Showing papers by "University of Hertfordshire published in 1973"

A photostable pyrethroid.

Abstract: THE natural pyrethrins (see refs 1 and 2 for references) (for example, pyrethrin I (1)) and related synthetic insecticides3 (allethrin (2), bioallethrin (3), resmethrin (4), bioresmethrin (5), Cismethrin (6) and the ethanochrysanthemate (7)) are unstable in air and light (see refs 1 and 2 for references, and ref. 4). This property restricts their use, particularly against pests of agricultural crops, in spite of other favourable characteristics (see refs 1–3 for references) (outstanding potency against many insect species, rapid action, and low mammalian toxicity5). We describe here new synthetic esters, ten to one hundred times more stable in light than previous pyrethroids, yet as active against insects as bioresmethrin (5) and with low mammalian toxicity.

Plant growth responses to vesicular‐arbuscular mycorrhiza v. phosphate uptake by three plant species from p‐deficient soils labelled with 32p

Abstract: Summary The uptake of phosphorus from 32P-labelled soil solution by three plant species, with and without mycorrhiza, was measured. All soils contained very little CaCl2- and NaHCO3-soluble phosphorus. In two soils the specific activity of phosphorus taken up by mycorrhizal and non-mycorrhizal Melinis minutiflora was very similar, indicating that even in very P-deficient soils mycorrhizal plants used the same source of phosphate as non-mycorrhizal. In two other soils non-mycorrhizal Paspalum notatum and Centrosema pebescens contained no 32P activity, suggesting that they had not taken up any soil phosphorus, whereas mycorrhizal plants of both species contained 32P activity and grew much better. It is suggested that non-mycorrhizal roots of some plant species do not utilize phosphate present at extremely low concentrations in the soil solution, but that mycorrhizal roots or fungal hyphae do. The implications of this finding for the mechanism of phosphate uptake by VA mycorrhiza are discussed.

Potent pyrethroid insecticides from modified cyclopropane acids.

Abstract: THE natural pyrethrins1–3, of which the most important constituent is pyrethrin I (1), are very active against a wide range of insect species, do not leave persistent residues, and have a long record of safe use; despite surprisingly high intravenous toxicity, they have low oral toxicity to mammals4. The related synthetic compound, bioresmethrin (2)5,6, has greater insecticidal activity (for example, about fifty times that of pyrethrin I, by topical application5, to a normal strain of houseflies), yet is even less toxic to mammals, both orally and intravenously4,7. Pyrethrin I and bioresmethrin are esters of (+)-trans [1R,3R]-chrysan-themic acid. We have now found that a simple modification of the acid side chain in bioresmethrin by which the four carbon atoms in the isobutenyl group are redisposed to a but-1-enyl substituent (as in 7) produces still greater insecticidal activity (about 100 times that of pyrethrin I to houseflies) whilst retaining low mammalian toxicity. Other changes of the acid side chain in bioresmethrin increase insecticidal activity further; for example the compound (10) with a cis-(Z)-butadienyl group and the dichlorovinyl compound (12) are both 2–3 times as potent as bioresmethrin.

Effect of Metal Cations on the Swelling and Gelatinization Behaviour of Large Wheat Starch Granules

Abstract: The effect of metal cations on the swelling and gelatinization behaviour of large wheat starch granules has been studied by observing their behaviour in the presence of 24 different chlorides in aqueous solutions. With most salts, increasing concentration results in gelatinization temperatures being first raised, then depressed, and then raised again. Increasing salt concentration may also cause the initial loss of anisotropy to occur at the granule surface instead of at the hilum, and result in an apparent solution of starch rather than swollen granules. The gelatinization phenomena have been classified into three major types, and these are described in detail. It is suggested that both water and partially hydrated salts can act as gelling agents for starch granules, and that the interplay of these two agencies can explain the observed complex relation between gelatinization temperature and salt concentration.

The Size Distribution Among Starch Granules in Wheat Endosperm

Abstract: Starch granules of less than 10 μm in diameter have been separated from a sample of Cappelle Desprez wheat by a micro-sieving technique. These smaller granules were found to contribute some 30% of the total weight of the starch.

