Showing papers by "Utrecht University published in 1978"
TL;DR: In this article, it is shown that the topological operators and the gauge field operators form a closed algebra from which it is deduced that this system can be in one of the four different phases: (i) spontaneous breakdown via an explicit or composite Higgs field, (ii) no Higgs fields but permanent confinement of gauge quantum numbers, (iii) Higgs effect and still confinement, presumably only if there is an unbroken subgroup, and (iv) an intermediate phase (critical point?) with massless particles.
1,321 citations
TL;DR: Capillary g.l.c. on SE-30 of trimethylsilylated (-)-2-butyl glycosides of d and l monosaccharides gives multiple peak patterns, which can be used for the assignment of the absolute configurations as mentioned in this paper.
818 citations
TL;DR: The polymorphic phase behavior of aqueous dispersions of phosphatidylethanolamines isolated from human erythrocytes, hen egg yolk and Escherichia coli have been investigated employing 31P NMR techniques as mentioned in this paper.
387 citations
TL;DR: It is proposed that the bilayer structure of lipids in biomembranes may be in dynamic equilibrium with other available phases and a mechanism of “flip-flop” phenomena in biological membranes is suggested.
333 citations
TL;DR: The present experiments aimed to investigate the effects of oxytocin administered intracerebroventricularly at various intervals after the learning trial on the retention of a passive avoidance response and the effect opposite to that of vasopressin.
314 citations
TL;DR: The nature of Ca2+-induced changes in bilayers containing negatively charged phospholipids is strongly dependent on the character of the polar headgroup of the negatively chargedospholipid involved.
291 citations
TL;DR: In this article, conductivity measurements have been performed on compressed powder specimens of Bi 2 O 3 in the temperature region 300-800°C and the conductivity in the β, γ, and δ phases is predominantly ionic.
288 citations
TL;DR: The results are interpreted to indicate that DTγE or a closely related peptide is an endogenous neuroleptic and may be that a reduced availability as a result of an inborn error in the generation ofDTγE is an etiological factor in psychopathological states for which Neuroleptic drugs are beneficial.
284 citations
TL;DR: In this article, the luminescence of single crystalline and powder specimens of β-Ga 2 O 3 has been studied in the temperature range 5 −300°K and the results indicated that the green emission was caused by the recombination of an electron in a V × o or Ga × i center and a hole trapped in a gallium ion vacancy.
282 citations
TL;DR: It is concluded that centrally released oxytocin may be a naturally occurring amnesic neuropeptide and appeared to be either facilitated or attenuated after subcutaneous Oxytocin administration.
225 citations
TL;DR: The close correlation between the results obtained here and previous X-ray studies confirms 31P NMR as a useful analytical procedure for investigating the polymorphic phase behaviour of hydrated phospholipids.
TL;DR: The rate determining step of reaction 2 is most probably the transfer of an electron from a π8* orbital of HO2 to the empty su* orbit of H2O2 as mentioned in this paper.
Abstract: — The Haber-Weiss cycle:
was investigated at low pH by radiolysis of oxygen or nitrogen saturated solutions of hydrogen peroxide. It was found that reaction 2 has a low rate constant: k2= 3.0 ± 0.6 M-1 s-1 (pH 2.3, 22°C). The rate determining step of reaction 2 is most probably the transfer of an electron from a π8* orbital of HO2 to the empty su* orbital of H2O2. Overlap between these two orbitals is hindered by the filled π8* orbitals of H2O2. Fe(HI)EDTA catalyses reaction 2.
TL;DR: In this paper, it was shown that the cut which is present as the leading singularity in the two-point function of the Ising field theory for $Tl{T}_{c}$ and $H=0$ breaks up into a sequence of poles for $H\ensuremath{
e}0$.
Abstract: We demonstrate that the cut which is present as the leading singularity in the two-point function of the Ising field theory for $Tl{T}_{c}$ and $H=0$ breaks up into a sequence of poles for $H\ensuremath{
e}0$. Both the positions and the residues of the low-lying poles are calculated.
TL;DR: In this article, the luminescence of β-Ga2O3 crystals and powder specimens has been studied in the temperature range 5-300 K. The measurements have been performed on nominally pure samples and on samples that had been doped with aliovalent cations.
TL;DR: Contrast detection thresholds for moving spatial sine wave gratings were obtained, at the fovea, and at eccentricities of 1°, 2°, 4°, 6°, and 8° on the nasal horizontal meridian, for two subjects as mentioned in this paper.
