Showing papers by "University of Antwerp published in 1977"
TL;DR: In this paper, a non-linear least-squares analysis of low-energy X-ray spectra obtained by tube-excited Xray fluorescence analysis is presented.
249 citations
TL;DR: A formal theory for predicting the success of information system development projects is developed and one important managerial tool to establish effective user-specialist communication is suggested.
Abstract: It is generally agreed between researchers and practitioners that user involvement is a key to the success of computer based information systems. This paper treats user involvement within the framework of a dyadic two party communication relationship between user and specialist. We add to previous work in three respects. First, the theoretical framework is enriched by specifying what we consider to be important contingency factors for the interaction between user and specialist. Second, a formal theory for predicting the success of information system development projects is developed. Third, one important managerial tool to establish effective user-specialist communication is suggested.
112 citations
TL;DR: In this article, a Gauss function and numerical corrections are incorporated into a non-linear least-squares fitting program used for the analysis of X-ray induced Xray fluorescence spectra.
106 citations
TL;DR: In this paper, the generator coordinate method is proposed as a fully quantum mechanical treatment of molecular spectra, which is based on the generator-coordinate method. But this method is not suitable for high-dimensional spectra.
58 citations
TL;DR: In this paper, a microscopic Hamiltonian that takes into account single particle orientational potential effects and rotational-translational coupling in molecular crystals is derived, which leads to an effective orientational interaction between nonspherical molecules.
Abstract: Starting from a repulsive overlap potential, we derive a microscopic Hamiltonian that takes into account single particle orientational potential effects and rotational–translational coupling in molecular crystals. This coupling leads to an effective orientational interaction between nonspherical molecules. Theoretical expressions for the elastic constants in the presence of this interaction are derived. The anomalous thermoelastic behavior which was discovered by Haussuhl for c 44 and c 11 in KCN and NaCN, and found by Rowe e t a l. in neutron measurements of TA phonons, is explained. The qualitative and quantitative agreement between theory and experiment is convincing.
53 citations
TL;DR: This analysis provides a model independent description of what muscle really does and how it behaves when its loading conditions are altered and should no longer be forcibly applied to the intact heart for ventricular function evaluation.
Abstract: Evaluation of ventricular muscle-pump function of the failing heart still constitutes a major problem in cardiology. More than a decade ago it was proposed that the mechanical performance of the heart should be approached as a muscle rather than as a pump. The purpose was to find properties of cardiac muscle which would help in distinguishing alterations of ventricular performance due to changes in loading conditions (Frank-Starling adaptation; heterometric autoregulation) from either positive (circulating catecholamines, changes in heart rate) or negative (myocardial or muscle failure) inotropic alterations (homeometric autoregulation; changes in contractility). Obviously, the pragmatic aim was to distinguish a good from a bad heart more accurately. Several contractile properties of isolated mammalian cardiac muscle have since been well characterised and recent studies have permitted a coherent and unifying description of cardiac muscle performance. The basis of it is that mechanical activity of myocardial muscle can be defined in terms of the interrelationship between force development, instantaneous length during shortening, and velocity of shortening, independently of the time course of activation. This analysis provides a model independent description of what muscle really does and how it behaves when its loading conditions are altered (Brutsaert, 1974).
Yet, the application of these basic muscle concepts to the intact heart still remains controversial for several reasons: insufficient understanding of basic cardiac muscle mechanics, failure to take into consideration some conceptual limitations, the many oversimplified assumptions in modelling the ventricle, the complex physiological loading of a combined muscle-pump system, etc. Pragmatic usefulness as the only justification for applying muscle concepts to the intact ventricle is no longer tenable as a sufficient argument. The ventricle is primarily a combined muscle-pump system and neither a papillary muscle nor even less a skeletal muscle. The nature of loading during muscle shortening in the ventricular wall is quite different from that in the isolated muscle since the ventricle is not called on to lift a weight but to eject a viscous fluid into a viscoelastic vascular system (Abbott and Gordon, 1975; Milnor, 1975). Muscle concepts as directly derived from skeletal muscle physiology should therefore no longer be forcibly applied to the intact heart for ventricular function evaluation. Instead, emphasis should be placed on the integration of muscle and pump function and on properties of heart muscle that help to define its behaviour as an integral part of the wall of a pumping system (Paulus et al. ,1976).
50 citations
TL;DR: Careful analysis of the bone marrow biopsy findings permitted the stage of the disease and hence the prognosis to be determined and the biopsy helps to make the distinction between Stage 3 of an unsuspected CML and acute myelocytic leukemia.
