Showing papers by "Radboud University Nijmegen published in 1987"
TL;DR: The development and application of computer-simulation methods to predict stress-related adaptive bone remodeling, in accordance with 'Wolff's Law' are developed and applied to investigate the relation between 'stress shielding' and bone resorption in the femoral cortex around intramedullary prostheses.
1,085 citations
TL;DR: An explanation for the existence of configurational conditions on transformations ond other linguistics rules is proposed and the basic design feature of IPG which gives rise to these psychologically and linguistically desiroble properties, is the “Procedures + Stack” concept.
542 citations
TL;DR: In this paper, it was shown that the conversion of spin-up into spin-down current near a ferromagnetic-nonferromagnetic metal interface gives rise to an electrochemical potential difference of spinup and spindown electrons.
Abstract: It is shown theoretically that the conversion of spin-up into spin-down current near a ferromagnetic-nonferromagnetic metal interface gives rise to an electrochemical potential difference of spin-up and spin-down electrons. The effect shows up as an additional boundary resistance. The situation is analogous to the normal-metal-superconductor interface. Experimental methods that may be used to observe the effects are discussed.
488 citations
TL;DR: At about 1 eV below the top of the valence band a dispersionless state was measured, almost completely of Mo 4d character, which is not predicted by band-structure calculations.
Abstract: The band structures of the semiconducting layered compounds ${\mathrm{MoSe}}_{2}$, ${\mathrm{MoS}}_{2}$, and ${\mathrm{WSe}}_{2}$ have been calculated self-consistently with the augmented-spherical-wave method. Angle-resolved photoelec- tron spectroscopy of ${\mathrm{MoSe}}_{2}$ using He i, He ii, and Ne i radiation, and photon-energy-dependent normal-emission photoelectron spectroscopy using synchrotron radiation, show that the calculational results give a good description of the valence-band structure. At about 1 eV below the top of the valence band a dispersionless state was measured, almost completely of Mo 4d character. Such a state, which is not predicted by band-structure calculations, has also been observed in metallic layered compounds. Suggestions are given for the explanation of this phenomenon.
456 citations
TL;DR: A new role is proposed for phospholipase A 2 in protecting membranes from oxidative injury by reducing and detoxifying fatty acid hydroperoxides in membranes.
427 citations
TL;DR: The known carcinogenic PAHs are of a large molecular type and show excess rates of lung cancers, and an important role is played by biological monitoring, i.e. the systematic registration of the exposure level of individual workers and groups of workers, measured in biological specimens.
410 citations
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TL;DR: Graph rewriting (also called reduction) as defined in Wadsworth [1971] was introduced in order to be able to give a more efficient implementation of functional programming languages in the form of lambda calculus or term rewrite systems.
Abstract: Graph rewriting (also called reduction) as defined in Wadsworth [1971] was introduced in order to be able to give a more efficient implementation of functional programming languages in the form of lambda calculus or term rewrite systems: identical subterms are shared using pointers.
362 citations
TL;DR: From band-structure calculations it is shown that MoSe2, MoS2, and WSe2 are indirect-gap semiconductors, and the wave function at the top of the valence band is shown to be a metal-nonmetal antibonding state, which explains the observed high stability of these materials in photoelectrochemical cells against photocorrosion.
Abstract: From band-structure calculations it is shown that ${\mathrm{MoSe}}_{2}$, ${\mathrm{MoS}}_{2}$, and ${\mathrm{WSe}}_{2}$ are indirect-gap semiconductors. The top of the valence band is at the \ensuremath{\Gamma} point and the bottom of the conduction band is along the line T of the hexagonal Brillouin zone, halfway between the points \ensuremath{\Gamma} and K. The A and B excitons correspond to the smallest direct gap at the K point. This assignment of the exciton peaks is shown to be consistent with the polarization dependence of their intensities, their effective masses, and the observed dependence of their splitting on the spin-orbit splittings of the constituent elements. The wave function at the top of the valence band is shown to be a metal-nonmetal antibonding state, which explains the observed high stability of these materials in photoelectrochemical cells against photocorrosion.
361 citations
TL;DR: In this article, a monoclonal antibody (RCK 105) was obtained after immunization of BALB/c mice with cytoskeletal preparations from T24 cells and characterized by one-dimensional and two-dimensional (2D) immunoblotting.
