The topic of amodal completion has often been investigated by using partly occluded shapes that are regular. In research that has typically been done with displays such as these regular shapes, it ...has been shown that global aspects of a shape can determine completion. To see how robust these global influences in the completion process are, we investigated quasi-regular shapes, ie shapes with a certain overall regularity but not based on metrical identities. First, in experiment 1 participants had to complete quasi-regular shapes in a drawing task. Then, in experiment 2 the primed-matching paradigm was used. Results from both experiments provided evidence for global completions. In experiment 3 we found that multiple global completions can be primed, which, as a control experiment showed, cannot be explained by some inability of the visual system to see the difference between the different completions. These data support the notion that global influences on visual occlusion are apparent even when the partly occluded stimulus is outside the domain of regular shapes. Implications for a global approach are provided.
Separate Features Versus One Principle Van Lier, Rob
Journal of experimental psychology. Human perception and performance,
02/2000, Letnik:
26, Številka:
1
Journal Article
Recenzirano
In his article "Perception of Complex Line Drawings,"
A. Shimaya (1997)
proposed a quantitative theory that was
designed to predict perceived segmentations and amodal completions
of line drawings. ...Shimaya further evaluated the integrative approach
of structural information theory (SIT;
R. Van Lier, P. Van
der Helm, & E. Leeuwenberg, 1994
) to pattern interpretation. It is
argued in this comment that Shimaya's evaluation of the SIT approach
is based on a misconception of SITs basic assumptions and an
inappropriate data analysis.
We report the preparation of the 7α-cyano derivative of the isomeric (17α,20
E/
Z)-
125
I
iodovinyl-19-nortestosterones (IVNT) together with their binding affinity for the androgen receptor (AR) and ...their biodistribution in two different animal models. The cyano group was introduced at the 7α-position by hydrocyanation of 4,6-estradien-17β-ol-3-one with diethylaluminum cyanide. Selective protection of the A-ring enone system as the dienol ether followed by ethynylation and deprotection under base and acid hydrolysis condition gave 7α-cyano-17α-ethynyl-19-nortestosterone. The stannyl derivatives were prepared by addition of tri-
n-butylstannyl hydride and converted stereospecifically to the corresponding
125
I
iodovinyl analog using
125
I
NaI and H
2O
2. The
125
I
iodovinylsteroids were intravenously administered to male rats and estrogen-primed immature female rats and tissue uptake was measured up to 6
h post-injection. Co-administration of NLP-004 or ORG-2058, highly selective ligands for the progesterone receptor, to the female rats did not affect uterus uptake of the
125
I
-ligands. However co-injection of testosterone to DES-primed male rats induced a marked increase in prostate uptake of the 20
Z-isomer of 7α-cyano-
125
I
-IVNT. The relative binding affinity (RBA) of either 7α-cyano-(17α,20
E/
Z)-IVNT isomer for the AR is low (RBA=4 and 3, respectively, versus 100 for 5α-dihydrotestosterone (DHT)), suggesting the absence of a possible role of the AR in the localization process. These findings contrast previously reported data for the analogous 7α-methyl-
125
I
-IVNT where co-administration of testosterone was shown to result in a 50% drop in prostate uptake. These data indicate that the addition of an electron withdrawing 7α-cyano group to
123
I
-labeled nortestosterone derivatives does not improve their potential to serve as SPECT agents for the imaging of AR densities in the prostate.
The biodegradability and first-order hydrolysis coefficient of maize silage have been assessed from batch experiments using different types of inoculum and substrate to inocula (S/I) ratios, and from ...CSTRs working at different hydraulic retention times (HRTs). In the batch experiments, the assessed maximum biodegradability of the maize silage was 68 (±2.7)% and 73(±2.9)% while the first order hydrolysis was 0.26 (±0.01) and 0.27(±0.02) d-1, using granular and a mixture of granular and suspended inoculum, respectively. In the CSTR experiment biodegradability ranged from 41–65% depending on the HRT applied whereas the calculated first order hydrolysis coefficient was 0.32 d-1. It is concluded that batch experiments can be used to assess first order hydrolysis constants and biodegradability provided that a well balanced inoculum is guaranteed. Further, it is shown that CSTR reactors digesting maize silage and operating at HRTs as low as 20 days can attain 88% of maximum biodegradability as long as pH fluctuations are minimized. 2 mmol NaHCO3 per gram maize silage was calculated to suffice for the purpose.
The 2-methyl-1,4-naphthoquinone (MQ) sensitized photooxidation of nucleic acid derivatives has been studied by laser flash photolysis and steady state methods. Thymine and thymidine, as well as other ...DNA model compounds, quench triplet MQ by electron transfer to give MQ radical anions and pyrimidine or purine radical cations. Although the pyrimidine radical cations cannot be directly observed by flash photolysis, the addition of N,N,N',N'-tetramethyl-1,4-phenylenediamine (TMPD) results in the formation of the TMPD radical cation via scavenging of the pyrimidine radical cation. The photooxidation products for thymine and thymidine are shown to result from subsequent chemical reactions of the radical cations in oxygenated aqueous solution. The quantum yield for substrate loss at limiting substrate concentrations is 0.38 for thymine and 0.66 for thymidine. The chemistry of the radical cations involves hydration by water leading to C(6)-OH adduct radicals of the pyrimidine and deprotonation from the N(1) position in thymine and the C(5) methyl group for thymidine. Superoxide ions produced via quenching of the quinone radical anion with oxygen appear to be involved in the formation of thymine and thymidine hydroperoxides and in the reaction with N(1)-thyminyl radicals to regenerate thymine. The effects of pH were examined in the range pH 5-8 in both the presence and absence of superoxide dismutase. Initial C(6)-OH thymine adducts are suggested to dehydrate to give N(1)-thyminyl radicals.
Functional studies revealed that two groups of B chronic lymphocytic leukemia (B-CLL) can be distinguished based on their capacity to mount a proliferative response following B-cell antigen receptor ...(BCR) cross-linking. The molecular basis for the functional distinction between these B-CLL groups most probably resides within or proximal to the BCR since non-responsive B-CLL, in marked contrast to responsive B-CLL, do not respond to BCR ligation with tyrosine phosphorylation of cellular substrates and increases in the free intracellular Ca++. Detailed biochemical analysis showed overall structural identity between responsive and non-responsive B-CLL with respect to both transmembrane and intracellular associates of the BCR complex. However expression levels of the protein tyrosine kinase syk, which is a key enzyme for the early signalling through the BCR, were found to be markedly lower in non-proliferating B-CLL. Here, we will review current functional and biochemical data on responding and non-responding B-CLL and discuss the relevance of these findings for disease progression and our insight into the immunobiology of B-CLL.
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