Showing papers by "Katholieke Universiteit Leuven published in 1984"

A reliable approach to charge-pumping measurements in MOS transistors

Abstract: A new and accurate approach to charge-pumping measurements for the determination of the Si-SiO 2 interface state density directly on MOS transistors is presented. By a careful analysis of the different processes of emission of electrons towards the conduction band and of holes towards the valence band, depending on the charge state of the interface, all the previously ill-understood phenomena can be explained and the deviations from the simple charge-pumping theory can be accounted for. The presence of a geometric component in some transistor configurations is illustrated and the influence of trapping time constants is discussed. Furthermore, based on this insight, a new technique is developed for the determination of the energy distribution of interface states in small-area transistors, without requiring the knowledge of the surface potential dependence on gate voltage.

Algorithms for refining triangular grids suitable for adaptive and multigrid techniques

Abstract: Two general algorithms for refining triangular computational meshes based on the bisection of triangles by the longest side are presented and discussed. The algorithms can be applied globally or locally for selective refinement of any conforming triangulation and always generate a new conforming triangulation after a finite number of interactions even when locally used. The algorithms also ensure that all angles in subsequent refined triangulations are greater than or equal to half the smallest angle in the original triangulation; the shape regularity of all triangles is maintained and the transition between small and large triangles is smooth in a natural way. Proofs of the above properties are presented. The second algorithm is a simpler, improved version of the first which retains most of the properties of the latter. The algorithms can be used either for constructing irregular computational meshes or for locally refining any given triangulation. In this sense they can be adequately combined with adaptive and/or multigrid techniques for solving finite element systems. Examples of the application of the algorithms are given and two possible generalizations are pointed out.

Bone marrow histology in myelodysplastic syndromes. II. Prognostic value of abnormal localization of immature precursors in MDS.

Abstract: A study has been performed of 40 bone marrow trephine biopsies from patients with myelodysplastic syndromes (MDS). Histology, more specifically the abnormal localization of immature precursors (ALIP), cytology and karyotype analysis were correlated with survival time and the prognostic value of these factors was determined. The presence or absence of ALIP proved to be highly significant in predicting the duration of survival (P = 0.007): the presence of ALIP predisposes patients to early death with high probability of developing acute myeloid leukaemia (AML), whereas the absence of ALIP carries a better prognosis with more long-term survivors and low probability of transformation to AML. The presence or absence of ALIP was not correlated with increased mortality from infection and/or bleeding. In contrast with ALIP, the main histological parameter, we were not able to obtain statistically significant prognostic information for cytology (FAB classification) or karyotype analysis (normal or abnormal chromosomes). We conclude that bone marrow biopsy provides useful information for the prognosis of MDS and that the presence of ALIP has greater predictive value than the more commonly used parameters deduced from cytology and karyotype.

Nematic-Smectic- A Tricritical Point in Alkylcyanobiphenyl Liquid Crystals

Abstract: From adiabatic-scanning calorimetric results it is demonstrated that in mixtures of 9CB and 10CB, two compounds of the alkylcyanobiphenyl ($n\mathrm{CB}$) series, the nematic ($N$) to smectic-$A$ ($A$) transition becomes first order for narrow $N$ ranges. From the latent heats a tricritical point is located in the phase diagram. Measurements for 7CB+ 8CB mixtures show that the specific-heat exponent $\ensuremath{\alpha}$ depends on the width of the $N$ range for continuous $\mathrm{AN}$ transitions.

Biological and Thrombolytic Properties of Proenzyme and Active Forms of Human Urokinase – I. Fibrinolytic and Fibrinogenolytic Properties in Human Plasma In Vitro of Urokinases Obtained from Human Urine or by Recombinant DNA Technology

Abstract: The fibrinolytic and fibrinogenolytic properties of recombinant pro-urokinase (Rec-pro-UK) and recombinant urokinase (Rec- UK) obtained by expression of the human urokinase cDNA in E. coli, were compared with those of natural urokinase (Nat-UK) of urinary origin and of tissue-type plasminogen activator (t-PA) in a system, composed of a radioactive human plasma clot immersed in citrated human plasma. The specific fibrinolytic effects of Nat-UK, Rec-pro-UK and Rec-UK were very similar, causing significant clot lysis at concentrations of 100 IU/ml plasma or more. t-PA caused equivalent degrees of clot lysis at 10-fold lower concentrations. Activation of the fibrinolytic system in the plasma (fib- rinogenolysis), was not observed with t-PA in concentrations which induced complete clot lysis within 5 hr (20-30 IU/ml plasma). With Nat-UK and Rec-UK, all concentrations which caused significant clot lysis (100-200 IU/ml plasma) also caused extensive activation of the plasma fibrinolytic system. With Rec- pro-UK an intermediate response was obtained. The highest amounts required for complete clot lysis in 5 hr (200 IU/ml plasma) also caused significant fibrinogenolysis. At intermediate concentrations (50-100 IU/ml), however, significant clot lysis (40-80%) was observed without systemic fibrinolytic activation.