288 citations
TL;DR: The collicular role in saccade generation is modelled based on the idea, proposed earlier in the literature, that each movement cell causes a movement tendency in the direction of the external world point which it represents in the collicular map.
283 citations
TL;DR: It appears that an active enzyme has been recruited, unchanged, to an extra role as a structural protein in the lens without gene duplication and sequence divergence, which raises the possibility that other crystallins may similarly be enzymes expressed at high levels in lens as structural proteins.
Abstract: The major components of mammalian lenses are tissue-specific, soluble proteins, the α-, β- and γ-crystallins1–3. The lenses of other vertebrate classes often contain other major proteins, notably δ-crystallin in birds and reptiles4. A fourth distinct type, described as e-crystallin, is prominent in many bird and crocodile lenses5,6. Here we show that e-crystallin is an active glycolytic enzyme, lactate dehydrogenase (LDH) (EC 1.1.1.27) and that duck e-crystallin appears to be identical to duck LDH-B4. LDH is a normal metabolic component in other lenses7, but in duck is present in amounts far exceeding the requirements of any likely catalytic role. It appears that an active enzyme has been recruited, unchanged, to an extra role as a structural protein in the lens without gene duplication and sequence divergence. This surprising discovery raises the possibility that other crystallins may similarly be enzymes expressed at high levels in lens as structural proteins.
TL;DR: It is concluded that this particular inbred strain of rats of the WAG/Rij strain may be useful as an additional model of absence epilepsy.
TL;DR: It is concluded that the commonly used main-sequence description of saccades is incomplete and can be extended usefully by including skewness, and it is suggested that the marked differences in dynamic properties among different saccade types may reflect processes in the visuomotor rather than in the motor system.
TL;DR: Sequence comparison with the recently cloned U2 snRNP‐specific B′ protein revealed two extremely homologous regions located in the carboxy‐terminal and amino‐ terminal part of the proteins, which indicates that proteins A and B′, although located in different snR NP particles, may have identical functions.
Abstract: Sera from patients with connective tissue diseases often contain antibodies against snRNA-associated proteins. Using one of these sera in an immunological screening of a human lambda gt11 expression vector cDNA library, two cDNA clones for the U1 snRNP-specific A protein, termed lambda HA-1 and lambda HA-2, were isolated. Monospecific antibodies, eluted from the beta-galactosidase fusion protein of either clone reacted with the U1 snRNP-specific A antigen. The identity of the clones was confirmed by in vitro translation of hybrid selected mRNA. RNA blot analysis revealed a single polyadenylated transcript of about 1.4 kb in human cells. A cDNA of 1.2 kb, isolated from the same lambda gt11 expression library by cross-hybridization with a lambda HA-2 restriction fragment, covered the complete coding sequence of the A protein as demonstrated by in vitro translation of an RNA transcript synthesized from this cDNA. The deduced amino acid sequence contains one very hydrophilic region, and internal sequence duplication and a region highly homologous to the RNP consensus sequence that seems to be common to RNA binding proteins. Sequence comparison with the recently cloned U2 snRNP-specific B" protein revealed two extremely homologous regions located in the carboxy-terminal (homology of 86%) and amino-terminal part (homology of 77%) of the proteins. This structural relationship indicates that proteins A and B", although located in different snRNP particles, may have identical functions.
TL;DR: In this article, the development of children's knowledge of the situations that provoke emotion was examined and the first study, English and Dutch children aged 5, 7, 10 and 14 years were presented.
Abstract: In two studies, the development of children's knowledge of the situations that provoke emotion was examined. In the first study, English and Dutch children aged 5, 7, 10 and 14 years were presented...
TL;DR: This work provides evidence for colocalization of the classical neurotransmitters 5-HT and GABA in single cells of the ventral medulla oblongata, some of which project to the spinal cord.
14 Sep 1987
TL;DR: A sequential implementation of Clean on a conventional machine is described and its performance is compared with other systems to show that Clean can be efficiently implemented.
