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Showing papers by "University of Groningen published in 1989"


Journal ArticleDOI
TL;DR: On a mesure les limites d'absorption des rayons X de l'oxygene 1s d'une serie d'oxydes de metaux de transition 3d dans les etats inoccupes du caractere metallique principal.
Abstract: The oxygen 1s x-ray-absorption edges of a series of 3d-transition-metal oxides have been measured. The structures at the edge arise from covalent mixing of the metal and oxygen states, which introduces oxygen p character in unoccupied states of mainly metal character. The spectra can be divided into two regions: The first is a double-peaked sharp structure near threshold, which can be related to the metal 3d states; the second is a broader structure 5--10 eV above the edge and is related to the metal 4s and 4p bands. We attribute the oxygen p character up to 15 eV above threshold to mainly oxygen 2p character. The data are analyzed in terms of ligand-field and exchange splittings. It is shown that the splitting between the two sharp peaks near threshold is related closely to the ligand-field splitting, but the relative intensities of the peaks are not fully explained at the present time.

972 citations


Book ChapterDOI
01 Jan 1989
TL;DR: The purpose of this paper is to give a tutorial exposition of what the authors consider to be the basic mathematical concepts in the theory of dynamical systems.
Abstract: The purpose of this paper is to give a tutorial exposition of what we consider to be the basic mathematical concepts in the theory of dynamical systems.

437 citations


Journal ArticleDOI
TL;DR: Degradation of trichloroethylene by the methanotrophic bacterium Methylosinus trichosporium OB3b was studied by using cells grown in continuous culture, finding that TCE degradation was a strictly cometabolic process, requiring the presence of a cosubstrate, preferably formate, and oxygen.
Abstract: Degradation of trichloroethylene (TCE) by the methanotrophic bacterium Methylosinus trichosporium OB3b was studied by using cells grown in continuous culture. TCE degradation was a strictly cometabolic process, requiring the presence of a cosubstrate, preferably formate, and oxygen. M. trichosporium OB3b cells degraded TCE only when grown under copper limitation and when the soluble methane monooxygenase was derepressed. During TCE degradation, nearly total dechlorination occurred, as indicated by the production of inorganic chloride, and only traces of 2,2,2-trichloroethanol and trichloroacetaldehyde were produced. TCE degradation proceeded according to first-order kinetics from 0.1 to 0.0002 mM TCE with a rate constant of 2.14 ml min-1 mg of cells-1. TCE concentrations above 0.2 mM inhibited degradation in cell suspensions of 0.42 mg of cells ml-1. Other chlorinated aliphatics were also degraded by M. trichosporium OB3b. Dichloromethane, chloroform, 1,1-dichloroethane, and 1,2-dichloroethane were completely degraded, with the release of stoichiometric amounts of chloride. trans-1,2-Dichloroethylene, cis-1,2-dichloroethylene, and 1,2-dichloropropane were completely converted, but not all the chloride was released because of the formation of chlorinated intermediates, e.g., trans-2,3-dichlorooxirane, cis-2,3-dichlorooxirane, and 2,3-dichloropropanol, respectively. 1,1,1-Trichloroethane, 1,1-dichloroethylene, and 1,3-dichloropropylene were incompletely converted, and the first compound yielded 2,2,2-trichloroethanol as a chlorinated intermediate. The two perchlorinated compounds tested, carbon tetrachloride and tetrachloroethylene, were not converted.

