Showing papers by "Katholieke Universiteit Leuven published in 1983"

Cloning and expression of human tissue-type plasminogen activator cDNA in E. coli

Abstract: Bacterial clones containing human tissue-type plasminogen activator (t-PA) cDNA sequences were identified in a cDNA library prepared using gel-fractionated mRNA from human melanoma cells. A plasmid containing the Escherichia coli trp promoter and the cDNA sequence coding f or the 527-amino acid mature t-PA protein was constructed for expression in E. coli. A polypeptide was produced having the fibrinolytic properties characteristic of authentic human t-PA.

Regulation of the immune response by prostaglandins

Abstract: Of all the arachidonic acid metabolites, only prostaglandin E (PGE) has been shown to have a clear role in the regulation of cellular and humoral immune responses. In cellular immune responses such as T cell proliferation, lymphokine production, and cytotoxicity, PGE usually acts as a feedback inhibor of the response. This is also true of macrophage and natural killer cytotoxicity. In some instances PGE is responsible for cellular activation rather than inhibition. This is clearest in the control of humoral immunity, where PGE production is a necessary component in the generation of some type of T suppressor cells. Disturbances in immune function found in several human conditions and diseases have been linked to changes in PGE mediated immunoregulation. Either increased production of PGE or increased sensitivity to PGE results in depressed cellular immunity. Conversely drugs which inhibit PGE production act as stimulants of cellular immune functionin vitro andin vivo.