Abstract: Clean is an experimental language for specifying functional computations in terms of graph rewriting. It is based on an extension of Term Rewriting Systems (TRS) in which the terms are replaced by graphs. Such a Graph Rewriting System (GRS) consists of a, possibly cyclic, directed graph, called the data graph and graph rewrite rules which specify how this data graph may be rewritten. Clean is designed to provide a firm base for functional programming. In particular, Clean is suitable as an intermediate language between functional languages and (parallel) target machine architectures. A sequential implementation of Clean on a conventional machine is described and its performance is compared with other systems. The results show that Clean can be efficiently implemented.
TL;DR: The adequacy of crosscorrelation procedures to detect and estimate neural connectivity has been investigated by means of computer simulations of small networks composed of fairly realistic modelneurons, finding excitatory connections are easier to detect than inhibitory ones.
Abstract: Crosscorrelation analysis of simultaneously recorded activity of pairs of neurons is a common tool to infer functional neural connectivity. The adequacy of crosscorrelation procedures to detect and estimate neural connectivity has been investigated by means of computer simulations of small networks composed of fairly realistic modelneurons. If the mean interval of neural firings is much larger than the duration of postsynaptic potentials, which will be the case in many central brain areas excitatory connections are easier to detect than inhibitory ones. On the other hand, inhibitory connections are revealed better if the mean firing interval is much smaller than post-synaptic potential duration. In general the effects of external stimuli and the effects of neural connectivity do not add linearly. Furthermore, neurons may exhibit a certain degree of timelock to the stimulus. For these reasons the commonly applied "shift predictor" procedure to separate stimulus and neural effects appears to be of limited value. In case of parallel direct and indirect neural pathways between two neurons crosscorrelation analysis does not estimate the direct connection but instead an effective connectivity, which reflects the combined influences of the parallel pathways.
TL;DR: A unifying equation relating the saccade parameters amplitude, maximum velocity and skewness, which is valid for both normal and slow saccades, is proposed.
TL;DR: In this paper, densitometric measurements on contact-microradiographs of transverse sections of the roots were calculated, and the rate of demineralization (Vdem) became zero at a pIOHA-value of 105.3 +/- 0.4; this is substantially lower than the corresponding value of 118 +/- 1 for enamel.
TL;DR: Results indicate that fur expression can be used to discriminate between these two types of human lung cancer, nonsmall cell lung carcinomas, but not in small cell lung cancer.
Abstract: The recently discovered fur gene encodes a membrane-associated protein with a recognition function. To further characterize the gene, we studied its expression by Northern blot analysis using poly(A)-selected RNA from a variety of organs of African green monkey and rat. The fur gene appeared to be differentially expressed, relatively high levels of fur mRNA being present in specimens of liver and kidney, low levels in brain, spleen, and thymus, and very low levels in heart muscle, lung, and testis. mRNA levels in specimens of human lung tissue without neoplastic lesions were also very low. Similar analyses of primary human lung carcinomas of different histopathological types revealed a highly selective and strong elevation of fur expression in nonsmall cell lung carcinomas, but not in small cell lung carcinomas. These results indicate that fur expression can be used to discriminate between these two types of human lung cancer.
TL;DR: The present results support the view that the 5-HT hyperinnervation following neonatal 6-OHDA treatment is a collateral sprouting response induced by lesioning of the striatal DA neurons.
TL;DR: The 2D solid-state nutation NMR expt. for the detn. of quadrupole parameters, as introduced by Samoson and Lippmaas (1983) is evaluated in this paper.
TL;DR: In this article, a single-subject study on a free-living chimpanzee mother-infant relationship was conducted to investigate the development of contact-and distance regulation for free living chimpanzee mothers and infants.
