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Showing papers by "Flinders University published in 1979"


Journal ArticleDOI
TL;DR: Communication between 3T3 and HEL 37 cells was inhibited by inclusion of the tumor promoting agents, 12-0-tetradecanoylphorbol-13-acetate and phorbl-12,13-didecanoate during coculture, and non-promoting derivatives of these phorbol esters did not inhibit transfer of label.

312 citations


Journal ArticleDOI
TL;DR: Blood concentrations of local anaesthetics after perineural injection are not closely related to age, weight or pregnancy but may be influenced by diseases associated with haemodynamic changes and by other drugs given at or around the time of regional blockade.
Abstract: The introduction of the new long acting local anaesthetics, bupivacaine and etidocaine, has stimulated an expansion of interest in regional anaesthesia, particularly for obstetrical applications and pain therapy. Systemic toxicity following injection of local anaesthetics occurs albeit infrequently, and tentative correlations have been made between the onset of CNS and cardiovascular effects and circulating drug concentrations in both adults and neonates. Amongst other factors, interpretation of these relationships depends upon blood distribution and plasma binding of the agents, sampling sites and acid-base balance. The disposition kinetics and placental transfer of the amide type agents have been well characterised. In adults their clearance is almost entirely hepatic but in neonates an increase in the renal component is, in part, a reflection of the immaturity of some of the enzymes responsible for their metabolism. Ester type agents are rapidly hydrolysed by plasma pseudocholin-esterase and this has led to a preference for chloroprocaine in some obstetric procedures. Major determinants of the systemic absorption of the agents after perineural administration include their physicochemical and vasoactive properties, perfusion and tissue binding at the site of injection and whether or not adrenaline has been added. In respect of blood drug concentrations achieved after various regional anaesthetic procedures, the margin of systemic safety appears to favour bupivacaine and etidocaine compared to shorter acting analogues such as lignocaine and mepivacaine. The time course of local anaesthetic remaining at the site of injection has been calculated following intravenous regional anaesthesia and peridural block. This has allowed prediction of the local and systemic accumulation of the drugs following continued dosage. Blood concentrations of local anaesthetics after perineural injection are not closely related to age, weight or pregnancy but may be influenced by diseases associated with haemodynamic changes and by other drugs given at or around the time of regional blockade.

280 citations


Journal ArticleDOI
TL;DR: Not only does Stewart provide misleading references, but also he completely neglects masses of careful data showing that hypertension is a major risk factor for coronary disease, including all of that from Framingham, the Pooling Project, and much more.

247 citations


Journal ArticleDOI
TL;DR: In this article, the authors used disjoint sequence methods from the theory of Riesz spaces to study compact operators on Banach lattices and showed that each positive map from a Banach Lattice E to a BL T with compact majorant is itself compact provided the norms on E and T are order continuous.
Abstract: Disjoint sequence methods from the theory of Riesz spaces are used to study compact operators on Banach lattices. A principal new result of the paper is that each positive map from a Banach latticeE to a Banach latticeF with compact majorant is itself compact provided the norms onE′ andF are order continuous.

224 citations


Journal ArticleDOI
TL;DR: Investigation of receptors for substance P in the longitudinal muscle of the guinea-pig ileum showed substance P-like immunoreactivity in nerve terminals of both the myenteric and submucous plexuses, suggesting that these nerves release a substance similar to or identical with substance P.
Abstract: The desensitization of receptors for substance P in the longitudinal muscle of the guinea-pig ileum has been studied. Receptors for substance P in the muscle became desensitized in the presence of relatively large concentrations of synthetic substance P; a desensitizing concentration of substance P of 7.5×10−9 M shifted the concentration-response curve for substance P about 20-fold to the right, while a desensitizing concentration of 7.5×10−8 M shifted the curve about 300-fold to the right. This desensitization appeared specific; concentration-response curves for carbachol, DMPP, 5-HT and bradykinin were not significantly affected by substance P, 7.5×10−8 M. Furthermore, substance P in concentrations up to 7.5×10−8 M did not modify transmission from either cholinergic nerves or enteric inhibitory nerves when these were stimulated electrically. However, hyoscine-resistant contractions produced by stimulation of nerves in the ileum at 10 Hz were abolished by exposure to concentrations of substance P of 7.5×10−9 M or greater, suggesting that these nerves release a substance similar to or identical with substance P. DMPP evoked small hyoscine-resistant contractions of the ileum. These contractions were also antagonised by desensitization of receptors for substance P. Immunohistochemical studies showed substance P-like immunoreactivity in nerve terminals of both the myenteric and submucous plexuses.

