Showing papers by "University of Hertfordshire published in 1981"

Testing Products and Materials for Their Contribution to Flashover in Rooms

Abstract: The first part of the paper describes briefly the calculation of the rate of heat release required to cause flashover in a compartment. It is possible from theory to suggest that the thermal feedback which controls the supply of gaseous fuel from a given area of combustibles may be generally less important than that which controls the extension of the area, although eigher can cause the rapid transition of flashover in the absence of the other. In the second part of the paper some implications for the testing of products and linings are explored and some suggestions are made for the way in which test data can be used to predict the behaviour of fires in rooms. Suggestions are made for the way in which test data can be used to predict the behaviour of fires in rooms. Suggestions are made for the development of test having a more direct meaning, in terms of both hazard and quantitative theory.

Preventing phosphorus losses during perchloric acid digestion of sodium bicarbonate soil extracts

Abstract: Between 10 and 40% of P was lost during perchloric acid digestion of NaHCO3 soil extracts for measurement of organic P. This observation was confirmed by 32P tracer experiments. Addition of MgCl2 prevented P loss, reduced variability of replicate determinations and ensured virtually 100% recovery of P added to NaHCO3 solution and NaHCO3 soil extracts before digestion. Losses were due both to P volatilisation and conversion of P to forms other than ortho-P in the digestion mixture.

SOME in vitro AND in vivo ACTIONS OF THE NEW HISTAMINE H2-RECEPTOR ANTAGONIST, RANITIDINE

Abstract: 1 Ranitidine has been investigated as an antagonist of the H2-receptor-mediated responses to histamine of guniea-pig atrium and rat uterus in vitro and as an inhibitor of gastric acid secretion in the rat. 2 Ranitidine competitively antagonized histamine-induced increases in contraction frequency of the guinea-pig isolated rat atrium. Ranitidine had a pA2 of 7.2 and was 7.9 and 4.5 times more potent than metiamide and cimetidine respectively. 3 Ranitidine competitively antagonized histamine-induced relaxations of the rat isolated uterine horn. Ranitidine had a pA2 of 6.95 and was 3.6 and 5.9 times more potent than metiamide and cimetidine respectively. 4 Ranitidine, even at high concentrations, did not affect responses of the guinea-pig isolated atrium or rat isolated uterus to (-)-isoprenaline. Similarly it was without effect on either histamine or bethanechol-induced contractions of guinea-pig isolated ileum. 5 Ranitidine inhibited histamine- and pentagastrin-induced gastric acid secretion in the perfused stomach preparation of the anaesthetized rat. Ranitidine was 5.2 and 7.0 times more potent on a molar basis than metiamide and cimetidine respectively, as an inhibitor of histamine-induced gastric acid secretion. 6 It is concluded that ranitidine is a potent, competitive and selective antagonist of histamine at H2-receptor sites and and effective inhibitor of gastric acid secretion in vivo.

Recent developments in serological methods suited for use in routine testing for plant viruses

Abstract: SUMMARY Since the mid 1950s, there have been many developments in serological techniques for testing for plant viruses. Certain of these can provide great savings in time, labour and cost in routine testing situations and are well suited for use by advisory services, certification schemes and healthy stock programmes, statutory and quarantine authorities, and plant breeders. The recent developments are described under the headings flocculation in liquid media, gel diffusion, labelled antibodies and electron microscope serology, Flocculation tests depend on observation of aggregates formed in a liquid medium. The microprecipitin and chloropiast agglutination tests are simple forms which are still widely employed routinely. However, sensitivity is greatly improved by using flocculation tests in which antibodies are adsorbed to the surface of larger inert carrier particles, such as polystyrene latex spheres, tanned red blood cells or bentonite. Latex particles are the most widely used of these because they are easy to sensitise with antibodies, little antiserum is required and the sensitised latex can be stored for years without loss of activity. The latex test is also very simple to do, is well suited for routine checks on either small or large numbers of samples which can be grouped and can be used with many virus–crop combinations. Gel diffusion tests depend on observation of precipitin lines formed in an agar gel medium. They are of two main types, single (= simple) diffusion and double diffusion. Both can be used effectively with viruses which have isometric or ‘near isometric’ particles but not with those which have elongated particles because these do not diffuse readily through agar. Recent developments which involve breaking elongated particles into sub-units or fragments which can diffuse through agar now permit gel diffusion to be applied with almost all viruses. Various treatments are useful in breaking particles, the most effective of which employ detergents or other disruptive chemicals such as pyridine, pyrrolidine and ethanolamine, However, although gel diffusion tests which incorporate one or other of these treatments have been employed routinely for testing for viruses in several different crops, such tests are relatively insensitive, require much antiserum and conditions must be carefully controlled to avoid formation of nonspecific precipitin lines. Antibodies can be labelled to make virus—antibody aggregates readily observable, or to obtain increased sensitivity in testing, or both. The only form of labelled antibody test widely employed in routine screening for plant viruses is enzyme-linked immunosorbent assay (ELISA), in which antibody is labelled with an enzyme and positive results are observed as an enzyme-mediated colour reaction. Since its introduction to plant virology in 1976, ELISA has been very widely applied in situations where large numbers of either individual or grouped