Abstract: Several investigators discussed the need to know more about conditions which facilitate normal human development, especially the need for a better understanding of the processes at work during the development towards greater independence in normal and pathogenic human relationships The study reported in this paper aims to provide a description of the processes at work during the development of contact- and distance regulation for free-living chimpanzee mother-infant relationships We believe that such an ethological study contributes to human studies by providing methods of observing and analysing behaviour, and by providing hypotheses that can be tested Our study takes a systems approach to mother-infant contact- and distance regulation We looked at the history of mother-infant relationship in terms of the effects of changes in the mother's and infant's behaviour on the mother-infant dyad as a self-regulating homeostatic system A single-subject research design was used, because it has special advantages for the study of developmental processes, not shared by the usual experimental- or correlational designs We found that the infants' progress towards greater independence proceeds discontinuously in 5 jumps over the first 24 months With each jump the following drastic changes are found in the quality of the distance-regulation between mother and infant and/or the amount of time spent at a certain distance: 1 After month 2 maternal behaviour related to carrying and supporting the babies in the ventro-ventral position decreased sharply and the babies were forced to cling to the mother themselves 2 In month 5-6 a period of mother-infant conflict was found in which aggressive maternal rebuffs were aimed at breaking nipple- and ventro-ventral contact Before this age the mothers were primarily responsible for ventro-ventral contact, and after this age the infants were A relation was found between the rebuffs and the onset of dorsal riding and eating solid food These changes in the mother-infant interaction coincided with physical changes such as a change in the speed of growth and the eruption of teeth The findings are placed in the wider framework of mammalian development 3 After month 7 an explosion of the frequency of the infants' excursions was found and the infants now made short lasting excursions and remain within arm's reach from their mothers It is argued that such excursion behavior expresses the infants' concern with the distance to their mothers at this age 4 Around month 12 and month 18 periods of mother-infant conflict were found in which the aggressive maternal rebuffs were aimed at breaking body contact Both periods of mother-infant conflict were associated with peaks in the infants' responsibility for body contact and with rises in the amount of time spent in this contact Both periods of mother-infant conflict were followed by sharp drops in the amount of time spent in body contact, and after each drop time spent in body contact remained at a newly reached level Furthermore, after both periods of mother-infant conflict all infants made use of space more distant from their mothers We found that mothers do not promote the infants' independence as a whole in each confict period, but that they do so only for a particular aspect in training the infants how to adapt to other individuals and to the physical outer world when using the new ability It is argued that mothers recognize the ages that their infants are ready to reorganize their behaviour, upon which they force them to do so The periods of mother-infant conflict around month 12 and 18 are preceded by periods of regression: temporary shifts back to mainly staying in closer contact (= qualitative regressive shifts) and temporary increases in the amount of time spent in ventro-ventral contact (= quantitative regressive peaks) It is suggested that regressive behaviour is a common feature of normal development after a certain age We called a period in which the succession of regression and/or conflict and/or jump towards greater independence was found a labile period, as opposed to stabile periods In the general discussion the following topics are attended to: a) The possibility that "labile periods at specific ages" in the mother-infant relationship are a common feature in normal development b) The possibility that changes in maternal behaviour in each labile period are responsible for the phenomenon of jumps in the growing independence, provided that the infants are not pushed beyond their maturational abilities c) The possibility that regression, which precedes mother-infant conflict, is associated with maturational changes in the infant is discussed Several authors associated regressive behaviour with spurts in development d) The possibility that maturational changes are associated with developmental steps Infants contribute to changes in the mother-infant systems as they change maturationally The latter changes were established independently of their effect on the mother-infant relationship by PLOOIJ (1984) He looked for qualitative changes over development in behaviour and recognized 5 steps in the infant's first year of life It is discussed that the onsets of labile periods in the mother-infant relationship are associated with the developmental steps It seems that a developmental step triggers mother-infant conflict, and that mother's behaviour during this conflict is of vital importance in realizing the infant's developmental potential PETERFREUND's (1971) thinking on the relation between maturation and learning (reprogramming) suggests mother's helpful contributions to what happens around the times of occurrence of developmental steps We related our findings to BOWLBY's (1969, 1973, 1980) attachment theory The possibility is discussed that attachment takes different forms over age, depending on the proximity involved and the skills available to the infant, and that it is active and present from birth onwards
TL;DR: Free steroid assays were performed by applying the same procedure to equilibrium dialysates obtained after dialysing plasma against an equal volume of buffer, instead of measuring tracer distribution, and tended to follow the plasma free and salivary cortisol pattern, both within and between the study groups.
TL;DR: It is proposed that specific binding of glycoproteins by oral bacteria constitutes a mechanism for the degradation of salivary glycoprotein by the oral microflora and that S. sanguis II had a higher cell yield and consumed a higher proportion of the sugars and sialic acid in the glyCoproteins than did S. Sanguis I.
