Showing papers by "Aarhus University published in 1987"
TL;DR: A set of very simple estimators of efficiency are presented and illustrated with a variety of biological examples and a nomogram for predicting the necessary number of points when performing point counting is provided.
Abstract: The superior efficiency of systematic sampling at all levels in stereological studies is emphasized and various commonly used ways of implementing it are briefly described. Summarizing recent theoretical and experimental studies a set of very simple estimators of efficiency are presented and illustrated with a variety of biological examples. In particular, a nomogram for predicting the necessary number of points when performing point counting is provided. The very efficient and simple unbiased estimator of the volume of an arbitrary object based on Cavalieri's principle is dealt with in some detail. The efficiency of the systematic fractionating of an object is also illustrated.
3,396 citations
Book•
01 Jan 1987TL;DR: In this article, the Steinberg modules are used to represent the Frobenius kernels of finite algebraic groups and reduce them to reduction mod $p$ by using a simple reductive group.
Abstract: Part I. General theory: Schemes Group schemes and representations Induction and injective modules Cohomology Quotients and associated sheaves Factor groups Algebras of distributions Representations of finite algebraic groups Representations of Frobenius kernels Reduction mod $p$ Part II. Representations of reductive groups: Reductive group Simple $G$-modules Irreducible representations of the Frobenius kernels Kempf's vanishing theorem The Borel-Bott-Weil theorem and Weyl's character formula The linkage principle The translation functors Filtrations of Weyl modules Representations of $G_rT$ and $G_rB$ Geometric reductivity and other applications of the Steinberg modules Injective $G_r$-modules Cohomology of the Frobenius kernels Schubert schemes Line bundles on Schubert schemes Truncated categories and Schur algebras Results over the integers Lusztig's conjecture and some consequences Radical filtrations and Kazhdan-Lusztig polynomials Tilting modules Frobenius splitting Frobenius splitting and good filtrations Representations of quantum groups References List of notations Index.
2,009 citations
TL;DR: In this paper, the authors investigated the effect of straw and stubble of spring barley (Hordeum vulgare; 5t dry matter ha−1) being incorporated into soil annually for 18 years in two field experiments in Denmark.
Abstract: The straw and stubble of spring barley (Hordeum vulgare; 5t dry matter ha−1) were either burned or incorporated into soil annually for 18 yr in two field experiments in Denmark. Both experiments were on light soils situated at Studsgaard (loamy sand) and Ronhave (sandy loam).
At both sites 18 yr of annual straw incorporation increased total soil organic C by only 5% and total N by about 10% but produced large increases in microbial biomass measured by the CHCl3-fumigation method. The increases in biomass C were 45 and 37% at Studsgaard and Ronhave, respectively: the corresponding increases in biomass N were 50 and 46%. Biomass measurements thus gave an early indication of slow changes in organic matter content long before these could be measured accurately against the background of organic matter already present in the soils. Increases in biomass P due to straw incorporation appeared to be even greater. However, the amounts of P released by CHC13 were small so the measurements of biomass P were less accurate than those of biomass C or N.
During a 60-day laboratory incubation at 25°C, evolution of CO2-C was 55–79% greater in soil from straw incorporated plots than in soil from burned plots. Mineralization of N was 40–50% greater where straw had been incorporated, indicating thaf the long-term incorporation of straw had increased the quantity of mineralizable N in soil.
1,094 citations
TL;DR: In this paper, it was shown that low binding of these nuclei will lead to a neutronization of the nuclear surface and possibly to large cross-sections for Coulomb dissociation, which then offers a new way to study clusters and their binding energies.
Abstract: Empirical evidence suggests that neutron pairing plays an important role for the stability of nuclei near the neutron drip line. It is shown that the low binding of these nuclei will lead to a neutronization of the nuclear surface and possibly to large cross-sections for Coulomb dissociation, which then offers a new way to study clusters and their binding energies.
620 citations
TL;DR: It is concluded from the study that the biomechanical competence of vertebral trabecular bone depends not only on bone mass (ash density) but also on the continuity of the trABecular lattice, which changes with increasing age.
