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Rhodeo, Vol. 17, No. 6

  • Date: 1963-05-02
  • Subjects: Grahamstown -- Newspapers , Journalism, Students -- South Africa , Rhodes University -- Activate , Rhodes University -- Students , Student newspapers and periodicals -- South Africa
  • Language: English
  • Type: Text
  • Identifier: vital:14482 , http://hdl.handle.net/10962/d1019354
  • Description: Rhodeo is the Independent Student Newspaper of Rhodes University. Located in Grahamstown, Rhodeo was established in 1947, and renamed in 1994 as Activate. During apartheid Rhodeo became an active part of the struggle for freedom of expression as part of the now defunct South African Student Press Union. Currently Activate is committed to informing Rhodes University students, staff and community members about relevant issues, mainly on campus. These issues range from hard news to more creative journalism. While Activate acts as a news source, one of its main objectives it to be accessible as a training ground for student journalists. The newspaper is run entirely by the students and is published twice a term. Activate is a free newspaper which receives an annual grant from the Rhodes University Student Representative Council, however, majority of its revenue is generated through advertising.
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  • Date Issued: 1963-05-02

Rhodeo, Vol. 17, No. 4

  • Date: 1963-03-28
  • Subjects: Grahamstown -- Newspapers , Journalism, Students -- South Africa , Rhodes University -- Activate , Rhodes University -- Students , Student newspapers and periodicals -- South Africa
  • Language: English
  • Type: Text
  • Identifier: vital:14480 , http://hdl.handle.net/10962/d1019352
  • Description: Rhodeo is the Independent Student Newspaper of Rhodes University. Located in Grahamstown, Rhodeo was established in 1947, and renamed in 1994 as Activate. During apartheid Rhodeo became an active part of the struggle for freedom of expression as part of the now defunct South African Student Press Union. Currently Activate is committed to informing Rhodes University students, staff and community members about relevant issues, mainly on campus. These issues range from hard news to more creative journalism. While Activate acts as a news source, one of its main objectives it to be accessible as a training ground for student journalists. The newspaper is run entirely by the students and is published twice a term. Activate is a free newspaper which receives an annual grant from the Rhodes University Student Representative Council, however, majority of its revenue is generated through advertising.
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  • Date Issued: 1963-03-28

Rhodeo, Vol. 17, No. 3

  • Date: 1963-03-21
  • Subjects: Grahamstown -- Newspapers , Journalism, Students -- South Africa , Rhodes University -- Activate , Rhodes University -- Students , Student newspapers and periodicals -- South Africa
  • Language: English
  • Type: Text
  • Identifier: vital:14479 , http://hdl.handle.net/10962/d1019351
  • Description: Rhodeo is the Independent Student Newspaper of Rhodes University. Located in Grahamstown, Rhodeo was established in 1947, and renamed in 1994 as Activate. During apartheid Rhodeo became an active part of the struggle for freedom of expression as part of the now defunct South African Student Press Union. Currently Activate is committed to informing Rhodes University students, staff and community members about relevant issues, mainly on campus. These issues range from hard news to more creative journalism. While Activate acts as a news source, one of its main objectives it to be accessible as a training ground for student journalists. The newspaper is run entirely by the students and is published twice a term. Activate is a free newspaper which receives an annual grant from the Rhodes University Student Representative Council, however, majority of its revenue is generated through advertising.
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  • Date Issued: 1963-03-21

An investigation into the spelling ability of English-speaking and Afrikaans-speaking pupils in South African schools

  • Authors: Hayward, Fritz Reitz
  • Date: 1963
  • Subjects: English language -- Orthography and spelling -- Study and teaching , Afrikaans language -- Orthography and spelling -- Study and teaching
  • Language: English
  • Type: Thesis , Masters , MEd
  • Identifier: vital:1972 , http://hdl.handle.net/10962/d1012238 , English language -- Orthography and spelling -- Study and teaching , Afrikaans language -- Orthography and spelling -- Study and teaching
  • Description: The parlous state in which the English language finds itself in South Africa, both in its written and speech forms, is the cause ot grave concern to most English-speaking citizens, and to many Afrikaans-speaking people as well. This is the case not only in the commercial world and the civll service, but also in the schools and universities, and in fact in most walks of life. Although we are conscious of this state of affairs, and can quote many examples of the poor quality of English used, we have no measuring device through which we can assess exactly how bad the language used by any given group of people is. It is not possible to compare the performance in English of a certain school with standard English and to express the result as a percentage score. The aim of this investigation was to find out how well, or how badly, South African school children spell, and to compare the performances of English- and Afrikaansspeaking pupils. It was felt that the results would provide some concrete evidence and fairly accurate data which could be used to assess the standard of English spelling in our schools, and to pinpoint some of the major weaknesses. The writer hoped, thus, that the investigation might be of some practical usefulness to teachers of English spelling, and as spelling is basic to the written word and to some extent to the spoken word, it might make some small contribution to the drive towards better English in South African schools.
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  • Date Issued: 1963

