Showing papers by "University of Amsterdam published in 1975"

On the heat of formation of solid alloys

Abstract: We demonstrated recently that the available experimental data on the heat of formation of solid alloys of transition metals can be accounted for by means of a cellular model. The energy effect is derived from two contributions; a negative one, arising from the difference in chemical potential, ϑ∗, for electrons at the two types of atomic cells, and a second term, which reflects the discontinuity in the density of electrons, n ws , at the boundary between dissimilar atomic cells. Expressed as a formula, ΔH ~ [-Pe(Δϑ∗) 2 + Q(Δn ws ) 2 ] . In this paper we demonstrate that the second term is preferably to be written as Q 0 (Δn 1 3 ws ) 2 . Values for P and Q 0 can be derived from basic arguments. The advantage of this alteration is that the values for P and Q 0 are now nearly the same for widely different alloy systems (i.e., as different as intermetallic compounds of two transition metals, and liquid alloys of two non-transition metals). It is demonstrated that the description (and hence the predictions) for heats of formation of alloys of transition metals is sufficiently accurate to be of practical interest. The present model conflicts strongly with descriptions of heats of formation of transition metal alloys in terms of the Engel-Brewer theory.

IMMUNOLOGY OF DNA. III. CRITHIDIA LUCILIAE, A SIMPLE SUBSTRATE FOR THE DETERMINATION OF ANTI‐dsDNA WITH THE IMMUNOFLUORESCENCE TECHNIQUE*

Abstract: C. luciliae are hemoflagellates nonpathogenic for man and easy to culture. They have a giant mitochondrion, in which the mitochondrial DNA is concentrated in a single large network, the kinetoplast. When used as a substrate for the indirect immunofluorescence technique, studying sera from patients with SLE, we could demonstrate a very good correlation between this test and the Farr assay for the demonstration of antibodies to double-stranded DNA. Although the sensitivity of both techniques is on the same order of magnitude, the IF technique has the following advantages over the Farr assay. It is easy to perform in laboratories equipped for autoimmune serology. It possesses an intrinsic check on the immunoglobulin character of the DNA-binding activity. It allows one to determine the Ig classes and subclasses of antibodies to DNA. It permits study of complement fixation to antibodies without interference of Clq fixation to DNA or anticomplementarity of the serum. There is an absence of interference with antibodies to single-stranded DNA.

White pulp compartments in the spleen of rats and mice. A light and electron microscopic study of lymphoid and non-lymphoid celltypes in T- and B-areas.

Abstract: The spleen of rats and mice was studied with the light and electron microscope. Special attention was paid to the delineation and composition of the white pulp compartments: periarteriolar lymphatic sheath (PALS), follicles and marginal zone. These three compartments each have their specific lymphoid and non-lymphoid cells. Reticulum cells and reticulin fibres, although occurring in all three compartments, from a characteristic pattern in each compartment. In the PALS two areas can be distinguished: a central area, largely devoid of reticulum cells, and a peripheral area where reticulum cells are arranged in cylindrical shells. The central PALS FORMS THE THYMUS DEPENDENT AREA OF THE SPLEEN, THE PERIPHERAL PALS contains both T- and B-lymphocytes. T-B-interactions requiring cell contact could take place in the latter area. Lymph vessels originate from the shells of reticulum cells around the smaller arterioles; these vessels follow the central arteriole to the hilus of the spleen. Circumstantial evidence suggests that the lymph vessels form a recirculation pathway for T-cells and possibly also for B-cells. In two areas of the splenic white pulp characteristic non-lymphoid cells are present. The central PALS contains interdigitating cells (IDC), which show a close contact with surrounding T-lymphocytes. The light zone of the follicle centre exhibits dendritic cells (DC). B-cells are found between the ramifications of the DC. It is conceivable that these cells play a role in the homing of T-cells and B-cells respectively. In addition they might create a microenvironment supporting differentiation and proliferation of T- and B-cells. The marginal zone does not contain a characteristic non-lymphoid cell type. However, in this compartment B-cells are directly exposed to the circulating blood. It is suggested that this factor constitutes one of the essentials of the microenvironment in the marginal zone.

The regulation of carbohydrate metabolism in Klebsiella aerogenes NCTC 418 organisms, growing in chemostat culture.