488 citations
TL;DR: The predation and social bond hypotheses were not totally dismissed, but there was no evidence that fertilization ability was limited by copulation frequency (i.e. the fertilization hypothesis), and the sperm competition hypothesis was supported.
Abstract: Inter-specific variation in copulation behaviour among birds is described. The following factors explaining variation in copulation rate are examined: (i) the number of eggs which have to be fertilized (the fertilization hypothesis), (ii) the importance of the pair-bond (the social bond hypothesis), (iii) predation risk during copulation (the predation hypothesis), and (iv) cuckoldry risk (the sperm competition hypothesis). These hypotheses were investigated in preliminary analyses at the generic level using data on copulation behaviour in 131 bird species. The sperm competition hypothesis was supported by several lines of evidence: (i) frequent copulations among genera where males are not able to guard their mates (colonial birds, diurnal birds of prey, and owls), (ii) frequent copulations in polyandrous genera, (iii) copulations inside hole-nests of colonial birds but outside the hole-nests of solitarily nesting genera, and (iv) by the occurrence of forced pair copulations following extra-pair copulation in some species. The predation and social bond hypotheses were not totally dismissed, but there was no evidence that fertilization ability was limited by copulation frequency (i.e. the fertilization hypothesis).
396 citations
13 Apr 1987
TL;DR: The ability of a hash function to improve security and speed of a signature scheme is discussed: for example, it can combine the RSA-system with a collision free hash function based on factoring to get a scheme which is more efficient and much more secure.
Abstract: In this paper, we present a construction of hash functions. These functions are collision free in the sense that under some cryptographic assumption, it is provably hard for an enemy to find collisions. Assumptions that would be sufficient are the hardness of factoring, of discrete log, or the (possibly) more general assumption about the existence of claw free sets of permutations.
The ability of a hash function to improve security and speed of a signature scheme is discussed: for example, we can combine the RSA-system with a collision free hash function based on factoring to get a scheme which is more efficient and much more secure.
Also, the effect of combining the Goldwasser-Micali-Rest signature scheme with one of our functions is studied. In the factoring based implementation of the scheme using a k-bit modulus, the signing process can be speeded up by a factor roughly equal to kċO (log2(k)), while the signature checking process will be faster by a factor of O (log2(k)).
391 citations
TL;DR: The relation of patterns of variation in badge size to dominance was studied in male house sparrows, Passer domesticus, and males with large badges were more dominant in winter flocks, irrespective of age, body size and body condition index.
290 citations
TL;DR: Two hybridomas producing monoclonal antibodies to proliferating cell nuclear antigen (PNCA)/cyclin were generated from spleen cells of BALB/c mice immunized with purified PCNA from rabbit thymus and suggested that some human anti-PCNA may share epitopes with 19A2 and 19F4, but in addition recognize different epitopes on the PCNA molecule.
249 citations
TL;DR: Three novel fim genes of Escherichia coli, fIMF, fimG and fimH, were characterized and were shown to be involved in the adhesive property and longitudinal regulation of these structures.
Abstract: Three novel fim genes of Escherichia coli, fimF, fimG and fimH, were characterized These genes were not necessary for the production of fimbriae but were shown to be involved in the adhesive property and longitudinal regulation of these structures Complementation experiments indicated that both the major fimbrial subunit gene, fimA, and the fimH gene in combination with either the fimF or the fimG gene were required for mannose-specific adhesion The fimF, fimG and fimH gene products were likewise shown to play a major role in the fimbrial morphology as longitudinal modulators The amount of FimF, FimG and FimH proteins appeared to control the length and number of the fimbriae The DNA sequence of a 2050 bp region containing the three genes was determined The corresponding protein sequences all exhibited homology with the fimbrial subunit protein, FimA
234 citations
TL;DR: It is speculated that loss of SS neurons, which presumably innervate the inhibitory GABAergic (γ-aminobutyric acid) interneurons, may induce hyperactivity stimulating the Ca-1 neurons to death.
