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Showing papers by "University of Dundee published in 1969"


Journal ArticleDOI
W. E. Spear1
TL;DR: In this article, a platelet specimen is fitted with electrodes on opposite sides and charge carriers are generated near the top electrode by a fast excitation pulse, and a steady or pulsed applied field draws one type of carrier across the specimen and the transit time is determined either by charge integration or from the observed current transient.
Abstract: The paper reviews in some detail the principles and experimental techniques involved in drift mobility measurements. These are particularly suitable for transport studies in highly resistive, low mobility solids and examples of their application to crystalline and non-crystalline materials are given. A platelet specimen is fitted with electrodes on opposite sides and charge carriers are generated near the top electrode by a fast excitation pulse. Both light and electron pulses have been used and the particular advantages of electron beam excitation are discussed. A steady or pulsed applied field draws one type of carrier across the specimen and the transit time tt is determined either by charge integration or from the observed current transient. This leads directly to the drift mobility. A section of the paper deals with the effects of trapping on the measurements. Shallow centers, possessing a release time constant τ r « t t , lead at lower temperatures to a transport controlled by multiple trapping and release. Measurements in this range give information about such centres. Deep traps introduce disturbing polarisation effects and ultimately limit the applicability of the method. Details of a space charge neutralisation technique are given. A different, more “static” method developed by Davis is briefly described.

346 citations


Journal ArticleDOI
18 Oct 1969-Nature
TL;DR: The firm identification of the heterocysts as the sites of nitrogenase activity marks them out also as the site of nitrogen fixation in blue green algae.
Abstract: The firm identification of the heterocysts as the sites of nitrogenase activity marks them out also as the site of nitrogen fixation in blue green algae.

185 citations


Journal ArticleDOI
TL;DR: Potato mop-top virus (PMTV) was best detected in field soils by air-drying them for more than a week before remoistening and growing seedlings of Nicotiana tabacum or N. debneyi for a 6-10 week period as discussed by the authors.
Abstract: SUMMARY Potato mop-top virus (PMTV) was best detected in field soils by air-drying them for more than a week before remoistening and growing seedlings of Nicotiana tabacum or N. debneyi for a 6–10 week period. Infection of N. tabacum was assessed by inoculating sap from roots and shoots to Chenopodium amaranticolor. Similar inoculations from N. debneyi were far less convenient for detecting PMTV than recording leaf symptoms, but slightly more efficient. Air-dry soil retained PMTV infectivity for 9 months, when passed through a 50 μ sieve or when diluted with 103 but not 104 parts of steamed soil. Tobacco seedlings were not infected when their roots were steeped in PMTV-containing tobacco sap. Infective soils contained Spongospora subterranea, spore balls of which resisted air-drying for more than a year and passed a 50 μ sieve. Roots of susceptible seedlings were infected with PMTV when exposed to spore balls of S. subterranea taken from powdery scabs on PMTV-infected potato tubers, or to suspensions obtained by steeping, in nutrient solution, roots infected with virus-carrying cultures of S. subterranea. Plants in several families were hosts of S. subterranea, but probabilities of infection when exposed to spore balls differed greatly between families and only species of Solanaceae were good hosts. The ten species infected with PMTV when grown in infective soil or when exposed to spore balls of S. subterranea taken from PMTV-infected potato tubers are all members of this family. PMTV seems to be carried internally in S. subterranea spore balls and survived in them for at least a year. PMTV was transmitted by S. subterranea to Arran Pilot potato, causing yellow blotches in some leaves and spraing in many tubers. However, when newly infected with PMTV in the field, not all Arran Pilot tubers developed spraing. Also, although many spraing-affected or symptomless but PMTV-infected tubers carried PMTV-containing spore balls of S. subterranea, powdery scabs were rarely found near the centres of the rings of primary spraing. PMTV became established in virus-free soil when PMTV-infected tubers carrying S. subterranea were planted as ‘seed’ but not when virus-free tubers bearing powdery scabs were used. 5. subterranea seems the main, and possibly the only, vector of PMTV in the soils examined. S. subterranea did not transmit potato aucuba mosaic virus from potato to N. debneyi or Capsicum annuum.