An investigation of the radio emission by the planet Jupiter on 18 Mc/s & 22 Mc/s

  • Authors: Gruber, Georg Maria
  • Date: 1963
  • Subjects: Radio astronomy , Jupiter (Planet) -- Observations , Radio sources (Astronomy)
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:5524 , http://hdl.handle.net/10962/d1012113 , Radio astronomy , Jupiter (Planet) -- Observations , Radio sources (Astronomy)
  • Description: This thesis describes the investigation carried out of the radio noise emitted by the planet Jupiter on 18 Mc/s and 22 Mc/s. Chapter I gives a brief introduction and outlines radioastronomical as well as astronomical ideas concerning Jupiter. A detailed survey of the research done to date including some of the hypotheses formulated by previous workers is presented in Chapter II . Chapter III deals with the apparatus used in this research. Two similar sets of apparatus were used. The aerials were folded dipoles. The signals were fed to the receiver, an R 206 , via a 300 ohm impedance line. To increase the gain an extra I -F. stage was included. This gave a gain of better than a 120 dB. To match the signals into the recorder a cathode follower was used. The operating procedure appears in the fourth chapter. The results obtained are discussed and tabulated at the end of the chapter. They agree with the findings made by previous workers, within the experimental limit. Histograms of the occurrence probability versus the revised System III coordinates are presented for each frequency and compared to previous ones. The final chapter contains the author ' s interpretation of the observed effects. A model based on a radiation analogous to the Cerenkov effect is found to be not inconsistent with the available data . Ending the chapter suggestions for further research are made.
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  • Date Issued: 1963

An x-ray investigation of the thermal decomposition of unirradiated and irradiated silver permanganate.

  • Authors: Woods, Geoffrey Steward
  • Date: 1963
  • Subjects: Decomposition (Chemistry) , Materials -- Thermal properties , Solids -- Thermal properties , Permanganates , Silver compounds
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4511 , http://hdl.handle.net/10962/d1013450
  • Description: [From Introduction] The first step in the study of the thermal decompositions of solids is an examination of the kinetics, since this casts much light on the mechanism of the reaction. It must be borne in mind, however, that a theoretical expression, derived on the basis of a particular mechanism, even if it fits the observed experimental results, is not conclusive proof of the validity of the mechanism when applied to the decomposition under examination.
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  • Date Issued: 1963

Aspects of form and style in Beethoven's string quartets

  • Authors: Biesheuvel, Barbara
  • Date: 1963
  • Subjects: Beethoven, Ludwig van, 1770-1827 -- Quartets -- strings
  • Language: English
  • Type: Thesis , Masters , MMus
  • Identifier: vital:2678 , http://hdl.handle.net/10962/d1007645
  • Description: Many books have been written which deal with the subject of form and style in Beethoven's works. Most writers, however, seem to be satisfied with superficial descriptions - in some cases merely programatic - which do not explain the underlying problems and treatment of form. Furthermore, no book exists, to my knowledge, which delves so deeply and with such detail as to deduce with almost certain accuracy the inner coherency of the form. It is the aim of this analysis to approach the problem in this way. The edition used for this purpose is that one published by Ernst Eulenberg Ltd. London WI, which was edited from the autograph M.S. by Professor Dr. Wilhelm Altman. No comparisons are made with other editions, and possible printer's and other errors are not considered. I chose the works to be studied here, the three quartets Op. 59, for two reasons: 1) the string quartet medium is one of the most suitable types of instrumental music for the study of form, 2) the Op. 59 quartets belong to a period in Beethoven's life when he was particularly intent upon experimentation in form and development of dimension.
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  • Date Issued: 1963

Between Renaissance and Baroque: a study of the keybord works of Frescobaldi

Contributions to our knowledge of the biology of Machiloides Delanyi Wygodzinsky and Ctenolepisma Longicaudata Escherich : (Hexapoda Thysanura)