Abstract: Contrast detection thresholds for moving spatial sine wave gratings were obtained, at the fovea, and at eccentricities of 1°, 2°, 4°, 6°, and 8° on the nasal horizontal meridian, for two subjects. The target field subtended 30 × 30 minutes of arc. The spatial frequency range extended from 2 cpd up to the spatial resolution limit, the temporal frequency range from 0.1 Hz up to the CFF. Mean retinal illuminance was 10 trolands. We find for these conditions: (i) Contrast detection thresholds are higher, the higher the spatial and/or temporal frequency of the stimulus. (ii) Acuity appears to be independent of the temporal frequency, the CFF appears to be independent of the spatial frequency. (iii) The higher the eccentricity, the higher the contrast detection threshold for any drifting sine wave pattern. The threshold doubles roughly any 2°–3° for spatial frequencies of 2–20 cpd, except that the visual field for a given fineness of grating is blind beyond a certain critical eccentricity. This critical eccentricity is a monotonically decreasing function of the spatial frequency of the grating. These measurements do not support the hypothesis that coarse patterns are preferentially detected at extrafoveal sites in the visual field.
TL;DR: In the last decennium great progress has been made in the development of more stable and highly active pyrethroids and in the near future more widespread application of these compounds may be expected.
Abstract: Natural pyrethrins, also called "pyrethrum" or "'pyrethrum extract", have long been known as insecticides. They are extracted from the flowers of Chrysanthemum cinerariaefolium Vis which contain six insecticidally active components, of which pyrethrin I and pyrethrin II are the most active (Head 1973, Elliott & Janes, 1973). Pyrethrins are widely used for domestic purposes and for the protection of stored food, but for general pest control in agriculture they are applied on a limited scale only. The total world production does not exceed about 350 tons per yr: cf. organophosphates, about 100,000 tons (Glynne-Jones, 1973: Fest & Schmidt. 1973). Their Limited use is due in part to economic reasons. Other factors restricting their use are their low photostability and high (bio) degradability, and pyrethrins are usually applied in combination with metabolic synergists. Apart from these problems, the pyrethrins possess excellent insecticidal properties combined with remarkably low mammalian toxicity. Their insect (topical) to mammalian (oral) toxicity ratio is much better than for the majority of other organic insecticides (Elliott, 1977). In mammals and other animals pyrethrins are rapidly metabolized and practically no residues are left in the biosphere. These favourable properties have stimulated the search for synthetic insecticides based on the structure of the pyrethrins. The production of synthetic pyrethroids on a commercial basis started with allethrin and cyclethrin around 1950 (O'Brien, 1967). These early compounds, however, still lacked sufficient stability and they are less effective against many species of insects than the natural product. At the moment the total yearly production of allethrin is some 100 tons. In the last decennium great progress has been made, notably by Ellion and co-workers, in the development of more stable and highly active pyrethroids and in the near future more widespread application of these compounds may be expected. Because of the complex molecular structure, the most important features of the pyrethroid molecule will be described briefly before the mode of action is discussed. Excellent reviews on the structural requirements of insecticidal active pyrethroids can be found elsewhere (Elliott, 1971, 1976a, b, 1977; Elliott eI al., 1974a). Most of the information presented in the next section is derived from these reviews. GENERAL FEATURES OF THE PVRETHROID MOI.ECLI,I."
TL;DR: A model is proposed which accounts for the effect of bilayer thickness on the amphotericin B-induced permeability changes in membranes.
TL;DR: Recordings from three patients in cardiac arrest are shown to illustrate the importance of monitoring pulmonary perfusion by means of the capnogram as a continuous guide to the cardiac output achieved by cardiac massage and resuscitation.
TL;DR: The frequency response demonstrates unequivocally that the lateral-line organ of Xenopus laevis functions as a water velocity detector.
Abstract: The stimulus response relation of the epidermal lateral-line organ of Xenopus laevis was studied by recording activity of single afferent nerve fibres in isolated preparations. Linear frequency response analysis over a frequency range of 0.1–100 Hz was performed under steady-state conditions, using small amplitude, plitude, sinusoidal water displacements produced by a glass sphere at a short distance from the skin. Period histograms of afferent nerve activity were computed, and amplitude, phase and mean activity of the response were determined by means of Fourier analysis. A standardization procedure at the start of each experiment made scaling of the frequency responses of different preparations unnecessary. The results show that for small stimulus amplitudes the response of the lateral-line organ over the whole range of frequencies studied can adequately be described as a modulation of the spontaneous activity. The amplitude of the response is proportional to the stimulus amplitude, and the phase of the response is independent of stimulus amplitude. The lateral-line organ of Xenopus laevis can thus be regarded as a linear system for stimuli which produce modulation of the spontaneous activity. The frequency response demonstrates unequivocally that the lateral-line organ of Xenopus laevis functions as a water velocity detector. For frequencies of stimulation from 0.1–20 Hz the gain increases with a slope of 7.5 dB/oct, and up to 5 Hz the response is almost in phase with the water velocity. The extent to which the different transmission steps between stimulus and response will contribute to the frequency response is discussed.