408 citations


Journal ArticleDOI
TL;DR: In this paper, the authors investigated the effect of adding a point polarizability to a SPC like rigid water model in molecular dynamics simulations and proposed a new algorithm for calculating the induced dipole moments based on a predictive, instead of an iterative, scheme.
Abstract: We have investigated the effect of adding a point polarizability to a SPC like rigid water model in molecular dynamics simulations A new algorithm for calculating the induced dipole moments based on a predictive, instead of an iterative scheme, is presented The predictive scheme considerably reduces the demand on computer time Both schemes gives identical results for energy, structure and dynamics In the liquid phase simulations of the polarizable water model the total dipole moment is enhanced from its static gas phase value of 1·85 D to 3·2 D The radial distribution functions indicate an increased structure as compared to SPC water Dynamic properties are slower than for the original SPC model Further adjustments of the hard core of the polarizable SPC model to yield a better energy estimate reduces the total dipole moment to 2·9 D This model, the polarizable SPC (PSPC) water, enhances the agreement with the original SPC structure and improves the dynamical properties of the model In order to si

407 citations


Journal ArticleDOI
TL;DR: In this paper, a photo-initiated chain crosslinking of the liquid-crystalline diacrylate 1,4-phenylene bis{4-[6-(acryloyloxy)hexyloxy]benzoate} (1) is studied.
Abstract: Synthesis, mesomorphism, orientation and photo-initiated chain crosslinking of the liquid-crystalline diacrylate 1,4-phenylene bis{4-[6-(acryloyloxy)hexyloxy]benzoate} (1) are studied. Monomer 1 exhibits a broad nematic phase between 108 and 155°C and a monotropic smectic phase below 88°C. The monomer is uniaxially oriented in its nematic phase at a substrate which has been coated with polyimide and unidirectionally rubbed with tissue. At the transition temperature to the smectic phase the order parameter is measured to be 0,7. During polymerization, the ordering of the mesogens is frozen-in, yielding a uniaxially crosslinked network. The clear films of oriented poly(1) exhibit a birefringence Δn between 0,12 and 0,15, depending on the polymerization temperature. In the highest oriented state of 1 a small reduction of the degree of order is observed during the crosslinking reaction, whereas at higher temperatures and lower ordering of 1, the uniaxially orientation increases upon reaction. A special feature of the oriented networks is that the ordering is maintained while heating at high temperatures. The polymerization of the acrylate groups in the mesomorphic phases proceeds fast and to high conversion. Below 90°C the polymerization behaviour is similar to that of conventional isotropic diacrylates. Above 90°C the polymerization reaction of the liquid-crystalline diacrylate proceeds faster than that of an isotropic diacrylate.

394 citations


Journal ArticleDOI
TL;DR: It is argued that these O $2p$ holes have a very large antiferromagnetic exchange interaction with neighboring neighboring ${\mathrm{Ni}}^{2+}$ (${d}^{8}$) spins, which makes them appear like low-spin states in macroscopic magnetic measurements.
Abstract: Using oxygen $K$-edge x-ray-absorption spectroscopy we show that the holes compensating the ${\mathrm{Li}}^{1+}$ impurity charge in ${\mathrm{Li}}_{x}{\mathrm{Ni}}_{1\ensuremath{-}x}\mathrm{O}$ are located primarily in the O $2p$ states rather than in the conventionally assumed Ni $3d$ states These holes are bound to the ${\mathrm{Li}}^{1+}$ impurities forming states in the NiO band gap We also argue that these O $2p$ holes have a very large antiferromagnetic exchange interaction with neighboring ${\mathrm{Ni}}^{2+}$ (${d}^{8}$) spins, which makes them appear like low-spin ${\mathrm{Ni}}^{3+}$ states in macroscopic magnetic measurements This is similar to what could be happening in the Cu-based high-${T}_{c}$ superconductors

311 citations



Journal ArticleDOI
TL;DR: A pair of vectors for expression of heterologous genes in Lactococcus lactis contain a multiple cloning site flanked by gene expression signals originating from L. lactis subsp.
Abstract: A pair of vectors for expression of heterologous genes in Lactococcus lactis was constructed. In addition to an origin of replication that has a broad host range, these vectors contain a multiple cloning site flanked by gene expression signals originating from L. lactis subsp. cremoris Wg2. The two vectors, about 3.7 kilobase pairs in size, differ only in the type of antibiotic resistance they confer to their hosts. pMG36 carries a kanamycin resistance marker, which was replaced by an erythromycin resistance marker in pMG36e. As an example of the use of these vectors, the hen egg white lysozyme-coding sequence was inserted. A fusion protein of the expected size was detected in a transformed L. lactis subsp. lactis strain by using Western blotting (immunoblotting).