Bionomics of aphids reared on cereals and some Gramineae

Abstract: SUMMARY In controlled temperature, light and relative humidity, Metopolophium dirhodum and Sitobion avenae multiplied more on young Proctor barley than on Blenda oats, and less on Cappelle wheat. Rhopalosiphum padi increased in number fastest on barley and slowest on oats. More survived, and generation lengths seemed shorter, on barley for M. dirhodum and S. avenae and on wheat for R. padi. Tests with young cereals outdoors generally agreed with those in controlled conditions. On mature plants, there were more M. dirhodum on barley, more R. padi on wheat and more S. avenae on oats than on the other cereals. Given a free choice in large cages outdoors, most aphids were found on barley. When allowed to choose between grasses, more M. dirhodum were on Dactylis glomerata, Poa pratensis and Festuca pratensis, more R. padi on Lolium perenne and F. pratensis, and more S. avenae on D. glomerata and L. perenne. Most aphids of all species combined were on F. pratensis, Lolium and Phleum, and fewest on Festuca rubra and Holcus mollis.

The effect of oral and inhaled beclomethasone dipropionate on adrenal function.

Abstract: Summary Beclomethasone dipropionate differs from other steroids previously tried by inhalation in bronchial asthma in having marked topical potency and relatively weak systemic glucocorticoid effects. Experiments in human volunteer subjects demonstrating the effect of this steroid on the hypothalamo-pituitary adrenal axis (HPA axis) are described. These are part of a larger investigation into the reasons for the selectivity of beclomethasone dipropionate in bronchial asthma. From the evidence so far obtained, it may be concluded that suppression of the HPA axis is unlikely to occur at doses up to 1.0 mg/per day by inhalation.

A Note on Minimization Algorithms which make Use of Non-quardratic Properties of the Objective Function

Abstract: * The scalar n* in (1) is intended to reflect the non-quadratic properties of/(x). A value off/* is chosen at each iteration so that r}*s£yk is, in some sense, a better estimate than fifvfc of the true directional second derivative 8jV/(xt)5fc. In the original paper it was proposed that n* be calculated by expressing f(xk+adk) in the form c£(a) = A\«—a\+b, A > 0, p > 1 (3) and determining the "dominant degree", p, and hence a suitable n*, using the value of the function and gradient at xk and xk+8t. However, while computational experience has shown that efficient algorithms for unconstrained minimization can be based on (1), the calculation of//* from (3) has proved a little cumbersome in that it involves the solution of a pair of non-linear equations. In order to avoid this we now propose calculating n* by representing f(xk+tx8k) by the cubic model '(a) = d/da q>(a) and if //* is defined by

The pathogenicity of Nodamura virus for insects.

Abstract: NODAMURA virus, which was originally isolated from mosquitoes from Nodamura, near Tokyo, multiplies in several insect and tick species, apparently without causing symptoms. It is transmissible to suckling mice by infected Aedes aegypti, and is fatal1. In Japan young pigs have been found with antibodies to the Nodamura virus, which has been classified as an unusual kind of arbovirus because it is resistant to ether2. This property, together wjth other features of the virus particles3 are reminiscent of acute bee-paralysis virus4 and we therefore examined its effect on the honey-bee, Apis mellifera. We also tested its pathogenicity for the wax moth, Galleria mellonella.

Aphid colonization of spring cereals

Abstract: SUMMARY In 1970-1, Metopolophium dirhodum, Rhopalosiphum padi and Sitobion avenae were the commonest alatae trapped from April/May to August, with most in July and early August. The first alatae appeared in the Rothamsted survey suction trap 0–34 days before aphids were found on the cereals, but during May and June no relationship was found between the numbers trapped and the number on the crop. Most species occurred first near the sheltered edge of the crop, but M. dirhodum was widespread over the field. Most infestations were quickly dispersed by the movements of older morphs; adults only stayed in one place for about 2 days. Alate M. dirhodum moved more often than apterae, but both morphs of S. avenae moved equally often and more frequently between larvipositions than did those of M. dirhodum. Apterae deposited more nymphs in a ‘group’ than alatae, and M. dirhodum deposited more than S. avenae. Few ‘groups’ persisted for more than a week. Although M. dirhodum occupied the crop area faster than S. avenae, all 0–3 m lengths of row sampled being infested within 2–5 wk of their first appearance, most or all of the tillers were colonized only in late July 1970.

