Showing papers by "Radboud University Nijmegen published in 1978"

Low-energy nucleon-nucleon potential from Regge-pole theory

Abstract: The results from a potential model for the low-energy $\mathrm{NN}$ interaction based on Regge-pole theory are presented. The forces are due to the dominant parts of the $\ensuremath{\pi}$, $\ensuremath{\eta}$, ${\ensuremath{\eta}}^{\ensuremath{'}}$, $\ensuremath{\rho}$, $\ensuremath{\omega}$, $\ensuremath{\varphi}$, $\ensuremath{\delta}$, $\ensuremath{\epsilon}$, ${S}^{*}$ trajectories in the complex $J$ plane, which are the well-known one-boson-exchange forces. Novel features are the dominant $J=0$ parts of the Pomeron, $f$ ${f}^{\ensuremath{'}}$ and ${A}_{2}$ trajectories. At the Reggeon vertices we use exponential form factors, as suggested by high-energy fits. The Pomeron, $f$, and ${f}^{\ensuremath{'}}$ trajectories lead essentially to repulsive central Gaussian potentials. This soft-core, partially nonlocal potential model fits the $\mathrm{NN}$ data with $\frac{{\ensuremath{\chi}}^{2}}{\mathrm{data}}=2.09$, which is lower than any other model we know of. The $\mathrm{NN}$ coupling constants have reasonable values, and the contributions of the Pomeron and tensor trajectories agree with estimates from high-energy fits.

TABORD, a program for structuring phytosociological tables

Abstract: Since Benninghoff & Southworth (1964) published an abstract of their computer program for ordering phytosociological tables according to the Braun-Blanquet (1964) method along the lines developed by R. Tuxen and collaborators in the 1930’s (which were first described in detail by Ellenberg 1956, see also Mueller-Dombois & Ellenberg 1974), many similar programs have been devised. They have been briefly reviewed by Westhoff & van der Maarel (1973), who distinguished two types of program: a. for tables with comparatively many releves and few species, b, for tables with comparatively few releves and many species. The Type a programs concentrate on finding groups of species with a similar distribution within the table which can be used in finding species/releve blocks. Typical examples are the programs by Moore (1973, Moore et al. 1970), Ceska & Roemer (1971) and Stockinger & Holzner (1972, see Holzner, Werger & Ellenbroek 1978).

Semantic errors or statistical flukes? A note on Allport's "On knowing the meaning of words we are unable to report."

Abstract: Allport (1977) has claimed that normal subjects who view briefly a multi-word array, which is then pattern-masked, produce semantic errors analogous to those made by subjects with “deep dyslexia”. We claim that the rate at which normal subjects make such errors is consistent with their arising purely by chance.

On the development of the cerebellum of the trout, Salmo gairdneri

Abstract: Patterns of cell migration in the cerebellum of Salmo gairdneri RICHARDSON, 1836 were studied in fish ranging in length from 4.5 to 230 mm. Sagittal and transverse series were stained with haematoxylin-eosin or according to Nissl or Golgi. The cerebellum of the trout comprises three main parts, i.e. the massive corpus cerebelli, the folded valvula cerebelli and the transversely oriented lobus vestibulolateralis. The early cerebellar anlage is a simple plate, which is delimited from the tectum mesencephali by the fissura rhombo-mesencephalica. The histogenesis may be divided into three phases. During the first phase the matrix layer produces the mantle layer. During the second phase the three typical cerebellar layers are formed. The third phase is characterized by growth. As regards the first phase, the mantle layer develops throughout almost the entire extent of the cerebellar anlage. Only in a narrow paramedian strip (matrix zone M) this layer does fail to appear. In regions where the mantle layer is formed, the matrix no longer occupies the whole width of the wall and is termed the ventricular matrix. The largest part of the ventricular matrix is gradually exhausted. However, in some places this matrix persists as a layer of proliferating cells. This holds for the matrices of the caudal border of the cerebellum: matrix zone L, surrounding the lateral recesses of the fourth ventricle, and matrix zone P, connecting the matrix zones L. The mantle layer produced in the first phase of histogenesis mainly develops into the ganglionic layer. The second phase of histogenesis is characterized by the formation of a secondary matrix. Newly produced cells of the matrix zones M, L and P migrate away from their sites of origin towards the regions where a mantle layer previously has been formed. The majority of these cells develops into granule cells. Migration of the cells produced in the first phase of histogenesis occurs in the radial direction. Because of the curvature of the cerebellum this direction changes with respect to the main longitudinal axis of the brain from region to region. The migration paths of the granule cells show variable directions, namely (a) tangential followed by radial, for granule cells in the corpus cerebelli and in the medial parts of the valvula cerebelli and the lobus vestibulolateralis, (b) tangential, for granule cells in the lateral parts of the valvula and (c) radial, for granule cells in the lateral parts of the lobus vestibulolateralis. The analysis of these migration patterns elucidates both the histogenesis and the morphogenesis of the cerebellum of the trout.