170 citations


Journal ArticleDOI
TL;DR: Using an electrolytic hygrometer, the Transepidermal Water Loss from the skin was measured in normal individuals and in patients with dermatitis and it was found that there was a close correlation between T.W.L. and the state of activity of the dermatitis.
Abstract: SUMMARY.— Using an electrolytic hygrometer, the Transepidermal Water Loss (T.W.L.) from the skin was measured in normal individuals and in patients with dermatitis (eczema). It was found that there was a close correlation between T.W.L. and the state of activity of the dermatitis; and that there was a gradual reduction in abnormally raised T.W.L. in parallel with the return to normal of the skin response (dermatitis). Sweating did not contribute to the increased insensible water loss in dermatitis under the fixed limits of ambient temperature and humidity of this investigation.

86 citations


Journal ArticleDOI
01 Dec 1969-Planta
TL;DR: Detached soybean nodules reduce acetylene at a constant rate for at least 8 hours provided that only small quantities of nodules per unit volume of gas are used.
Abstract: Detached soybean nodules reduce acetylene at a constant rate for at least 8 hours provided that (1) only small quantities of nodules per unit volume of gas are used, (2) when incubated in aqueous media they are given sufficient oxygen and shaken, (3) they are not allowed to dry out.

72 citations


Journal ArticleDOI
TL;DR: It is shown that at higher levels of fat intake the unabsorbed fat may interfere profoundly with the absorption of calcium, and that there may be an association between the type and amount of fat that an infant receives and hypocalcaemic tetany.

64 citations


Journal ArticleDOI
TL;DR: In this paper, the authors used differential thermal analysis and X-ray powder diffraction studies to determine the temperatures of phase transitions in each of these compounds, and observed a phase transition in CdSiP2 at 1098° C some 22° C below the melting point.
Abstract: ZnSnP2, ZnGeP2, ZnSiP2, CdGeP2 and CdSiP2 have been prepared in single or polycrystalline form by direct synthesis from the elements, combination of the group IV element with the II-V2 phosphide, vapour transport or solution growth. Differential thermal analysis and X-ray powder diffraction studies have been used to determine the temperatures of phase transitions in each of these compounds. Of particular interest is the observation of a phase transition in CdSiP2 at 1098° C some 22° C below the melting point. The thermal analysis studies of ZnSnP2 indicate a peak, the cause of which is uncertain, at 720° C which is well separated from the melting temperature of 930° C; further ZnSnP2 does not appear to be congruently melting and has a freezing point at 970° C. c/a ratios have been determined for all five compounds to 1 part in 2000.

56 citations


Journal ArticleDOI
TL;DR: Electron microscopy of thin sections of Longidorus elongatus (de Man) fed on plants infected with raspberry ringspot and tomato black ring viruses showed virus-like particles in the lumen of the buccal capsule and in the space between the stylet and the guiding sheath.
Abstract: SUMMARY Electron microscopy of thin sections of Longidorus elongatus (de Man) fed on plants infected with raspberry ringspot and tomato black ring viruses showed virus-like particles in the lumen of the buccal capsule and in the space between the stylet and the guiding sheath. In sections of L. elongatus fed on plants infected with arabis mosaic virus, which it does not normally transmit, a few virus particles were seen in the buccal capsule but none was associated with the stylet guiding sheath. It is suggested that the association of virus particles with the cuticular guiding sheath is an explanation of the specificity of virus transmission evident in L. elongatus.

55 citations



Journal ArticleDOI
TL;DR: The present study was undertaken to investigate the possibility that even under normal conditions some women may be severely hypoxaemic during pregnancy and to measure the effect of maternal age and the duration of pregnancy on the arterial oxygen tension.