Neuronal Operations in the Visual Cortex

Abstract: 1 The Visual System of Cat and Monkey Compared.- 1.1 The Basic Layout of the Visual System in Cat, Owl Monkey, and Rhesus Monkey.- 1.1.1 The Retina.- 1.1.2 The Optic Chiasm and Optic Tract.- 1.1.3 The Dorsal Lateral Geniculate Nucleus (dLGN).- 1.1.4 Visual Cortex.- 1.1.5 Pulvinar.- 1.1.6 Callosal Connections.- 1.2 Quantitative Aspects of the Retino-Geniculo-Cortical Projections.- 1.2.1 The Overall Numbers of Cells in the Visual Pathway.- 1.2.2 Distribution of Retinal Cell Populations.- 1.2.3 Magnification Factors.- 1.3 Conclusion.- 2 The Visual Cortical Areas of the Cat.- 2.1 Description of the Visual Cortical Areas.- 2.1.1 Area 17: The Prototype of Visual Cortical Areas.- 2.1.2 Areas 18 and 19.- 2.1.3 The Lateral Suprasylvian Areas.- 2.1.4 Areas 20 and 21.- 2.1.5 Additional Visual Areas?.- 2.2 The Levels of Processing in the Visual Cortical System of the Cat.- 2.3 Additional Observations on the Retinotopic Organization in the Primary Complex.- 2.3.1 Variability of the 3 Cortical Maps.- 2.3.2 RF Scatter.- 2.3.3 The 17-18 Border and the Question of the Naso-Temporal Overlap.- 2.3.4 The 18-19 Border and the Question of the Visual Field Islands.- 2.4 Conclusion.- 3 Afferent Projections to Areas 17, 18, 19 of the Cat: Evidence for Parallel Input.- 3.1 The Relay of Retinal Afferents: The Dorsal Lateral Geniculate Nuclear Complex.- 3.2 The Geniculocortical Projection.- 3.3 Functional Streams in the Retino-Geniculocortical Projection.- 3.3.1 Functional Properties of Retinal and Geniculate X, Y, W Cells.- 3.3.2 Correlation with Retinal Morphology.- 3.3.3 Separation of Functional Streams at LGN Level.- 3.3.4 Correlation with LGN Morphological Types.- 3.3.5 Distribution of Functional Streams in dLGN Nuclear Complex.- 3.3.6 Input to Different Areas of Primary Visual Complex.- 3.4 Physiological Identification of the Functional Type of Afferents to Areas 17, 18 and 19.- 3.5 The Termination of Geniculate Afferents in the Visual Cortex.- 3.6 Other Subcortical Afferents: Pulvinar-Lateralis Posterior Complex, Intralaminar Nuclei, Claustrum, and Brainstem.- 3.7 The Ipsilateral Corticocortical Connections.- 3.8 The Connections Through the Corpus Callosum.- 3.9 Conclusion.- 4 Receptive Field Organization in Areas 17, 18 and 19 of the Cat.- 4.1 Twenty Years with the Simple-Complex-Hypercomplex Scheme.- 4.2 Criteria for Classifying Cortical RFs.- 4.2.1 The ON-OFF Overlap or the Parcellation of the RF into Subregions.- 4.2.2 Position Test.- 4.2.3 RF Dimensions.- 4.2.4 End-Stopping or the Hypercomplex Property.- 4.3 The A, B, C, S Scheme.- 4.3.1 Properties and Distribution of Cell Types.- 4.3.2 The S and A Families.- 4.3.3 Responses to Other Stimuli.- 4.4 Correspondence of the A, B, C, S Scheme with Other Classification Schemes.- 4.5 Conclusion.- 5 Parameter Specificity of Visual Cortical Cells and Coding of Visual Parameters.- 5.1 The Tuned Cells as Bandpass Filters: The Multichannel Representation of a Parameter.- 5.2 Are All Tuned Cells Simple (Passive) Bandpass Filters or Are Some of Them Active Filters?.- 5.3 Cells with Thresholds as High-Pass Filters: Single or Multichannel Representation of a Parameter.- 5.4 Conclusion.- 6 Influence of Luminance and Contrast on Cat Visual Cortical Neurons.- 6.1 Contrast-Response Curves Obtained with Sinusoidal Gratings.- 6.2 Contrast-Response Curves Obtained with Slits.- 6.3 The Extreme Contrast Sensitivity at the 18-19 Border.- 6.4 Influence of Contrast and Luminance on Other Response Properties.- 6.5 Conclusion.- 7 Coding of Spatial Parameters by Cat Visual Cortical Neurons: Influence of Stimulus Orientation, Length, Width, and Spatial Frequency.- 7.1 Orientation Tuning of Cortical Cells.- 7.1.1 Definitions and Criteria.- 7.1.2 Quantitative Determinations: Orientation-Response Curves.- 7.1.3 Qualitative Determination: Hand-Plotting.- 7.1.4 Distribution of Preferred Orientations.- 7.1.5 Orientation Columns.- 7.1.6 Conclusion.- 7.2 Influence of Stimulus Length on Cortical Cells.- 7.3 Selectivity of Cortical Neurons for Spatial Frequency and Stimulus Width.- 7.3.1 Selectivity for Spatial Frequency.- 7.3.2 Spatial Frequency and Coding of Stimulus Dimensions.- 7.3.3 Linearity of Cortical Cells.- 7.3.4 The Visual Cortex as a Fourier Analyzer.- 7.3.5 Spatial Frequency: Conclusion.- 7.4 Spatial Parameters: Conclusion.- 8 Coding of Spatio-Temporal Parameters by Cat Visual Cortical Neurons: Influence of Stimulus Velocity Direction and Amplitude of Movement.- 8.1 Influence of Stimulus Velocity.- 8.2 Influence of the Direction of Movement.- 8.3 Influence of Stimulus Movement Amplitude.- 8.4 Conclusion.- 9 Binocular Interactions in Cat Visual Cortical Cells and Coding of Parameters Involved in Static and Dynamic Depth Perception.- 9.1 The Binocularity of Cortical Cells and the Ocular Dominance Scheme.- 9.2 Position Disparity Tuning Curves and the Coding of Static Depth.- 9.3 Orientation Disparity, Another Mechanism for Static Depth Discrimination?.- 9.4 Neuronal Mechanisms Underlying Dynamic Depth Perception (Motion in Depth).- 9.5 Conclusion.- 10 The Output of the Cat Visual Cortex.- 10.1 The Projections of Layer V to the Superior Colliculus, Pons, Pretectum, and Pulvinar-LP Complex.- 10.2 The Projections of Layer VI to the dLGN and the Claustrum.- 10.3 The Commissural Projections.- 10.4 The Associative Corticocortical Projections.- 10.5 Conclusion.- 11 Correlation Between Geniculate Afferents and Visual Cortical Response Properties in the Cat.- 11.1 Electrical Stimulation of the Visual Pathways.- 11.2 The Question of ON or OFF Cell Input to Cortical S Cells.- 11.3 Other Attempts to Identify the LGN Input to Cortical Cells.- 11.4 Conclusion.- 12 Intracortical Mechanisms Underlying Properties of Cat Visual Cortical Cells.- 12.1 The Role of Intracortical Inhibition.- 12.1.1 Orientation Selectivity.- 12.1.2 Direction Selectivity.- 12.1.3 End-Stopping.- 12.1.4 Ocular Dominance.- 12.1.5 Velocity Upper Cut-Off.- 12.1.6 Absence of Response to Two-Dimensional Noise.- 12.2 Properties of the Intracortical Inhibitions.- 12.3 The Structural Counterpart of Inhibitions.- 12.4 Conclusion.- 13 Non-Visual Influences on Cat Visual Cortex.- 13.1 Non-Visual Sensory Inputs to the Visual Cortex.- 13.2 Influence of Eye Movements on Visual Cortical Cells.- 13.3 The Influence of Sleep and Anesthesia.- 14 Response Properties of Monkey Striate Neurons.- 14.1 Retinotopic Organization of Area 17.- 14.2 The Input-Output Relations of Monkey Striate Cortex.- 14.3 Receptive Field Organization and Size.- 14.4 Color Specificity in Monkey Striate Cortex.- 14.5 Influence of Light Intensity and Contrast on Monkey Striate Neurons.- 14.6 Influence of Spatial Parameters.- 14.7 Influence of Spatio-Temporal Parameters.- 14.8 Ocular Dominance Distribution and Depth Sensitivity.- 14.9 Columnar Organization and Functional Architecture of Striate Cortex.- 14.10 Correlation Between Response Properties and Afferent Input.- 14.11 Conclusion.- 15 Conclusion: Signification of Visual Cortical Function in Perception.- 15.1 Operating Principles in Cat Visual Cortex.- 15.1.1 Retinotopic Organization.- 15.1.2 Filtering.- 15.1.3 "Columnar" Organization.- 15.1.4 Distributed Processing in the Primary Complex.- 15.1.5 Changes with Eccentricity.- 15.1.6 Parallel Streams Within each Area.- 15.2 The Cat and Monkey Visual Cortex as a Model: The Question of the Relationship Between Animal Physiology and Human Visual Perception.- 15.3 The Role of the Primary Visual Cortex in Visual Perception: The Significance of Parameter Specificities for Object Recognition.- References.