287 citations


Journal ArticleDOI
TL;DR: While the fluorescent pseudomonads are characterized by their inability to make PHB, they appear to share the capacity to produce PHAs, which may be useful in the optimization of PHA production for biopolymer applications.
Abstract: The fluorescent pseudomonads are classified as a group, one characteristic of which is that they do not accumulate poly-3-hydroxybutyrate (PHB) during nutrient starvation in the presence of excess carbon source. In this paper we show that prototype strains from this subclass, such as Pseudomonas aeruginosa, Pseudomonas putida, and Pseudomonas fluorescens, do accumulate poly-3-hydroxyalkanoates (PHA) when grown on fatty acids. These PHAs are composed of medium-chain-length (C6 to C12) 3-hydroxy fatty acids. The ability to form these polyesters does not depend on the presence of plasmids. A specificity profile of the enzymes involved in the biosynthesis of PHA was determined by growing Pseudomonas oleovorans on fatty acids ranging from C4 to C18. In all cases, PHAs were formed which contained C6 to C12 3-hydroxy fatty acids, with a strong preference for 3-hydroxyoctanoate when Ceven fatty acids were supplied and 3-hydroxynonanoate when Codd fatty acids were the substrate. These results indicate that the formation of PHAs depends on a specific enzyme system which is distinct from that responsible for the synthesis of PHB. While the fluorescent pseudomonads are characterized by their inability to make PHB, they appear to share the capacity to produce PHAs. This characteristic may be helpful in classifying pseudomonads. It may also be useful in the optimization of PHA production for biopolymer applications.

286 citations


Journal ArticleDOI
TL;DR: A long term follow up study is presented of 73 patients with myasthenia gravis, living in Amsterdam between 1926 and 1965, and the evolution of their clinical state represents the natural course of MG.
Abstract: A long term follow up study is presented of 73 patients with myasthenia gravis, living in Amsterdam between 1926 and 1965. In the period 1961-65 the annual incidence was 3.1, the prevalence 53 per million. Maximum severity of the disease occurred during the first seven years after onset in 87%. Eighteen (29%) patients died, of whom eight had a thymoma (TH). Spontaneous improvement or remission occurred at any time during the follow up. At the end of the study (1985) 16 (22%) patients were in a complete clinical remission, 13 (18%) had improved considerably (3 with prednisone), 12 (16%) had improved moderately, 12 (16%) had remained unchanged and two had deteriorated. If the early deaths are excluded the outcome is similar in the early and the late onset group without TH. Patients with TH had a less favourable course. Associated autoimmune diseases were diagnosed in 25% (n = 58). Because most of these patients were treated with anticholinesterases only, the evolution of their clinical state represents the natural course of MG.

285 citations


Journal ArticleDOI
TL;DR: It was shown that whereas the caudal solitary tract nucleus has predominant long ascending connections, the projections from the anterior taste related region of the nucleus of the solitary tract have only limited forebrain projections which do not reach beyond the level of the anterior dorsal hypothalamic nucleus.

Journal ArticleDOI
TL;DR: Evidence was obtained for a two-step mechanism in which termini are recognized by NFIV and used as a starting point for subsequent translocation as shown by methidiumpropyl EDTA footprinting and electron microscopy.

Journal ArticleDOI
TL;DR: In this article, a method for enforcing nuclear Overhauser effect (NOE) distance restraints in molecular dynamics simulations is presented, in which a term is included in the force field such that the distance restraint need only be satisfied as a ǫ r −3 −1/3 weighted time average over the simulation trajectory.