Allergenic and Agricultural Implications of Airborne Ascospore Concentrations from a Fungus, Didymella exitialis

Abstract: THE occurrence of seasonal asthma resulting from fungal spores in late summer is well recognized. Cladosporium and Alternaria have been extensively studied as allergens1 because of their worldwide distribution. Herxheimer et al.2 used skin and bronchial testing when investigating allergic causes of recurrent summer asthma. They showed that certain types of basidiospores and one type of ascospore are antigenic in man. Seasonal symptoms occurring in late summer in Great Britain due to Leptosphaeria (Phoma) spp. have also been described3. Very large concentrations of ascospores, particularly in August, were noted by Hyde and Adams4. The clinical importance, especially of the large numbers of one-septate ascospores, has never been evaluated.

The Nitrifying Bacteria in Soils from Rothamsted Classical Fields and Elsewhere

Abstract: Summary. Ammonia oxidizing autotrophic nitrifying bacteria in soil samples from 3 classical Rothamsted fields and elsewhere were counted by a modified 2-layered silica gel plating method. Counts ranged from 0-18000/g of dry soil, the maximum number being found in the Broadbalk farmyard manure plot. Nitrosomonas europaea was isolated in pure culture and detected only in soils treated with dung or other organic fertilizer. Nitrosocystis coccoides and Nitrosospira spp. were found in other soils. Nitrobacter spp. were present in many soils and of the 18 pure cultures isolated there seemed to be 3, or possibly 4, different colony types.

Large-Scale Experiments on the Spreading of Oil at Sea and its Disappearance by Natural Factors

Abstract: This paper describes those considerations that are of importance in undertaking large-scale oil-spreading experiments. One such experiment involving a discharge of 120 tons of Iranian Light Crude Oil in the North Atlantic is described, and the spreading pattern observed is reported in detail. The observations continued over a period of four days, after which the bulk of the oil had disappeared by natural factors, leaving only a few patches of thicker oil, largely in the form of a water-in-oil emulsion, which was also rapidly disappearing. Blokker constants have been calculated for the observed spreading of the slick, and these are reasonably constant throughout the four-day period.

Digital integrated circuits

Abstract: In order to eliminate the expense of dicing an integrated circuit into chips, testing the chips, selecting, packaging and retesting the chips, the wafer is left undiced and each chip includes switching and control circuits which enable a chip to be linked to any one of its neighbours. A chain of good chips is built up by sending control signals down the existing part of the chain (which starts with one chip) to cause a new chip to be added to the chain. Test signals are then used to ascertain if the added chip is good. If it is the next chip is added; if not, the chip is disconnected and the control signals utilised to select another neighbouring chip as the added chip. Faulty chips are thus simply by-passed by the chain which is built up of good chips only to form a long shift register for example. Grids of power and clock lines are provided to all chips and a fast data line grid may be used for accessing all chips in a content addressable memory application.

Elevated Ozone Levels in the Air of Central London

Abstract: AMONG the reactions of primary pollutants with one another and with substances naturally present in air, the reactions induced by light are particularly important. The occurrence of such reactions is related to the accumulation of strongly oxidizing species, particularly ozone1, which occurs naturally in the atmosphere to the extent of 20–50 p.p.b. during daylight2,3. Ozone can be detected by smell by sensitive individuals at 100 p.p.b.4, which value is a suitable threshold for an air quality evaluation, having been proposed as an air quality standard in the USA5.

Metabolism of chlorophenols by Rhodotorula glutinis

Abstract: A phenol-utilizing strain of Rhodotorula glutinis was isolated from Rothamsted soil. Washed, phenol-grown R. glutinis cells oxidized 3- and 4-chlorophenols to 4-chlorocatechol, and 4-bromophenol presumably to 4-bromocatechol. Phenol-grown cells consumed O 2 in the presence of 2-, 3- or 4-chlorophenol, 4-bromophenol, 2,4-dichloro- and 2,4-dibromophenol. Benzoate-grown cells showed O 2 -uptakes in the presence of 2-, 3- or 4-chlorobenzoate but the formation of catechol compounds was not definitely established.

Mycotic infections in frogs due to a Phialophora-like fungus.

Abstract: A fungal epizootic among captive frogs in U.S.A. was investigated histologically and mycologically. It was not possible to determine which of the fungi (Cladosporium herbarum, Scolecobasidium humicola or Phialophora sp., probably gougerotii) was the pathogen.

