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  • photoinhibition  (3)
  • ArtCAM  (2)
  • Springer  (5)
  • Oxford University Press
  • 1
    Electronic Resource
    Electronic Resource
    Creating machinable textures for CAD/CAM systems (1998)
    Springer
    The international journal of advanced manufacturing technology 14 (1998), S. 269-279 
    Details
    ISSN: 1433-3015
    Keywords: ArtCAM ; Artwork ; Computer-aided design and computer-aided manufacturing (CAD/CAM) ; Three-dimensional texture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Texture is applied on three-dimensionally modelled surfaces in computer graphics to enhance visual effect. This research focuses on the development of three-dimensional textured surfaces which are suitable for manufacturing. Three approaches for creating the three-dimensional texture are presented. The first approach is to process a design from either an artist's sketch or an image from a two-dimensional scan. The second approach uses a three-dimensional scanned texture. Both these approaches depend on the quality of the scanned image and are more tedious than the third approach, which is to convert texture using parameters and is a more direct approach. In the user interface design, two custom-made forms are developed to cater for both regular and irregular textures. The case studies have shown that the textures created are not only good for a visual effect, but are also machinable. The development work is incorporated into the ArtCAM system which is a specialised CAD/CAM system that is capable of generating three-dimensional shapes from two-dimensional artwork.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01199882
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  • 2
    Electronic Resource
    Electronic Resource
    Checking for machinability on surface patches (1998)
    Springer
    The international journal of advanced manufacturing technology 14 (1998), S. 806-814 
    Details
    ISSN: 1433-3015
    Keywords: ArtCAM ; Computer-aided design and computer-aided manufacturing (CAD/CAM) ; Machinability ; Surface patches
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Toolpaths generated from a CAD model do not necessarily produce a part which exactly matches the model part. To close up the gap between a CAD model and a machined model, this paper focuses on the development of a program to check the machinability of surface patches in relation to the cutting tool. A machinability check engine is formulated and implemented for verifying the machinability of surface patches. The structure of the machinability check engine consists of three components: the input parameters, the checking algorithm and the output surface map. The output surface map is called the Chow map. The algorithms for checking a single surface and multiple surface patches are presented. Sample runs of the machinability check engine are performed on three types of surface patch: standard-shaped surfaces, complex surfaces and textured surfaces. The machinability check engine can be incorporated into a CAD/CAM system for better surface design.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01350765
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  • 3
    Electronic Resource
    Electronic Resource
    Photosystem II function and herbicide binding sites during photoinhibition of spinach chloroplasts in-vivo and in-vitro (1989)
    Springer
    Photosynthesis research 21 (1989), S. 17-26 
    Details
    ISSN: 1573-5079
    Keywords: chlorophyll fluorescence ; herbicide binding ; photoinhibition ; photosynthesis ; photosystem II ; temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The time courses of some Photosystem II (PS II) parameters have been monitored during in-vivo and in-vitro photoinhibition of spinach chloroplasts, at room temperature and at 10 °C or 0 °C. Exposing leaf discs of low-light grown spinach at 25 °C to high light led to photoinhibition of chloroplasts in-vivo as manifested by a parallel decrease in the number of functional PS II centres, the variable chlorophyll fluorescence at 77K (F v /F m ), and the number of atrazine-binding sites. When the photoinhibitory treatment was given at 10 °C, the former two parameters declined in parallel but the loss of atrazine-binding sites occurred more slowly and to a lesser extent. During in-vitro photoinhibition of chloroplast thylakoids at 25 °C, the loss of functional PS II centres proceeded slightly more rapidly than the loss of atrazine-binding sites, and this difference in rate was further increased when the thylakoids were photoinhibited at 0 °C. During the recovery phase of leaf discs (up to 9 h) the increases in F v /F m preceded that of the number of functional PS II centres, while only a further decline in the number of atrazine-binding sites was observed. The recovery of variable chlorophyll fluorescence and the concentration of functional PS II centres occurred more rapidly at 25 °C than at 10 °C. These results suggest that the photoinhibition of PS II function is a relatively temperature-independent early photochemical event, whereas the changes in the concentration of herbicide-binding sites appear to be a more complex biochemical process which can occur with a delayed time course.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00047171
