Showing papers by "University of Hertfordshire published in 1970"

Studies of chemical exchange by nuclear magnetic relaxation in the rotating frame

Abstract: The exchange of protons between sites with different chemical shift is studied by means of N.M.R. relaxation time measurements (T 1ρ ) in the presence of an r.f. magnetic field. The system studied is chair-to-chair isomerization in cyclohexane. The exchange rate and chemical shift are measured in the temperature range 215°k to 250°k. The method is compared with other N.M.R. techniques for studying chemical exchange and is found to have advantages particularly at high exchange rates.

Air movement near windbreaks and a hypothesis of the mechanism of the accumulation of airborne insects

Abstract: SUMMARY Different components of wind were measured to leeward of artificial windbreaks to show which most affected accumulations of airborne insects there. Horizontal motion was the most important. Accumulations of small airborne insects in sheltered places are probably caused when the insects are diffused or convected into the recirculating air behind barriers. The concentrations likely to occur theoretically in this way were compared with concentrations measured in the field.

Scanning Electron Microscopy of Wheat Starch II. Structure of Granules Modified by Alpha-Amylolysis – Preliminary report

Abstract: Wheat starch granules were subjected to alpha-amylolysis after which they were examined in the Scanning electron microscope. Much variation exists among starch granules; thus conclusions based on the observation of the precise mode of α-amylase attack on a few individual granules may not be generally applicable. It has been found, however, that where a groove is present in a granule, α-amylase attack generally occurs here, complete penetration either occurring exclusively at this feature or accompanying penetration at apparently randomly located sites on the major surfaces. This preliminary investigation of starch granules attacked by amylase has provided new information which augments the results of studies by other microscopical methods. Observation of the detailed structure of the equatorial groove in modified granules is particularly relevant to a better understanding of this feature in starch granules.

Distribution of aphids in cereal crops

Abstract: SUMMARY Cereal crops were examined weekly for aphids during 1969. Plants in twenty samples of row 0.3 m long were examined in a sheltered perimeter of a crop and along a transect 36.6 m into the crop. Aphids were usually first found within 1–4 weeks of the first alatae caught in a suction trap operating 12.2 m above ground. When first alatae caught in a suction trap operating 12.2 m above ground. When the first found from 10 to 27% of the 0.3 m lengths sampled contained aphids. Rhopalosiphum padi, first found late in May, were scarce (< 0.53/0.3 m) throughout June and July. Sitobium spp. and Metapolophium dirhodum, which appeared in mid-June, were more numerous than R. padi; most occurred during the second half of July, and populations decreased just before harvest in early August. Sitobium avenae was more abundant (max. 19.3/sample) than either S. fragariae (0.91) or M. dirhodum (2.51). More aphids occurred in oats (max. 52/0.3 m) during July than in wheat (45), and barley had fewer (6.8). S. avanae was more abundant than M. dirhodum in sheltered areas of barley and wheat, and in exposed areas of the same crop M. dirhodum was commonest. Along sheltered perimeters, the ratio of S. avenae to M. dirhodum was largest in barley (11:1), intermediate in oats (6:1) and smallest in wheat (3.7:1). Sitobium spp. were most numerous on the ears, when most M. dirhodum were on the leaves. Regression analyses of log. S2 on log. m suggested that S. avenae was more evenly distributed within (36.6 m) the field (b = 1.056 + 0.109) than along the sheltered perimeter (b = 1.432 + 0.132), though it seemed similarly distributed along perimeters of barley, oats and wheat. The distributions of M. dirhodum and Sitobium spp. along sheltered perimeters of all crops were apparently similar.

Binding of Calcium to Phospholipids

Abstract: It has often been assumed that phospholipids play an important part in the binding of calcium to cell membranes. The calcium contained in the cell is largely concentrated in the phospholipid-rich membrane fractions, while the concentration of ionized calcium in the intracellular fluid is minimal (Thiers & Vallee, 1952; Hofer & Kleinzeller, 1963; Hodgkin & Keynes, 1957; Harris, 1957).