169 citations


Journal ArticleDOI
TL;DR: The present results, which show that 5‐HT has little or no direct effect on the circular muscle of the ileum and colon, imply that, if 5‐ HT is a transmitter in enteric reflexes, it must be released from interneurones.
Abstract: 1 The sites of action of 5-hydroxytryptamine (5-HT) were examined in isolated segments of guinea-pig intestine. Mechanical records were taken from the longitudinal muscle of the ileum and proximal colon and from the circular muscle of the ileum and distal colon. 2 In order to examine direct actions of 5-HT, nerve-mediated responses were blocked with tetrodotoxin (0.2 μg/ml). There was a gradient in the responsiveness of the longitudinal muscle of the ileum; in the proximal ileum it was usually unresponsive, whereas in the distal ileum about 30% of the amplitude of contraction was caused by a direct effect on the muscle. In the circular muscle from all parts of the ileum, direct effects on the muscle were weak or absent. In the distal colon, the circular muscle was almost always unresponsive to direct effects of 5-HT even when concentrations of 5-HT as great as 100 μg/ml were used. All direct actions of 5-HT on intestinal muscle were blocked by methysergide (1 μg/ml), which itself did not affect nerve-mediated responses. 3 Excitatory cholinergic nerves and excitatory and inhibitory nerves which released unidentified substances were all stimulated by 5-HT. The contractions mediated through cholinergic nerves were blocked by hyoscine (0.6 μg/ml). 4 Tachyphylaxis to the action of 5-HT occurred both for effects mediated through nerves and for direct effects on the muscle. Responses returned promptly after 5-HT was washed from the organ bath. 5 While 5-HT blocked its own action on neural receptors, it did not antagonize the stimulation of nicotinic receptors on cholinergic neurones by 1-1 dimethyl-4-phenylpiperazinium iodide (DMPP). Moreover, pentolinium markedly reduced contractions caused by DMPP without significantly affecting responses to 5-HT. In contrast, (+)-tubocurarine, another nicotinic receptor antagonist, was effective in reducing contractions caused by 5-HT. 6 Phenyldiguanide, which has been reported to antagonize the stimulant action of 5-HT on cholinergic neurones in the mouse small intestine, did not cause any significant reduction in the action of 5-HT on cholinergic neurones in the guinea-pig ileum unless a concentration of 1 mg/ml was used. However, contractions elicited by carbachol and DMPP were antagonized to a similar extent by phenyldiguanide at this concentration. Antagonism of the action of 5-HT at neural receptors by bromolysergic acid and by tryptamine was found but it was not specific, these drugs causing comparable decreases in responses to 5-HT, carbachol and DMPP. 7 The present results, which show that 5-HT has little or no direct effect on the circular muscle of the ileum and colon, imply that, if 5-HT is a transmitter in enteric reflexes, it must be released from interneurones.

156 citations


Journal ArticleDOI
TL;DR: Findings support the hypothesis that in the central nervous system (CNS) DFP tolerance and cholinomimetic subsensitivity may involve the m-AChR.

145 citations


Journal ArticleDOI
TL;DR: The projections of VIP neurons from the myenteric plexus to the circular muscle correspond to the expected projections of enteric inhibitory neurons determined by functional studies.

133 citations


Journal ArticleDOI
TL;DR: Regression analyses confirmed that the selective breeding procedure was successful in establishing a line with increased sensitivity to DFP, but that it failed to produce a line more resistant than the original population.
Abstract: A selective breeding study was undertaken to test the hypothesis that genetic factors are involved in sensitivity of physiological and behavioral variables in rats to the irreversible anticholinesterase diisopropyl fluorophosphate (DFP) Three variables (drinking behavior, body weight, and core body temperature) were used as indices of the effects of DFP (1 mg/kg, im) and selection was based on a composite score that gave equal weight to each variable From the original parents, the six most resistant males were mated with the six most resistant females and the six most sensitive males were mated with the six most sensitive females Subsequent generations were produced by mating the six most resistant pairs from the resistant line and the six most sensitive pairs from the sensitive line When separation between the two lines appeared well advanced (F5), randomly bred males and females were introduced into the testing procedure Regression analyses confirmed that the selective breeding procedure was successful in establishing a line with increased sensitivity to DFP, but that it failed to produce a line more resistant than the original population Analyses of variance of the results for the F6, F7, and F8 generations revealed that the sensitive line was more sensitive than either the randomly bred line or the resistant line, while the latter two groups were not significantly different from each other Biochemical studies indicated that the genetic differences in sensitivity to DFP were not related to differences in cholinesterase or acetylcholinesterase activity