Abstract: Repeated bone marrow biopsies of 12 patients with chronic myelocytic leukemia (CML) and 13 patients with idiopathic myelofibrosis (IMF) were compared. The amount of cellularity, the composition of the cell population, and the stromal changes were assessed. Both diseases were divided into four stages, each with a consistent morphologic pattern. In CML, Stage 1 presented a tremendous increase in granulocytes and a drop of the erythroid series; Stage 2 showed a shift to myelocytes and a moderate increase of blasts; in Stage 3 there was a strong increase of blasts and the reappearance of red cells; and in Stage 4 hematopoietic cells disappeared with metastases of abnormal blasts to many organs. The stroma showed a progressive fibrosis so that by Stage 4 there was a totally fibrotic marrow. With IMF, Stage 1 presented a dysharmonic trilinear proliferation; in Stage 2 there was a maximum of cellularity, which remained trilinear; in Stage 3 there was a decrease of hematopoietic cells; and in Stage 4 these cells disappeared, but hematopoietic cells in dilated sinusoids of the empty marrow became apparent. The stroma showed a progressive fibrosis, ending by Stage 4 in a totally fibrotic marrow indistinguishable from the similar stage of CML. Careful analysis of the bone marrow biopsy findings permitted the stage of the disease and hence the prognosis to be determined; Stage 3 for CML means death within a short period of time. In clinically “acute” myelocytic leukemia, the biopsy helps to make the distinction between Stage 3 of an unsuspected CML and acute myelocytic leukemia.
49 citations
TL;DR: The elemental composition of aerosol particles collected at 5220 meters altitude from Chacaltaya Mountain, Bolivia, in the eastern cordillera of the altiplano, has been determined by X-ray, neutron activation and atomic absorption techniques as discussed by the authors.
48 citations
TL;DR: In this article, gas chromatography-mass spectrometry with computerized data acquisition was used to detect aliphatic and polyaromatic hydrocarbons, fatty acids and heterocyclic arenes.
46 citations
TL;DR: In this paper, the Hamiltonian of a gas of interacting polarons was studied using a canonical transformation and the Hartree-Fock ground state of the reduced Hamiltonian was analyzed.
Abstract: Using a canonical transformation the Hamiltonian of a gas of interacting polarons is studied. After elimination of the phonons the reduced Hamiltonian describes a system of charged particles interacting through an effective interparticle potential. The Hartree-Fock ground state of the reduced system is analysed.
Mit einer kanonischen Transformation wird der Hamiltonian eines Gases wechselwirkender Polaronen untersucht. Nach der Eliminierung der Phononen beschreibt der reduzierte Hamiltonian ein System von geladenen Teilchen, die uber ein effektives lnterteilchenpotential wechselwirken. Der Hartree-Fock-Qrundzustand des reduzierten Systems wird analysiert.
45 citations
TL;DR: In this paper, two samples of particulate matter from a coke oven emission source were collected with an Andersen cascade impactof to obtain size-graded fractions and analysis of 12 major polycyclic aromatic hydrocarbons was performed for all stages, by means of a gas chromatograph-mass spectrometer used in the mass fragmentography mode.
TL;DR: In this article, the major organic constituents of airborne particulate matter are determined by Soxhlet extraction with benzene and methanol, which is performed by the internal standard technique using a mass chromatographic approach.
TL;DR: Preliminary results are reported demonstrating that poly(A)‘-mRNP particles of Artemia dormant gastrulae are transformed into an inactive state by the possible presence of translational control RNA.
TL;DR: The first description of this particular ventricular arrhythmia appeared in the French literature in 1966 and was given the name ‘torsade de pointe&dquo; and was almost always associated with a long QT time.
Abstract: The first description of this particular ventricular arrhythmia appeared in the French literature in 1966.1 It was given the name &dquo;torsade de pointe&dquo; and was almost always associated with a long QT time. It is a distinct electrocardiographic and clinical entity, distinguished from other ventricular tachyarrhythmias for etiologic, morphologic, and therapeutic reasons.’ It also must be distinguished from such familial disorders as the Jervell-Lange-Nielsen or the Romano-Ward syndrome.3-5 In the English literature similar ECG patterns have been described under different names, like ventricular tachycardia flutter, fibrillation, and chaotic or polymorphous ventricular tachycardia. But these patterns were never identified as a distinct electrocardiographic and clinical syndrome.6-1o We propose to call it ven tricularfibrillo-flut ter, in analogy with its atrial counterpart. The following electrocardiographic criteria, described by Slama et al.,
TL;DR: Several sample preparation methods for waters for energy-dispersive x.r.f. were examined, as well as the influence of sample size on the analytical characteristics as discussed by the authors, and the most satisfactory simple, rapid method proved to be spotting of 1.5 ml of water sample on a Whatman-41 cellulose filter paper provided with a wax ring of 29mm diameter and evaporating the water with an unheated air stream from underneath.