Leadership Style, Confidence in Management, and Job Satisfaction

Abstract: A sample of persons drawn from all functions and from all levels of two companies in the United Kingdom were invited to express a preference for one of four leadership styles-the tells, the sells, the consults, and the joins. Each respondent was then asked to state which style most closely described his own immediate manager. (Alternatively, he could reply that his own manager did not correspond at all closely to any of the styles.) These answers were then related to replies to other questions concerned with describing managerial behaviour and with measuring job satisfaction, satisfaction with the employing organisation, and confidence in management.The results indicate that the four descriptions of leadership styles are meaningful to people. The consultative style was the one most consistently preferred. Most people were able to see their own managers as fitting one of the four descriptions. Those who felt that their own managers did not correspond at all closely to any one of the four styles showed leas...

The influence of work softening on the viscoelastic properties of butter and margarine.

Abstract: Creep compliance-time studies at low stresses give more information about the structural changes in work softened butter and margarine than the Cone Penetrometer. They show that margarine undergoes a greater structural change than butter. Margarine loses most of its instantaneous elasticity in an unrecoverable manner. However, most of the Newtonian viscosity loss is recovered. Butter loses much less of its instantaneous elasticity, and most of what is lost is recovered during aging, but less of the Newtonian viscosity which is lost is recovered. Retardation spectra derived from creep compliance-time curves for both butter and margarine before work softening show a peak at ∼104 sec. In contrast to margarine, butter does not lose this peak when work-softened. For margarine, the peak slowly redevelops during aging and occurs at ∼102 sec. Past interpretation of Cone Penetrometer data has been based on the simplified concept of primary irreversible bonds and secondary reversible bonds, and the changes in their relative proportions during work softening. The present approach avoids the allocation of bond strengths into these arbitrary categories, and is based on the realization that butter and margarine contain a wide range of bond strengths.

Needle nematodes (Longidorus spp.) and stubby-root nematodes (Trichodorus spp.) harmful to sugar beet and other field crops in England.

Abstract: SUMMARY Longidorus attenuatus produces galls at the tips of roots of field crops, including sugar beet, growing in alkaline, sandy soils in eastern England. L. elongatus produces similar, but often larger, galls on the roots of sugar beet and other crops in sandy soils in the W. Midlands and in Fen peats. Trichodorus spp. cause ‘stubby root’ of sugar beet and can feed on many field crops. Seven species of Trichodorus were found in sandy soils in eastern England. L. attenuatus, L. elongatus and Trichodorus spp. aggregate around roots and stunt sugar beet and other crop plants. L. attenuatus is commoner below plough depth than in the topsoil, whereas T. cylindricus, T. pachy-dermus and T. anemones are more abundant in the topsoil. These nematodes cause some forms of ‘Docking disorder’.

Silver Staining of Insect Central Nervous Systems by the Bodian Protargol Method

Abstract: Improved fixation of ganglia of the central nervous system of Periplaneta americana and Schistocerca gregaria for silver staining by Power's (1943) modification of the Bodian protargol method is given by alcoholic Bouin aged for at least 40 days at 60° C. During impregnation of sections, increased copper and decreased pH give paler staining, more selective for nerve fibres. Prolonging impregnation from 24 to 48 hours weakens the stain and decreases selectivity. The intensity of the stain depends chiefly upon the amount of unreduced (developable) silver combined with the tissues; selectivity is determined mainly by the number and distribution of the reduced silver particles (‘nuclei’). In development, increased sodium sulphite gives more differentiation, increased hydroquinone gives less. Optimum developer composition depends upon impregnation, and thick sections need more differentiation than thinner ones. Within limits, change in one of the factors that control staining can be balanced by changes in others, but by suitable adjustment of the conditions the result can be varied from almost total staining of nerve fibres, for general neuroanatomy, to highly selective staining for tracing individual fibres.