Techniques for studying the infection of plants by vesicular‐arbuscular mycorrhizal fungi under axenic conditions

Abstract: SUMMARY Methods of growing axenic seedlings infected by vesicular arbuscular mycorrhizal fungi are described, using agar, paper or glass as a support. Two of the techniques are particularly suitable for studying the interaction between the fungus and the host plant, for example the germination of the spore inoculum, hyphal growth around the roots before the symbiosis has been initiated and the early stages of root penetration.

Contamination of vegetation with synthetic sex‐attractant released from traps for the pea moth, cydia nigricana

Abstract: Observations of the attraction of males of the pea moth, Cydia nigricana (F.), to vegetation which had been in the immediate vicinity of sex-attractant traps are described. The moths exhibited sexual activity on arrival and the vegetation remained attractive for at least 60 min after removal of the traps. By increasing the dose of attractant in a trap, it was possible to contaminate adjacent vegetation with enough attractant to be detectable by electroantennographic and gas chromatographic techniques. ZUSAMMENFASSUNG Kontamination der Vegetation mit synthetischem Pheromon aus Fallen fur den Erbsenwickler Cydia nigricana Es werden Beobachtungen beschrieben uber die Anlockung von Weibchen des Erbsenwicklers, Cydia nigricana durch Vegetation, die in unmittelbarer Nahe von Pheromonfallen gewesen war. Die Falter waren bei der Ankunft sexuell aktiv und die Vegetation blieb fur mindestens 60 Minuten nach Entfernung der Fallen attraktiv. Durch Steigerung der Pheromonmenge in einer Falle wurde es moglich, die benachbarte Vegetation so zu kontaminieren, dass Pheromon mit elektroantennographischen und gaschromatographischen Methoden nachweisbar wurde.

The relative abundance of the hymenopterous parasites attacking Metopolophium dirhodum (Walker) and Sitobion avenae (F.) (Hemiptera: Aphididae) on cereals during 1973–79 in southern England

Abstract: In studies in southern England, the relative abundance of the hymenopterous parasites attacking Metopolophium dirhodum (Wlk.) and Sitobion avenae (F.) differed between their hosts, between years (1973–79) and on whether they were assessed using field or laboratory-reared mummies. Species of the complex of Aphidius uzbekistanicus Luzhetzki were usually the commonest parasites, especially from mummies of M. dirhodum , while Aphidius picipes (Nees) was less common and tended to attack mainly S. avenae ; Toxares deltiger (Hal.) was common only in 1979. Species of hyperparasites emerged most frequently from mummies of M. dirhodum , except for Dendrocerus carpenteri (Curt.), which emerged most often from S. avenae .

Nasonov pheromone of the honey bee,Apis mellifera L. (Hymenoptera, Apidae). part III. : Regulation of pheromone composition and production.

Abstract: GC and GC-MS analyses of the multicomponent Nasonov pheromone of the honey bee, and of the air above insects releasing the pheromone, show that constant composition is maintained during release, despite differing volatilities of the components. The regulating mechanism may involve a specific enzyme process, detected in excised Nasonov glands, which converts the major component geraniol into the more volatile (E)-citral. Analysis of honey bees of known ages and at different times of year shows that maximum secretion occurs when foraging is most likely.

Surgical cushion for cooling an organ

Abstract: A cushion for cooling an organ of the body during surgery. The cushion is flexible and of open form to allow cooling fluid to flow into it and out of it. A flexible tube extends from the cushion for draining off cooling fluid from the cushion and regions adjacent thereto.

The use of egg counts and suction trap samples to forecast the infestation of spring-sown field beans, Vicia faba, by the black bean aphid, Aphis fabae.