38 citations


Journal ArticleDOI
TL;DR: In this paper, a single crystal ZnGeP2 has been prepared by slow cooling from the melt and by vapour transport of the constituent elements in a phosphorus atmosphere, and thermal analysis measurements give a phase change at (952 ± 2) °C, probably disordering of chalcopyrite to zinc blende, and congruent melting at 1025 °C.
Abstract: Single crystal ZnGeP2 has been prepared by slow cooling from the melt and by vapour transport of the constituent elements in a phosphorus atmosphere. X-ray powder studies lead to a c/a ratio for the chalcopyrite-structured ZnGeP2 of 1.961. Thermal analysis measurements give a phase change at (952 ± 2) °C, probably disordering of chalcopyrite to zinc blende, and congruent melting at 1025 °C. Resistance-temperature investigations suggest that acceptor levels at 0.10 and 0.62 eV control the free carrier concentration above and below room temperature, respectively. Undoped ZnGeP2 is always p-type. Minority carrier studies point to an electron mobility between 103 and 104 cm2/Vs. Photoconductivity and optical absorption measurements lead to the conclusion that the direct energy gap in ZnGeP2 is 2.25 eV. ZnGeP2-Einkristalle wurden durch langsame Abkuhlung aus der Schmelze und durch Transport der Komponenten in einer Phosphoratmosphare erhalten. Rontgenstrahlenuntersuchungen des Pulvers ergaben ein c/a-Verhaltnis fur die Chalcopyrit-Struktur des ZnGeP2 von 1,961. Eine thermische Analyse ergab eine Phasenanderung, vermutlich von der Chalcopyrit- zur Zinkblendestruktur, bei (952 ± 2) °C und einen kongruenten Schmelzpunkt bei 1025 °C. Eine Untersuchung der Temperaturabhangigkeit des Widerstands zeigt, das Akzeptorniveaus bei 0,10 und 0,62 eV die Konzentration der freien Ladungstrager oberhalb bzw, unterhalb Zimmertemperatur steuern. Undotiertes ZnGeP2 ist immer p-leitend. Untersuchungen der Minoritatsladungstrager weisen auf eine Elektronenbeweglichkeit zwischen 103 und 104 cm2/Vs hin. Messungen der Photoleitfahigkeit und der optischen Absorption ergeben eine direkte Bandlucke in ZnGeP2 von 2,25 eV.

Journal ArticleDOI
25 Jan 1969-Nature
TL;DR: The physical nature of the wound collagen, that is, fibre shape and weave, probably plays an important part in determining these properties and it was decided to look at the structure of the wounds directly to see if this could explain the mechanical findings.
Abstract: ENGINEERING techniques have shown that the apparently “healed” incised skin wound in the rat is weaker and more brittle than unwounded skin up to 5 months after the beginning of healing. Tensile strength increases with time, but there is no tendency for extensibility to recover after the first month1,2. The physical nature of the wound collagen, that is, fibre shape and weave, probably plays an important part in determining these properties3. We therefore decided to look at the structure of the wounds directly to see if this could explain the mechanical findings.

Journal ArticleDOI
01 Feb 1969-Heredity
TL;DR: The population genetics of insect introduction, including Genetics of marginal populations of Drosophila willistoni, 1968, and the population Biology of the butterfly, Euphydras editha IV, 1968.
Abstract: DOBZHANSKY, T., HUNTER, A. S., PAVLOVSKY, 0., SPASSKY, B., AND WALLACE, B. 1963. Genetics of natural populations. XXXI. Genetics of an isolated marginal population of Drosophila pseudobscurra. Genetics, 48, 91. DODD, A. P. 1940. The Biological Campaign against Prickly-Pear. Commonwealth PricklyPear Board, Brisbane. FRENCH, c. 1893. A Handbook of the Destructive Insects of Victoria. Part II; Government Printer, Melbourne. MASON, L. G., EHRLICH, P.R., AND EMMEL, T. C. 1968. The population Biology of the butterfly, Euphydras editha. IV. Phenetics of the Jneper Ridge colony, 1965-66. Evolution, 22, 46. ELTON, C. S. 1958. The Ecology of Invasions by Animals and Plants. Methuen, London. REMSNGTON, C. L. 1968. The population genetics of insect introduction. Ann. Rev. Entomol., 13, 415. TOwNSEND, j. I., JR. 1952. Genetics of marginal populations of Drosophila willistoni. Evolution, 6, 428. TURNER, J. R. 0., AND WILLIAMSON, M. H. 1968. Toleration of a Genetic Load. Nature, 218, 5142, 700.