A DTA technique for identifying the phase inversion temperature of O/W emulsions

Abstract: A simple differential thermal analysis procedure is described for determining the phase inversion temperature (PIT) of O/W emulsions stabilized by polyoxyethylene surfactants With Nujol as the standard and a heating rate of 072°C, the PIT is defined by a sharp endothermic peak The PIT is not affected by the volume concentration of oil, although it has a slight effect on the height of the peak, nor by the size distribution of oil particles The chemical nature of the surfactant and that of the oil phase both influence the PIT In general, it was found that with a given oil phase the PIT increased linearly as the HLB (hydrophile-lipophile balance) of the surfactant, or surfactant blend, increased

Effects of decreasing the light intensity on the growth of agropyron repens (l.) beauv. in the field

Abstract: Summary. Small plots of Agropyron repens (L.) Beauv, were shaded with ‘Tygan’ screening fabric which transmitted approximately 46% of daylight. In 1968, plots were either shaded or unshaded throughout the experiment (from mid-May until September) and in 1969, some plots were also shaded early (mid-May to mid-July) or late (mid-July to September). In both experiments continuous shading halved rhizome dry weight but had a much smaller effect on shoot dry weight. It also decreased rhizome dry matter by 5%. With early shading there were fewer shoots and ears until mid-July but this difference disappeared by September, because plants shaded early produced more shoots and ears after mid-July than unshaded plants. Early shading slightly decreased the final percentage of shoots that developed ears. Early shading increased shoot height by mid-July and late shading increased it by the end of the experiment. Effets de la diminution de l'intensie lumineuse sur la croissance de l'Agropyron repens (L.) Beauv, au champ Resume. De petites parcelles d'Agropyron repens (L.) Beauv. ont ete ombragies avec du ‘Tygan’ecran en treillis qui ne laisse passer que 46% environ de la lumere du jour. En 1968, les parcelles furent ombragees ou non pendant toute la duree de l'experience (de mi-mai a septembre); en 1969 certaines parcelles furent aussi ombragees precocement (de mi-mai a mi-julliet) ou tardivement (de mi-jmllet a septembre). Dans les deux experiences, l'ombrage continu reduisit de moitie le poids sec des rhizomes mais eut un effet beaucoup plus faible sur le poids sec de la partie aerienne. II reduisit egalement de 5% la matiere seche des rhizomes. Avec un ombrage precoce, il y eut moins de tiges et d'epis jusqua mi-juillet, mais cette difference n'existait plus en septembre paree que les plantes ombragees precocement produisirent apres la mi-juillet, plus de tiges et d'epis que les plantes non ombragees. L'ombrage precoce diminua le pourcentage final des tiges qui produisirent des epis. L'ombrage precoce augmenta la hauteur des tiges a la mi-juillet et l'ombrage tardif eut le meme effet a la fin de I'experience. Auswirkungen verringerter Lichtintensitat auf das Wachstum von Agropyron repens (L.) Beauv. Im Feld Zusammenfassung. Kleine Parzellen mit Agropyron repens (L.) Beauv. wurden mit ‘Tygan’ Abschirmmaterial, das etwa 46% des Tageslichts durchliess, beschattet. Im Jahre 1968 wurden die Parzellen wahrend der gesamten Versuchadauer (von Mitte Mai bis September) entweder beschattet oder nicht beschattet; 1969 wurden auch einige Parzellen fruh (von Mitte Mai bis Mitte Juli) oder spat (von Mittc Juli bis September) beschattet. In beiden Experimenten reduzierte durchgehende Beschattung das Rhizom-trockengewicht um die Halfte, hatte jedoch eine weit geringere Auswirkung auf das Trockengewicht der oberirdischen Teile. Die Rhizomtrockensubstanz war um 5% vermindert, Bei fruher Beschattung wurden bis Mitte Juli weniger Schosse und Ahren gebildet; dieser Unterschied war jedoch bis September wieder verschwunden, da beschattete Pflanzen ab Mitte Juli mehr Schosse und Ahren produzierten als unbeschattete. Fruhe Besehattung fuhrte zu einer leiehten Verringerung des Prozentsatzes der Schosse, die Ahren bildeten. Die Lange der Sehosse war Mitte Juli durch fruhe Beschattung vergrossert und am Ende des Experiments durch spate Besehattung.

The effect of D-D, chloropicrin and previous crops on numbers of migratory root-parasitic nematodes and on the growth of sugar beet and barley.

Abstract: SUMMARY Thirty-three gal D–D or chloropicrin/acre (371 l/ha) injected during winter into well-drained, sandy soils controlled Longidorus attenuatus, Trichodorus spp. and other migratory root-parasitic nematodes and resulted in greatly increased yields of sugar beet for at least 3 years; 2 years of bare fallow was less effective than soil fumigation. Trichodorus spp. multiplied more on sugar beet than on barley, whereas L. attenuatus multiplied more on barley and clover than on sugar beet.

