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1

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The Future of Biology (1969)

MARTIN, E. S. ; TURNER, M. R.

[s.l.] : Nature Publishing Group

Nature 222 (1969), S. 1310-1310

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ISSN: 1476-4687

Source: Nature Archives 1869 - 2009

Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics

Notes: [Auszug] SIR,-The recent letter from Dr Jennings and Dr Brad-shaw concerning the training of PhDs in biological subjects (Nature, 222, 1209; 1969) criticized the inflexible attitude of postgraduates without offering any solution to this problem. It seems inevitable that a training in original research must ...

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1038/2221310c0

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Texture discrimination by Gabor functions (1986)

Turner, M. R.

Springer

Biological cybernetics 55 (1986), S. 71-82

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ISSN: 1432-0770

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Computer Science , Physics

Notes: Abstract A 2D Gabor filter can be realized as a sinusoidal plane wave of some frequency and orientation within a two dimensional Gaussian envelope. Its spatial extent, frequency and orientation preferences as well as bandwidths are easily controlled by the parameters used in generating the filters. However, there is an “uncertainty relation” associated with linear filters which limits the resolution simultaneously attainable in space and frequency. Daugman (1985) has determined that 2D Gabor filters are members of a class of functions achieving optimal joint resolution in the 2D space and 2D frequency domains. They have also been found to be a good model for two dimensional receptive fields of simple cells in the striate cortex (Jones 1985; Jones et al. 1985). The characteristic of optimal joint resolution in both space and frequency suggests that these filters are appropriate operators for tasks requiring simultaneous measurement in these domains. Texture discrimination is such a task. Computer application of a set of Gabor filters to a variety of textures found to be preattentively discriminable produces results in which differently textured regions are distinguished by firstorder differences in the values measured by the filters. This ability to reduce the statistical complexity distinguishing differently textured region as well as the sensitivity of these filters to certain types of local features suggest that Gabor functions can act as detectors of certain “texton” types. The performance of the computer models suggests that cortical neurons with Gabor like receptive fields may be involved in preattentive texture discrimination.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00341922

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Underestimation of visual texture slant by human observers: a model (1991)

Turner, M. R. ; Gerstein, G. L. ; Bajcsy, R.

Springer

Biological cybernetics 65 (1991), S. 215-226

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ISSN: 1432-0770

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Computer Science , Physics

Notes: Abstract The perspective image of an obliquely inclined textured surface exhibits shape and density distortions of texture elements which allow a human observer to estimate the inclination angle of the surface. However, it has been known since the work of Gibson (1950) that, in the absence of other cues, humans tend to underestimate the slant angle of the surface, particularly when the texture is perceived as being “irregular.” The perspective distortions which affect texture elements also shift the projected spatial frequencies of the texture in systematic ways. Using a suitable local spectral filter to measure these frequency gradients, the inclination angle of the surface may be estimated. A computational model has been developed which performs this task using distributions of outputs from filters found to be a good description of simple-cell receptive fields. However, for “irregular” textures the filter output distributions are more like those of “regular” textures at shallower angles of slant, leading the computational algorithm to underestimate the slant angle. This behavioral similarity between human and algorithm suggests the possibility that a similar visual computation is performed in cortex.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00206219

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Photosensory mechanisms in the lettuce seedling hypocotyl (1969)

Turner, M. R. ; Vince, D.

Springer

Planta 84 (1969), S. 368-382

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ISSN: 1432-2048

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary A number of differences in the responses of ‘Great Lakes’ lettuce seedlings to blue and far-red light indicate that more than one photo-sensitive pigment is involved in the photo-inhibition of hypocotyl elongation under ‘highenergy’ conditions. In far-red light the inhibitory effect is restricted to young seedlings and is of limited duration; after 24 hours in far-red a rapid growth rate similar to that of plants maintained in darkness is resumed, despite continued irradiation. The onset of inhibition is relatively slow. Blue light, in contrast, exerts a strongly inhibitory effect on elongation at any age, and a slow rate of growth persists throughout the entire irradiation period. The onset of inhibition is very rapid. Furthermore, even when the inhibition in far-red had already been exhausted after prolonged exposure, transfer to blue light resulted in a prompt reduction in growth rate. Also the effect of far-red is almost completely lost after a pre-irradiation with red light which does not affect the response to blue. It is concluded that the responses to blue and far-red light in ‘Great Lakes’ lettuce are not mediated by a single pigment system and that a distinct blue-sensitive pigment is present in addition to phytochrome. Red light has a number of different effects depending on conditions: (1) a pretreatment with red light almost completely prevents the inhibitory effect of a subsequent far-red irradiation, (2) a brief terminal treatment with red increases the inhibitory effect of either far-red or blue light; this is reversed by far-red, and (3) prolonged exposure to red light given alone increases the growth rate relative to darkness, because the more rapid elongation rate characteristic of young seedlings continues for longer with red light than in plants grown in darkness throughout.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00396429

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5

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Characterization of silane-modified ZrO2 powder surfaces (1997)

Turner, M. R. ; Duguet, E. ; Labrugère, C.

Chichester [u.a.] : Wiley-Blackwell

Surface and Interface Analysis 25 (1997), S. 917-923

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ISSN: 0142-2421

Keywords: x-ray photoelectron spectroscopy ; infrared spectroscopy ; NMR ; silane, γ-MPS ; zirconia ; zircon ; Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Physics

Notes: Polymerizable organic silane molecules such as 3-(trimethoxysilyl)propylmethacrylate (γ-MPS) have been grafted onto the surface of ZrO2 powders, via hydroxyl groups, to obtain hybrid ‘macromonomers’. A combination of x-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy and 29Si nuclear magnetic resonance (NMR) spectroscopy have been employed to study the interaction between organic silane molecules and the surface of the ZrO2 powders. The core-level XPS regions, Zr3d, O1s, C1s and Si2p, have been studied to determine the nature of chemical bonding between the organic grafted monomer and inorganic phase and correlated with NMR results. Based upon the results obtained, it is proposed that grafting results in γ-MPS bonded to the ZrO2 powder surface via Zr—O—Si bonds accompanied by interlinkage of γ-MPS molecules through Si—O—Si bonding. © 1997 John Wiley & Sons, Ltd.

Additional Material: 8 Ill.

Type of Medium: Electronic Resource

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