125 citations


Journal ArticleDOI
TL;DR: It is argued that a multidisciplinary approach is required to elucidate the role of receptor alterations in drug tolerance and that numerous investigators have reported alterations in receptor binding following chronic drug treatment but these two phenomena have seldom been studied in the same experiment.

118 citations


Journal ArticleDOI
TL;DR: It is proposed that the secondary biotransformation of 1MX to IMU is mediated by xanthine oxidase, and excretion increased at the expense of 1‐methyluric acid (IMU) during the allopurinol treatment phase.
Abstract: The effects of allopurinol on the plasma clearance and metabolism of theophylline in man were investigated under single-dose and multiple-dosing conditions. No change in theophylline clearance was found with the concomitant use of allopurinol but 1-methylxanthine (1MX), a theophylline metabolite not previously described in man, was detected in urine during control and allopurinol treatment phases under both single- and multiple-dosing conditions. 1MX excretion increased at the expense of 1-methyluric acid (IMU) during the allopurinol treatment phase. It is proposed that the secondary biotransformation of 1MX to IMU is mediated by xanthine oxidase.

Journal ArticleDOI
TL;DR: It has been concluded that a process of esterified-cholesterol exchange between human serum lipoproteins may be rapid enough to have the potential of major physiologic importance.
Abstract: Lipoproteins labeled with 3 H in the free- and esterified-cholesterol moieties were isolated from the serum of rabbits that had been injected 14 hr before with 3 H-mevalonic acid and from human serum that had been incubated with 3 H-cholesterol for 6 hr at 37°C. Each of the labeled lipoprotein fractions of each species was subsequently incubated in vitro at 37°C with unlabeled lipoprotein fractions isolated from the same species in the presence of an inhibitor of lecithin:cholesterol acyltransferase (LCAT) activity. Incubations contained either the lipoprotein-free (the dialysed 1.21 g/ml infranate) fraction of serum or an equivalent volume of buffer. In incubations of both rabbit and human lipoproteins there was a significant bidirectional transfer of esterified 3 H-cholesterol between each pair of lipoproteins so long as the 1.21 g/ml infranate was present, but in its absence there were no transfers. A minimum estimate of the rate at which esterified cholesterol exchanged between human lipoproteins was obtained; expressed as μmole/liter serum/hr, it was 30–166 between very low density lipoproteins (VLDL) and low density lipoproteins (LDL) 31–156 between VLDL and high density lipoproteins (HDL) and 97–140 between LDL and HDL. In subsequent experiments, labeled human VLDL was incubated with unlabeled human LDL in the presence of the 1.21 g/ml infranate isolated from the serum of different species. In terms of promoting a transfer of esterified 3 H-cholesterol into the LDL, the rabbit 1.21 g/ml infranate proved to be more effective than that of the human, but the 1.21 g/ml infranate of rat serum was totally ineffective. It has been concluded that a process of esterified-cholesterol exchange between human serum lipoproteins may be rapid enough to have the potential of major physiologic importance.

Journal ArticleDOI
TL;DR: Experiments with transmural stimulation showed that excitatory nerve pathways involving substance P neurons extend for less than 4 cm along the intestine.
Abstract: Acid extracts from both normal and extrinsically denervated ileum contained a compound which was indistinguishable from synthetic substance P; this compound was assayed by examining its contractile effect on the longitudinal muscle of segments of ileum in which receptors for acetylcholine and histamine were blocked. Contractions caused by the compound were markedly and selectively antagonized when the ileum was made insensitive to the action of substance P. The activities in the extract and of synthetic substance P were both destroyed by chymotrypsin but were not affected by trypsin or carboxypeptidase B. The concentrations of substance P-like material in normal and extrinsically denervated segments were not significantly different, being equivalent to 0.48 μg of substance P per g of external muscle plus myenteric plexus. A compound with substance P-like activity was liberated by stimulation of intramural nerves, either electrically or by dimethylphenylpiperazinium, in both normal and extrinsically denervated segments of ileum. The release of this compound was prevented by tetrodotoxin and its action on the muscle was blocked when the ileum was made insensitive to the action of substance P. Experiments with transmural stimulation showed that excitatory nerve pathways involving substance P neurons extend for less than 4 cm along the intestine.