Journal ArticleDOI
TL;DR: The conclusion is that siphon size is one of the main factors determining the burying depth of benthic bivalves and thus plays a critical role in their survival.
Abstract: This paper analyses the significance of siphon investment in the life strategy of benthic bivalves. It describes the relationships between siphon weight, burying depth and shell size in Mya arenaria, Cerastoderma edule. Scrobicularia plana and Macoma balthica. All data were collected on an intertidal flat in the Dutch Wadden Sea during seven successive winter and summer periods. The four species have in common that (1) the increase of depth in relation to size can be described with an S-curve; (2) there is a linear relationship between log siphon weight and log shell size; (3) siphon investment is maximal for the size classes with the greatest increase in their depth; (4) siphon weight, in proportion to total body weight, decreases gradually for the larger size classes whose depth does not increase; (5) burying depth increases with siphon weight if individuals within a same size class are compared, but burying depth levels off above a certain siphon weight. Macoma balthica and Scrobicularia plana live twice as deep in winter as in summer, although siphon weight for both seasons is about the same. In summer both species use a part of the siphon to graze the surface around the burrow, whereas deposit feeding does not occur in winter. This might explain the seasonal variation in burying depth. On the other hand Cerastoderma edule and Mya arenaria, which are both suspension feeders, show hardly any increase of depth in winter as compared to summer. For benthic bivalves the risk of being taken by a predator decreases with depth. The burying depth levels off where individuals reach the depth refuge (though in winter Scrobicularia plana live at greater depth). The conclusion is that siphon size is one of the main factors determining the burying depth of benthic bivalves and thus plays a critical role in their survival.

Journal ArticleDOI
TL;DR: The action of aminoglycoside antibiotics on transduction by hair cells was investigated in isolated preparations of the bullfrog's sacculus, consistent with am inoglycosides' plugging the poorly ion-selective transduction channels of hair cells.

Journal Article
TL;DR: There is a remarkable coincidence between the first appearance of MZ B cells with adult features, and the time of acquisition of the ability to mount an immune response to polysaccharides, including encapsulated bacteria.
Abstract: The immune response to polysaccharide Ag as present in the capsule of certain virulent bacteria has been demonstrated to be related to a functionally intact spleen This immune response is almost completely defective in infancy Because of this the development of cellular compartments in the human spleen was studied immunohistologically in frozen and paraffin tissue sections of 32 infant spleens (less than 2 y of age) and 6 spleens from children Six cases of sudden infant death syndrome and 7 cases of infection or sepsis which were included showed no significant differences compared to the other cases Whereas all other cellular compartments have completed their maturation to an adult-type immunophenotype and morphology within the first 5 mo, the infant marginal zone B cells show essentially different features compared to the adult situation The main characteristics of the infant marginal zone B cells are the absence of CD21-(C3d/EBV-R) expression and the high percentage of cells strongly coexpressing IgM and IgD As the marginal zone is supposed to be the site of the initiation of the immune response to polysaccharide Ag, there is a remarkable coincidence between the first appearance of MZ B cells with adult features, and the time of acquisition of the ability to mount an immune response to polysaccharides, including encapsulated bacteria

Journal Article
TL;DR: The consistent aneuploidy of testicular GCTs of adults might be helpful in the differential diagnosis of primary nongerm cell tumors of the testis, and in differentiating between metastases of testSexual orientation-related tumors and primary extragonadal malignant G CTs.

Journal ArticleDOI
TL;DR: A gene bank from the chlorinated hydrocarbon-degrading bacterium Xanthobacter autotrophicus GJ10 was prepared in the broad-host-range cosmid vector pLAFR1 and the haloalkane dehalogenase gene was identified by the known N-terminal amino acid sequence of its product and found to encode a 310-amino-acid protein of molecular weight 35,143.
Abstract: A gene bank from the chlorinated hydrocarbon-degrading bacterium Xanthobacter autotrophicus GJ10 was prepared in the broad-host-range cosmid vector pLAFR1. By using mutants impaired in dichloroethane utilization and strains lacking dehalogenase activities, several genes involved in 1,2-dichloroethane metabolism were isolated. The haloalkane dehalogenase gene dhlA was subcloned, and it was efficiently expressed from its own constitutive promoter in strains of a Pseudomonas sp., Escherichia coli, and a Xanthobacter sp. at levels up to 30% of the total soluble cellular protein. A 3-kilobase-pair BamHI DNA fragment on which the dhlA gene is localized was sequenced. The haloalkane dehalogenase gene was identified by the known N-terminal amino acid sequence of its product and found to encode a 310-amino-acid protein of molecular weight 35,143. Upstream of the dehalogenase gene, a good ribosome-binding site and two consensus E. coli promoter sequences were present.