Abstract: SUMMARY Daily suction trap samples at a height of 12·2 m collected throughout the year, winter egg and ‘spring’ population counts on the spindle tree, Euonymus europaeus, and initial infestations of the black bean aphid, Aphis fabae, on field bean, Vicia faba, crops are available from Southern England since 1970. In different areas, estimates of the sizes of the autumn migrations, the over-wintering egg populations, the spring fundatrigeniae and the spring migrations, have been used to forecast field bean crop infestation levels which, in turn, project subsequent trap catches of alatae. The forecasts of crop infestation become progressively more accurate from the autumn migration to the following spring migration, accounting for 28%, 54%, 54% and 64% of the variance respectively. In areas where traps are sited, the spring migration trap samples give the most accurate estimate of the size and timing of crop infestation. Autumn trap catches are particularly useful as very early forecasts of likely very large or very small populations on field beans about 8 months later, but otherwise they lack precision. Egg sampling in winter provides a considerably more accurate forecast approximately 5 months before crop infestations. In spring (May), fundatrigeniae sampled on spindle are most useful for predicting time of migration, and provide approximately 2 weeks' warning for insecticide application, if needed. Finally, trap sampling of the spring migration provides the latest estimate of both the sizes of crop infestations and the timing of insecticide treatment. The E. europaeus and aerial sampling systems are complementary, the traps providing systematic, continuous information and the E. europaeus samples greater detail. Combined, they can provide excellent long-term fore-warning of the need for chemical control and short-term warning of control timing. Forecasts have been 90% correct in eight years out of nine. The error in the ninth year may be due to immigration from the European mainland.

Deposition of Particles Liberated in Gusts of Wind

Abstract: Theoretically, the aerial transport and deposition of fungal spores near to their source dependon the way in which they become airborne. Spores of some fungi are injected into the air, independentof wind speed, whereas others are blown from the host mainly by gusts. We calculated the collectionefficiency of vertical, sticky cylinders for spores released continuously and steadily, and for spores released intermittently when the wind exceeded a certain speed. We tested these calculations in the fieldby trapping on cylinders of different diameters Lycopodium spores released steadily from an artificialsource, spores of Erysiphe graminis blown from a barley crop and Lycopodium spores blown from a fiatplate or a short crop. The collection efficiency E of vertical sticky cylinders depends on wind speed, and the averageefficiency for an experiment was obtained by averaging E over all speeds during spore release. Thecatch of the spores released continuously can be predicted adequately from E at the mean w...

Glutamine metabolism in higher plants.

Abstract: Publisher Summary This chapter discusses metabolism and the role of glutamine in the flow of nitrogen. Under certain conditions, all the nitrogen assimilated by bacteria could pass through glutamine. The plant enzyme, in common with that from other sources, exhibits a number of activities that have been the basis of a number of different assays. In plants, as in other tissues, there are enzymes other than glutamine synthetase (GS) that may catalyze the transferase assay and thus, the assay is unlikely to be specific. The role of GS is highlighted by the build-up of glutamine at the expense of glutamate and other amino acids—as glutamate levels fall, presumably other free amino acids are transaminated to the available 2-oxoglutarate in an attempt to maintain the level of glutamate. Glutamate dehydrogenase (GDH) does not operate to assimilate NH 3 , even though the concentration of NH 3 is greatly increased and there is an excess of 2-oxoglutarate.

Relationship between eyespot severity and yield loss in winter wheat

Abstract: SUMMARY Between 500 and 1000 winter wheat plants were taken at random immediately before harvest from crops with naturally or artificially created attacks of eyespot (Pseudocercosporella herpotrichoides (Fron) Deighton) at eight sites in eastern England from 1975 to 1979. The individual shoots of each plant were placed in one of four categories: healthy, or slightly, moderately or severely infected with eyespot. Healthy shoots were sub-divided into those from plants with all shoots healthy and those from plants with at least one infected shoot. Ears were threshed individually and average dry weight of grain per ear, grain number per ear and 1000-grain dry weight were computed for each infection category and both healthy shoot categories. Slight eyespot had no effect on yield. Moderate eyespot reduced yield per ear, grain number per ear and 1000-grain weight by 10, 8 and 5 per cent respectively; severe eyespot caused corresponding losses of 36, 29 and 15 per cent. Healthy shoots showed no apparent compensation for yield loss in eyespot-infected shoots on the same plant. The equation y= O.lX1+ 0.36x2, where y= percentage yield loss, x1= percentage of moderately infected shoots and x2= percentage of severely infected shoots, was applied to the results of ADAS winter wheat disease surveys from 1975 to 1980. National yield losses due to eyespot in these years were estimated tobe 0.9, 0.3, 1.1, 1.2, 0.7 and 0.3 per cent respectively.