NORA: a racefree dynamic CMOS technique for pipelined logic structures

Abstract: Describes a new dynamic CMOS technique which is fully racefree, yet has high logic flexibility. The circuits operate racefree from two clocks /spl phi/ and /spl phi/~ regardless of their overlap time. In contrast to the critical clock skew specification in the conventional CMOS pipelined circuits, the proposed technique imposes no restriction to the amount of clock skew. The main building blocks of the NORA technique are dynamic CMOS and C/SUP 2/MOS logic functions. Static CMOS functions can also be employed. Logic composition rules to mix dynamic CMOS, C/SUP 2/MOS, and conventional CMOS will be presented. Different from Domino technique, logic inversion is also provided. This means higher logic flexibility and less transistors for the same function. The effects of charge redistribution, noise margin, and leakage in the dynamic CMOS blocks are also analyzed. Experimental results show the feasibility of the principles discussed.

The discrete memoryless multiple access channel with partially cooperating encoders (Corresp.)

Abstract: We introduce the communication situation in which the encoders of a multiple access channel are partially cooperating. These encoders are connected by communication links with finite capacities, which permit both encoders to communicate with each other. First we give a general definition of such a communication process (conference). Then, by proving a converse and giving an achievability proof, we establish the capacity region of the multiple access channel with partially cooperating encoders. It turns out that the optimal conference is very simple.

Minority carrier recombination in heavily-doped silicon

Abstract: A review of our present understanding about the minority carrier recombination in silicon with dopant concentration in the range of 1018–1020 cm−3 is presented. After providing a short phenomenological description of carrier recombination processes and lifetime, the main theories of carrier recombination in a semiconductor are briefly reviewed and their expected contributions to carrier recombination in silicon at heavy doping are indicated. The various methods used for measuring the minority carrier lifetime in heavily doped silicon are described and critically examined. Four different mechanisms are examined to explain the available lifetime data. Two of these involve SRH-type phononic recombination (i) via deep level traps generated by dopant introduced defects and (ii) through shallow donor/acceptor states. The other two non-phononic mechanisms are: (iii) Band to band Auger recombination and (iv) trap assisted Auger recombination. Mechanism (i) can not explain the observed insensitivity of lifetime to processing conditions and the dopant atoms, and contribution of (ii) remains insignificant up to the heaviest doping. Phonon assisted band to band Auger recombination appears to explain the measured lifetimes satisfactorily in p-type silicon. However, for n-type silicon this mechanism predicts considerably higher values of lifetime than the measured results and it is likely that mechanism (iv) (and probably (i) also) competes with this process. Calculations indicate that the rate of trap-assisted Auger recombination through the dopant generated acceptor states in p-type silicon and through donor states in n-type silicon becomes large enough to compete with the band to band Auger process at heavy doping. In n-type silicon Auger recombination through crystal defects like vacancies may also become important. Perhaps all these processes contribute to the carrier recombination at heavy doping but which of these controls the lifetime in n-type silicon is not known.