Journal ArticleDOI
TL;DR: It is suggested that in many cases of craniomandibular pain and dysfunction TMJ osteoarthrosis is the basic disorder.

Journal ArticleDOI
TL;DR: Detailed studies of the transport processes of lactic acid bacteria during growth and starvation have been performed in cytoplasmic membrane vesicles of these organisms in which a foreign proton pump has been introduced to generate a high proton motive force.
Abstract: During the last few years the studies about the physiology and bioenergetics of lactic acid bacteria during growth and starvation have evolved from a descriptive level to an analysis of the molecular events in the regulation of various processes. Considerable progress has been made in the understanding of the modes of metabolic energy generation, the mechanism of homeostasis of the internal pH, and the mechanism and regulatory processes of transport systems for sugars, amino acids, peptides, and ions. Detailed studies of these transport processes have been performed in cytoplasmic membrane vesicles of these organisms in which a foreign proton pump has been introduced to generate a high proton motive force.

Journal ArticleDOI
TL;DR: The number of deaths due to ischaemic heart disease was significantly lower (80% reduction) than expected and therefore the authors conclude that haemophilia offers protection against ischaemia heart disease.
Abstract: Mortality figures were calculated for a group of 717 Dutch haemophiliacs over the period 1973-86. Follow-up was on average 10.9 years; no patients were lost to follow-up. The data were compared to the general male population by actuarial methods and patient-year analysis. Forty-three patients died, while 20 deaths were expected in a hypothetical group of non-haemophiliacs of the same age distribution. Hence, overall mortality was 2.1 times higher than in the general population. This leads to a calculated life expectancy of 66 years, as compared to 74 years in the general male population. Mortality did not differ much by severity of haemophilia. A possibly beneficial effect of prophylaxis on longevity was observed. Haemorrhage occurred in half of all deaths and among these traumatic bleeding was the most prevalent. The number of deaths due to ischaemic heart disease was significantly lower (80% reduction) than expected and therefore the authors conclude that haemophilia offers protection against ischaemic heart disease. Cancer mortality was significantly higher (2.5 times) than expected.

Journal ArticleDOI
TL;DR: The outcome of childhood asthma is primarily predicted by the initial degree of bronchial obstruction and airway responsiveness to histamine, and does not appear to be related to sex, smoking habits, or age of onset of respiratory symptoms.
Abstract: The outcome of childhood asthma was studied in 101 adults who came from a group of 119 asthmatic children (85%) 6 to 14 yr of age who had originally been investigated between 1966 and 1969. Changes in respiratory symptoms, spirometry, and airway responsiveness to histamine in childhood and adult life were analyzed. It was found that 43 of the 101 adults (43%) had current symptoms; 29 of the 43 (67%) were receiving maintenance therapy. In the first study, 83 of the 101 children (82%) showed a response on inhalation of histamine (PC10-histamine ⩽ 16 mg/ml). The number of subjects in the second study who still had a PC10-histamine ⩽ 16 mg/ml fell to 29, suggesting that airway responsiveness decreases from childhood to adulthood. During the second survey (in adults), 25 of the 43 (59%) subjects with current symptoms and four of the 58 (7%) without respiratory symptoms responded to histamine. Adults with current symptoms had a significantly lower %FEV1 in both childhood and adulthood than did adults without cu...

Journal ArticleDOI
TL;DR: The Pseudomonas OCT plasmid-encoded alkane hydroxylase gene (alkB) and its promoter are identified and the amino-terminal sequence resembles that of several bacterial integral membrane proteins and is not cleaved off following translation.