Abstract: The present experiments were aimed at studying the degradation of salivary glycoproteins by the oral microflora. To this end, S. sanguis I strain Ny476 and S. sanguis II (S. mitior) strain Ny581 were grown continuously in human-whole saliva. Under these conditions, the strains produced a variety of cell-associated hydrolytic activities, including glycosidases, exo- and endopeptidases, and esterases. S. sanguis II generally exhibited higher levels of enzyme activity than did S. sanguis I, in particular of neuraminidase that was produced only by S. sanguis II. In accordance, S. sanguis II had a higher cell yield and consumed a higher proportion of the sugars and sialic acid in the glycoproteins than did S. sanguis I. Interestingly, S. sanguis I, which is devoid of neuraminidase, is known to have a lectin with specificity for sialic acid, whereas S. sanguis II has affinity for galactose residues in the glycoproteins. We propose that specific binding of glycoproteins by oral bacteria constitutes a mechanism to collect nutrients in the vicinity of the cell. The special ability of S. sanguis II to utilize saliva for growth was further exemplified by its selection in batch-wise enrichments of dental plaque on saliva. The microflora in these enrichment cultures always consisted of Peptostreptococcus micros, S. sanguis II, and Fusobacterium nucleatum as the dominant organisms. Further, S. mitis and Gemella haemolysans were generally found to be present. The enrichment cultures produced a wide variety of mainly cell-bound hydrolytic enzymes. This resulted in almost complete breakdown of salivary glycoproteins in the culture.
TL;DR: In this paper, the authors present aperiodic crystals from a unifying point of view, showing why it is justified to call them crystals, despite the lack of a three-dimensional lattice periodicity, and discuss in what sense they differ from periodic crystals in structure, symmetry and other physical properties.
Abstract: The aim of this review is to present aperiodic crystals from a unifying point of view, showing why it is justified to call them crystals, despite the lack of a three-dimensional lattice periodicity, and to discuss in what sense they differ from periodic crystals in structure, symmetry and other physical properties. The extension of the concept of crystal has been based, during the last two decades, on investigation of incommensurate crystal phases. Among these, the most important ones are the modulated crystals. Their crystallographic nature, already apparent in the diffraction pattern, could be made explicit on the symmetry level by embedding in a higher-dimensional Euclidean space. The recent discovery of quasicrystal phases (representing a fairly different class of aperiodic crystals than the modulated ones) can also be approached in a similar way. Furthermore, it now appears that another class of incommensurate crystals, the so-called composite structures, represents a kind of intermediate ca...
TL;DR: It was found that the threaded ring behaves as a relatively rigid implant shielding the trabecular bone and enhancing load transfer through the cortical shells.
Abstract: The load-transfer mechanism and stress patterns in the acetabulum reconstructed with a threaded cup were investigated relative to the normal hip using the Finite Element Method (FEM). Several models were applied in the analysis to investigate the effects of axisymmetric 3-D versus 2-D approaches, inclusion of the femoral head, and local stress patterns around the threads in three types of implant/bone bonding modes. It was found that the threaded ring behaves as a relatively rigid implant shielding the trabecular bone and enhancing load transfer through the cortical shells. Load transfer from ring to bone is concentrated at the first and last threads where the subchondral bone layer is penetrated. Stress peaks of up to 24 MPa occur in these regions.
TL;DR: The authors found that in nearly all these nations, kissing, flirting and sexual involvement of one of the partners with an interloper evoked jealousy, while dancing, hugging, and sexual fantasies led, on the average, to a neutral reaction in all nations surveyed.
Abstract: This paper focuses on cross‐cultural differences in sexual jealousy. It is assumed that cultures differ (a) in the incidence of sexual jealousy, (b) in the range of acceptable strategies for coping with a jealousy situation, and (c) in the behavior evoking sexual jealousy. We addressed the last aspect. Subjects were 2,079 students from seven industrialized nations: Hungary, Ireland, Mexico, the Netherlands, the Soviet Union, the United States, and Yugoslavia. Results showed that in nearly all of these nations, kissing, flirting, and sexual involvement of one of the partners with an interloper evoked jealousy. On the other hand, dancing, hugging, and sexual fantasies led, on the average, to a neutral reaction in all nations surveyed. Nevertheless, there were striking cross‐national differences in the relative value attached to a particular behavior. Furthermore, there were cross‐cultural sex differences. In all seven nations, women became more upset when their partner kissed someone else, and men reacted r...