Journal ArticleDOI
TL;DR: A 1/2% sample of metropolitan Adelaide households was selected using multi-stage cluster sampling and employed and unemployed workers were asked to complete a questionnaire which measured work values, patterns of home and leisure activity, locus of control (Rotter, 1966) and number of frequent health and stress symptoms as discussed by the authors.
Abstract: A 1/2% sample of metropolitan Adelaide households was selected using multi-stage cluster sampling. Employed and unemployed workers were asked to complete a questionnaire which measured work values, patterns of home and leisure activity, locus of control (Rotter, 1966) and number of frequent health and stress symptoms. A 70% response rate was obtained for employed workers and the response rate for unemployed was 80%. Comparisons between the two groups were made using ‘t’ tests and discriminant function analysis. It was found that unemployed workers when compared to employed workers had significantly more physical health symptoms, lower work values (they desired less influence, interaction and pressure in their work), a higher external control orientation, and made more use of community helping agencies. Differences in reported stress and life satisfaction were not statistically significant. However, reported stress was positively correlated with time spent looking for work. Definite causal inferen...

Book ChapterDOI
TL;DR: This chapter focuses on the symmetric (e, 2e) reaction at high and intermediate energies—that is, the regime of (e) 2e collisions that can yield reliable information on the momentum distribution of the struck electrons for transitions to definite final ion states.
Abstract: Publisher Summary The study of (e, 2e) collisions has expanded rapidly since the first coincidence measurements of the two emitted electrons in the electron impact ionization of helium This chapter focuses on the symmetric (e, 2e) reaction at high and intermediate energies—that is, the regime of (e, 2e) collisions that can yield reliable information on the momentum distribution of the struck electrons for transitions to definite final ion states This chapter deals with only those experiments designed to yield detailed information on the electronic structure of atoms and molecules This is the regime of symmetric kinematics at intermediate and high electron energies The chapter outlines some of the experimental techniques employed in these investigations The basic theory necessary for describing the reaction mechanism and for extracting all the structure information is developed The theory for atoms is extended to cover the case of molecular targets The reaction mechanism at intermediate to high energies is investigated in the chapter for atomic targets in both the coplanar and noncoplanar symmetric geometry Some of the structure information that has been obtained on atoms and molecules that include electron–electron correlation effects in both the target and final ion states are also discussed in the chapter

Journal ArticleDOI
TL;DR: It is shown that the inhibitors synthesised with the reticulocyte or interferon-mediated enzymes, i.e. (2-5′)An synthetases, behave identically on thin-layer chromatography and electrophoresis and have the same biological activity in the inhibition of cell-free protein synthesis.
Abstract: We have previously shown that a low-molecular-weight inhibitor (pppA2′p5′A2′p5′A) of cell-free protein synthesis, effective at subnanomolar concentrations, is formed on incubation of extracts from interferon-treated cells or rabbit reticulocytes with double-stranded RNA and ATP. The inhibitors synthesised with the reticulocyte or interferon-mediated enzymes, i.e. (2′-5′)An synthetases, behave identically on thin-layer chromatography and electrophoresis and have the same biological activity in the inhibition of cell-free protein synthesis. Here we show that they also behave identically on chromatography on DEAE-Sephadex in the presence of urea and yield identical products on enzymic and sequential degradation by periodate oxidation and β-elimination. As previously shown with the interferon inhibitor, preparations of the reticulocyte pppA2′p5′A2′p5′A also include the corresponding biologically inactive dimer, pppA2′p5′A, and biologically active tetramer, ppp(A2′p)35′A, and occasionally higher oligomers in decreasing amounts. Further purification of the pppA2′p5′A2′p5′A yielded small amounts of the corresponding 5′-diphosphates and 5′-monophosphates. The 5′-diphosphate has the same specific biological activity in the inhibition of cell-free protein synthesis as the triphosphate. The 5′-monophosphate is essentially inactive. Milligram quantities of the reticulocyte inhibitor can be conveniently synthesised by incubating the (2′-5′)An synthetase from these cells bound either to poly(I) · poly(C)-Sepharose or poly(I) · poly(C)-paper with ATP. Simple methods for the fractionation of the resultant (2′-5′)An, into its individual components are described. Proton and phosphorus nuclear magnetic resonance spectra were obtained for the putative pppA2′p5′A2′p5′A and the corresponding 5′-monophosphate and 5′-diphosphate from this material and for the A2′p5′A2′p5′A ′core′ derived from these by treatment with bacterial alkaline phosphatase. The spectra were compared with those for chemically synthesised A2′p5′A2′p5′A and commercially available A3′p5′A3′p5′A, AMP, ADP and ATP. The results are in accord with the proposed structure. Phosphorylation of chemically synthesised A2′p5′A2′p5′A yielded material with chromatographic properties and a specific biological activity in the inhibition of cell-free protein synthesis apparently identical to those of biologically synthesised pppA2′p5′A2′p5′A.