Journal ArticleDOI
TL;DR: This Clinical Guideline supports the Questions and Answers that appear in PDS for tests referenced in this document and is provided for informational purposes.

Journal ArticleDOI
TL;DR: The results indicated that the adherence of micro-organisms on pellicle-coated substrata was influenced by the material's s.f.e.; there was an association between the s.e. of the substrata and the supragingival plaque extension in vivo, and high surface free-energy substrata in the oral cavity attracted more micro- organisms than did low energetic materials.
Abstract: The purpose of this study was to examine the change in plaque area over nine days in vivo on four materials with different surface free-energies (s.f.e.). Twelve healthy dental students participated in a cross-over, split-mouth, double-blind study. Supragingival plaque formation was recorded over a nine-day period, on four different materials: fluorethylenepropylene (Teflon) (FEP), parafilm (PAR), cellulose acetate (CA), and enamel (E) with s.f.e. of 20, 26, 57, and 88 erg/cm2, respectively. Strips made from the first three materials were stuck to the buccal surface of an upper incisor. The remaining incisor was carefully polished and served as an enamel surface. The increase in plaque was evaluated after three, six, and nine days. A planimetrical analysis was used so that the plaque area could be expressed as a percentage of the total buccal tooth surface. This procedure was repeated on each subject, so that at the end, each pair of central or lateral incisors received the four tested materials. The results indicated that the adherence of micro-organisms on pellicle-coated substrata was influenced by the material's s.f.e.; there was an association between the s.f.e. of the substrata and the supragingival plaque extension in vivo. High surface free-energy substrata in the oral cavity attracted more micro-organisms than did low energetic materials. Additionally, the bacterial adhesion seemed very weak on surfaces with a low s.f.e.

Journal ArticleDOI
TL;DR: In this paper, the error component model (ECM) is used to analyze panel data in econometrics and two estimators (quadratic unbiased and maximum likelihood) for the ECM are presented.

Journal ArticleDOI
TL;DR: In this article, the X-ray diffraction intensities of crystals of p-hydroxy-benzoate hydroxylase, complexed with the substrate p -hydroxy benzoate, were measured to a resolution of 1.9 A.

Journal ArticleDOI
TL;DR: The X-ray structure of α-terthienyl reveals two identical, crystallographically independent molecules in the unit cell as discussed by the authors, and great care should be taken in using calculations of this type for geometrical optimizations of polythiophenes.

Journal ArticleDOI
TL;DR: It is concluded that the age-related differences in human sleep EEG power spectra are not identical to the changes in EEGPower spectra observed in the course of the sleep episode and cannot be completely explained by assuming a reduced need for sleep in older subjects.

Journal ArticleDOI
01 Dec 1989-Sleep
TL;DR: Analysis of baseline sleep of 13 men and 15 women and published data on the effects of sleep deprivation on EEG power spectra did not suggest a common mechanism underlying sleep deprivation effects and the sex difference in sleep EEGs, but it was concluded that sex differences in EEG powerSpectral analysis detected significantly higher power densities during non-REM sleep over a wide frequency range in the female versus male subjects.
Abstract: Baseline sleep of 13 men (mean age of 23.5 years) and 15 women (21.9 years) was analyzed. Visual scoring of the electroencephalograms (EEGs) revealed no significant differences between the sexes in the amounts of slow-wave sleep and rapid-eye-movement (REM) sleep. Spectral analysis, however, detected significantly higher power densities during non-REM sleep over a wide frequency range (0.25-11.0 Hz) in the female versus male subjects. Also, during REM sleep, power densities were higher in the females. Analysis of the time course of EEG power density during sleep revealed that the differences between males and females persisted throughout the sleep episode. Comparison of these differences with published data on the effects of sleep deprivation on EEG power spectra did not suggest a common mechanism underlying sleep deprivation effects and the sex difference in sleep EEGs. It is concluded that sex differences in EEG power spectra are not likely to be caused by sex differences in sleep regulatory mechanisms but may, for instance, be caused by sex differences in skull characteristics.