Abstract: Somatostatin (SS)- and cholecystokinin (CCK)-immunopositive cell somata in the rat hippocampus were quantitated at day 1, 2, 3 and 4 after cerebral ischemia. A significant (P<0.01) 60%–80% loss of hilar and CA-3c SS neurons took place. No CCK neurons were lost. Damage to SS neurons was significant on the second postischemic day and preceded the delayed loss of CA-1 neurons. We speculate that loss of SS neurons, which presumably innervate the inhibitory GABAergic (γ-aminobutyric acid) interneurons, may induce hyperactivity stimulating the Ca-1 neurons to death.
TL;DR: The asynchronous arrival pattern may leave some early-arriving swallows in a deteriorating breeding condition because the local food resource has to be divided between more individuals.
TL;DR: The results indicate that chemical conditions within periphyton communities differ considerably from the immediate surroundings and that boundary-layer development is a key factor affecting the metabolism of peripHYton communities.
Abstract: Phosphate uptake kinetics of periphyton were evaluated by addition of carrier-free radiophosphate under controlled laminar flow conditions. In most cases, excluding only poorly colonized substrata, tracer fluxes were found to be limited by boundary-layer mass transfer. Tracer flux could be described as a power function of flow velocity and as a negative power function of distance from the leading edge of the communities, as expected from mass transfer calculations. Observed deviations from theoretical functions were interpreted as effects of community patchiness and of internal water flow in the periphyton matrix. Phosphate turnover by periphyton in suspension was within the range of values for lake plankton, when related to biomass. Kinetic calculations based on these turnover measurements indicated that internal recycling of phosphate and recycling from the boundary layer, rather than external uptake, accounted for most phosphate turnover within intact periphyton films. This situation is likely typical under oligotrophic conditions. Boundarylayer thickness was within the range of published estimates from littoral systems. The results indicate that chemical conditions within periphyton communities differ considerably from the immediate surroundings and that boundary-layer development is a key factor affecting the metabolism of periphyton communities.
TL;DR: Cyclin, also known as PCNA or the auxiliary protein of mammalian DNA polymerase δ, is a stable cell cycle regulated (synthesized mainly in S‐phase) nuclear protein of apparent M r 36 000 whose rate of synthesis correlates directly with the proliferative state of normal cultured cells and tissues.
TL;DR: Depth distributions of bacterial respiration of O2, NO3− and SO42− were compared with geochemical data for Mn, Fe and S in coastal sediments from water depths between 26 and 520 m.
TL;DR: The 23 S RNA genes representative of each of the main archaebacterial subkingdoms, Desulfurococcus mobilis an extreme thermophile, Halococcus morrhuae an extreme halophile and Methanobacterium thermoautotrophicum a thermophilic methanogen, were cloned and sequenced.
TL;DR: The significance of CAM as a carbonconserving mechanism in two submerged aquatics, Littorella uniflora (L.) Aschers and hoetes lacustris L., was evaluated by determining (1) the loss of previously fixed CO2, released through decarboxylation of malic acid and (2) the quantitative importance of CAM relative to external CO2 uptake in photosynthesis as discussed by the authors.
Abstract: Summary
The significance of CAM as a carbon-conserving mechanism in two submerged aquatics, Littorella uniflora (L.) Aschers and hoetes lacustris L., was evaluated by determining (1) the loss of previously fixed CO2, released through decarboxylation of malic acid and (2) the quantitative importance of CAM relative to external CO2 uptake in photosynthesis.
Using a 14C-labelling technique it was found that the loss of CO2 derived from decarboxylation of malic acid constituted less than 2 % of nocturnal carbon uptake, confirming that the diurnal rhythm of acidity provides a good measure of the incorporation of carbon via CAM.