Journal ArticleDOI
TL;DR: The Skillogallee Dolomite Formation in some areas overlies an earlier dolomitic unit, informally named the Callanna Beds, typified by abundant pseudomorphs after sulphate minerals as mentioned in this paper.
Abstract: Microcrystalline dolomite and related carbonate minerals have been forming throughout the Quaternary in shallow ephemeral alkaline lakes on the coastal plain of the Coorong area in southern Australia. These Coorong dolomites differ significantly from sabkha-type dolomites. They form in areas where evaporation rates during summer months exceed groundwater inflow rates to a series of alkaline lakes. This results in the lakes becoming desiccated during summer months. Brines resulting from this drying phase are then refluxed out of the system into seaward-flowing groundwaters of an unconfined coastal aquifer. Dolomites and other fine-grained carbonates remain behind, whilst saline and sulphate evaporite minerals are flushed out of the system. Progressive restriction by sedimentation in and around the Holocene coastal dolomite lakes results in an upward-shoaling sedimentary cycle. Basal sediments which formed in a restricted marine environment pass upwards to lacustrine dolomites or magnesites exhibiting desiccation and groundwater resurgence structures such as mudcracks and teepees. The upper Proterozoic Skillogallee Dolomite Formation, an early rift basin unit of the Adelaide Supergroup, contains dolomites which show many of the features characteristic of the peculiar groundwater hydrology which plays an important role in Coorong dolomite genesis. These features include aphanitic dolomites which lack relict saline or sulphate evaporite minerals. The Skillogallee Dolomite Formation in some areas overlies an earlier dolomitic unit, informally named the Callanna Beds, typified by abundant pseudomorphs after sulphate minerals. Sabkha style dolomites characterizing the Callanna Beds are replaced up-section by the Coorong-type dolomite of the Skillogallee Dolomite Formation. This implies the development of an increasingly more active groundwater regime. The ultimate source and mode of concentration of the necessary Mg required to form both the modern and ancient dolomites remain imperfectly understood.

Journal ArticleDOI
TL;DR: It is concluded that somatostatin is possibly a neurotransmitter in the intestine that is released at neuro-neuronal junctions and causes an inhibition of intestinal movements.

Journal ArticleDOI
TL;DR: Control continuous intravenous infusion of pethidine produced stable blood concentrations and provided excellent pain control and significant blood concentrations of the metabolite norpethidine were found although clinically no toxic effects were observed.
Abstract: In an attempt to improve postoperative pain management an intravenous infusion of pethidine was designed to provide stable therapeutic blood concentrations. Ten female patients undergoing elective abdominal hysterectomy were studied. After commencement of the infusion, blood pethidine concentrations increased rapidly and exceeded 0.46 microgram/ml after four hours. The mean steady-state concentration of 0.67 microgram/ml was reached by twenty-four hours. This infusion regimen resulted in the abolition of severe pain after three hours and analgesia continued for the duration of the two day study. Significant blood concentrations of the metabolite norpethidine were found although clinically no toxic effects were observed. Side effects of pethidine were infrequent. Controlled continuous intravenous infusion of pethidine produced stable blood concentrations and provided excellent pain control.