  • Authors: Heeg, J. (Jan)
  • Date: 1963
  • Subjects: Insects -- Adaptation , Insects -- Physiology , Thysanura , Apterygota
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:5856 , http://hdl.handle.net/10962/d1012261 , Insects -- Adaptation , Insects -- Physiology , Thysanura , Apterygota
  • Description: Among the South African Thysanura, the order Lepismatoidea has spread over the whole sub-continent, while all except one species of the order Machiloidea are confined to the discontinuous forest belt which lies below the escarpment of the inland plateau. The Machiloidea are not , however, strictly confined to the actual forests within their geographical region, some species invading regions of considerable aridity. Investigations on the ecology, water relations and orientation behaviour of a representative species of each order have been carried out. These have revealed that: (i) the physical conditions in the typical niche of the Machiloidea are extremely stable, whereas those in the habitat of the Lepismatoidea are subject to some considerable fluctuation. (ii) the Lepismatoidea are more resistant to desiccation than the Machiloidea; in both cases this resistance is due in part to physical barriers in the cuticle and partly to an active metabolic process. (iii) the Machiloidea rely on their eversible vesicles, situated on the abdominal coxosternites, for the uptake of water which cannot be drunk, such as a thin film of water or soil capillary water. (iv) the Lepismatoidea are able to absorb water from a subsaturated atmosphere. (v) the behavioural responses of both in respect of humidity, temperature, light and gravity, are such as to keep them in conditions within the range of their physiological limitations. From these results it is concluded that the Machiloidea can survive outside the shelter of forests, provided that water is readily available in some form in which it can be absorbed by the animals. The general implications of the results are such as to permit the erection of an hypothesis explaining the distribution of the Thysanura in South Africa in terms of t he availability of wate. The results also lead to speculations on the evolution of the Pterygota.
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  • Date Issued: 1963

On the physiology of the lantern retractor muscle of Parechinus angulosus

  • Authors: Boltt, R E
  • Date: 1963
  • Subjects: Echinodermata -- Physiology
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:5900 , http://hdl.handle.net/10962/d1013513
  • Description: From Resumé: The lantern retractor muscles of regular echinoids act in almost isometric conditions and a study of their control was considered to be of interest. The retractor muscles cannot be indirectly stimulated from the radial nerves, but proved to be very photosensitive. Their responses to light were therefore studied. The muscles show a complex pattern of contraction in response to illumination, which includes both excitatory and inhibitory components. The possible genesis of these patterns is discussed and examined in the light of the responses of the muscles to direct current stimulation and to drugs. It is concluded that many of the features of the response are undoubtedly neurogenic in origin, but that myogenic activity may possibly also be involved.
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  • Date Issued: 1963

Prototypes of black wattle tannins and their stereochemistry

  • Authors: Drewes, Siegfried Ernst
  • Date: 1963
  • Subjects: Tannins -- Anthocyanidis Stereochemistry
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:4460 , http://hdl.handle.net/10962/d1011437
  • Description: A number of interrelated flavonoid compounds, present in trace quantities in mature black wattle (Acacia mearnsii De Wild) bark, have been isolated and identified for the first time. They include a) the resorcinol-pyrogallol analogues, (+)-leuco-robinetinidin (7,5',4',5'-tetrahydroxyflavan-3,4-diol), dihydrorobinetin (7,5',4',5'-tetrahydroxyflavan-3-ol-4-one) and robtein (2',4',5,4,5- pentahydroxychalcone) and b) the resorcinol-catechol analogues, (+)-leuco-fisetinidin (7,3',4'-trihydroxyflavan-3,4-diol), fustin (7,3',4'-trihydroxyflavan-3-ol-4-one), (-)-fisetinidol (7,3',4'trihydroxyflavan- 3-ol), butein (2',4',3,4-tetrahydroxychalcone) and butin (7,5',4'-trihydroxyflavan-4-one). In addition, two flavonol glycosides, myricitrin (3,5,7,3',4',5'-hexahydroxyflavone-3-rhamnoside ) and quercitrin (5,5,7,5',4'-pentahydroxyflavone-3-rhamnoside), which belong to the phloroglucinol-pyrogallol and phloroglucinolcatechol class of flavonoids respectively, were isolated from immature bark. These represent the only glycosides isolated hitherto from wattle bark or heartwood extracts. Summary, p. i.
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  • Date Issued: 1963