Suspected Insecticide Resistance Mechanism in the Peach–Potato Aphid

Abstract: POPULATIONS of the peach–potato aphid, Myzus persicae (Sulzer), that have survived exposure to organophosphorus insecticides are sometimes received for identification in the British Museum (Natural History). Microscopical examination reveals that resistant populations have better developed lateral abdominal tubercles on segments 2–4 than susceptible populations. The resistance of Myzus persicae to demeton-methyl is not stable, a twenty-five-fold resistance being acquired during seven clonal generations exposed to it and lost during thirty generations not exposed1. Experiments being done at Rothamsted Experimental Station (C. J. B., in preparation) made it possible to study the morphology of aphids from susceptible and resistant aphid populations and to compare them with each other and with susceptible members of a previously resistant population.

An investigation into the high temperature strength and reinforcement of natural rubber

Abstract: The failure criterion for amorphous polymers relating hysteresis at break with energy input to failure in tensile stress-strain tests was found to be obeyed only at very high or very low temperatures in natural rubber Tensile results between about 80° C and 130° C show a high degree of scatter, and this behavior is attributed to the ability of natural rubber to crystallize at high strains The modification of tensile properties by the addition of carbon black in natural rubber is also discussed and compared with published results from SBR The effect of changing the degree of crosslinking on the failure properties in both dicumyl peroxide and sulfur-cured vulcanizates of natural rubber is also considered It is found that differences in failure properties can be accounted for by the use of a crosslinking parameter from simple rubber elasticity theory in some of the failure equations

Repellents for Stomoxys calcitrans (L.), the stable fly: techniques and a comparative laboratory assessment of butyl methylcinchoninate.

Abstract: An in vitro test, based on the molasses sandwich-bait test, for mass screening of new compounds for general insect repellency is described. This is followed by a detailed account of a laboratory technique for comparing the initial potency of contact repellents for the stable fly Stomoxys calcitrans (L.). Methods for rearing S. calcitrans of standardised aggressiveness and making comparative assessments of contact repellents against this fly are described. For initial potency, a standard area of the treated close-clipped abdominal skin of mice lying outside the cage was exposed through an orifice to standardised flies. A treated 0·5-cm-wide screen was incorporated as a border round the exposed area of treated skin so that flies biting the mouse were obliged to make tarsal contact with repellent. Using this method, and the organdie bag x human hand method for determining persistence on an inert substrate, each of the following repellents was compared with butyl 3-methylcinchoninate, a new repellent for S. calcitrans : dimethylphthalate; 2-ethyl-1, 3-hexanediol; butoxypolypropylene glycol; dibutyl succinate; N,N-diethyl-m-toluamide; di-n-propyl isocinchomeronate; 2,3,4,5-bis (Δ 2 -butenylene)-tetrahydrofurfural; 2-hydroxyethyl n-octyl sulphide and N-benzoyl piperidine. In each case butyl 3-methylcinchoninate was found to be superior. In the initial potency tests, the 50% repellency application rate was found to lie between 0·002 and 0·007 mg/cm 2 , while on organdie, rates of 0·2, 0·4, 0·8 mg/cm 2 gave mean protection periods of 9, 19 and 34 days, respectively.

Fat crystals and the flow rheology of butter and margarine

Abstract: The viscosities of fat crystals extracted by 1 % Aerosol O.T. from butter and margarine have been studied using a Weissenberg Rheogoniometer. By applying the Brodnyan (1959) equation for non-spherical particles to the viscosity data at high rates of shear, after correcting for secondary flow phenomena, it was deduced that the axial ratios of the margarine fat crystals were between 3.05 and 3.94, with the fat crystals from butter lying midway between the two extremes. By applying viscosity equations of the exponential type to such data, it should be possible to calculate the viscosity of butter and margarine at very high rates of shear when the viscosity of the liquid oil in the fat phase and the volume concentration of water drops are known. This information could be useful for predicting the spreadability characteristics of butter and margarine.

Studies on the growth of seedlings of agropyron repens (l.) beauv and agrostis gigantea roth.

