Showing papers by "University of Groningen published in 1974"
TL;DR: In this paper, the stable carbon isotope fractionation between gaseous CO 2 and dissolved bicarbonate has been measured from 5 to 25°C by a method of high precision.
1,579 citations
TL;DR: The concept of behavioural states in the young infant has been used in two connotations: (1) as a descriptive categorisation of behaviour; and (2) as an explanation of brain mechanisms which modify the responsiveness of the infant.
998 citations
211 citations
TL;DR: In this article, it was proposed that nuclei (away from closed shells and from regions of large deformation) be described as a boson gas and exploited the underlying O(5) symmetry analytic expressions for the eigenvalues of the boson Hamiltonian and for the transition matrix elements.
124 citations
TL;DR: In this article, a phase diagram of polyethylene/1,2,4,5-tetrachlorobenzene and hexamethyl-benzene was calculated for χ = 0.37, which gave a eutectic temperature of 135°C.
112 citations
TL;DR: Electron microscopy of the dissociation products of α-hemocyanin of the snail Helix pomatia reveals two distinctly different conformations of 1 10 -size molecules: a C(compact)-form at high ionic strength and pH near 8, and an L(loose-form at low ionicstrength and/or higher pH.
98 citations
TL;DR: A new magnetic spectrograph, the QMG/2, has been designed for the Kernfysisch Versneller Instituut, Groningen as mentioned in this paper, which includes a second multipole, a straight focal plane, constant dispersion, constant angle of incidence (45°) on the detector, and a device called a "snake" used to adjust mechanically the effective shape of the field boundaries after manufacture.
95 citations
TL;DR: The results indicate that cathepsin D is not essential for degradation of proteins by liver lysosomal enzymes and that hepatocyte lysOSomes contain a set of proteases sufficient for rapid and extensive degradation of albumin.
94 citations
TL;DR: In this article, an experiment was performed to determine whether there would be a difference in insight between an inferential problem expressed in a symbolic and in a realistic form, and the results showed that the crucial underlying variables in the realistic condition may be revealed by manipulating those variables in concrete material which affect insight.
Abstract: An experiment was performed to determine whether there would be a difference in insight between an inferential problem expressed in a symbolic and in a realistic form. The task consisted of the selection of cards which, if turned over, could violate a given rule. The logical relation which the rule expressed was that of material implication, presented in four different linguistic forms. In addition, the rule expressed either an arbitrary relation between symbols, or a realistic relation between supposed states of affairs. There was a large difference between the symbolic condition and realistic condition: only 7 out of 24 subjects made the correct response in the symbolic condition, whereas 18 of them did so in the realistic condition. There was an interaction between the linguistic form of the rule and the mode of presentation of the problem, and a different error pattern for different linguistic forms. It is argued that the crucial underlying variables in the realistic condition may be revealed by manipulating those variables in concrete material which affect insight.
92 citations
TL;DR: In this paper, the various contributions to the hyperfine interactions as measured with the Mossbauer Effect technique, namely the isomer shift, the magnetic hyperfine interaction and the quadrupole interaction are summarized.
86 citations
TL;DR: It is suggested that intermittant illumination may, at least in part explain the observed coexistence of both types of purple sulfur bacteria in nature.
Abstract: The purpose of this study was to find a possible explanation for the coexistence of large and small purple sulfur bacteria in natural habitats. Experiments were carried out withChromatium vinosum SMG 185 andChromatium weissei SMG 171, grown in both batch and continuous cultures. The data may be summarized as follows: (a) In continuous light, with sulfide as growth rate-limiting substrate, the specific growth rate ofChr. vinosum exceeds that ofChr. weissei regardless of the sulfide concentration employed. Consequently,Chr. weissei is unable to compete successfully and is washed out in continuous cultures. (b) With intermittant light-dark illumination, the organisms showed balanced coexistence when grown in continuous cultures. The “steady-state” abundance ofChr. vinosum was found to be positively related to the length of the light period, and that ofChr. weissei to the length of the dark period. (c) Sulfide added during darkness is rapidly oxidized on subsequent illumination, resulting in the intracellular storage of reserve substances, which are later utilized for growth. The rate of sulfide oxidation/mg cell N/hr was found to be over twice as high inChr. weissei as inChr. vinosum. The observed coexistence may be explained as follows. In the light, with both strains growing, most of the sulfide will be oxidized byChr. vinosum [see (a)]. In the dark, sulfide accumulates. On illumination, the greater part of the accumulated sulfide will be oxidized byChr. weissei [see (c)]. A changed light-dark regimen should then have the effect as observed [see (b)]. These observations suggest that intermittant illumination may, at least in part explain the observed coexistence of both types of purple sulfur bacteria in nature.
TL;DR: In this article, a contracted double zeta basis set of 168 gaussian type functions was used to calculate the energy of the disproportionation reaction 2TCNQ − − TCNQ+TCNQL + TCNQL 2−.
