Showing papers by "Katholieke Universiteit Leuven published in 1988"

Quantitative analysis of radiocaesium retention in soils

Abstract: The fallout of radiocaesium after the Chernobyl accident has renewed interest in its environmental behaviour. How it behaves in soils and sediments is important, for example, for the modelling of radiocaesium transport and retention in soils, and transfer from soil to plants and hence into the food chain. The traditional approach is highly empirical and is based on the measurement of solid–liquid distribution coefficients (KD values) and transfer factors. It is generally believed that radiocaesium retention in soils and sediments is due to the presence of a small number of highly selective sites. Neither their abundance nor their Cs-selectivity has been quantitatively determined. Here we report a new methodology which achieves such characterization. Previously studies of radio-caesium in soils have foundered because KD values have been derived under conditions very different from those in situ. We show that in situ KD values can be predicted from readily measurable soil properties, thus enabling information about the mobility of radiocaesium in soils to be reliably and easily obtained. These findings can be generally applied to a wide variety of soils.

Tannaka-Krein duality for compact matrix pseudogroups. Twisted SU(N) groups

Abstract: The notion of concrete monoidalW *-category is introduced and investigated. A generalization of the Tannaka-Krein duality theorem is proved. It leads to new examples of compact matrix pseudogroups. Among them we have twistedSU(N) groups denoted byS μ U(N). It is shown that the representation theory forS μ U(N) is similar to that ofSU(N): irreducible representations are labeled by Young diagrams and formulae for dimensions and multiplicity are the same as in the classical case.

Enhancement of experimental allergic encephalomyelitis in mice by antibodies against IFN-gamma.

Abstract: Acute experimental allergic encephalomyelitis (EAE) was induced in C57BL/6J and SJL/J mice by injection of isologous spinal cord homogenate given in conjunction with Bordetella pertussis and Freund's adjuvant. SJL/J mice showed a highly aggressive and 100% lethal form of the disease; C57BL/6J mice were much less susceptible as they had low morbidity rates (20 to 40%), low disease scores, and mostly no mortality. Treatment of these low susceptibility mice with neutralizing mAb against IFN-gamma caused an increase in morbidity rates as well as significant mortality (up to 80%). Similar antibody treatment did not affect the course of the disease in the high susceptibility SJL/J mice. However, treatment of these mice with IFN-gamma resulted in reduced morbidity and mortality. A similar but less pronounced inhibition of the disease in SJL/J mice could be obtained by administration of IFN-alpha/beta or by acute infection with lactate dehydrogenase virus. The results indicate that endogenous as well as exogenous IFN can exert a down-regulating effect on the development of EAE. They also indicate that endogenous IFN-gamma is produced during the development of EAE and plays a disease-limiting role.

Consistent model for the hot-carrier degradation in n-channel and p-channel MOSFETs

Abstract: A model is derived using the charge-pumping technique for the evaluation of the interface characteristics, in combination with the behavior of the drain and the substrate currents after degradation For n-channel transistors the degradation is mainly caused by the generation of interface traps Only in the region of hole injection (V/sub g/ approximately=V/sub t/) is the degradation dominated by the trapped holes, which mask the effect of the generated interface traps The degradation of p-channel transistors, although completely different at first sight, occurs by the same mechanisms For this case, the degradation is caused by trapped negative charge, which masks the influence of the interface traps The latter are nevertheless generated in comparable amounts as in n-channel transistors Based on these insights, improved procedures for accelerated-lifetime experiments are proposed for both channel types Finally, the peculiar degradation behavior of n-channel transistors under alternating injection conditions is discussed and fully explained based on the static stress degradation model >

Intravenous tissue plasminogen activator and size of infarct, left ventricular function, and survival in acute myocardial infarction.