Rhodes University Graduation Ceremony 1963

  • Authors: Rhodes University
  • Date: 1963
  • Language: English
  • Type: text
  • Identifier: vital:8097 , http://hdl.handle.net/10962/d1004418
  • Description: Rhodes University Graduation Ceremonies on Saturday 6 April 1963 at 11 a.m. in the University Great Hall [and] Saturday 4 May 1963 at 11 a.m. in the University Great Hall.
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  • Date Issued: 1963

Some properties of a model F1 layer of the ionosphere

  • Authors: De Jager, Gerhard
  • Date: 1963
  • Subjects: Ionosphere , Ionospheric electron density
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:5515 , http://hdl.handle.net/10962/d1011046 , Ionosphere , Ionospheric electron density
  • Description: The present work was initially aimed at providing an explanation for some of the phenomena that occur in the ionosphere at sunrise. The approach that was taken was to determine the changes that take place on a theoretical model of the ionosphere and then to compare these with observations. A prerequisite for this approach was a theoretical model that would show, among other things, a bifurcation of the F layer during daytime without making unjustified arbitrary assumptions. The absence of such a model, particularly as far as non-equilibrium conditions are concerned, resulted in the present attempt to provide such a model for the F1 region.
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  • Date Issued: 1963

Studies on certain aspects of the neuromuscular physiology of insects

  • Authors: Moran, V. C. (V. Cliff)
  • Date: 1963
  • Subjects: Insects -- Physiology
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:5866 , http://hdl.handle.net/10962/d1012879
  • Description: It is well known that high potassium ion concentrations depolarize nervous tissue and it has been suggested that the nerve sheath surrounding the peripheral nerves of insects serves as a protective barrier for the exclusion of potassium ions, in the haemolymph, from the immediate environment of axons. Further it is known that the concentration of potassium ions in the haemolymph of phytophagous insects is far higher than that in predatory forms; this has led to the suggestion that the nerve sheath in plant feeding insects should be more highly developed than that of entomophagous insects. In this work the structure of the nerve sheath in phytophagous and predatory insects has been studied and this assumption has been shown to be groundles. However, preliminary experiments on the effects of ions and drugs on the peripheral nerves of phytophagous and predatory insects have shown that there is a definite difference in susceptibility between the nerves of these two forms and this has led to the postulate of a diffusion barrier beneath the level of the nerve sheath, which is more highly developed in phytophagous than in predatory forms. The properties of this second barrier are discussed. Part 1. , During the course of the work which has been described in Part 1- an outbreak of large saturniid moths Nudaurelia cytherea capensis Stoll.) occurred in the Grahamstown area. It was felt that an investigation into the properties of the flight motor of this moth, which has an extremely low wing beat frquency, might be rewarding as our knowledge of the flight motor in insects is limited to those with very much higher wing beat frequencies than that of this moth. The anatomy, innervation and histology of the flight muscles of Nudaurelia are described and it is shown that the flight motor of this moth is functionally different to that of other insects which have been investigated. Further, Nudaurelia shows a characteristic warm-up fluttering of the wings prior to flight - this phenomenon has also been examined in the following investigation. This study has yielded information about the location of a warm-up centre in the central nervous system of this moth. Part 2.
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  • Date Issued: 1963

Studies on the behaviour of unfed blue tick larvae (Boophilus decoloratus)

  • Authors: Goldsmid, John Marsden
  • Date: 1963
  • Subjects: Boophilus -- South Africa , Ticks -- Behavior -- South Africa , Ticks -- Physiology -- South Africa
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:5852 , http://hdl.handle.net/10962/d1012044 , Boophilus -- South Africa , Ticks -- Behavior -- South Africa , Ticks -- Physiology -- South Africa
  • Description: Ticks "are not merely annoying pests but surpass all other anthropods in the number and variety of disease agents for which they are carriers (Chandler 1955). This statement is certainly true of Boophilus decoloratus (Koch), the blue tick, which is probably one of the most important ticks in South Africa. Various studies have been made on the blue tick in Africa, among which are investigations on taxonomy (Hoogstraal 1956); distribution (Theiler 1949 and 1962); ecology (Kraft 1961); disease transmission (Neitz and du Toit 1938; du Toit 1947; Neitz 1956 a and b); control and resistance to insecticides (du Toit, Graf and Bekker 1941; Whitnall and Bradford 1947; Whitehead 1958 and 1959) To date, the behaviour of Boophilus decoloratus has not been studied to any extent. The aim of the present work is to analyse the behaviour of the unfed larvae into its constituent patterns in order to determine what are the significant environmental factors which affect this behaviour. It is also hoped that the present laboratory studies might help in understanding their behaviour in the field. Intro., p. 1.
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  • Date Issued: 1963