The exchange pattern of inorganic carbon and oxygen was measured for plants incubated in open flow-through systems. The contribution of internal and external CO2 to photosynthesis was determined as the difference in CO, uptake and oxygen release, where excess oxygen release reflected the assimilation of CO2 released from deacidification of malic acid. Despite a rapid deacidification, uptake of external CO2 was stimulated by 15 to 30% at intermediate external CO2 concentrations. It is suggested that this effect was due to a reduced photorespiratory activity caused by an enhanced internal CO2 concentration generated from malic acid. The simultaneous uptake of inorganic carbon from high internal and low external CO2 concentrations can only be explained by assuming a non-linear CO, gradient from the lacunal air to the bulk medium, with the CO2 concentration in the outermost cell layers being lower than both the bulk medium and the lacunal air.
The relative contribution of CAM to the total uptake of CO2 in daytime declined from 95% (both species) at an external CO2 concentration of 30μ CO2 to 38% (Littorella) and 34% (Isoetes) at 200μ CO2. This resulted from increased uptake of external CO2 at high external CO2 concentrations and a parallel suppression of internal decarboxylation of malic acid.
The observed suppression of decarboxylation was confirmed by following the time course in the content of titratable acidity of the leaves. A reversible inhibition of daytime deacidification was seen for external CO2 concentrations higher than 3.0 to 5.4 mM CO2 in both Littorella and Isoetes.
The functional significance of CAM for aquatics rests in the enhanced capacity for obtaining inorganic carbon resulting from the extension of the diel period in which inorganic carbon can be accumulated and in the high reassimilation efficiency of nocturnal respiratory CO2.
TL;DR: Cheating in the status signalling system is controlled socially by frequent challenges of house sparrows having large throat patches, tested experimentally how deception is controlled in such aStatus signalling system.
Abstract: Signalling of dominance status is a plausible explanation for variation in throat patch size in male house sparrows Passer domesticus. I tested experimentally how deception is controlled in such a status signalling system. In aviaries, experimentally dyed brids were involved in more aggressive encounters than controls. Active encounters made up a similar fraction of all interactions involving experimental and control birds. Dyed sparrows did not win relatively more encounters than controls. Experimental house sparrows were involved in more aggressive encounters with conspecifics having larger throat patches than expected whereas controls interacted with conspecifics with a throat patch size that did not deviate from expectation. The throat patch size of winning contestants was larger than that of losing birds both within and between experimental and control groups. Dyed house sparrows did not achieve higher dominance rank than controls. Cheating in the status signalling system is thus controlled socially by frequent challenges of house sparrows having large throat patches.
TL;DR: It is found that antiprotons yield much larger cross sections than protons do, which supports the interpretation that the observed charge effect is due to an interference effect in the outermost shell.
Abstract: Single and multiple ionization of He, Ne, and Ar has been studied experimentally by impact of fast protons and antiprotons. The single-ionization cross sections obtained with protons and antiprotons are found to be the same. The double-ionization cross sections obtained with antiprotons, however, are much larger than those obtained with protons at equal velocity. This difference is found for all three gases but the effect is largest for He and Ne, where the difference is about a factor of 2 at 1 MeV/amu. The difference is discussed in terms of interference between two collision mechanisms which both result in double-electron escape. Experimental information on the magnitude of the interference term is obtained by inclusion of double-ionization data, partly obtained in this work, for fast electron and \ensuremath{\alpha}-particle impact. For triple ionization of Ne, we also find that antiprotons yield much larger cross sections than protons do. Identical cross sections, however, are found for triple ionization of Ar with protons and antiprotons. This is believed to be due to the fact that triple ionization of Ar is mainly a consequence of a single vacancy produced in an inner shell followed by electronic rearrangement. This observation supports the interpretation that the observed charge effect is due to an interference effect in the outermost shell.
TL;DR: Investigating adaptive mechanisms to orthostatic pressure changes in giraffes revealed that arterial pressure near the giraffe heart is about twice that in humans, to provide more normal blood pressure and per-fusion to the brain.
Abstract: Because it is so tall, the giraffe, Giraffa camelopardalis, provides an important animal model for investigating adaptive mechanisms to orthostatic (gravitational) pressure changes. Previous physiological studies of the giraffe have concentrated on arterial blood pressures in the heart and neck. Briefly, these investigations revealed that arterial pressure near the giraffe heart is about twice that in humans, to provide more normal blood pressure and perfusion to the brain. Another important question is that of how giraffes avoid pooling of blood and tissue fluid (oedema) in dependent tissues of their extremities. As monitored by radiotelemetry, the blood and tissue fluid pressures that govern transcapillary exchange vary greatly with exercise. These pressures, combined with a tight skin layer, move fluid upward against gravity. Other mechanisms that prevent oedema include precapillary vasoconstriction and low permeability of capillaries to plasma proteins.