Abstract: STUDY OBJECTIVE--To assess effect of intravenous recombinant tissue type plasminogen activator on size of infarct, left ventricular function, and survival in acute myocardial infarction. DESIGN--Double blind, randomised, placebo controlled prospective trial of patients with acute myocardial infarction within five hours after onset of symptoms. SETTING--Twenty six referral centres participating in European cooperative study for recombinant tissue type plasminogen activator. PATIENTS--Treatment group of 355 patients with acute myocardial infarction allocated to receive intravenous recombinant plasminogen activator. Controls comprised 366 similar patients allocated to receive placebo. INTERVENTION--All patients were given aspirin 250 mg and bolus injection of 5000 IU heparin immediately before start of trial. Patients in treatment group were given 100 mg recombinant tissue plasminogen activator over three hours (10 mg intravenous bolus, 50 mg during one hour, and 40 mg during next two hours) by infusion. Controls were given placebo by same method. Full anticoagulation treatment and aspirin were given to both groups until angiography (10-22 days after admission). beta Blockers were given at discharge. END POINT--Left ventricular function at 10-22 days, enzymatic infarct size, clinical course, and survival to three month follow up. MEASUREMENTS AND MAIN RESULTS--Mortality was reduced by 51% (95% confidence interval -76 to 1) in treated patients at 14 days after start of treatment and by 36% (-63 to 13) at three months. For treatment within three hours after myocardial infarction mortality was reduced by 82% (-95 to -31) at 14 days and by 59% (-83 to -2) at three months. During 14 days in hospital incidence of cardiac complications was lower in treated patients than controls (cardiogenic shock, 2.5% v 6.0%; ventricular fibrillation, 3.4% v 6.3%; and pericarditis, 6.2% v 11.0% respectively), but that of angioplasty or artery bypass, or both was higher (15.8% v 9.6%) during the first three months. Bleeding complications were commoner in treated than untreated patients. Most were minor, but 1.4% of treated patients had intracranial haemorrhage within three days after start of infusion. Enzymatic size of infarct, determined by alpha hydroxybutyrate dehydrogenase concentrations, was less (20%, 2p = 0.0018) in treated patients than in controls. Left ventricular ejection fraction was 2.2% higher (0.3 to 4.0) and end diastolic and end systolic volumes smaller by 6.0 ml (-0.2 to -11.9) and 5.8 ml (-0.9 to -10.6), respectively, in treated patients. CONCLUSION--Recombinant tissue type plasminogen activator with heparin and aspirin reduces size of infarct, preserves left ventricular function, and reduces complications and death from cardiac causes but at increased risk of bleeding complications4+

Intravenous and intrapulmonary recombinant tissue-type plasminogen activator in the treatment of acute massive pulmonary embolism.

Abstract: Eight centers participated in a study in which intrapulmonary and intravenous administration of recombinant tissue-type plasminogen activator (rt-PA) were compared in 34 patients with acute massive pulmonary embolism. All patients received intravenous heparin in a bolus of 5,000 IU followed by 1,000 IU/hr. After 50 mg rt-PA given over 2 hr the severity of embolism, determined from pulmonary angiograms, declined by 12% in the intrapulmonary drug group (p less than .005) and 15% in the intravenous drug group (p less than .005); mean pulmonary arterial pressure fell from 31 +/- 7 to 22 +/- 6 mm Hg (p less than .005) and from 31 +/- 12 to 21 +/- 9 mm Hg (p less than .005) in the respective groups. After a further 50 mg given over 5 hr (22 patients), the angiographically determined severity of embolism had decreased by 38% from baseline in the intrapulmonary drug group and by 38% in the intravenous drug group. The mean pulmonary arterial pressure further declined to 18 +/- 7 and 12 +/- 5 mm Hg in the respective groups. Fibrinogen levels dropped to 48% of baseline after 50 mg and to 36% of baseline after 100 mg rt-PA. Some degree of bleeding at puncture and/or operation sites was noted in 16 patients, including four who required a transfusion of two or more units of blood and had been operated on an average of 7.5 days (range 2 to 13) before thrombolytic treatment was started.(ABSTRACT TRUNCATED AT 250 WORDS)

Visible spectroscopy of methylene blue on hectorite, laponite B, and barasym in aqueous suspension

Abstract: The absorption spectra of methylene blue ion exchanged on hectorite, Laponite B, Barasym, or sepiolite in dilute aqueous suspensions show the presence of the monomer, the protonated monomer, the dimer, and the trimer. Due to conformational differences, the absorption band maximum of the monomer with respect to its maximum in aqueous solution is red shifted when it is adsorbed on the external surface and blue shifted when it is adsorbed on the interlamellar surface. The availability of the interlamellar surface for methylene blue as a function of the type of clay and/or the counterion present thereby can be probed. The results indicate that 0.6-0.7% of the cation-exchange capacity of Barasym consists of acid sites capable of protonating methylene blue. Counterions of low hydration energy were found to induce a small number of similar sites in hectorite and Laponite B; hence, these sites must be situated on the external surface. Dimers formed on external surfaces show one absorption band. Dimers formed on the interlamellar surface of hectofite yield spectra having two absorption bands. The trimer was formed only at the external surface. With increasing loading of the clays, the spectra of methylene blue showed metachromasy. The metachromatic behavior can be fully explained by dye aggregation, which is the result of its concentration on the surface. No 7r-electron interaction with the surface oxygens need be invoked.