Kinetics of carbamazepine and carbamazepine-epoxide, determined by use of plasma and saliva.

Abstract: The concentration-time curves of carbamazepine (CBZ) and its metabolite (carbamazepine-10,11-epoxide; CBZ-epoxide) were determined in patients undergoing long-term antiepileptic drug treatment with the use of plasma and saliva data. Plasma and saliva samples were assayed concurrently for each patient by liquid chromatography. There was excellent linear correlation between CBZ levels in saliva and plasma (r = 0.991, p less than 0.001) over a large concentration range. The saliva/plasma ratio for CBZ concentration was 0.26 +/- 0.01 (SD). Since CBZ binding to plasma proteins is in the order of 76%, saliva CBZ concentration seems to reflect the unbound fraction of the drug in plasma. CBZ-epoxide has not been detected in saliva. The pharmacokinetic parameters of CBZ-epoxide were determined in 6 patients. The pharmacokinetic parameters of CBZ obtained from saliva concentrations were in excellent agreement with those obtained from plasma concentrations. Thus, CBZ determination in saliva is convenient for controlling blood levels in patients as well as for studying pharmacokinetics. The half-life, the relative body clearance of CBZ, and the metabolite concentration during steady-state, expressed as percent the parent compound, appear to be significantly different in patients on single and combined drug therapy.

Identification of three sulphur-containing urinary metabolites of styrene in the rat.

Abstract: 1. After administration of styrene (1) to rat, three sulphur-containing urinary metabolites were isolated in the molar ratio of III : IV : V equal to 65 : 34 : 1. 2. These metabolites were identified as N-acetyl-S-(1-phenyl-2-hydroxyethyl)cysteine (III), N-acetyl-S-(2-phenyl-2-hydroxyethyl)cysteine (IV) and N-acetyl-S-(phenacyl)cysteine (V). 3. After a single dose (250 mg/kg, 2.4 mmol/kg) styrene, the totally excreted mercapturic acids in the urine amounted to 10.7 +/- 1.0% (n = 5) of the dose.

Theory and practice of a posteriori “Wiener” filtering of average evoked potentials

Abstract: In this study a theoretical and practical analysis of the technique of a posteriori “Wiener” filtering of averaged evoked potentials is presented. It is shown that spectral smoothing plays a central role in obtaining a reliable estimate. Attention is paid to some practical problems that arise when the method is applied in discrete time. In an illustrative case study results are compared to theoretical Wiener filtering, while the influence of slow amplitude modulation has also been investigated. Some of the conflicting results regarding the method that have been reported in several recent papers are discussed. It is concluded, that when the method is applied with prudence, it may lead to an improved estimation of those evoked potentials that can be assumed to be approximately stationary. If the latter assumption is not valid, application of a time-varying filter technique is recommended instead.

Developmental biology of Pneumocystis carinii, an alternative view on the life cycle of the parasite

Abstract: In this paper we present, based on elaborate ultrastructural studies, data on the existence of both intracellular and extracellular stages of Pneumocystis carinii, which result in a proposal of a new life cycle of the parasite. Up to now the formation of daughter cells in thick-walled pneumocysts is supposed to be the only way of multiplication. The present study shows that in rats treated with cortisone acetate the formation of daughter cells also takes place within thin-walled pneumocysts. In our opinion this way of multiplication is important for the understanding of the rapid increase in number of the parasites in an infected lung.