The pollination of hybrid kale ( Brassica oleraceae L.)

Abstract: Honeybees were able to distinguish between the flowers of two different oultivars of kale grown to produce hybrid seed and most foraged only on one or other of them.

Measurements on a Negative-Thixotropic Fluid

Abstract: I HAVE carried out some measurements on an alkaline perbunan latex dispersion which shows distinctive negative-thixotropic properties. The latex is normally a milky fluid but, when vigorously shaken, rapidly turns into a gelatinous mass. On resting it reverts to fluid in 15 to 30 min depending on the concentration.

Molecular properties of the starch components and their relation to the structure of the granule

Abstract: It is now generally accepted that the properties of starch granules from a given botanical source are not static, but rather change during the growth of the species. In particular, the amount of iodine bound by starches from various sources (wheat,' maize,'. 3 barley,', 5 tobacco leaves,\" peas,' and potato tubers * ) has been found to increase quite dramatically as growth proceeds. This observation has usually been interpreted as showing that the relative amount of amylose (the essentially linear component of starch) increases as more starch is formed. The amylose content of the starch is calculated from the ratio of the iodine-binding capacity of the starch to that of the pure amylose component, and the latter is assumed to have a value of approximately 19-20 mg iodine bound per 100 mg polysaccharide. Matheson,u however, has pointed out that this assumption may not be justified, znd that the iodine-binding capacity of the amylose fraction may itself vary during development. Certainly, the results of Wood lo on the development of wheat starch, and of Briones and colleagues on rice starch, show that the iodine-binding capacity of the isolated amylose fractions does increase with maturity. This could be due to an increase in the molecular size of the amylase,'? or to a decrease in the extent of the branching in this component.13 The above studies demonstrate that in addition to studying the morphology and properties of the developing granules, it is necessary to determine what changes, if any, occur at the molecular level in the amylose and arnylopectin components. We present here a review of our work on this subject, and a summary of the conclusions we have reached in relating the fine structures of the components to the biosynthetic mechanism by which the starch granule is formed.

Determination of ionization potentials from photoelectron spectra

Abstract: The theory of the determination of vertical (I v ) and adiabatic (I a ) ionization potentials from molecular photoelectron spectra is examined. It is shown that it is the centroid of the vibrational structure rather than the position of maximum intensity which gives the correct value for I v . The results are applied to the photoelectron spectra of H2 and H2O. The value of I v so determined for the H2 → H2 + transition is in satisfactory agreement with that expected from the theoretical energy levels of H2 +.

Variation in growth of seedlings and clones of agropyron repens (l) beauv.