Insulin stimulates the synthesis of plasminogen activator inhibitor 1 by the human hepatocellular cell line Hep G2.

Abstract: Secretion of plasminogen activator inhibitor 1 (PAI-1) by cultures of human umbilical vein endothelial cells and human hepatocellular cell line Hep G2 was evaluated after insulin stimulation. The secretion of PAI-1 antigen and activity was measured in the conditioned medium and the cellular extracts after incubation of confluent cultures with 1% serum medium for 24 hours. Insulin induced a dose dependent increase of the PAI-1 secretion by Hep G2 cell line. At 10(-8) M a two fold increase of PAI-1 antigen and activity were observed whereas alpha 2 antiplasmin and fibrinogen were not significantly modified. No effect of insulin was observed on PAI-1 antigen and PAI activity production by human endothelial cells whereas endotoxin resulted in a two fold increase in PAI-1 secretion. In recent clinical studies we have demonstrated that the level of plasma insulin correlated with that of PAI-1. Thus we hypothesize that hepatocytes represent a physiological source of plasma PAI-1 which is modulated by plasma insulin level.

Tissue-type plasminogen activator antigen and plasminogen activator inhibitor in diabetes mellitus.

Abstract: Parameters of fibrinolysis, including euglobulin fibrinolytic activity, tissue-type plasminogen activator (t-PA) antigen, plasminogen activator inhibitor (PA-inhibitor) activity, and plasmin-alpha 2-antiplasmin complex (PAP) were studied in 62 patients (35 women and 27 men; ages 53 +/- 16 years) with either insulin-dependent (IDDM) or noninsulin-dependent (NIDDM) diabetes mellitus Compared to a control group of similar age (n = 57), the diabetic patients had a significantly lower mean euglobulin fibrinolytic activity (12 +/- 07 vs 17 +/- 11 ng/ml, p less than 001) but significantly higher mean t-PA antigen (157 +/- 84 vs 66 +/- 29 ng/ml, p less than 0001) and PA-inhibitor activity (26 +/- 13 vs 15 +/- 07 IU/ml, p less than 0001) levels Significant univariate correlations were observed between PA-inhibitor activity and age (r = 032, p less than 005), diastolic blood pressure (r = 042, p less than 001) and euglobulin fibrinolytic activity (r = -040, p less than 001) In multivariate analysis, only body mass index (positively) and euglobulin fibrinolytic activity (negatively) remained significantly related to PA-inhibitor activity in the total diabetic population as well as in the NIDDM group The only parameter in the IDDM group significantly related to PA-inhibitor activity was diastolic blood pressure These results suggest that PA-inhibitor plays a role in the regulation of fibrinolysis in diabetes patients and that factors like obesity and hypertension may be related to reduced fibrinolysis via PA-inhibitor levels

Compliant robot motion II. A control approach based on external control loops

Abstract: A control approach for the execution of robot tasks in contact with the environment is worked out. The input to the con troller consists of the task specification described in part I. The control a...

Magnetoliposomes. Formation and structural characterization.

Abstract: The adsorption of different types of phosphatidylglycerols onto magnetizable solid particles is studied. The super-paramagnetic magnetite spheres used have an average diameter of only 14 nm and are stabilized by lauric acid to keep them in solution. During incubation and dialysis of this water-based magnetic fluid in the presence of preformed sonicated phospholipid vesicles, magnetoliposomes are formed which are captured from solution with high efficiency by high-gradient magnetophoresis. Support for the bilayer character of the phospholipid coat is derived from both theoretical calculations and experimental data. Phospholipids which form the inner monolayer are adsorbed very quickly with their charged head-group orientated towards the iron oxide surface. The high-affinity character of the binding is reflected in the adsorption isotherms and is further illustrated by their non-extractability with high concentrations of Tween 20. The outer layer assembles through interaction with the exposed hydrocarbon chains. As compared to the inner layer, the phospholipids adsorb at a much slower rate and are displaced by Tween 20 concentrations which usually disrupt conventional membranes. The adsorption isotherms for this layer obey the Langmuir expression. The affinity constants, derived from them, progressively increase as the hydrophobic nature of the phosphatidylglycerols is more pronounced.