Blood gases at several levels of oxygenation in rats with a left-shifted blood oxygen dissociation curve.

Abstract: Theoretical deductions have shown that a shift of the blood O2 dissociation curve (ODC) to the right might improve O2 transport to tissues at normoxia and at mild hypoxia whereas at severe hypoxia the organism should be better off with an ODC shifted to the left (Turek et al., 1973b; Turek and Kreuzer, 1976). The present study was performed in order to ascertain this ambiguous effect of an ODC shift depending on the degree of hypoxia in intact animals. A major displacement of the ODC to the left was achieved in rats by chronic administration of sodium cyanate (NaOCN). Control animals received sodium chloride (NaCl) instead. Arterial and mixed-venous $$P_{{\text{O}}_{\text{2}} }$$ , $$P_{{\text{CO}}_{\text{2}} }$$ , and pH were measured at normoxia and during breathing 14.9, 8.0, or 5.6% O2 in N2 in both groups. From $$P_{{\text{O}}_{\text{2}} }$$ , pH, ODC and arterial hematocrit, arterial and mixed-venous O2 contents were estimated and $$({\text{a}} - {\text{v)}}_{{\text{O}}_{\text{2}} }$$ as an index of blood O2 extraction was obtained. At normoxia and during breathing 14.9% O2 the NaOCN rats had a lower mixed-venous $$P_{{\text{O}}_{\text{2}} }$$ than the NaCl rats without any difference in pH. Arterio-venous O2 difference did not differ at normoxia but was lower in NaOCN rats at 14.9% O2. However, at 8.0 and 5.6% O2 the NaOCN rats had a higher mixed-venous $$P_{{\text{O}}_{\text{2}} }$$ , an increased $$({\text{a}} - {\text{v)}}_{{\text{O}}_{\text{2}} }$$ , and a higher pH (arterial and mixed-venous). At 5.6% O2 the NaCl rats developed a severe acidosis concomitant with pronounced hypocapnia. These findings confirm that rats with a left-shifted ODC have an impaired O2 transport to tissues at normoxia and mild hypoxia but a more efficient O2 transport at severe hypoxia as compared with rats with an unshifted ODC, in agreement with our previous theoretical studies.

Leaf size and leaf consistence of a riverine forest formation along a climatic gradient

Abstract: The riverine forest formation on the levees along the Orange River in South Africa shows a shift in floristic composition as the river traverses various climatic zones on its course through the temperate area in the eastern parts of the subcontinent, the central semi-desert region, and the desert area near the Atlantic in the west. Leaf size classes and leaf consistency types of the woody species in the riverine forest were determined for each community. Analysis of these data revealed a diversification of leaf sizes as the climate changed from temperate to hot and arid and particularly microphylls became relatively less important and were replaced by smaller leaves in the hot areas. In the same direction malacophylls, which are of the "low-cost, quick-profit" strategy type and are well represented in the temperate, frosty areas, disappear and xeromorphic leaves ("high-cost, slow-profit" strategy type) increase in importance. It is suggested that the cooler conditions with higher wind speeds and higher degrees of average air humidity near the Atlantic coast are reflected by an increase in mesophylls which are sclerophyllous as an adaptation to the frequently and rapidly changing temperature conditions here.

Atonia after carbachol microinjections near the locus coeruleus in cats.

Abstract: The effect of microinjections of carbachol into the dorsolateral pontine tegmentum on the behaviour of cats is investigated. Injections of small amounts (50 and 500 ng) of carbachol into the pontine reticular formation induced muscular atonia in otherwise awake animals. The atonia is not due to cholinergic stimulation of the noradrenergic cells of the locus coerulus of the dorsolateral pons, since the most effective sites were situated ventrally to the locus coeruleus and alpha- and beta-adrenergic blocking agents did not affect the atonia. The results are discussed in view of the postulated role of the locus coeruleus in paradoxical sleep.