substituted dibenzyl (methoxycarbonyl)phosphonates were prepared and found to be hydrolytically unstable giving predominantly the diesters, benzyl (methoxycarbonyl)phosphonates. This instability arose from the electron-withdrawing effect of the carbonyl group promoting nucleophilic attack at phosphorus. It was possible to influence the mechanism and, to some extent, the rate of hydrolysis of the phosphonoformate triesters to the diesters by varying the electronic nature of the substituent in the 4-position of the aromatic ring. Strongly electron-withdrawing groups increased the sensitivity of phosphorus to nucleophilic attack, thus promoting P-O .bond cleavage and rapid hydrolysis. Conversely, weakly electron-withdrawing substituents encouraged C-O bond fission, presumably through resonance stabilisation of the benzyl carbonium ion. The loss of the protecting group on phosphorus was in competition with nucleophilic attack at the carbonyl group, resulting in P-C bond cleavage with dibenzyl phosphite formation. The high instability and P-C bond fission make triesters unsuitable prodrug forms of phosphonoformate. A range of chemically stable triesters of phosphonoacetate were synthesised and their bioactivation investigated. Di(benzoyloxymethyl) (methoxycarbonylmethyl)phosphonates degraded to the relevant benzoyloxymethyl (methoxycarbonylmethyl)phosphonate in the presence of esterase. The enzymatic activation was restricted to the removal of only one protecting group from phosphorus, most likely due to the close proximity of the benzoyloxy ester function to the anionic charge on the diester. However, in similar systems di(4-alkanoyloxybenzyl) (methoxycarbonylmethyl)phosphonates degraded in the presence of esterase with the loss of both protecting groups on phosphorus to give the monoester, (methoxycarbonylmethyl)phosphonate, via the intermediary of the unstable 4-hydroxy benzyl esters. The methoxycarbonyl function remained intact. The rate of enzymatic hydrolysis and subsequent removal of the protecting groups on phosphorus was dependent on the nature of the alkanoyl group and was most rapid for the 4-nbutanoyloxybenzyl and 4-iso-butanoyloxybenzyl esters of phosphonoacetate. This provides a strategy for the design of a prodrug with sufficient stability in plasma to reach the central nervous system in high concentration, wherein rapid metabolism to the active drug by brain-associated enzymes occurs.

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The temporal lobe is a major site of pathology in a number of neurodegenerative diseases. In this chapter, the densities of the characteristic pathological lesions in various regions of the temporal lobe were compared in eight neurodegenerative disorders, viz., Alzheimer’s disease (AD), Down’s syndrome (DS), dementia with Lewy bodies (DLB), Pick’s disease (PiD), corticobasal degeneration (CBD), progressive supranuclear palsy (PSP), sporadic Creutzfeldt-Jakob disease (sCJD), and neuronal intermediate filament inclusion disease (NIFID). Temporal lobe pathology was observed in all of these disorders most notably in AD, DS, PiD, sCJD, and NIFID. The regions of the temporal lobe affected by the pathology, however, varied between disorders. In AD and DS, the greatest densities of ?-amyloid (A?) deposits were recorded in cortical regions adjacent to the hippocampus (HC), DS exhibiting greater densities of A? deposits than AD. Similarly, in sCJD, greatest densities of prion protein (PrPsc) deposits were recorded in cortical areas of the temporal lobe. In AD and PiD, significant densities of neurofibrillary tangles (NFT) and Pick bodies (PB) respectively were present in sector CA1 of the HC while in CBD, the greatest densities of tau-immunoreactive neuronal cytoplasmic inclusions (NCI) were present in the parahippocampal gyrus (PHG). Particularly high densities of PB were present in the DG in PiD, whereas NFT in AD and Lewy bodies (LB) in DLB were usually absent in this region. These data confirm that the temporal lobe is an important site of pathology in the disorders studied regardless of their molecular ‘signature’. However, disorders differ in the extent to which the pathology spreads to affect the HC which may account for some of the observed differences in clinical dementia.

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The impact of hybrid erbium-doped fiber amplifier (EDFA)/Raman amplification on a spectrally efficient coherent-wavelength-division-multiplexed (CoWDM) optical communication system is experimentally studied and modeled. Simulations suggested that 23-dB Raman gain over an unrepeatered span of 124 km single-mode fiber would allow a decrease of the mean input power of ~6 dB for a fixed bit-error rate (BER). Experimentally we demonstrated 1.2-dB Q-factor improvement for a 2-Tb/s seven-band CoWDM with backward Raman amplification. The system delivered an optical signal-to-noise ratio of 35 dB at the output of the receiver preamplifier providing a worst-case BER of 2 × 10 -6 over 49 subcarriers at 42.8 Gbaud, leaving a system margin (in terms of Q -factor) of ~4 dB from the forward-error correction threshold.