Abstract: Summary. The growth of seedlings of Agropyron repens (L.) Beauv. and Agrostis gigantea Roth, in pots was studied in two experiments in 1968 and 1969. In Experiment 1 their growth was compared with that of wheat and in Experiment 2 they were grown in sandy loam (Woburn) and silt loam (Rothamsted) soil at four levels of nitrogen. Both species grew faster than wheat, mainly because they had a larger leaf area ratio. Tillering began earlier in wheat, but continued longer in the grasses, which eventually had many more shoots. Ears emerged in the order: wheat before Agropyron before Agrostis. Although Agrostis had much lighter seeds than Agropyron, it grew faster, but Agropyron initiated rhizomes sooner, usually when it had 1–2 tillers and 4 leaves. Agrostis did not initiate rhizomes until it had at least 10 tillers and 6 leaves. In Experiment 2 the seedlings at first grew more in Woburn than in Rothamsted soil but later more in Rothamsted than in Woburn soil. There was no evidence of a species/soil interaction but nitrogen had more effect on both species in Woburn than in Rothamsted soil. Neither soil type nor nitrogen affected the time at which rhizomes were initiated. Etude de la croissance de plantules d'Agropyron repens (L.) Beauv. et d'Agrostis gigantea Roth. Resume. La croissance de plantules A'Agropyron repens (L.) Beauv. et d'Agrostis gigantea Roth, cultivdes en pots a eteetudiee au cours de deux experiences en 1968 et 1969. Dans la premiere experience, leur croissance fut compareee a celle du ble et dans une seconde experience, ces deux especes furent cultivees sur un sol sablo-limoneux (Woburn) et sur un sol argilo-limoneux (Rothamsted) a quatre niveaux d'azote. Les deux mauvaises herbes pousserent plus vite que le ble, principalement en raison de leur rapport plus ealeve de surface foliaire. Le tallage commenga plus tot chez le bie, mais se poursuivit plus longtemps chez les deux mauvaises herbes qui, en fin de compte, eurent plus de tiges. L'epiaison se produisit dans l'ordre suivant: blea, Agropyron, Agrostis. Bien que I'Agrostis ait des semences plus petites que I'Agropyron, il poussa plus vite, mais I'Agropyron emit des rhizomes plus tot, habituellement au stade 1 a 2 talles et 4 feuilles. L'Agrostis n'emit pas de rhizome avant d'atteindre au moins le stade 10 talles et 6 feuilles. Dans la deuxieme experience, les plantules pousserent d'abord plus dans le sol de Woburn que dans celui de Rothamsted mais, plus tard, plus dans le sol de Rothamsted que dans Celui de Woburn. II ne fut pas decele d'interaction entre le sol et les especes, mais I'azote fit un effet plus marque sur les deux especes dans le sol de Woburn que dans celui de Rothamsted. Ni le type de sol, ni le niveau d'azote n'eurent d'influence sur l'epoque a laquelle les rhizomes commencerent de croitre. Untersuchungen zum Wachstum von Keirnpjlanzen von Agropyron repens (L.) Beauv. Und Agrostis gigantea Roih. Zusammenfassung. Das Wachstum von Keimpfianzen von Agropyron repens (L.) Beauv. und Agrostis gigantea Roth, in Topfen wurde 1968 und 1969 in zwei Versuchen untersucht. In Versuch II wurde das Wachstum mit dem von Weizen verglichen. In Versuch II wurden sie in sandigen Lehmboden (Woburn) und Silt-Lehm-(Rothamsted) Boden bei vier Stickstoffstufen angezogen. Beide Arten wuchsen in erster Linie wegen ihres grosseren Blattflachenanteils schneller als Weizen. Die Bestockung begann fruher bei Weizen, zog sich jedoch bei den Grasern, die schliesslich wesentlich mehr Halme hatten, langer hin. Ahrenschieben erfolgte am fruhesten bei Weizen, dann bei Agropyron und schliesslich bei Agrostis. Obgleich Agrostis viel leichtere Samen hatte als Agropyron, wuchs es schneller, doch entwickelte Agropyron fruher Rhizome, nornialerweise bei 1–2 Bestockungstriebe und 4 Blattern. Agrostis entwickelte Rhizome nicht ehe es mindestens 10 Bestockungstriebe und 6 Blatter hatte. In Versuch II wuchsen die Keimpflanzen zunachst besser in Woburn- als in Rothamsted-Boden, spater wieder besser in Rothamsted als in Woburn-Boden. Es gab keine Anhalts-punkte fur eine Interaktion zwisehen den Arten und dem Boden, doch wirkte Stickstoff bei beiden Arten besser in Woburn- als in Rothamsted-Boden. Weder Bodentyp noch Stickstoffmenge beeinflussten den Beginn der Rhizombfldung.