TL;DR: In this article, a review of the available information in the field of low-energy ion reflection from metal surfaces is given, focusing on the so-called binary collision approach and its ranges of validity.
TL;DR: The excretory pattern of harmol and harmalol can be explained by different rates of conjugation of these substrates by UDP glucuronyltransferase and phenolsulfotransferase, as found in vitro.
TL;DR: Direct experimental evidence, concerning the relative selective values of electrophoretic variants is scarce, and in one well-documented case, Yamazaki11 did not find selective differences between esterase-5 variants in D. pseudoobscura.
Abstract: Lewontin and Hubby1 have shown, by means of protein electrophoresis, that about one third of the loci in Drosophila pseudoobscura populations are polymorphic. Comparable studies by others have provided similar figures for a variety of species including man2,3. Some authors4–6 have argued that the observed protein variation is merely a product of mutation and drift of neutral variants and is not maintained by selection. This view is severely criticised by others7,8, who stress the importance of selective forces. Indications for the operation of selective forces have mainly come, until now, from studies on geographical variation9,10. Direct experimental evidence, concerning the relative selective values of electrophoretic variants is, however, scarce. In one well-documented case, Yamazaki11 did not find selective differences between esterase-5 variants in D. pseudoobscura.
TL;DR: The results suggest that the degree of the diazepam effect is directly proportional to plasma concentrations and reCiprocal clearance values of diazepAM and N‐desmethyldiazepam.
Abstract: Fifteen nonpsychotic patients suffering from acute anxiety in a crisis situation, admitted for a short inpatient treatment, were treated orally with diazepam (Valium), 20 mg daily, for a period of at least 5 consecutive days. Measurements were made on 3 levels: (1) psychometric measurements, using rating scales, for the degree of improvement of a wide variety of anxiety symptoms, (2) pharmacochemical measurements of plasma levels of diazepam and its main active derivative N‐desmethyldiazepam, (3) clearance rates relative to body weight were calculated, (4) correlation between improvement ratings on the one hand and plasma concentrations and clearance ratings of both substances on the other hand. A control group consisted of 15 similar patients receiving placebo. The design was double‐blind and randomized. Our results suggest that the degree of the diazepam effect is directly proportional to plasma concentrations and reCiprocal clearance values of diazepam and N‐desmethyldiazepam. The minimal effective plasma concentration in the steady state is 400 ng per milliliter. The desmethyl metabolite has a slightly different action than diazepam, even a disturbing action on certain symptoms, with plasma levels of 300 ng per milliliter or more. Monitoring of diazepam treatment on the basis of plasma concentrations seems to be advisable.
TL;DR: The good moistening and lubricating qualities of the bovine saliva, as well as its ability to protect the mucosa, may be supposed to be due to its high content of mucins.
TL;DR: In this paper, computer simulations of the mononuclear Cu(II) EPR spectra of the nitrite-treated hemocyanins, using a spin Hamiltonian with orthorhombic symmetry and assuming an anisotropic linewidth, are reported.
TL;DR: Both the details of the dissolution behaviour as well as the surface morphology observed indicate the presence of screw dislocations in the single crystals with the dislocation line parallel to the c-axis.
Abstract: The dissolution of hydroxyapatite single crystals is highly anisotropic. Parallel to the c-axis the dissolution is fast, while perpendicular to the c-axis dissolution is negligible. In 5 M citric acid solutions at 37°, the acid penetrates into the single crystals parallel to the c-axis with a velocity of approximately 60 nM/sec. Scanning electron microscopy shows that the single crystals are twisted along the c-axis. Both the details of the dissolution behaviour as well as the surface morphology observed indicate the presence of screw dislocations in the single crystals with the dislocation line parallel to the c-axis.
TL;DR: A new agarolytic flexibacterium isolated from the IJsselmeer, a fresh-water lake that was in open contact with the North Sea until 1932, and adjacent areas in the central part of The Netherlands was investigated using enrichment culture techniques.
Abstract: The occurrence of agarolytic microorganisms in a variety of natural environments was investigated using enrichment culture techniques. From samples taken from the IJsselmeer, and adjacent areas in the central part of The Netherlands a new agarolytic flexibacterium was isolated. Enrichments inoculated with samples from other sources were unsuccessful. The yellow-pigmented organism exhibits gliding motility, but spreading was only occasionally detected. Since neither fruiting bodies nor microcysts were observed, the organism was placed into the genus Cytophaga and designated as Cytophaga flevensis sp. nov. The occurrence of this species is probably restricted to the IJsselmeer, a fresh-water lake that was in open contact with the North Sea until 1932, and some other lakes which are in direct contact with the IJsselmeer. The organism utilizes only carbohydrates as a carbon and energy source for growth and is strictly aerobic. When the organism is grown on agar, on its components or on melibiose, an extracellular agarase is produced. This enzyme is highly specific for polysaccharides containing neoagarobiose units and hydrolyzes neoagaro-oligosaccharides with a degree of polymerization of more than four.