Nucleotide sequence of a crustacean 18S ribosomal RNA gene and secondary structure of eukaryotic small subunit ribosomal RNAs.

Abstract: The primary structure of the gene for 18 S rRNA of the crustacean Artemia salina was determined. The sequence has been aligned with 13 other small ribosomal subunit RNA sequences of eukaryotic, archaebacterial, eubacterial, chloroplastic and plant mitochondrial origin. Secondary structure models for these RNAs were derived on the basis of previously proposed models and additional comparative evidence found in the alignment. Although there is a general similarity in the secondary structure models for eukaryotes and prokaryotes, the evidence seems to indicate a different topology in a central area of the structures.

In vivo metal-ion release from porous titanium-fiber material

Abstract: Dense and porous Ti, Ti-alloy, and stainless steel specimens were implanted in canine trabecular bone. After 6 and 12 months the specimens were retrieved together with bone tissue immediately adjacent. The trace metal content in the tissue samples was determined using neutron activation analysis, differential pulse polarography, graphite furnace atomic-absorption spectrophotometry, electron microprobe analysis, and laser microprobe analysis. The results are discussed in view of (i) the release of Ti ions, which is larger for porous than for bulk specimens, (ii) the various artifacts arising in electron microprobe (EMP) and laser microprobe mass analysis (LAMMA) determination of compositional gradients of trace metal-ion content in bone tissue, (iii) the absence of measurable quantities of V in bone tissue, and (iv) the difference in local tissue accumulation between Ti, released from Ti specimens, and Ni, released from stainless steel specimens.

A Micropower CMOS-Instrumentation Amplifier

Abstract: A CMOS switched capacitor instrumentation amplifier is presented. Offset is reduced by an auto-correlation technique and effects due to charge injection are attenuated by a special amplifier configuration. The circuit which is realized in a 4 ?m double poly process has a typical offset (?) of 370 ?V, an RMS input referred integrated noise (0-f c /2) of 79 ?V and consumes only 21 ?W (f c = 8 kHz, V DD = 3 V).

Chronic leg pain in athletes due to a recurrent compartment syndrome

Abstract: A series of 29 patients, all engaged in sports activity on a regular basis, suffering from recurrent compart mental syndrome, is reported. The syndrome is not restricted only to long distance runners but to athletes involved in a variety of sports activities (soccer, volley ball, cycle racing, gymnastics, judo, physical education, and long distance running). Although most patients presented activity-related leg pain, some patients mainly complained of ankle weakness and recurrent ankle distortions at fatigue.The wick catheter technique proved to be most useful to determine which compartments were involved. The severity of clinical symptoms correlated highly with the anomalies of the tissue pressure measurements. The predominance of deep posterior compartment and mul tiple compartment involvement are in contrast with most previous reports. Conservative treatment was unsuccessful in every patient, whereas surgical de compression of the involved compartments yielded fa vorable results in those cases where al...

Low dose cytosine arabinoside (Ara C) in myelodysplastic syndromes

Abstract: Myelodysplastic syndromes (MDS) are acquired bone-marrow disorders, characterized by a decreased ability of the haemopoietic cell to differentiate, resulting in peripheral cytopenias. The majority of patients will die either from acute myeloid leukaemia or from infection and/or haemorrhage. Thirty-eight courses of low dose Ara C were administered in 26 MDS patients. Nineteen courses (50%) were associated with good (12) or partial (7) response. Three complete remissions were observed. The median duration of response overall was 19.5 weeks, 26 weeks for the good and 10 weeks for the partial responders. A high incidence of treatment failure was seen in patients treated after transition to AML. Major complications were observed during 14 courses and mortality was directly related to therapy in five patients. Platelet transfusions were required during 26 courses. Aggravation of peripheral-blood cytopenia during the first weeks and hypocellularity of bone-marrow aspirates at the end of therapy suggest that low-dose Ara C exerts its main activity by suppression of leukaemic growth, rather than by induction of differentiation in malignant cells. Our results in MDS patients demonstrate that low-dose Ara C can be of value in severe cytopenia and can decrease the proportion of leukaemic cells in the bone marrow, but the danger of treatment should not be underestimated.