Journal ArticleDOI
TL;DR: The chronic polymorphic light eruptions are a miscellaneous group of cutaneous reactions in which the responsible action spectrum probably lies in the sunburn range and in the long u.v. (320 to 400 nm.) and visible and visible ranges.
Abstract: SUMMARY.— The chronic polymorphic light eruptions are a miscellaneous group of cutaneous reactions in which the responsible action spectrum probably lies in the sunburn range (290 to 320 nm.) and in the long u.v. (320 to 400 nm.) and visible (above 400 nm.) ranges. A group of 25 such cases is described and details are given of the results of phototesting, using a high pressure Xenon arc light source with appropriate filters. Evidence is presented in support of the possibility that in this group there may be a specific entity which occurs most often in females, appearing for the first time usually before adult life and lasting for up to 30 to 40 years. In this group no abnormality of porphyrin metabolism can be detected. The action spectra appear to lie both within and above the sunburn range: there is some evidence to suggest that a border zone between 305 and 325 nm. may be particularly relevant.

Journal ArticleDOI
TL;DR: English isolates of raspberry ringspot (RRV) and tomato black ring viruses (TBRV) showing slight serological differences were associated in the field with the nematode Longidorus elongatus and were all transmitted equally efficiently by this species in laboratory experiments.
Abstract: SUMMARY Scottish isolates of raspberry ringspot (RRV) and tomato black ring viruses (TBRV) showing slight serological differences were associated in the field with the nematode Longidorus elongatus and were all transmitted equally efficiently by this species in laboratory experiments. Forms of both viruses from southern England and Germany that are distantly serologically related to the Scottish isolates were also transmitted experimentally by L. elongatus, although in the field they are associated with other Longidorus species. L. elongatus transmitted English isolates of RRV almost as efficiently as the Scottish isolates but it transmitted English and German isolates of TBRV only occasionally. Four isolates each of TBRV and RRV were detected by inoculating plants with extracts of nematodes; the results paralleled those of the vector studies.

Journal ArticleDOI
TL;DR: Only small fractions of populations of Bacillus subtilis, known as competent fractions, can take up transforming DNA and integrate it into their chromosomes, and it is proposed that the single-stranded regions in each associate by hydrogen bonding leads to integration of transforming DNA into the chromosome and eventually, following some repair, to alteration of genetic information.

Journal ArticleDOI
TL;DR: Conidia of Cochliobolus sativus incubated on natural soil became perforated by holes 0·5–4 μ m diam, apparently developing from pits eroded into the surface.
Abstract: Conidia of Cochliobolus sativus incubated on natural soil became perforated by holes 0·5–4 μ m diam. Normal and perforated conidia were examined with conventional and scanning electron microscopes. The wall of the conidium consisted of three distinct layers. The two inner fibrillar layers, septa and cell contents were disrupted in perforated conidia, leaving the outer layer breached by several holes. The holes occurred at random over the conidium, apparently developing from pits eroded into the surface.

Journal ArticleDOI
TL;DR: Rates of fruit maturation varied according to the chemical stimulus inducing parthenocarpy, and treatment with 2-N0A led to a longer period of fruit development and relatively larger fruits at maturity in spite of a low rate of growth throughout the second growth phase.
Abstract: Growth-rates of receptacles developing after pollination were compared with those of a similar set developing parthenocarpically after treatment with 2-naph thoxyacetic acid (2-N0A). The latter grew slightly more rapidly during the first 10 days, and entered the final ripening phase at the same time as the pollinated receptacles, but in the intervening period the growth-rate of parthenocarpic receptacles was much reduced. Applications of 2-N0A and gibberellic acid separately and in combination were compared at anthesis, and the effects of supplementary treatments 10 days later were investigated. Either chemical was capable of stimulating initial partheno carpic development and maturation of the ripe fruit, but neither one alone maintained rapid growth throughout the second phase of fruit development. Com binations of 2-N0A and gibberellic acid at high levels, and 2-N0A and a mixture of gibberellins A4 and A, at lower levels, applied either together at anthesis, or sequentially during development effectively maintained growth rates throughout the whole developmental period. Rates of fruit maturation varied according to the chemical stimulus inducing parthenocarpy. Treatment with gibberellins resulted in early maturity and relatively small fruits. Treatment with 2-N0A led to a longer period of fruit development and relatively larger fruits at maturity in spite of a low rate of growth throughout the second growth phase.