Why and How Chromatic Adaptation Has Been Studied

Abstract: The question of why chromatic adaptation has been studied has two answers: to explore the functioning of the visual mechanism and to provide useful engineering data. The question of how is answered by reviewing a series of techniques that have been used to study chromatic adaptation.

Interrelationship between nitrogen concentration in grain, grain yield and added fertiliser nitrogen in wheat experiments of South-east England

Abstract: Results from 20 years of wheat experiments were used to compare responses of grain-N% and grain yield to increasing amounts of fertiliser-N. Grain-N% for both winter and spring wheat increased, mostly linearly, throughout the range, whereas many of the grain yield curves reached a maximum and then declined with further additions of N. Provided curve sections exhibiting dilution effects were excluded, the linear or near-linear relationship between grain-N% and fertiliser-N allowed linear regression models to be fitted. This showed that, over a range of 50-175 kg N ha−1, an average of 32 kg ha−1 of fertiliser-N was required for an increase of 0.1% N in grain dry matter of winter wheat or 56 kg N ha−1 for an increase of 1% protein. Results from 3 years of experiments conducted by the Agricultural Development and Advisory Service (ADAS) agreed closely with those obtained from Rothamsted. Using the linear relationship between grain-N% and fertiliser-N, curves were plotted of grain yield against grain-N, adjusted for comparable additions of fertiliser-N (75, 100, 125, 150 kg ha−1). The curves tended to have sections with rising yield for small applications of N, to exhibit a maximum in a central zone and descending sections for large applications. There was no well-defined ‚critical level’ of grain-N%, beyond which this and grain yield were inversely related.

Evaluation of the various components of the nasonov pheromone used by clustering honeybees

Abstract: . Of the various components of the Nasonov pheromone, geraniol, (E)-citral and nerolic acid were the most important for inducing clustering. The presence of (Z)-citral with (E)-citral, or in a mixture of components including (E)-citral, did not diminish clustering and sometimes increased it. Geranic acid alone encouraged clustering, but was less effective with nerolic acid or the citrals. Nerol and (E, E)-farnesol had little obvious influence on clustering. A 1:1:1 mixture of geraniol + nerolic acid + (E)- and (Z)-citrals was as effective as a mixture of all the seven components in equal proportions, which was in turn as effective as a mixture containing the components in the proportions present naturally in the Nasonov gland.

Factors determining the release of nasonov pheromone by honeybees at the hive entrance

Abstract: . Worker bees recently denied access to their colony expose their Nasonov glands, thereby releasing pheromone, at the entrance to their hive. Odours of the following induced this response: empty comb, purified beeswax, honey, pollen, propolis, a live queen, the (E)-9-hydroxy-2-decenoic acid component of a queen's mandibular glands, live drones and workers, inert material on which workers had walked inside the hive, and synthetic Nasonov pheromone. The total odour of a foreign colony also induced worker bees to expose their Nasonov glands but was less effective than the odour of their own colony. Odours of the following were not effective: the (E)-9-oxo-2-decenoic acid component of a queen's mandibular glands, recently killed drones and workers, worker brood (eggs, larvae, pupae).

Broken rail/bond detectors

Abstract: A track circuit receiver is driven by the signal across an impedance bond and operates a relay to disconnect the signal so causing the relay to cycle. In series with the receiver input is a signal from the center tap of the impedance bond, which is normally at earth potential and does not affect the relay cycling. In the event of a rail break a significant output is obtained from the center tap, which either cancels or replaces the original receiver input signal but on a permanent basis uncontrolled by the relay. The relay therefore ceases to cycle in either event and thus provides a break indication.

The use of combined high performance liquid chromatography negative ion chemical ionization mass spectrometry to confirm the administration of synthetic corticosteroids to horses

Abstract: Negative ion chemical ionization mass spectra of some corticosteroids have been obtained by direct syringe introduction on to the Finnigan moving belt high-performance liquid chromatography-mass spectrometer interface. Proprietary preparations based upon dexamethasone, betamethasone and prednisolone were administered to horses at therapeutic dose level. Urine samples were extracted, the extracts purified by Sephadex LH-20 chromatography and the presence of the parent steroids in the eluates was confirmed by combined high-performance liquid chromatography negative ion chemical ionization mass spectrometry using ammonia as reagent gas.