Thick-film metallization for solar cell applications

Abstract: The use of an integral printing technique for the fabrication of silicon solar cells is attractive due to its throughput rate, materials utilization, and modular, automatable design. The transfer of this technology from single crystal to semicrystalline silicon requires a significant amount of process optimization. Processing parameters found to be critical include the optimum glass frit content in the silver-based inks, the silver ink firing temperature, and the formation of the back-surface field using screen-printed aluminum layers. Open-circuit voltages as high as 617 mV have been achieved using a novel BSF approach on 4-in wafers. Important mechanisms controlling ink contact resistance, ink sheet resistivity, and ohmic contact on and silicon materials are discussed in this paper. The solar cell stability is a function of the glass frit and the firing temperature of the silver-based inks. Finally, a simple economic analysis, based on the IPEG technique, indicates that screen printing is a cost-effective option when the cell manufacturing is done on a large scale.

Biological and thrombolytic properties of proenzyme and active forms of human urokinase--III. Thrombolytic properties of natural and recombinant urokinase in rabbits with experimental jugular vein thrombosis.

Abstract: The thrombolytic properties of recombinant pro-urokinase (Rec-pro-UK), recombinant active urokinase (Rec-UK) and natural urinary urokinase (Nat-UK) were compared with those of tissue-type plasminogen activator (t-PA) in rabbits with a radiolabeled thrombus in the jugular vein. The thrombolytic agents were infused intravenously over a time period of 4 hr and the extent of thrombolysis measured two hours later. In control animals the extent of thrombolysis was 11 +/- 2% (n = 8) after 6 hr. Nat-UK and Rec-UK had very similar thrombolytic properties. Significant thrombolysis was only obtained with infusion of 240,000 IU per kg (41 +/- 2%, n = 4 for Nat-UK and 37 +/- 4%, n = 4 for Rec-UK) and this was associated with a marked systemic activation of the fibrinolytic system, as evidenced by consumption of plasminogen and alpha 2-antiplasmin and fibrinogen breakdown. Infusion of Rec-pro-UK induced thrombolysis at a dose of 60,000 IU per kg (44 +/- 8%, n = 3) but without associated systemic activation of the fibrinolytic system. In this respect the properties of Rec-pro-UK were similar to those of t-PA, which, however, had a 2- to 4-fold higher specific thrombolytic activity (30,000 IU/kg yielding 48 +/- 1% lysis, n = 4). It is concluded that Rec-UK has very similar thrombolytic properties as Nat-UK and that Rec-pro-UK has a better thrombus-selectivity and less systemic side effects than the active enzymes.

Influence of Vitamin D Status on Insulin Secretion and Glucose Tolerance in the Rabbit

Abstract: The influence of vitamin D status on insulin secretion and glucose tolerance was studied by a longitudinal design in the rabbit. Intravenous glucose tolerance tests were performed in Dutch rabbits (n = 12) before and after nutritional vitamin D deficiency, characterized by an absence of circulating 25-hydroxyvitamin D3, a 50% decrease in 1,25-dihydroxyvitamin D3, and a 16% decrease in serum calcium concentrations. Glucose- induced insulin secretion was reduced by 41% as early as 2 months after the start of the vitamin D-deficient diet and was associated with an impairment of glucose tolerance. An iv calcium infusion restored the serum calcium concentration of the vitamin D-deficient rabbits (n = 5), but did not improve glucose-mediated insulin secretion. When these animals received a single ip injection of 100 ng 1,25-dihydroxyvitamin D3 10 h before the glucose test, their insulin responses significantly increased. Supplementation with 25-hydroxyvitamin D3 for 2 weeks in another group of rabbits (n = 4) r...

Observation of Low-Lying J π = 0 + States in the Single-Closed-Shell Nuclei Pb 1 9 2 − 1 9 8

Abstract: First experimental evidence for a low-lying ${J}^{\ensuremath{\pi}}={0}^{+}$ excited state in $^{192\ensuremath{-}198}\mathrm{Pb}$ is obtained by study of the $\ensuremath{\beta}$ decay of mass-separated Bi isotopes. It is shown that such excited states correspond to deformed two-particle, two-hole configurations.