Journal ArticleDOI
TL;DR: The time and frequency of occurrence of granular cytoplasmic bodies in oocytes of the golden hamster has been investigated and the possible significance of the bodies is discussed.
Abstract: The time and frequency of occurrence of granular cytoplasmic bodies in oocytes of the golden hamster has been investigated. The bodies are first seen immediately after birth when most of the germ cells have commenced meiotic prophase. They increase in frequency until approximately twelve days post-natal, at which time most oocytes have attained the dictyate stage. After this, frequency of occurrence of the bodies declines. Very few have been noted in adult material. The possible significance of the bodies is discussed.



Journal ArticleDOI
TL;DR: It is suggested that the culturing excised embryos on sterile nutrient medium may prove useful in the production of hybrids from other lily species-combinations which are not normally viable.
Abstract: Lilium lankongense crossed with some related species of Lilium produced seeds without endosperm and with very small embryos which would not germinate in soil. Hybrid plants have been obtained from a number of these crosses by culturing excised embryos on sterile nutrient medium. It is suggested that the technique may prove useful in the production of hybrids from other lily species-combinations which are not normally viable.

Journal ArticleDOI
TL;DR: Mycoplasma-like bodies were found by electron microscopy of sections of sieve tubes, both from shoots and roots of potato plants affected by Scottish witches' broom disease and from graft-inoculated tomato shoots.
Abstract: SUMMARY Mycoplasma-like bodies were found by electron microscopy of sections of sieve tubes, both from shoots and roots of potato (Solanum tuberosum) plants affected by Scottish witches' broom disease and from graft-inoculated tomato shoots. The bodies were bounded by a unit membrane, contained ribosome-like material and mostly measured 200–800 nm in diameter. Most were oval in cross-section but some had lobes or slender protrusions. Some of the bodies were found in the mouths of sieve pores.

Journal ArticleDOI
TL;DR: Theorem 3.1 is a criterion for a nilpotent metabelian p-group to be regular as mentioned in this paper, and Theorem 4.3 is an explicit bound for the exponent of AB in terms of the exponents of A and B. In the case of AB, it is shown that AB has finite exponent i r a and B have.
Abstract: Several investigations have been made of the relation between power structure and commutator structure in metabelian groups, especially metabelian p-groups; see for instance Meier-Wunderli [5] and Gupta and Newman [2]. In the present paper we undertake a more detailed study of two classes of nilpotent metabelian p-groups, denoted by ~p and g'p respectively. It turns out that these classes have very special properties even though each generates the variety 92~ of all metabelian groups. Let p be a fixed prime. If p > 2 then we define ~p to be the class of all regular metabelian p-groups. That ~p generates 9J~ is proved in [4 I. The general resemblance between metabelian p-groups and regular p-groups, such as commutator relations that are adapted to calculation, gives some interest to the investigation of ~p which we undertake in w 3. The main result, Theorem 3.1, is a criterion for a nilpotent metabelian p-group to be regular. Since regularity is defined in terms of two-generator subgroups, it is hardly surprising that our criterion is also in terms of two-generator subgroups. Next we define ~'p to be the class of all nilpotent groups of the form AB where A and B are both abelian p-groups. It is a theorem of It6 [3] that ensures t r that ~p consists of metabelian groups, and the fact that ~p generates 9J~ is an easy consequence of the proof of the main result in [4]. Our attention was drawn to ~'p by Kegel at the International Conference on the Theory of Groups, Canberra, 1965. He raised and has since answered affirmatively two questions about the group AB where A and B are periodic abelian: (i) Is A B periodic? (ii) Does A or B contain an element of given prime order if AB does? It follows from the answer to (i) and by a standard argument with Cartesian products that AB has finite exponent i r a and B have. In the case that A and B are abelian p-groups, we are able to give in Theorem 4.3 an explicit bound for the exponent of AB in terms of the exponents of A and B. Our Corollary 4.2 and Theorem 4.3 below have been improved following a comment of Kegel, whom we thank for his help. The classes gp and ~'p are defined by pleasant properties and in a certain sense form large subclasses of 9J~. It is therefore mildly surprising that we can

Journal ArticleDOI
TL;DR: In this article, it was shown that the addition of butyl lithium to pyridine has been observed using NMR spectroscopy in the 4-position, but not in the 6-position.