Evidence for Paracrine Interaction between Gonadotrophs and Lactotrophs in Pituitary Cell Aggregates

Abstract: Pituitary cell aggregates prepared from 14-day-old male or female rats and maintained for 4-5 days in culture were superfused with LHRH during periods of 20 or 90 min LHRH provoked a rapid and sustained rise of PRL release at concentrations similar to those stimulating LH release (10(-11)-10(-8) M) Dopamine, at a concentration inhibiting PRL release for 90%, weakened but did not prevent this stimulation LHRH also stimulated PRL release in aggregates prepared from adult male rat pituitary cells, but the effect was weaker and seen only after a more prolonged period in culture There was no PRL response to LHRH in aggregates of lactotroph-enriched populations, obtained by gradient sedimentation at unit gravity, in which only few and small gonadotrophs are present When a lactotroph-enriched/gonadotroph-poor population was coaggregated with a highly enriched population of large gonadotrophs, LHRH very effectively stimulated PRL release, the extent of stimulation being dependent on the proportional number of gonadotrophs in the coculture Superfusion of lactotroph-enriched/gonadotroph-poor aggregates with medium in which the gonadotroph-enriched aggregates had previously been incubated for 3 h with 1 nM LHRH (gonadotroph-conditioned medium) also provoked a clear-cut rise in PRL release This effect was not due to LH, FSH, or the small amounts of PRL present in the gonadotroph-conditioned medium The LHRH antagonist [D-Phe2-D-Ala6]LHRH was capable of blocking the PRL response to LHRH but not that to the gonadotroph-conditioned medium In the lactotroph-gonadotroph coaggregates TRH stimulated PRL release but had no effect on LH release TRH was also ineffective in releasing LH or FSH in populations containing both gonadotrophs and thyrotrophs The present data suggest that gonadotrophs can activate the secretory activity of the lacotrophs through the release of a paracrine humoral factor

Clot-selective coronary thrombolysis with tissue-type plasminogen activator

Abstract: Coronary thrombolysis, an intervention that can abort the sequelae of acute myocardial infarction, was accomplished within 10 minutes in dogs by intravenous administration of clot-selective, tissue-type plasminogen activator. In addition to inducing clot lysis, this promising fibrinolytic agent restored intermediary metabolism and nutritional myocardial blood flow, detectable noninvasively with positron tomography, without inducing a systemic fibrinolytic state.

Materials for photothermal solar energy conversion

Abstract: Commencally or potentially available selective and non-selective absorber surfaces for solar heat collectors are reviewed and the state-of-the-art of solar collector corrosion processes is outlined. The review of available published literature has indicated that a lack of quantitative information exists, relative to corrosion of collector surfaces. Available information (mostly qualitative) on durability aspects and corrosion of solar receiver surfaces is described to indicate potential corrosion problem areas and corrosion prevention possibilities. An outline of appropriate durability tests is presented.

Dipyridamole inhibits platelet aggregation in whole blood.

Abstract: Dipyridamole possesses antithrombotic properties in the animal and in man but it does not inhibit platelet aggregation in plasma. We evaluated the effect of dipyridamole ex vivo and in vitro on platelet aggregation induced by collagen and adenosine-5'-diphosphate (ADP) in human whole blood with an impedance aggregometer. Two hundred mg dipyridamole induced a significant inhibition of both ADP- and collagen-induced aggregation in human blood samples taken 2 hr after oral drug intake. Administration of the drug for four days, 400 mg/day, further increased the antiplatelet effect. A significant negative correlation was found between collagen-induced platelet aggregation in whole blood and dipyridamole levels in plasma (p less than 0.001). A statistically significant inhibition of both collagen (p less than 0.0025) and ADP-induced (p less than 0.005) platelet aggregation was also obtained by incubating whole blood in vitro for 2 min at 37 degrees C with dipyridamole (3.9 microM). No such effects were seen in platelet-rich plasma, even after enrichment with leukocytes. Low-dose adenosine enhanced in vitro inhibition in whole blood. Our results demonstrate that dipyridamole impedes platelet aggregation in whole blood by an interaction with red blood cells, probably involving adenosine.