TL;DR: In this article, the authors generalized the Nerlove-Arrow model of optimal dynamic advertising policies by incorporating a continuously distributed lag between advertising expenditures and increases in the stock of goodwill, which leads to a control problem where the equation of motion is given by an integro-differential equation.
Abstract: The Nerlove-Arrow model of optimal dynamic advertising policies is generalized by incorporating a continuously distributed lag between advertising expenditures and increases in the stock of goodwill. This leads to a control problem where the equation of motion is given by an integro-differential equation. The transitory and steady-state properties of the optimal policies are examined, both for a general lag function and for a gamma distributed lag. The dependence of the steady-state solution on the parameters of the gamma distribution is also investigated. An example is given using specific demand and cost functions.
TL;DR: In this paper, the authors reported the observation of a half-field transition in the EPR spectrum of tetramethylammonium-manganese trichloride (TMMC) with the microwave field parallel to the static magnetic field.
Abstract: We report the observation of a half-field transition in the EPR spectrum of tetramethylammonium-manganese-trichloride (TMMC). The observation of this new resonance is a direct consequence of the one-dimensionality of the spin dynamics of this manganese salt. We present a theory which accounts for many of the observed features in a very satisfactory way. The experiments are performed with the microwave field parallel to the static magnetic field. The most important characteristics of the transition are the scaling of the linewidth with the EPR spectrum obtained with the microwave field perpendicular to the static magnetic field, and its highly anisotropic intensity.
TL;DR: Poly(A)-containing ribonucleoprotein (poly(A)+-RNP) particles in the post-mitochondrial supernatant of cryptobiotic embryos of Artemia salina were characterized by hybridization to [3H]-poly(U).
Abstract: Poly(A)-containing ribonucleoprotein (poly(A)+-RNP) particles in the post-mitochondrial supernatant of cryptobiotic embryos of Artemia salina were characterized by hybridization to [3H]-poly(U). By sucrose isopycnic centrifugation, approximately 2/3 of poly(A)+-RNPs was found to band at 1.27-1.30 (g/cm3) and the rest 1+/3 at 1.20-1.23 (g/cm3) and below 1.20 (g/cm3). The 1.27-1.30 RNPs could be separated into two density classes, 1.27-1.28 and 1.30 (g/cm3) respectively. The latter RNP class was apparently complexed with ribosomal components because they were completely converted to the former RNP class (free RNPs) by 25 mM EDTA treatment. Further, the 1.30 (g/cm3) RNPs were resolved into several RNP species having sedimentation coefficients above 50 S. which were transformed mostly to 20-30 S rnps in the presence of 25 mM EDTA. The free 20-30 S RNPs contained 8-14 S poly(A)+-RNAs, having the highest template activity in a wheat embryo cell-free system, whereas the 1.20-1.23 poly(A)+-RNPs consisted of 10 S and 16 S RNPs, both of which contained 4 S poly(A)-containing sequences without any template activity.
TL;DR: It is suggested that HLA typing in HI can dissociated benign from malignant conditions.
TL;DR: Patients with the defect appear to be very sensitive to dietary purine, and at least some of the adenine metabolites may have a dietary origin.
Abstract: Partial adenine phosphoribosyltransferase (APRTase) deficiency has been considered hitherto as relatively benign in that the only detectable abnormality of purine metabolism has been hyperuricaemia varyingly accompanied by hyperuricosuria in some, but not all, cases (3). Elsewhere in this symposium we present clinical details of a child apparently homozygous for APRTase deficiency with urolithiasis due to 2,8-dihydroxyadenine stone formation (11). An identical case of complete APRTase deficiency with 2,8-dihydroxy-adenine stone formation has been described by Cartier and Hamet (2). In both cases the stones were originally misdiagnosed as uric acid because of the non-specificity of the methods routinely used (2,8). The metabolic basis for the stone formation results directly from the enzyme deficiency. In the absence of APRTase adenine is oxidised to the extremely insoluble purine 2,8-dihydroxyadenine. The nephrotoxicity of 2,8-dihydroxyadenine has been known since 1898 and is discussed by Cameron et al. However, free adenine is not normally readily detectable in man, and the pathway for its production via adenosine and nucleoside Phosphorylase has very low activity in mammalian tissues (9,5). On this basis, endogenous adenine production would appear unlikely in normal circumstances.
TL;DR: In this paper, the authors show that CO and CO2 are very sensitive probe molecules for investigating the location of unshielded mono-and divalent cations in zeolites.