TL;DR: The 31P NMR results indicate that when both species are in the liquid crystalline state the preferential interaction of cholesterol with the phosphatidylcholine component is maintained, and the effects do not therefore arise due to a preference of cholesterol for phospholipids in bilayer or non-bilayer phases.
TL;DR: The gene A protein of bacteriophageΦX174 has been used in vitro to convert ΦX RFI DNA into the relaxed RFII form by nicking the viral strand and the nucleotide sequence at the 3′ end of the nick gives the exact position of the origin of Φx RF DNA replication.
Abstract: The gene A protein of bacteriophage ΦX174 has been used in vitro to convert ΦX RFI DNA into the relaxed RFII form by nicking the viral strand. The nucleotide sequence at the 3′ end of the nick has been determined as – – T G C T C C C C C A A C T T GOH. This sequence gives the exact position of the origin of ΦX RF DNA replication.
TL;DR: A significant flow of radioactivity from the pituitary to the brain, particularly to the hypothalamus, is suggested, and transport to other brain areas may occur via the cerebrospinal fluid, but a neural route cannot be excluded.
TL;DR: It is shown that a smaller area, measuring several just resolvable distances across, has to be stimulated before successive or simultaneous contrast detection is possible at all.
Abstract: Contrast detection thresholds for moving sine wave gratings were obtained at the fovea and at eccentricities of 6°, 21°, and 50° on the nasal horizontal meridian. The targets subtended from 30 × 30 minutes of arc up to 16° × 16°. We have found that the contrast detection thresholds depend critically on the extent of the target field. If this extent is large enough peripheral detection thresholds are on a par with those measured at the fovea, only the sensitivity range is shifted to lower spatial frequencies. We show that if the just resolvable distance at any eccentricity is taken as a yardstick, and field width and spatial frequency are scaled accordingly, then the spatio-temporal contrast detection thresholds become identical over the whole visual field. It is shown that a smallest area, measuring several just resolvable distances across, has to be stimulated before successive or simultaneous contrast detection is possible at all. Detection performance improves if the stimulated area is enlarged up to diameters of at least 102 just resolvable distances. The just resolvable distance correlates well with mean interganglion cell distance, and with the cortical magnification factor.
TL;DR: It was found that at 25 and 37°C rat liver microsomal phosphatidylcholine was completely and rapidly available for replacement by egg phosphate, and vesicles prepared from totalmicrosomal lipids could only be exchanged for about 60%, compared with about 60% with intact microsomes.
TL;DR: In this paper, contrast detection thresholds for moving sine wave gratings were obtained at the fovea and at eccentricities of 6°, 12°, 21°, 32°, and 50° on the nasal horizontal meridian.
Abstract: Contrast detection thresholds for moving sine wave gratings were obtained at the fovea and at eccentricities of 6°, 12°, 21°, 32°, and 50° on the nasal horizontal meridian. The field subtended 4° × 4°. Spatial frequencies ranged from 0.25 cpd up to the resolution limit, temporal frequencies from 0.1 Hz up to the CFF. Mean retinal illuminance was 10 trolands. We find for these conditions: (i) For any eccentricity there exists a unique combination of spatial frequency and velocity for which the threshold is a minimum. (Extremes are 2 cpd and 2° s−1 at the fovea, and 0.5 cpd and 12° s−1 at an eccentricity of 50°. (ii) Acuity depends little on velocity, the CFF only little on spatial frequency. (iii) The higher the eccentricity, the higher the threshold for any drifting sine wave pattern. Except for this the qualitative threshold behavior as a function of spatial and temporal frequency is identical at the fovea and at eccentricities up to 50°. The thresholds double every 12° for spatial frequencies of 0.25–2 cpd. For a given spatial frequency the visual field is blind beyond a certain critical eccentricity. This critical eccentricity is a monotonically decreasing function of spatial frequency.
TL;DR: It is suggested that the glucose concentration in the blood as related to the amount of available fatty acids and their degree of unsaturation may be factors governing the synthesis of surfactant lipids.
TL;DR: Evidence is presented which strongly suggests that the isotropic motion of microsomal phospholipids does not arise from tumbling of themicrosomal vesicles or from lateral diffusion of phospholips around these vesicle, with implications for possible transitory formation of intramembrane non-bilayer lipid configurations.