Journal ArticleDOI
01 May 1969-Cancer
TL;DR: The histoenzymatic activity of numerous hydrolytic and oxidative enzymes was determined in cryostat sections of fresh tissues obtained surgically from patients with gastric carcinoma, 18 normal subjects, and 28 patients with chronic atrophic gastritis and intestinal metaplasia.
Abstract: The histoenzymatic activity of numerous hydrolytic and oxidative enzymes was determined in cryostat sections of fresh tissues obtained surgically from 15 patients with gastric carcinoma, 18 normal subjects, and 28 patients with chronic atrophic gastritis and intestinal metaplasia. The average enzyme activity in malignant cells was less than that found in intestinal metaplasia but greater than that found in normal gastric surface epithelium. Stromal inflammatory cells exhibited activity for acid phosphatase and B‐glucuronidase, and smooth muscle fibers stained for the lactic and succinic dehydrogenases and DPN and TPN diaphorases. These elements and the islands of intestinal metaplasia found in malignancy‐bearing stomachs may contribute to the elevated levels of certain enzymes found biochemically in gastric secretions and tissue homogenates from patients with gastric carcinoma. Lactic dehydrogenase and the diaphorases were found in many carcinomata whereas succinic dehydrogenase was found in only one case. This pattern may be related to the high glycolytic rate characteristic of most malignant tumors, including those arising in the stomach.

Journal ArticleDOI
TL;DR: E eggplant mosaic virus (EMV), obtained from Solanum melongena L. from Trinidad, is readily transmitted by inoculation of sap to several solanaceous and a few non-solanaceous plant species, but is more virulent than Andean potato latent virus.
Abstract: SUMMARY Eggplant mosaic virus (EMV), obtained from Solanum melongena L. from Trinidad, is readily transmitted by inoculation of sap to several solanaceous and a few non-solanaceous plant species. Purified preparations of EMV contain isometric particles 30 nm in diameter, and with sedimentation co efficients of either 111 or 53 S. The particles have thirty-two major morphological subunits. EMV is closely serologically related to Andean potato latent virus and has a similar host range, but is more virulent. Also, whereas EMV accumulates fastest in Nicotiana clevelandii leaves at 20–24 °C, Andean potato latent virus accumulates fastest at 15 °C, and fails to attain a serologically detectable concentration at 24 °C. A few symptomatologically or serologically distinguishable strains of EMV were obtained. EMV has properties typical of viruses of the Andean potato latent subgroup of the turnip yellow mosaic group of viruses, and its present cryptogram is */*:*/*:S/S:S/Cl.

Journal ArticleDOI
TL;DR: In this article, the authors extended the solution of Terrill and Shrestha [2] to include the effect of the elasticity of the fluid, and they found that the fluid comes into effect only when suction or blowing is present.
Abstract: The two-dimensional steady flow of an incompressible elastico-viscous fluid through a porous channel that has the fluid sucked or injected with different normal velocities V 1 and V 2 at the walls is considered. For the viscous case Terrill and Shrestha [2] have given a series solution for small suction Reynolds number. In this paper the solution of [2] is extended to include the effect of the elasticity of the fluid. It is found that the elasticity of the fluid comes into effect only when suction or blowing is present. The general expressions for the pressure distribution and the friction coefficient are given and are found to increase as the elastic parameter increases. Finally, the resulting solution is confirmed by numerical results.

Journal ArticleDOI
Neil Cooper1
01 Apr 1969-Mind

Journal ArticleDOI
TL;DR: Crop and weed plants were compared as hosts for Longidorus elongatus and the viruses it transmits, raspberry ringspot (RRV) and tomato black ring (TBRV), and on a favourable host at least 12 eggs were produced by a female.
Abstract: SUMMARY Crop and weed plants were compared as hosts for Longidorus elongatus and the viruses it transmits, raspberry ringspot (RRV) and tomato black ring(TBRV). For the nematode, strawberry (Fragaria × ananassa), grasses and clovers were the most favourable hosts but most of the crop plants were poor or non-hosts. All the weeds except Agropyron repens supported significantly greater populations of L. elongatus than the fallow controls. RRV and/or TBRV were detected in most of the experimental plant species during, or after, the 15-wk exposure to viruliferous nema-todes. The frequency of infection was generally highest amongst the weeds and was usually but not always related to suitability as a host for the nematode vector. The one is therefore not necessarily an index of the other. Feeding by L. elongatus caused distortion or swelling of the sub-terminal portion of a few roots in many of the plant species tested. On a favourable host at least 12 eggs were produced by a female.