TL;DR: This study demonstrates that early untreated diabetes in rats induced by injection of streptozocin is associated with decreases in [3H]ouabain binding-site concentration of 24-48% in various skeletal muscles and 16% in peripheral nerves as well as a decrease in K+-dependent 3-O-methylfluorescein phosphatase activity of 21% in the heart ventricle.
Abstract: Na+-K+-ATPase or the Na+-K+ pump is essential for some specific properties of muscle and nerve tissue such as contractility and excitability. Previous studies have shown conflicting variations in Na+-K+-ATPase activity or Na+-K+ pump concentration of muscle cells in experimental diabetes. Our study demonstrates that early untreated diabetes in rats induced by injection of streptozocin is associated with decreases in [3H]ouabain binding-site concentration of 24-48% in various skeletal muscles and 16% in peripheral nerves as well as a decrease in K+-dependent 3-O-methylfluorescein phosphatase activity of 21% in the heart ventricle. These effects could be prevented by insulin treatment. They probably represent a decrease in the concentration of Na+-K+ pumps. There was no evidence for more than one population of Na+-K+ pumps in intact samples of skeletal muscle and nerves from normal, diabetic, and insulin-treated animals. The decrease in Na+-K+ pump concentration in nerve cells may be due to atrophy of the axons. In skeletal muscles, myocardium, and peripheral nerves, the observed decrease in Na+-K+ pump concentration may be important for the pathophysiology of diabetes. We emphasize that quantification of Na+-K+-ATPase or the Na+-K+ pump in muscle and nerve tissue from diabetic animals should preferably be performed with either intact samples or crude homogenates of whole tissue.
TL;DR: It is concluded that the increased bone mass during the initial stages of fluoride treatment does not necessarily indicate an improved bone quality and the discrepancy between bone mass and strength could be either a permanent or a temporary phenomenon and requires further investigation.
Abstract: The aim of the investigation was to measure the effect of fluoride on vertebral trabecular bone compressive strength and to correlate this with fluoride-induced changes in bone density. This correlation would express changes in the quality of bone during fluoride treatment. Pigs were used in the experiment because their trabecular bone structure and remodeling sequences are very similar to the human. Eight animals receiving a supplement of 2 mg F−/kg b.w. per day from age 8–14 months were compared with 8 control animals. Morphologic measurements in the animals receiving fluoride supplement showed a significant increase of 17% in bone density and a smaller, insignificant increase of 3% in ash weight analyses. Meanwhile, the mechanical parameters for the fluorotic animals were unchanged (maximum compressive strength, maximum stiffness, and energy-absorption capacity) or decreased (normalized compressive strength=maximum compressive load corrected for ash density). It is concluded that the increased bone mass during the initial stages of fluoride treatment does not necessarily indicate an improved bone quality. The discrepancy between bone mass and strength could be either a permanent or a temporary phenomenon and requires further investigation.
TL;DR: A procedure for transformation and regeneration of the legume species Lotus corniculatus (Bird's-foot trefoil) has been developed and transcript levels from the nodule-specific leghemoglobin genes and the constitutive ubiquitin genes were similar in transformed and untransformed root nodules.
Abstract: A procedure for transformation and regeneration of the legume species Lotus corniculatus (Bird's-foot trefoil) has been developed. The Agrobacterium rhizogenes 15834 and 8196 strains were used to transform plant cells in wound site infections and transformed roots were propagated in vitro. Transformation was monitored by hybridization with pRi T-DNA sequences and by detection of agropine and mannopine. Transformation frequencies of up to 90% were obtained. Shoots spontaneously formed on hairy root cultures were excised, rooted and inoculated with Rhizobium. Root nodules formed on transformed plants had nitrogenase activities comparable to untransformed nodules. Transcript levels from the nodule-specific leghemoglobin genes and the constitutive ubiquitin genes were similar in transformed and untransformed root nodules. Transformed plants responded to R. loti and Bradyrhizobium sp. (Lotus) strains with phenotypes identical to phenotypes for untransformed plants.