TL;DR: In this article, high resolution absorption and laser induced emission spectra of the lowest B 3u (nπ * ) singlet state of s-tetrazine-h 2 and -d 2 in a benzene crystal at 1.8 K are presented and discussed.
TL;DR: In this paper, the Landau theory of phase transitions is applied to the case of a transition from 6h−4$ symmetry to 2h−16$ symmetry, and the restraints placed upon various thermodynamic quantities by the symmetry change are reported.
Abstract: The Landau theory of phase transitions is applied to the case of a transition from ${D}_{6h}^{4}$ symmetry to ${D}_{2h}^{16}$ symmetry. The restraints placed upon various thermodynamic quantities by the symmetry change are reported. It is shown that the MnP-type structure (space group ${D}_{2h}^{16}$) and the low-temperature form of NbS (space group ${C}_{6\ensuremath{
u}}^{4}$) are related distortions, as both correspond to the same irreducible representation ${M}_{4}^{\ensuremath{-}}$ of the NiAs-type structure (space group ${D}_{6h}^{4}$).
TL;DR: In this article, the X-ray photoelectron spectra of CuCr2Se4 and some other copper and chromium containing compounds were studied to reveal the valence state of the copper atom.
TL;DR: In this paper, the authors studied the emissions of biacetyl excited at 4200 A at pressures down to 10−3 torr and showed that after excitation, the molecule rapidly transferred (rate constant kS→T) to the triplet state, giving rise to the nanosecond decay time; and can then transfer back to the singlet state (Rate constant kT→S), giving up to the microsecond emission.
TL;DR: In this article, a necessary and sufficient frequency-domain condition for the existence of a non-positive definite solution to the Riccati equation is shown to be necessary but not sufficient.
Abstract: The purpose of this correspondence is to correct a claim of [1]. Reference [1, theorem 4] states a necessary and sufficient frequency-domain condition for the existence of a nonpositive definite solution to the algebraic Riccati equation. This condition is, however, not correct, since the stated condition is necessary but not sufficient. This will be demonstrated by means of a counterexample.
TL;DR: Electron micrographs of erythrocruorin molecules from the polychaete Oenone fulgida reveal the presence of centrally placed subunits which are lacking in other giant erystrocru orins and chlorocruorins and are correlated with an increased sedimentation velocity.
TL;DR: In some depressive patients, regarded as therapy-resistant, the antidepressive effect of 1-5-hydroxytryptophan (in combination with a peripheral decarboxylase inhibitor) was ehanced by clomipramine at a dosage which, as such, was suboptimal.
Abstract: In some depressive patients, regarded as therapy-resistant, the antidepressive effect of 1-5-hydroxytryptophan (in combination with a peripheral decarboxylase inhibitor) was ehanced by clomipramine at a dosage which, as such, was suboptimal. This probably means that the therapeutic effect of 1-5-hydroxy-tryptophan is based on increase of serotonin at central serotonin receptors.
TL;DR: Helix pomatia α-hemocyanin can dissociate stepwise into 12-size, 110-size and 120-size molecules, and its intermolecular interactions appear to be predominantly electrostatic.
TL;DR: The results indicate that the formation of 5‐HT in the cerebral cortex from exogenous l‐5‐HTP, after inhibition of the peripheral aromatic amino acid decarboxylase, occurs predominantly in 5-HT containing nerve endings possibly by a specific 5‐ HTP‐decarboxyating enzyme.
Abstract: —l-5-Hydroxytryptophan (l-5-HTP) was administered intravenously to rats (12 mg/kg) after inhibition of the peripheral aromatic l-amino acid decarboxylase with l-α-hydrazino-α-methyl dopa (MK 486). The accumulation of 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid in the cerebral cortex was measured 1, 2 and 4 h after injection of 5-HTP with automated assay techniques. Besides controls two groups of rats were studied: rats after inhibition of tryptophan-5-hydroxylase with p-chlorophenylalanine (pcpa) and subjects with a chronic lesion in the area of the raphe nucleus. The net accumulation of both measured 5-hydroxyindoles was diminished in rat cerebral cortex after degeneration of 5-HT containing nerve endings, compared with control animals and pcpa-treated rats. These results indicate that the formation of 5-HT in the cerebral cortex from exogenous l-5-HTP, after inhibition of the peripheral aromatic amino acid decarboxylase, occurs predominantly in 5-HT containing nerve endings possibly by a specific 5-HTP-decarboxylating enzyme.
01 Jan 1974
TL;DR: This material plays a part in the evolution of our galaxy as mentioned in this paper, it can absorb energy which otherwise might escape, it plays a role in the formation of stars; it has, at least locally, gravitational effects.
Abstract: This material plays a part in the evolution of our galaxy. It can absorb energy which otherwise might escape. it plays a role in the formation of stars; it has, at least locally, gravitational effects. Further it interacts with stars and stellar radiation.