Blood neutrophil function in primary myelodysplastic syndromes

Abstract: Ten different tests of blood neutrophil function were studied in 20 patients with primary myelodysplastic syndromes (PMDS). The patients were selected according to the new diagnostic criteria for PMDS of the FAB-cooperation group. Impairments of granulocyte functions were found in all patients. Moreover, several steps in the mobilization of granulocytes at the site of injury seemed to be affected: decreased adhesion (P less than 0.05), deficient chemotaxis (P less than 0.05), decreased enzyme content (P less than 0.001), 'slower' chemiluminescence (P less than 0.005), decreased phagocytosis (P less than 0.05) and impaired microbicidal capacity (P less than 0.025). No significant correlation between disease category and severity of granulocyte dysfunction was discerned, though an increasing number of blasts was associated with more severe granulocytic disability. Results in seven patients with abnormal karyotypes were not significantly different from 13 others with normal karyotypes. Our results indicate that defects in blood neutrophil function are a common feature in PMDS and might account for the increased frequency of infection in these patients.

Liquid-chromatographic assay and identification of mono- and diester conjugates of bilirubin in normal serum.

Abstract: This liquid-chromatographic procedure for determining bilirubin mono- and diester conjugates in normal serum is based on pre-analysis conversion of bilirubin monosugar and disugar conjugates to the corresponding methyl esters by alkaline methanolysis. Here, extracted unconjugated bilirubin, bilirubin monomethyl esters, bilirubin dimethyl ester, and internal standard are separated on a reversed-phase column within 15 min, detected in the effluent at 436 nm, and quantified from their peak areas. Carotenoids do not interfere. Within-day and day-to-day CVs range from 5 to 13%. The smallest concentrations of monoconjugated and diconjugated pigments that are detectable and measurable are about 10 and 20 nmol/L, respectively. Such data are given for sera from 43 healthy adults. Total bilirubin concentrations in serum tended to be lower in women than in men, but the relative amounts of the various bilirubin fractions in sera from men and women were comparable. Analysis of ethyl anthranilate azoderivatives from serum permitted identification of the bilirubin ester conjugates in normal serum as bilirubin 1-O-acyl glucuronides.

The shortening of the action potential by DNP in guinea-pig ventricular myocytes is mediated by an increase of a time-independent K conductance

Abstract: 1. The mechanism of the well known shortening of the cardiac action potential by 2,4-dinitrophenol (DNP, a classical uncoupler of oxidative phosphorylation) was studied in single ventricular myocytes using a two microelectrode voltage clamp technique. 2. Single ventricular cells were isolated from the heart of adult guinea-pigs. These cells were superfused with Tyrode solution containing 1.8 or 3.6 mM Ca. 3. After application of 0.1 mM DNP initially a small depolarization and a prolongation of the action potential is observed. This effect is most likely related to an inhibition of the electrogenic sodium pump caused by ATP depletion. 4. The marked shortening of the action potential which follows the initial prolongation is accompanied by a very pronounced increase of the outward current. This DNP-induced outward current component is time-independent. This current shows a reversal potential negative to the resting potential indicating that it is mainly carried by potassium ions. 5. The DNP-induced current attenuates and abolishes the N-shape of the steady-state current-voltage relationship. When the inward-rectifying potassium current is blocked by pretreatment with 20 mM Cs or 1 mM Ba, large DNP-induced currents which show outward rectification can be seen. The increase in outward-rectifying potassium current by DNP is responsible for the shortening of the action potential and the loss of plateau. 6. In addition, DNP also seems to cause an increase of inward-rectifying potassium current. This effect appears later than the increase in outward rectifier; it does not contribute to the shortening of the action potential but causes a hyperpolarization of the cell. 7. In the latest phase of the DNP effect, which occurs only after the action potential has completely lost its plateau, changes of the amplitude and time constant of inactivation of the slow inward current can sometimes be observed. 8. The effect of DNP on the potassium conductance is discussed in terms of increased cytosolic calcium activity.

Drop-out during in-patient treatment of anorexia nervosa: A clinical study of 133 patients*

Abstract: Although anorexia nervosa patients are notorious for their ‘resistance’ to treatment, the phenomenon of drop-out during in-patient treatment of these patients is scarcely described in the literature. In a consecutive series of 133 hospitalized female anorexia nervosa patients the authors found a remarkably high drop-out rate of about 50 per cent, spread over different phases in the therapeutic process. In order to find some ‘risk factors’ concerning the probability of premature discharge against medical advice, some clinical, demographic and follow-up data were analysed in a retrospective way. Dropping-out appears to be a function of age at admission, duration of illness, educational level, social class and treatment method. These findings are interpreted with respect to different types of resistance to psychotherapeutic treatment both on the part of the patient and her family. In most cases a drop-out has to be considered as a crisis-related event in the treatment process. It does not only require specific attention, but also reconsideration of the whole therapeutic approach to anorexia nervosa patients.