Abstract: Summary. The growth of Agropyron repens seedlings, or of clones derived from them, raised from seeds collected from different areas was compared; the growth of seedlings raised from seeds from single spikes and from seeds of a cross of two clones was also compared. The number and length of shoots and the amount of rhizome produced differed between seedlings from different areas. Seedlings with a large weight of rhizomes often had a small weight of shoots. Many of the differences found between seedlings from different areas were confirmed by comparing clones established from some of them. Comparisons of both seedlings and clones showed that the percentage of shoots that developed spikes differed between genotypes; clones with the least weight of rhizome tended to have most weight of spikes. Large variations also occurred between clones established from seedlings from a given area, particularly in the way their dry weight was partitioned between primary and secondary shoots and in the time the spikes emerged. The amount of rhizome per seedling varied greatly between seedlings from seeds from single spikes and from seeds from a cross of two clones. There was some evidence of a negative correlation between per cent shoot and per cent rhizome dry weight with seedlings from single spikes and between number of shoots and number of rhizomes per seedling with seedlings from a cross of two clones. Variation en croissance de plantules issues de semences et de clones d' Agropyron repens (L) Beauv. Resume. La croissance de plantules d'Agropyron repens ou de clones derives de eelles-ci, plantules issues de semences provenant de diverses regions a ete coniparee; on a compareeegalement la croissance de plantules issues de semences provenant d'un seul epi, ainsi que du croisement de deux clones. Le nombre et la longueur des tiges et la quantity de rhizomes produits variaent enlre les plantules provenant de regions differentes. Les plantules avec un poids eleve de rhizomes ne prentaient souvent qu'un faible poids de tiges. Beaucoup des differences constates entre plantules de regions differentes furent confirmees par la comparaison des clones obtenus a partir de certaine de ces plantules. La comparaison des plantules et des clones montra que le pourcentage des tiges fertiles differait selon les genotypes; les clones avec les plus faibles poids de rhizomes montrirent une tendance i porter le plus grand poids d'epis. De grandes differences apparurent aussi entre les clones obtenus a partir de semences provenant d'une meme region, differences qui porterent en particulier sur la repartition des poids sees entre les tiges primaires et les tiges secondaires, ainsi que sur repoquc de l'epiaison. La quantite de rhizome par plantule varia beaucoup selon que ces plantiles povenaient d'epis unique ou du croisement de deux clones. II y eut quelques indices d'une correlation negative entre le pourcentage de poids sec des racines et celui des rhizomes avee les plantules provenant d'epis uniques ainsi qu'entre le nombre de tiges et le nombre de rhizomes par plantule provenant d'un eroisement entre deux clones. Unterschiede in Wachstum der Keinlinge und Klone von Agropyron repens (L.) Beauv. Zusammenfassung. Es wurde das Wachstum von Agropyron repens-Jungpflanzen oder Klonen derselben, die aus Samen verschiedener Gegenden stammten, verglichen; desgleichen das Wachstum von Jungpflanzen aus Samen einzelner Ahren mit denen aus Samen einer Kreuzung von zwei Klonen. Die Zahl und Lange der Sprosse und die gebildete Menge an Rhizomen waren bei Jungpflanzen aus verschicdenen Gegenden unterschiedlich. Jungpflanzen mit einem grosen Rhizomgewicht hatten haufig ein niedriges Sprossgcwicht. Viele der festgestellten Unterschiede zwischen den Jungpflanzen von verschiedenen Standorten wurden durch ihre Klone bestatigt. Vergleiche von Jungpflanzen und Klone zeigten, dass der prozcntuale Anteil der ahrenbildenden Sprosse genotypisch bedingt war; Klone mit dem geringsten Rhizomgewicht hatten in der Tendenz das hochste Ahrengewicht. Grose Unterschiede traten auch zwischen den Klonen aus Jungpflanzen einer bestimmten Gegend auf, besonders was die Verteilung des Trockengewichts zwisehen Primar- und Sekundarsprosse und das Erseheinen der Ahren betraf. Die Menge an Rhizomen je Jungpfanze variierte ziemlich stark zwischen Jungpfanzen aus Samen einzelner Ahren und Samen aus der Krequzung zweier Klone, Es ergaben sich Anhaltspunkte fur eine negative Korrelation zwischen dem prozentualen Spross- und Rhizom-Trockengewicht der Jungpflanzen aus einzelnen Ahren und zwischen der Anzahl der Sprosse und Rhizome bei Pflanzen aus der Kreuzung.

Trimethoprim-sulfamethoxazole in the treatment and prevention of purulent exacerbations of chronic bronchitis.

Abstract: In the treatment of purulent exacerbations of bronchitis, the usually recommended dose of trimethoprim-sulfamethoxazole (TMP-SMZ) was inadequate. Treatment with 480 mg of TMP and 2,400 mg of SMZ daily was very successful. Compared with 2,000 mg of tetracycline hydrochloride daily in a double-blind trial in 197 patients, this dose of TMP-SMZ seemed superior in reducing purulence of the sputum and improving the clinical state of the patient. It was significantly better in preventing deterioration, both during and up to a month after treatment. In the prevention of purulent exacerbations of chronic bronchitis, 40 hospital inpatients with advanced chronic bronchitis were given 320 mg of TMP and 1600 mg of SMZ daily for 10 weeks. In a strictly double-blind trial their progress was compared with that of 20 patients given a placebo for 10 weeks. Highly significant clinical and bacteriologic differences favored the patients given chemotherapy. Side-effects were minimal, and tolerance was excellent. The combination of TMP and SMZ in the above doses should be one of the first choices of chemotherapeutic agents in the treatment and prophylaxis of chronic purulent bronchitis.

Genetic determination of honeybee (Apis mellifera L.) foraging preferences

Abstract: SUMMARY Progeny from different honeybee queens that were reared in, and foraged from, the same colony sometimes differed in their floral preferences, confirming that these are to some extent innately determined.