Pharmacokinetic profile of orally administered itraconazole in human skin.

Abstract: Itraconazole is an orally effective antifungal agent with a high affinity for tissues. The skin kinetics in human volunteers have been studied after administration of 100 and 200 mg of itraconazole daily. From day 7 onward, tissue levels in the beard region and on the back were consistently higher than the corresponding plasma levels. The levels in the palmar stratum corneum were lower than the corresponding plasma levels but persisted for 3 weeks after discontinuation of therapy. Stratum corneum levels in the beard area were still measurable 4 weeks after the end of therapy. With the 200-mg dose, sweat levels became detectable 24 hours after the first drug intake. The sweat levels were usually lower than the corresponding plasma levels and followed the same curve as the plasma levels. Sebum levels of itraconazole were 10 times as high as the corresponding peak plasma levels. Sebum levels were undetectable 14 days after discontinuation of therapy. The results indicate that oral intake of itraconazole will result in therapeutic levels in the skin and these levels vary, depending on the region of skin tested. There are at least three routes of delivery of itraconazole to the skin: (1) passive uptake by keratinocytes in the basal layer (as shown by the continued presence of the drug in the palmar stratum corneum at a moment when plasma, sebum, and sweat levels are again undetectable); (2) a less significant excretion through the sweat glands (as shown by the lower drug levels compared with the plasma levels); and (3) a massive excretion through the sebaceous glands (as shown by the sebum levels compared with the plasma levels).

Hierarchical classes: Model and data analysis

Abstract: A discrete, categorical model and a corresponding data-analysis method are presented for two-way two-mode (objects × attributes) data arrays with 0, 1 entries. The model contains the following two basic components: a set-theoretical formulation of the relations among objects and attributes; a Boolean decomposition of the matrix. The set-theoretical formulation defines a subset of the possible decompositions as consistent with it. A general method for graphically representing the set-theoretical decomposition is described. The data-analysis algorithm, dubbed HICLAS, aims at recovering the underlying structure in a data matrix by minimizing the discrepancies between the data and the recovered structure. HICLAS is evaluated with a simulation study and two empirical applications.

Cyclic GMP-dependent protein kinase phosphorylates phospholamban in isolated sarcoplasmic reticulum from cardiac and smooth muscle.

Abstract: Phospholamban of isolated sarcoplasmic reticulum of cardiac and smooth muscle is phosphorylated by cyclic GMP-dependent protein kinase (G-kinase). Concomitantly, the affinity of the Ca2+ pump for Ca2+ is increased. These effects are very similar to those seen with cyclic AMP-dependent protein kinase (A-kinase). The phosphate incorporation into phospholamban and the stimulatory effects of both kinases on the Ca2+ pump are not additive, suggesting that G-kinase phosphorylates the same serine residue as A-kinase. A possible physiological role for phosphorylation of phospholamban by G-kinase is discussed.

Determination of Si-SiO/sub 2/ interface recombination parameters using a gate-controlled point-junction diode under illumination

Abstract: A novel method is presented to determine Si-SiO/sub 2/ interface recombination parameters. The device used is a polysilicon-oxide-semiconductor capacitor with a microscale central junction (a gate-controlled point-junction diode). Data analysis has been performed using a numerical scheme to find a quasi-exact solution for the current combining at the interface. It was found that the interface recombination parameters depend only weakly on trap energy in a wide range around midgap. The cross-section for capturing electrons was found to exceed the cross-section for capturing holes by a factor of 10/sup 2/ to 10/sup 3/. >

Compliant robot motion: I. A formalism for specifying compliant motion tasks

Abstract: A formalism is developed for specifying compliant motion tasks. It is based on the hybrid control functional specification method described by Mason. However, some new concepts are introduced: trac...

Human T cell activation with phytohemagglutinin. The function of IL-6 as an accessory signal.