Abstract: Adsorption of CO and CO2 has been studied on zeolite Y in which Na+ ions have been partially exchanged for Ca2+ ions. Physisorption of CO and CO2 provides a sensitive method for the observation of the population of Na+ and Ca2+ ions in supercage positions. The results indicate that Ca2+ ions introduced into a NaY zeolite by aqueous ion exchange preferentially enter sites in the small cavities on subsequent dehydration. When the degree of Ca2+ exchange stays below 35%, all the Na+ ions initially present in the small cavities as well as the incoming Ca2+ ions seem to remain inaccessible for CO and CO2 molecules.
However, a Na+ replacement of 35 to 45% leaves the Ca2+ ions unaffected by CO and CO2 but causes an important migration of inaccessible Na+ ions to accessible supercage positions. Further exchange (>45%) results in Ca2+ ions occupying locations exposed to the supercages. This work establishes that CO and CO2 are very sensitive probe molecules for investigating the location of unshielded mono- and divalent cations in zeolites.
TL;DR: In this article, a simple, sensitive and fast titrinetric method for sulfur determinations with the silver sulfide membrane electrode is described, which is applied to the determination of sulfur in steel, some petroleum products and aerosols.
TL;DR: One week of treatment appears sufficient to judge whether the individual patient benefits from the drug or not, and diphenhydramine consumption became significantly lower in the active drug group from the second day onwards, whereas a gradual increase and continuous need were seen in the greater part of the control group.
Abstract: The efficacy of the new anti-allergic compound oxatimide was tested in a double-blind study against a placebo during the pollen season of 1976 in 215 patients (4 1/2--69 years) with hay fever. Adult patients were instructed to take two tablets (= 20 mg) three times a day for 2 weeks, children received one tablet/10 kg of body weight daily; in addition, they were given a supply of diphenhydramine as a potential supplement. Twelve patients, six from either group, were excluded from the analysis. A significantly higher proportion of patients from the active drug group (n = 104) experienced no or only a few days of complaints, i.e. rhinitis and conjunctivitis, as well as asthma-like complaints, as compared with those of the control group (n = 99). Also, diphenhydramine consumption became significantly lower in the active drug group from the second day onwards, whereas a gradual increase and continuous need were seen in the greater part of the control group. One week of treatment appears sufficient to judge whether the individual patient benefits from the drug or not.
TL;DR: The results showed that the main sources of references to periodical literature were citations at the ends of articles in journals and books, and the increasing role of the current awareness type of publication in assisting in the selection of relevant articles and decreased use of conventional abstract journals.
Abstract: This article studies the pattern of users' interaction with information sources in science, technology and social sciences at the Antwerp State University Centre. The results showed, first, that the main sources of references to periodical literature were citations at the ends of articles in journals and books, second, the increasing role of the current awareness type of publication in assisting in the selection of relevant articles and, third, decreased use of conventional abstract journals. Computerized information services scored very low, but greater usage of machine-readable data bases is expected upon introduction of interactive on-line systems.
TL;DR: In this article, the structure and conformations of trans-and cis-bicyclo[4.0]nonane have been studied in the gas phase, where the force field of Ermer and Lifson were used to obtain geometrical constraints, vibrational amplitudes and perpendicular vibrational corrections.
TL;DR: The radiological investigation shows that there is a connection between the frequency of fractures and the age of the victims and this connection is based on the degree of ossification of the throat-skeleton.
Abstract: The frequency of throat-skeleton fractures was investigated in a series of 30 unselected cases of strangulation Less than half of the victims showed fractures From the data obtained, it seems to prove that there is a connection between the frequency of fractures and the age of the victims The radiological investigation shows thatthis connection is based on the degree of ossification of the throat-skeleton This ossification starts often already at early age and should be considered as a process of ageing Notwithstanding the irregular occurrence of throat-skeleton fractures, these injuries are obviously of a vast diagnostic value
TL;DR: The hypothesis of “suicide” was maintained: the man administered himself a large doses of insulin; in hypoglycaemic coma he died from a bronchopneumonia in a “grave” dug by himself.
Abstract: The undressed body of a young man was discovered in a pit in a forest. The victim was a 27 year old depressed man, suffering from a severe diabetes. Besides personal objects, three empty insulin vials (400 I.U./vial) and empty ampules of distilled water, injection-needles and a syringe were also found in the pit. The investigation carried out at the scene, the questioning of his family and physicians, and the autopsy clarified this unusual case. In conclusion the hypothesis of “suicide” was maintained: the man administered himself a large doses of insulin; in hypoglycaemic coma he died from a bronchopneumonia in a “grave” dug by himself.