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  • 4
    Electronic Resource
    Electronic Resource
    Unifying model for the photoinactivation of Photosystem II in vivo under steady-state photosynthesis (1998)
    Springer
    Photosynthesis research 56 (1998), S. 1-13 
    Details
    ISSN: 1573-5079
    Keywords: photoinhibition ; Photosystem II ; primary radical pair ; singlet oxygen ; triplet P680
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We present a unifying mechanism for photoinhibition based on current obsevations from in vivo studies rather than from in vitro studies with isolated thylakoids or PS II membranes. In vitro studies have limited relevance for in vivo photoinhibition because very high light is used with photon exposures rarely encountered in nature, and most of the multiple, interacting, protective strategies of PS II regulation in living cells are not functional. It is now established that the photoinactivation of Photosystem II in vivo is a probability and light-dosage event which depends on the photons absorbed and not the irradiance per se. As the reciprocity law is obeyed and target theory analysis strongly suggests that only one photon is required, we propose that a single dominant molecular mechanism occurs in vivo with one photon inactivating PS II under limiting, saturating or sustained high light. Two mechanisms have been proposed for photoinhibition under high light, acceptor-side and donor-side photoinhibition [see Aro et al. (1994) Biochim Biophys Acta 1143: 113–134], and another mechanism for very low light, the low-light syndrome [Keren et al. (1995) J Biol Chem 270: 806–814]. Based on the exciton-radical pair equilibrium model of exciton dynamics, we propose a unifying mechanism for the photoinactivation of PS II in vivo under steady-state photosynthesis that depends on the generation and maintenance of increased concentrations of the primary radical pair, P680+Pheo−, and the different ways charge recombination is regulated under varying environmental conditions [Anderson et al. (1997) Physiol Plant 100: 214–223]. We suggest that the primary cause of damage to D1 protein is P680+, rather than singlet O2 formed from triplet P680, or other reactive oxygen species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005946808488
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  • 5
    Electronic Resource
    Electronic Resource
    Photoinactivation of photosystem II by cumulative exposure to short light pulses during the induction period of photosynthesis (1996)
    Springer
    Photosynthesis research 47 (1996), S. 51-59 
    Details
    ISSN: 1573-5079
    Keywords: chlorophyll fluorescence ; photoinhibition ; photon exposure ; photosynthetic induction ; susceptibility to light stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Photoinactivation of Photosystem (PS) II in vivo was investigated by cumulative exposure of pea, rice and spinach leaves to light pulses of variable duration from 2 to 100 s, separated by dark intervals of 30 min. During each light pulse, photosynthetic induction occurred to an extent depending on the time of illumination, but steady-state photosynthesis had not been achieved. During photosynthetic induction, it is clearly demonstrated that reciprocity of irradiance and duration of illumination did not hold: hence the same cumulative photon exposure (mol m−2) does not necessarily give the same extent of photoinactivation of PS II. This contrasts with the situation of steady-state photosynthesis where the photoinactivation of PS II exhibited reciprocity of irradiance and duration of illumination (Park et al. (1995) Planta 196: 401–411). We suggest that, for reciprocity to hold between irradiance and duration of illumination, there must be a balance between photochemical (qP) and non-photochemical (NPQ) quenching at all irradiances. The index of susceptibility to light stress, which represents an intrinsic ability of PS II to balance photochemical and non-photochemical quenching, is defined by the quotient (1-qP)/NPQ. Although constant in steady-state photosynthesis under a wide range of irradiance (Park et al. (1995). Plant Cell Physiol 36: 1163–1169), this index of susceptibility for spinach leaves declined extremely rapidly during photosynthetic induction at a given irradiance, and, at a given cumulative photon exposure, was dependent on irradiance. During photosynthetic induction, only limited photoprotective strategies are developed: while the transthylakoid pH gradient conferred some degree of photoprotection, neither D1 protein turnover nor the xanthophyll cycle was operative. Thus, PS II is more easily photoinactivated during photosynthetic induction, a phenomenon that may have relevance for understorey leaves experiencing infrequent, short sunflecks.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00017753
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