Journal ArticleDOI
TL;DR: It appears that a model with a similar route and rate of halothane biotransformation to man has been identified, and the lesion ofHalothane hepatotoxicity in this model appears to be similar to that reported in man — centrilobular hepatic necrosis.
Abstract: Centrilobular necrosis and a ten-fold elevation in serum alanine amino-transferase (ALT) consistently followed 2 hours of 1% halothane anaesthesia in an animal model. Conditional factors were the presence of enzyme induction and moderate hypoxia (14% oxygen), indicating an association between reductive metabolism and hepatotoxicity. Under these conditions there was at least a four-fold increase in reductive metabolites detected in the exhaled air. In clinical studies, reductive metabolites were also detected in the exhaled air of all patients examined, even after halothane anaesthesia with 100% oxygen. The amounts of reductive metabolites were comparable in man and the model, following equivalent halothane doses. It appears that a model with a similar route and rate of halothane biotransformation to man has been identified. The lesion of halothane hepatotoxicity in this model appears to be similar to that reported in man - centrilobular hepatic necrosis.

Journal ArticleDOI
TL;DR: The exchange of esterified cholesterol between human LDL and HDL is, therefore, rapid when considered in relation to other parameters of es terified cholesterol and lipoprotein metabolism.

Journal ArticleDOI
01 Sep 1979-Drugs
TL;DR: The range of agents currently available offers great versatility, combined with a sound knowledge of the clinical pharmacology of the individual local anaesthetics, enables the achievement of effective and safe regional block for a wide range of local anaesthetic techniques.
Abstract: The development of local anaesthetics from the single agent of the last centu ry, cocaine, through the first three decades of this century with the proliferation of the 'ester -caines', to the beginning in the 1940s and subsequent growth of the 'amide-caines' of the present , is a fascinating phase in the saga of anaesthesia. Agents that have survived th is evolutionary process have done so because they possess peculiar properties which justify their place in the range of agents used in contemporary medicine. Hence, the range of agents currently available offers great versatility. This , combined with a sound knowledge of the clinical pharmacology of the individual local anaesthetics, enables the achievement of effective and safe regional block for a wide range of local anaesthetic techniques. Currently , the local anaesthetic procedures most commonly employed are infiltration techniques, some topical applications and a considerable range of peripheral nerve blocks. The remainder, i.e. major plexus and central neural blockade techniques (table 0 , are , in most situations , the province of the specialist anaesthetist for reasons outlined below. It is beyond the scope of this article to describe how to perform blocks. The realm of 'how to' is documented in specialised texts of which those by Eriksson (1969) and Moore (1971) are essential reading. I. Backgroundto the Use of LocalAnaesthetic Agents



Journal ArticleDOI
TL;DR: Amniotic fluid from two fetuses with spina bifida contained AChE activity: one, with a gestational age of 21 weeks, was in the upper levels of the normal range (4.5 u/l), whereas the other, at 36 weeks, contained 1.9 times more activity than the next highest sample.

Journal ArticleDOI
TL;DR: The direct linear plot is an attractive estimation procedure since it essentially ignores “wild” points, yet gives virtually identical results to classical least squares methods when the points are “well-behaved”.

Journal ArticleDOI
TL;DR: Final equation autoregressive moving average models for Australian total live-births and final form transfer function models linking births to females in the reproductive age groups are constructed and a comparison of actual forecast performance using the various models is made.
Abstract: The relationship between classical demographic deterministic forecasting models, stochastic structural econometric models and time series models is discussed. Final equation autoregressive moving average (ARMA) models for Australian total live-births are constructed. Particular attention is given to the problem of transforming the time series to stationarity (and Gaussianity) and the properties of the forecasts are analyzed. Final form transfer function models linking births to females in the reproductive age groups are also constructed and a comparison of actual forecast performance using the various models is made. Long-run future forecasts are generated and compared with available projections based on the deterministic cohort model after which some policy implications of the analysis are considered.

Journal ArticleDOI
TL;DR: It is concluded that if the amine-handling neurons which are known to be intrinsic to the intestine synthesize an aromatic amine, it is almost certainly not a catecholamine, and is probably an indoleamine.

Journal ArticleDOI
TL;DR: The coproduct of a family of Kleene algebras is determined by describing the maximal homomorphic image of a De Morgan algebra in the subvariety of Kleinene spaces as discussed by the authors.
Abstract: The coproduct of a family of Kleene algebras is determined firstly by describing the maximal homomorphic image of a De Morgan algebra in the subvariety of Kleene algebras and, secondly, by characterizing the categorical product in the dual category of Kleene spaces.

Journal ArticleDOI
TL;DR: In this paper, 24 three-person groups each performed three types of intellective tasks (production, discussion, and problem solving) while employing one of four work organizations and the results were discussed in relation to the task typology employed and implications for research dealing with small group performance.