Studies on the emulsion scouring of raw wool

  • Authors: Grové, Christo Carel
  • Date: 1963
  • Subjects: Woolen and worsted manufacture
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4479 , http://hdl.handle.net/10962/d1012100 , Woolen and worsted manufacture
  • Description: Knowledge of the mechanism of detergency under various conditions has thus far been built up from laboratory studies. It is well known that the laboratory methods for determing detergency are on the whole not able to give results which agree with those obtained in practice, probably because the actual scouring conditions cannot be duplicated exactly in the laboratory. Detergency testing on a full industrial scale is virtually impossible in view of the high cost and the production losses involved. In commercial raw wool scouring, which is an extremely complex system, it would be very difficult to exercise proper and complete control. The study described here was carried out on a specially constructed pilot plant which is similar to a fullscale plant in that the lengths of the bowls are of the same order as those of industrial plants, but they are considerably narrower. The trials were carried out under strictly controlled conditions in which the effects to be studied were created by the necessary changes while all other factors were kept constant, The pilot plant experiments were planned from indications of laboratory studies and the results were expected to be more comparable with those obtained in industrial practice, The effect of several factors on the scouring of raw wool was studied from the detergent efficiency aspect. The factors investigated were: mechanical action, backflow, temperature and detergency builders. A number of detergents which were selected from the large range which is available were compared with regard to efficiency and economy of scouring. A difficulty which hinders quantitative laboratory work on nonionic detergents is the fact that there is no rapid, accurate method for the estimation of nonionic detergents. The analytical methods which are employed at present are interfered with by virtually all the impurities which are normally present in scouring liquors. Some of the existing methods have been investigated and tested for precision and reproducibility and an attempt was made at establishing a new method. The sorption of nonionic detergents by various substrates has not been fully investigated because of the above reason and also because the amounts of detergent sorbed by most substrates are very small and difficult to determine. Attempts were made at determining the sorption of nonionic detergents onto wool and impurities which are normally found in scouring liquors. A new method for the investigation of "inactivation" of detergent by contaminants present in scouring liquors, which may be regarded as an indirect indication of detergent sorption, was investigated.
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  • Date Issued: 1963

The crystal structure of caesium permanganate by x-ray diffraction

  • Authors: Nassimbeni, L R
  • Date: 1963
  • Subjects: Permanganates -- Crystallography , X-rays -- Diffraction , Crystals -- Piezoelectricity , Pyroelectricity
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4484 , http://hdl.handle.net/10962/d1012942
  • Description: The crystal structure of caesium permanganate has been determined. CsMn0₄ crystallises in the orthorhombic space group Pnma. There are four molecules per unit cell with a = 10.0692 Å, b = 5.8080 Å, c = 7.9470 Å. The structure was determined by Fourier syntheses on the (010) and (001) projections and refined by two-dimensional difference syntheses. The structure is similar to that of KMn0₄. The manganese is surrounded by four oxygen atoms at an average distance of 1.629 Å arranged in a slightly distorted tetrahedron. The caesium is surrounded by eight manganese atoms at an average distance of 4.381 Å.
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  • Date Issued: 1963

The design and construction of a recording spectrometer for the measurement of fluorescence excitation spectra in the vacuum ultra-violet region

  • Authors: Davidson, A T
  • Date: 1963
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:21177 , http://hdl.handle.net/10962/6761
  • Description: Summary: A recording spectrometer for the measurement of fluorescence excitation spectra in the visible and ultra-violet regions of the spectrum is described. A direct method of modulating the hydrogen light source of the spectrograph is presented, whereby the discharge is driven by an A.C. power oscillator. The use of tuned amplifiers in the detecting unit is investigated as a means of eliminating the D.C. component of the dark current. Aspects of the modulation method are discussed. Fluorescence and energy transfer in aromatic hydrocarbon is discussed with particular regard to anthracene. Some absorption, fluorescence, excitation and reflection spectra of anthracene obtained by previous workers are presented9 together with Tables listing the wavelengths of principal maxima for the above spectra published in the literature. Features of the excitation spectrum of anthracene are discussed and are related to its absorption and fluorescence spectra. The role of surface effects, defects and impurities are discussed in relation to the fluorescence of anthracene. The method of A.C. detection was unable to resolve the excitation spectrum of anthracene due to the high noise level associated with the method. However, peaks in the ultra-violet region of the hydrogen molecular spectrum were recorded at a modulation frequency of 400 Kc/sec. The noise level is explained and ways of improving the signal to noise ratio of the A.C. detection system are suggested. It is concluded that D.C. detection is a simpler and more direct way of measuring excitation spectra. No modulated signals were detected when the hydrogen discharge was excited at 6·5 Mc/sec. Signals were recorded at modulation frequencies of 400 Kc/sec . The degree of modulation at 400 Kc/sec. increased with decrease in the pressure of the hydrogen discharge.
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  • Date Issued: 1963