Abstract: Klebsiella aerogenes NCTC 418 was grown in chemostat cultures (D = 0.17 hr-1; pH 6.8;35 degrees C) that were, successively, carbon-, sulphate-, ammonia-, and phosphate-limited, and which contained as the sole carbon-substrate first glucose, then glycerol, mannitol and lactate. Quantitative analyses of carbon-substrate used and products formed allowed carbon balances to be constructed and direct comparisons to be made of the efficiency of substrate utilzation. With all sixteen cultures, carbon recoveries of better than 90% were obtained. Optimum utilization of the carbon substrate was invariably found with the carbon-limited cultures, the sole products being organisms and carbon dioxide. But the extent to which excess substrate was over-utilized varied markedly with both the nature of the growth-limitation and the identity of the carbon-substrate. In general, sulphate-, ammonia-, and phosphate-limited cultures utilized glycerol more efficiently than mannitol, mannitol better than lactate, and glucose least efficiently. Glucose-containing cultures also synthesized some extracellular polysaccharide. When the carbon source was in excess, a range of acidic compounds generally were excreted. Sulphate-limited cultures, growing on glucose, excreted much pyruvate and acetate, whereas similarly-limited cultures growing on glycerol, mannitol or lactate produced only acetate. Ammonia-limited cultures invariably excreted 2-oxoglutarate and acetate, whereas phosphate-limited cultures produced gluconic acid, 2-ketogluconic acid and acetate, when growing on glucose, but only acetate when growing on mannitol or lactate. From the rates of substrate and oxygen consumption, and the rates of cell synthesis, yield values for both substrate and oxygen were calculated. These showed different trends, but were similar in being highest under carbon-limitation and substantially lower under all other limitations. The physiological significance of these findings, and the probable nature of the regulatory mechanisms underlying "overflow metabolism" are discussed.

Historical background, principles and methods of intuitionism

Abstract: Publisher Summary This chapter discusses the historical background, principles, and methods of intuitionism. The historical development of the mental mechanism of mathematical thought is naturally closely connected with the modifications which, in the course of history, have come about in the prevailing philosophical ideas firstly concerning the origin of mathematical certainty; secondly, concerning the delimitation of the object of mathematical science. The mental mechanism of mathematical thought during so many centuries has undergone a few fundamental changes because of the circumstance that, in spite of all revolutions undergone by philosophy in general, the belief in the existence of properties of time and space, immutable, and independent of language, and experience, remained intact until far into the 19th century. It is found that for the elementary theory of natural numbers, the principle of complete induction, and more or less considerable parts of algebra and theory of numbers, exact existence, absolute reliability, and noncontradictority were universally acknowledged independently of language and without proof.

Tetralogy of Fallot: a morphometric and geometric study.

Abstract: Fourteen examples of tetralogy of Fallot were studied by morphometric and geometric methods, and the findings compared with results from 10 normal hearts. The data show that in Fallot's tetralogy the conal septum is deviated anteriorly. The infundibulum, although narrow, is similar to, or of greater length than, that of the normal heart. This finding is not in agreement with recent observations suggesting that the anomaly represents lack of growth of the pulmonary conus. Our results further demonstrate that the aorta is dextroposed in Fallot's tetralogy and that in the majority of cases absorption of the right extremity of the conoventricular flange has led to aortic-tricuspid fibrous continuity. The overall findings indicate that conal rotation has occurred in addition to anterior deviation. The data are interpreted as supporting a hypothesis of “lack of conal inversion” and conal malseptation as the morphogenetic mechanisms in tetralogy of Fallot.

Small States: A Tool for Analysis?

Abstract: The usefulness of the concept of “small states” as an analytical tool is discussed in a review of books by Edward Azar and Marshall Singer. The size of states has both domestic and international ramifications. Authors who use the concept of “small states” struggle with the problem of defining it. Such definitions can be clear and unambiguous but arbitrary at the same time; more sophisticated definitions are also more ambiguous and difficult to apply to concrete cases. Inquiry into the role of small states in international politics is shown to be still in a very elementary stage. Although there does of course exist a continuum of size of states in international relations, small states form too broad a category for purposes of analysis.

Determination of the Efficiency of Oxidative Phosphorylation in Continuous Cultures of Aerobacter Aerogenes

Abstract: For anaerobic glucose-limited chemostat cultures of Aerobacter aerogenes a values of 14.0 g/mole was found for Y ATP max and a value of 6.8 mmoles ATP/g dry weight/hr for the maintenance coefficient. Both values are much lower than those previously determined for tryptophan-limited anaerobic chemostat cultures. It is concluded that generally the largest part of the maintenance energy is not used for true maintenance processes. For aerobic glucose-limited chemostat cultures two phases could be differentiated. Acetate production started at μ values higher than 0.53. The slopes of the curves relating the specific rates of glucose- and oxygen consumption with μ became higher and lower respectively above the μ value of 0.53. Using the Y ATP values obtained in the anaerobic experiment a P/O ratio of about 1.3 could be calculated for glucose- and tryptophan-limited chemostat cultures. In sulfate-limited chemostat cultures acetate was produced at all growth rates. At high growth rates also pyruvate and α-ketoglutarate were produced. With the Y ATP values obtained in the anaerobic experiment a P/O ratio of about 0.4 was calculated for sulfate-limited chemostat cultures.

Cardiac manifestations of Fabry's disease. Report of a case with mitral insufficiency and electrocardiographic evidence of myocardial infarction

Abstract: The light and electron microscopic findings in the heart of a patient with Fabry's disease are described. The study revealed that all cardiac tissues, including the conducting tissues and the valves, were involved. The latter finding was of particular interest since the patient was known to have mitral insufficiency. The findings of diffuse ballooning of the mitral valve with localized "overshoot" and massive glycolipid storage in the valve substance suggest that the abnormal storage process was itself responsible for the valvular insufficiency. The widespread involvement of the myocardium and conducting tissues is consistent with the elelctrocardiographic changes indicating infarction, although myocardial necrosis was not observed. The findings in this case suggest that the cardiac manifestations in Fabry's disease can be either primary, that is, directly related to the enzyme deficiency, or secondary, that is, evolving with time as a consequence of the disease.