Photochromic phenomena in the solid phase

Abstract: Photochromic phenomena occurring in the solid phase are discussed first from the point of view of the influence of a polymer medium on the photochromic behavior and reaction reversibility. Inversely, in the second part, the influence of conformational changes of chain segments induced by chromophore isomerization is discussed with respect to the physical behavior of the polymer matrix, and especially concerning photomechanical effects.

Four urinary cations and blood pressure a population study in two belgian towns

Abstract: The relationship between blood pressure and the 24-hour urinary excretion of four cations (Ca, Mg, K, Na) was investigated in a random sample of 688 inhabitants of two Belgian towns. In 160 youths aged 10-19 years, systolic/diastolic blood pressure averaged 118 +/- 12.6/65 +/- 8.6 mmHg (mean +/- standard deviation) and the urinary excretion of the four urinary cations was broadly similar in both sexes. Adjusting for body weight removed the strong relationship between blood pressure and age, but a positive relationship between systolic pressure and pulse rate emerged. The only association between blood pressure and a urinary constituent was with calcium excretion, and this correlation was no longer apparent after adjusting for weight. In 528 adults aged greater than or equal to 20 years, systolic/diastolic pressure averaged 130 +/- 14.4/77 +/- 9.8 (p less than 0.001) higher in male than in female subjects. In these adults, both systolic and diastolic pressure were strongly and independently correlated with age and body weight. Systolic pressure in women was also significantly and positively related to pulse rate (r = +0.20; p less than 0.001). After adjusting for age and body weight, systolic and diastolic pressure in men were significantly and negatively correlated (p less than 0.001 and p less than 0.01, respectively) with urinary potassium excretion. Diastolic pressure in men was weakly but positively correlated with calcium excretion (p less than 0.05 after adjusting for body weight, age and urinary potassium excretion). The present study indicates that urinary potassium is a consistent and negative predictor of both systolic and diastolic pressure in adult men, whose diastolic pressure was also weakly and positively associated with urinary calcium. In youths and female subjects, the single 24-hour urinary excretion of the four cations did not contribute to the prediction of blood pressure.

Cost increases due to demand uncertainty in mrp lot sizing

Abstract: This paper analyzes the cost increases due to demand uncertainty in single-level MRP lot sizing on a rolling horizon. It is shown that forecast errors have a tremendous effect on the cost effectiveness of lot-sizing techniques even when these forecast errors are small. Moreover, the cost differences between different techniques become rather insignificant in the presence of forecast errors. Since most industrial firms face demand uncertainty to some extent, our findings may have important managerial implications. Various simulation experiments give insight into both the nature and the magnitude of the cost increases for different heuristics. Analytical results are developed for the constant-demand case with random noise and forecasting by exponential smoothing. It is also shown how optimal buffers can be obtained by use of a simple model. Although the analysis in this paper is restricted to simplified cases, the results merit further consideration and study. This paper is one of the first to inject forecast errors into MRP lot-sizing research. As such it attempts to deal with one of the major objections against the practical relevance of previous research in this area.

Temperature Dependence of the Static Relative Permittivity of Octylcyanobiphenyl (8CB)

Abstract: Measurements of the relative static permittivity e of octylcyanobiphenyl (8CB) in the smectic A, the nematic and the isotropic phases between 22°C and 140°C are reported. The resolution of the measurements was better than 0.01% and the temperature stability was better than 0.01 °C. Detailed measurements have been carried out near the AN and NI transitions. For the AN transition. no discontinuity in e|| or e| was observed, which is consistent with the second-order nature of this transition in 8CB. From the dielectric anisotropy in the N-phase, a critical exponent β ≃ 0.25 was obtained for the temperature dependence of the order parameter. This value of β is in support of the hypothesis of quasi-tricriticality for this transition. In the isotropic phase of 8CB, a pretransitional anomalous maximum in e was observed near T N1- The same effect was also measured for two other materials with cyano-end groups (undecylcyanobiphenyl and pentylcyanophenylcyclohexane). For two compounds without a cyano-end g...