01 Sep 1987
TL;DR: This paper is a tutorial introduction to BETA, a modern language in the SIMULA 67 tradition that supports the object-oriented perspective on programming and contains comprehensive facilities for procedural and functional programming.
Abstract: The BETA programming language is a modern language in the SIMULA 67 tradition. It supports the object-oriented perspective on programming and contains comprehensive facilities for procedural and functional programming. BETA replaces classes, procedures, functions and types by a single abstraction mechanism called the pattern . Patterns may be organized in a classification hierarchy by means of sub-patterns . The notion of virtual procedure is generalized to virtual pattern. Virtual patterns combined with sub-patterns make it possible to delay the specification of an attribute in a pattern. Attributes may then have different bindings in different sub-patterns. BETA also provides a unified framework for sequential, coroutine and concurrent execution. This paper is a tutorial introduction to BETA.
TL;DR: The soybean leghaemoglobin lBC3 gene promoter was analysed in transgenic Lotus corniculatus plants and Hybrid‐promoter constructions and 5′ deletions were studied using chimeric genes composed of the various promoters, the chloramphenicol acetyltransferase (CAT) coding sequence and the lbc3 3′ flanking region.
Abstract: The soybean leghaemoglobin lbc(3) gene promoter was analysed in transgenic Lotus corniculatus plants. Hybrid-promoter constructions and 5' deletions were studied using chimeric genes composed of the various promoters, the chloramphenicol acetyltransferase (CAT) coding sequence and the lbc(3) 3' flanking region. A 5' Bal31 deletion series mapped a strong positive regulatory element between -1100 and -950. A weaker element located between -230 and -170 defined the minimum 5' region required for detectable promoter activity. Reactivation of inactive promoters with deletion endpoints between -230 and the transcription initiation site was obtained employing the constitutive cauliflower mosaic virus (CaMV) 35S enhancer. The position of cis regulatory element(s) required for nodule-specific expression was defined to 37 bp between -139 and -102. This region contains sequences conserved in other leghaemoglobin and nodulin genes. No indispensable control elements were found on the lbc(3) 3' flanking region.
TL;DR: Treatment and follow-up to prevent recolonisation in pregnant women with group-B streptococci in the urine may reduce the frequency of preterm labour in these patients.
TL;DR: Subcutaneous oximetry seems capable of quantifying peripheral perfusion and may be clinically useful in dogs with unheated electrode placed in an implanted Silastic tonometer.
Abstract: Mean subcutaneous tissue Po2 (Psqo2) measurements were obtained in dogs with an unheated electrode placed in an implanted Silastic tonometer, while Pao2 was increased in increments from 40 to 600 torr during normal, increased, and reduced blood volume. These changes reflect that the mean Psqo2 is ap
TL;DR: Intraspecific nest parasitism was relatively frequent (overall 16·5% of 261 nests) among swallows, Hirundo rustica, during four consecutive years and was more frequent in large colonies than in groups of 1–4 pairs.
TL;DR: Alignment of the deduced amino acid sequences of all four genes revealed three domains of high homology interrupted by highly diverged regions due to numerous duplication and insertion events.
Abstract: The primary structure of two nodule specific soybean genes are presented. The two genes code for primary products of 20.0 (nodulin 20) and 22.7 (nodulin 22) kdaltons, respectively. Both genes are related to the nodulin 23 and 44 genes. Alignment of the deduced amino acid sequences of all four genes revealed three domains of high homology interrupted by highly diverged regions due to numerous duplication and insertion events. The first conserved domain codes for a putative signal peptide, while the two others each contain four Cys residues that can be arranged in a way reminiscent of the metal binding domains present in some enzymes and in several DNA binding proteins.