The development of a method for the determination of microgram amounts of magnesium by atomic absorption

  • Authors: Taylor, John Douglas
  • Date: 1963
  • Subjects: Atomic absorption spectroscopy -- Instruments , Magnesium
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4507 , http://hdl.handle.net/10962/d1013344
  • Description: This thesis includes a description of modifications of the Hilger atomic absorption apparatus, which was used for most of the work. These modifications were restricted to the atomiser and burner, which were replaced by a modified "Eel" flame. photometer atomiser-burner and resulted in improved sensitivity and instrumental stability for the atomic absorption of magnesium. A comparison of the performance of this unit with that of the unmodified Hilger apparatus is given. A "Handigas" butane-propane mixture)-air flame was used for most of this work, but a coal-gas-air flame was also studied and found to give slightly greater sensitivity. The method was found to be subject to interference from many elements. Strontium salts, employed as releasing agents to overcome the effect of other elements, were not completely effective as milligram amounts of several elements interfered even when strontium was present. Among the more serious interfering elements are: aluminium, iron, manganese and zirconium (less than 20 p.p.m. interfere); the alkali and alkaline earth metal salts (more than 200-500 p.p.m. interfere); phosphate (more than 100 p.p.m. P₂0₅ uranium (more than 4,000 p.p.m.); arsenate and vanadate. An attempt is made to explain the mechanism of some of these interfering effects. A combination of strontium salt and acetyl acetone was found to over-come the effects of small amounts of several elements that form complexes with acetyl acetone (e.g. iron and aluminium) far more effectively than strontium alone. Larger amounts of many interfering elements are removed by a solvent extraction procedure employing acetyl acetone and chloroform. Elements which cannot be removed by this means may be separated by anion-exchange, volatilisation, electrolysis or precipitation. A spiking technique, which compensates JT/GB for the effects of small amounts of interfering elements, is described and enables many samples to be analysed without prior separations. The method described has good sensitivity (the limit of determination is approximately 1 microgram of magnesium in 50 ml. of solution). It has been applied to the analysis of clay samples, iron ore, limestone and uranium metal, oxides and processing solutions. The coefficient of variation of the method was determined using two clay samples and results of 2.0 and 4.6 percent, at magnesium oxide concentrations of 0.65 and 0.22 percent respectively, wore obtained. The speed of the method compares favourably with others described for the determination of microgram amounts of magnesium, but increases if large amounts of interfering elements are present.
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  • Date Issued: 1963

The influence of temperature in the ecology of the intermediate host snails of Schistosoma and Fasciola (Trematoda) in southern Rhodesia

  • Authors: Shiff, Clive Julian
  • Date: 1963
  • Subjects: Schistosoma , Schistosomiasis , Fasciola , Snails -- Zimbabwe , Trematoda
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:5881 , http://hdl.handle.net/10962/d1013208
  • Description: The influence of temperature on the bionomics of Bulinus (Physopsis) globosus, Biomphalaria pfeifferi and Lymnaea natalensis has been studied both in the laboratory under controlled conditions and in the field under normal seasonal influences. Field studies were carried out in two different localities, one a semi-permanent pond and the other a temporary waterbody. For this purpose a sampling implement was developed. The results show the seasonal progression of these populations both with respect to estimated numbers and the size distribution of the snails. The rate of actual increase at different seasons was calculated for the three species where the data were sufficient. In the laboratory the snails were maintained at various temperatures, other conditions being kept standard. Daily records of mortality and fecundity of various cohorts reared from the egg stage enabled the compilation of life tables fof the speciesand from these data were calcualted the intrinsic rate of natural increase and other parameters. Effects of crowding in aquaria were studied. From the data obtained in the laboratory it was possible to predict the distribution and population potential for each species for snail of various environmental conditions. These predictions were, in fact, confirmed by field observation.
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  • Date Issued: 1963
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