Optically induced eye torsion

Abstract: Using a synoptophore and an objective photographic method, it was demonstrated that the eyes undergo a tonic cycloversion under the influence of a pattern with slanting stripes. A slight tilt with respect to the vertical had a greater effect than a tilt with respect to the horizontal. The maximum amplitude was of the order of 1 ∘. This optostatic eye torsion is considered to be the optomotor analogue of the “ ophthalmostatic ” otolithic reflex.

Post-inflammatory elastolysis and cutis laxa.

Abstract: Post-inflammatory elastolysis and cutis laxa (Marshall, Heyl & Weber, 1966) is a skin disease in African infants which appears to be comparatively common in at least two countries. Destruction of elastic tissue and atrophy are preceded by urticarial or by annular erythematous-popular lesions and result in severe disfigurement. The clinical features are intermediate between anetoderma (macular atrophy) and acquired cutis laxa, but sufficiently typical and characteristic to constitute a distinctive syndrome, which might represent an abnormal reaction to the bite of an arthropod.

On a soluble model of an antiferromagnetic chain with alternating interactions and magnetic moments

Abstract: The one-dimensional anisotropic XY model with alternating nearest-neighbour interactions and magnetic moments is investigated. The singularities of the susceptibility χ zz in the ground state are studied in detail. In the general anisotropic case χ zz can exhibit two logarithmic singularities at two different values of the applied magnetic field b . If the interactions satisfy a certain relation which will be reffered to as the pseudoisotropic condition (which includes the isotropic case), χ zz can have two power- 1 2 singularities at the upper side of the lower critical field and the lower side of the upper critical field. Deviations from this behaviour which occur for special values of the interaction constants are discussed in some detail. Finally the specific heat is studied in the low- and high-temperature limits.

On the exchange interactions in some 3d-metal ionic compounds: I. The 180° superexchange in the 3d-metal fluorides XMF3 and X2MF4 (X=K, Rb, Tl; M=Mn, Co, Ni)

Abstract: In the series of insulating antiferromagnetic compounds XMF3 and X2MF4 (X=K, Rb, Tl; M=Mn, Co, Ni) the superexchange paths connecting nearest magnetic neighbours are identical collinear (180°) M-F-M bonds. The available experimental data on the exchange constants, J/k, and the bond lengths, R, are reviewed. They enable one to give an estimate of the dependence of J/k on R, as well as the ratio of the J/k values of Mn2+, Co2+, and Ni2+ for a fixed bond length. Assuming a power-law dependence, |J/k|∼R−n, our analysis yields n≃12 for Mn2+, Co2+ as well as Ni2+, in the R range covered experimentally. The ratio of the J/k values of Mn2+, Co2+, and Ni2+ at fixed R=4.074 A is found to be 1:3.6:7.7. The experimental findings are compared with theoretical calculations based upon a recently proposed exchange-perturbation treatment for the cation-anion-cation unit in a three-centre four-electron model. The unpaired electrons on either cation are replaced by one effective electron and the closed-shell electrons of the anion by two spin-paired electrons. Qualitatively, the agreement with the experiment is good in that the model reproduces correctly the observed R dependences as well as the ratio of the J/k's of the three different cations. Also in quantitative respect a close agreement with the experimental J/k values can be obtained within the uncertainties inherent to the effective-electron model.

The introduction of the alien amphipodGammarus tigrinus Sexton, 1939 (Crustacea, Amphipoda) in The Netherlands and its competition with indigenous species

Abstract: In oligohaline watersGammarus tigrinus has a much greater reproductive capacity than any of the three indigenous (sub)speciesG. d. duebeni, G. zaddachi orG. p. pulex. The most important factors that enable this recently introduced species to compete the local species are: (a) its favourable reproductive period during the warm summer months, (b) its very short egg-incubation period, and (c) its very short time needed to reach sexual maturity.

The effect of a low-calcium diet in lactating rats; observations on the rapid development and repair of osteoporosis.

Abstract: Female rats were given a low-calcium diet (0.05%) during the last three weeks of the lactating period, followed by a normal diet (1.03% calcium) during the first three weeks after lactation. The resulting bone loss and its recovery were studied by means of microradiography, tetracycline-uptake, quantitative estimation of the cortical area of cross-sections from the femoral midshaft, and estimation of total body calcium. The cortical area in the femoral midshaft fell to 46% of its original value during depletion, and then rose to 78% during the first three weeks after weaning. Total body calcium fell from 1.12% to 0.60% of body weight and then increased to 0.89%. Removal of bone occurred mainly in the spongiosa and on the endosteal side of the cortex. Subsequently, new bone was laid down on the endosteal side, but also to some extent on the periosteal side of the cortex. The mineral density of this new bone was low. During the recovery phase resorption cavities within the cortex were filled in a concentric manner as in Haversian remodeling. Neither this feature nor the low mineral density of bone are normally present in the rat.