Abstract: T cell proliferation induced by the lectin PHA requires the presence of monocytes Here, we report that IL-6 represents part of the monocyte-derived helper activity for human T cell stimulation with PHA Resting T cells isolated from peripheral blood or tonsils and completely depleted of accessory cells (monocytes and NK cells) did not proliferate in response to PHA alone Addition of a cell-free monocyte culture supernatant (not containing IL-2) to the PHA-stimulated cultures resulted in T cell proliferation We identified IL-6 as an essential helper factor in these monocyte supernatants, because antisera to IL-6 (but not anti-IL-1-beta) completely neutralized the helper effect of the monocyte supernatant Moreover, addition of purified human IL-6 (but not IL-1-beta) to T cell cultures resulted in proliferation of PHA-stimulated T cells Although IL-1 could not restore the PHA-induced proliferative response of isolated T cells by itself, it strongly enhanced the helper effect of IL-6 In contrast to intact monocytes, IL-6 did not induce detectable IL-2 production in cultures of PHA-stimulated T cells Furthermore, an anti-IL-2R mAb (anti-Tac) did not block the proliferative response induced by PHA and IL-6, suggesting that an IL-2-independent pathway of T cell proliferation was involved In conclusion our results show that human IL-6, previously identified as a B cell hybridoma growth and a B cell differentiation factor, represents part of the monocyte helper function for PHA-induced human T cell activation and proliferation

Omeprazole (40 mg) is superior to ranitidine in short-term treatment of ulcerative reflux esophagitis

Abstract: The efficacy and safety of omeprazole, 40 mg once daily for four to eight weeks of treatment, were studied in 61 patients with ulcerative reflux esophagitis. A double-blind controlled study design was used, and the patients were randomly allocated to treatment with either omeprazole 40 mg once daily or ranitidine 150 mg twice daily. Endoscopy was performed prior to inclusion into the study, after four weeks and, if unhealed, again after eight weeks. Healing of esophagitis was defined as complete disappearance of all esophageal ulcerations. Symptoms were recorded before entry, after four weeks, and again after eight weeks in unhealed patients. Fifty-one patients were included in the per-protocol analysis at day 29, and 50 patients at day 57. The healing rate after four weeks of treatment was 22 of 26 patients (85%) treated with omeprazole and 10 of 25 patients (40%) treated with ranitidine (P<0.001). The corresponding figures after eight weeks were 24 of 25 (96%), and 13 of 25 (52%) (P<0.001). These results were confirmed in the intent-to-treat analysis. Patients treated with omeprazole showed a significantly faster and more profound relief in heartburn than patients treated with ranitidine: 85% had no heartburn after four weeks of treatment with omeprazole compared to 24% in patients treated with ranitidine (P=0.00007). The percentage of patients who were free of all reflux symptoms was significantly greater in the omeprazole-treated group as compared to the ranitidine-treated group (62% and 12% respectively, P=0.0001). There were no clinically significant changes in laboratory values in any of the treatment groups. Adverse events were few and mainly mild and transient.

Heterogeneity of GABAergic cells in cat visual cortex

Abstract: Antibodies against neuropeptides and against a vitamin D-dependent calcium-binding protein (CaBP) label small cells with nonpyramidal-like morphology in the cat visual cortex (areas 17, 18, and 19). Since GABAergic cells are interneurons, a double-staining procedure was used to test for the coexistence of cholecystokinin (CCK), somatostatin (SRIF), neuropeptide Y (NPY), corticotropin-releasing factor (CRF), vasoactive intestinal polypeptide (VIP), and CaBP with glutamic acid decarboxylase (GAD). Our results show that CRF and VIP do not coexist with GAD, while the 3 other peptides and CaBP do. Hence GAD-positive cells can be subdivided into 4 broad groups: (1) cells that are only GAD-positive, (2) cells that are GAD- and CaBP-positive, (3) GAD- positive neurons also containing CCK, and (4) GAD-positive cells that also contain SRIF. A small subset of class 2 also contains SRIF and most cells of class 4 also contain NPY. The 4 classes of GAD-positive cells differ in laminar position: class 1 predominates in layers IV and V, classes 2 and 3 in the upper laminae (II and III), and class 4 in the deepest layer (VI).

Hydraulic and soil mechanical aspects of rill generation on agricultural soils

Abstract: SUMMARY An attempt is made, using literature data, to clarify the relationship between the detachment capacity of overland flow and its hydraulic characteristics. Attention is paid to the influence of sediment properties and rainfall. Using these relationships and the concept of effective shear velocity, it was possible to establish a relationship for rill prediction which covers a variety of soils and a wide range of field conditions. Raindrop impacts do not seem to have an important influence on rill generation on cohesive materials.