The effect of small doses of nematicides on migratory root-parasitic nematodes and on the growth of sugar beet and barley in sandy soils.

Abstract: SUMMARY Smaller amounts of D–D (6–12 gal/acre) (68–135 1/ha) or ethylene dibromide (9 gal/acre) (100 1/ha) than are customarily used to disinfest field soils killed many root-parasitic nematodes (Trichodorus, Pratylenchus, Tylenchorhynchus and Longidorus attenuatus) when injected 6–8 in (15–20 cm) deep during early autumn in rows 10 in (25 cm) apart in well-drained sandy soils. They also increased the yield of sugar beet grown in fields infested with Trichodorus or Longidorus attenuatus, without affecting sugar percentage or juice purity of the roots, and in some places increased the yield of barley grown after the beet. D–D was much less effective when injected 8–12 in deep during late autumn or winter. Increasing nitrogen dressings to the seedbed from 1·5 to 3 cwt/acre (188 to 376 kg/ha) increased sugar beet yield in one field, decreased it in another and decreased juice purity in both. In two other experiments extra nitrogen did not affect sugar beet yield. Even smaller amounts of the nematicides ‘placed’ in the rows, before or after sowing sugar beet in them, killed many of the nematodes and also increased sugar yield. Phytotoxic nematicides can be placed in the rows during autumn, winter or spring but placement is simpler during spring, when the treated rows are indicated by the position of the marks of the tractor wheels left when the nematicide was applied. When applied during autumn or winter, the rows need to be indicated by drilling wheat or grass.

Oriverutus Lobatus Gen. N., Sp. N. and Sicaguttur Sartum Gen. N., Sp. N. (Nematoda: Dorylaimoidea) From Cultivated Soils in Africa

Abstract: Oriverutus gen. n. differs from Eudorylaimus in having large amphids, long dorsal gland duct, anterior position of the outlets of the subventral glands in the oesophageal enlargement and glandular tissue forming a collar around the cardia. O. lobatus sp. n. is described from soil around roots of Oryza saliva in Ibadan, Nigeria. Eudorylaimus sundarus, E. hastatus and Longidorella impar are transferred to Oriverutus, and Tylencholaimus hastatus is renamed as Oriverutus hastulatus nom. nov. Sicaguttur gen. n. is similar to Thornenema but has narrow lateral hypodermal chords, two ovaries and a pointed, heavily sclerotized lip region. S. sartum sp. n. is described from soil around roots of Citrus nobilis and Oryza sativa in Abu Naama, Central Sudan. A new structure, the endolid, is found in the subventral sector of the oesophageal lining at some distance in front of the nerve ring in Sicaguttur and several other dorylaimid genera.

Automatic test equipment utilizing a matrix of digital differential analyzer integrators to generate interrogation signals

Abstract: In computer-controlled automatic test or check-out equipment, interrogation signals for application to a unit under test are generated by a matrix of digital differential analyzer integrators, the digital outputs of the matrix be applied to digital-to-analogue converters so as to produce analogue signals to be fed to the unit under test The computer provides initial control signals to determine the connections within the matrix and to set in initial values in the registers of the integrators, after which the matrix is driven by its own clock pulse generator, leaving the computer free for processing the response signals from the unit under test

The influence of tectonics on the geotechnical properties of Calabrian rocks and the mapping of slope instability using aerial photographs

Abstract: Summary The Calabrian peninsula is undergoing rapid degradation at the present time by erosion and landsliding. These phenomena are aggravated by the reduced strength of many of the rock formations forming the peninsula, resulting from Alpine tectonic movements. Maps showing landslides and related features were prepared, with the aid of aerial photographs, in conjunction with the geological re-mapping of the peninsula at a scale of 1 : 25 000.