A study of the E region of the ionosphere
- Authors: Barnard, A J
- Date: 1950
- Subjects: Ionosphere -- Research
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5549 , http://hdl.handle.net/10962/d1013464
- Description: After a brief historical introduction, the apparatus used in the investigation of the ionosphere in Grahamstown, is described with special reference to the recording equipment, which consists essentially of a camera focussed on the screen of a C.R.O. with z-axis deflection. The equations of the magneto-ionic theory are quoted. The basic formulae of the theories of layer formation in an isothermal (Chapman's),and linear temperature gradient (Gledhill and Szendrei) atmosphere are also quoted.
- Full Text:
- Date Issued: 1950
- Authors: Barnard, A J
- Date: 1950
- Subjects: Ionosphere -- Research
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5549 , http://hdl.handle.net/10962/d1013464
- Description: After a brief historical introduction, the apparatus used in the investigation of the ionosphere in Grahamstown, is described with special reference to the recording equipment, which consists essentially of a camera focussed on the screen of a C.R.O. with z-axis deflection. The equations of the magneto-ionic theory are quoted. The basic formulae of the theories of layer formation in an isothermal (Chapman's),and linear temperature gradient (Gledhill and Szendrei) atmosphere are also quoted.
- Full Text:
- Date Issued: 1950
A new continuum mapping procedure at HartRAO
- Authors: Büchner, Sarah
- Date: 2012-06-19
- Subjects: Hartebeesthoek Radio Astronomy Observatory , Radio astronomy -- Methodology , Galactic cosmic rays
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5510 , http://hdl.handle.net/10962/d1007766 , Hartebeesthoek Radio Astronomy Observatory , Radio astronomy -- Methodology , Galactic cosmic rays
- Description: A basket weaving technique for making radio continuum maps has been developed at the Hartebeesthoek Radio Astronomy Observatory (HartRAO). This data reduction technique significantly reduces scanning effects by using independent maps scanned in orthogonal directions. The observation and data analysis procedures that were developed are presented. The technique was used to map the supernova remnant MSH 15-52 at frequencies of 5000 MHz and 8500 MHz. The flux spectral index for this supernova remnant was found to be 0.83 ± 0.02 in this frequency range. Two regions (A and B) of the Galactic plane were observed at 8500 MHz with a resolution of 6'. Region A covered the 5°x5° area 47.5°< k 52.5°, Ibl < 2.5°, and region B was the 4.2°x3° area 320.4°< I <334.6°, Ibl < 1.5°. Far infrared observations at 60 !lm were used in conjunction with the radio maps to separate the thermal and non-thermal components of the radio emission. The technique can be used to map the Galactic plane at 8500 MHz using dual polarisation once the receiver at HartRAO has been upgraded. This would fulfil a need for a medium resolution, high frequency survey of the southern Galactic plane. , Adobe Acrobat Pro 9.4.6 , Adobe Acrobat 9.46 Paper Capture Plug-in
- Full Text:
- Authors: Büchner, Sarah
- Date: 2012-06-19
- Subjects: Hartebeesthoek Radio Astronomy Observatory , Radio astronomy -- Methodology , Galactic cosmic rays
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5510 , http://hdl.handle.net/10962/d1007766 , Hartebeesthoek Radio Astronomy Observatory , Radio astronomy -- Methodology , Galactic cosmic rays
- Description: A basket weaving technique for making radio continuum maps has been developed at the Hartebeesthoek Radio Astronomy Observatory (HartRAO). This data reduction technique significantly reduces scanning effects by using independent maps scanned in orthogonal directions. The observation and data analysis procedures that were developed are presented. The technique was used to map the supernova remnant MSH 15-52 at frequencies of 5000 MHz and 8500 MHz. The flux spectral index for this supernova remnant was found to be 0.83 ± 0.02 in this frequency range. Two regions (A and B) of the Galactic plane were observed at 8500 MHz with a resolution of 6'. Region A covered the 5°x5° area 47.5°< k 52.5°, Ibl < 2.5°, and region B was the 4.2°x3° area 320.4°< I <334.6°, Ibl < 1.5°. Far infrared observations at 60 !lm were used in conjunction with the radio maps to separate the thermal and non-thermal components of the radio emission. The technique can be used to map the Galactic plane at 8500 MHz using dual polarisation once the receiver at HartRAO has been upgraded. This would fulfil a need for a medium resolution, high frequency survey of the southern Galactic plane. , Adobe Acrobat Pro 9.4.6 , Adobe Acrobat 9.46 Paper Capture Plug-in
- Full Text:
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.
- Full Text:
- Date Issued: 1963
- 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.
- Full Text:
- 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.
- Full Text:
- Date Issued: 1963
- 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.
- Full Text:
- Date Issued: 1963
Theoretical aspects of the generation of radio noise by the planet Jupiter
- Authors: Deift, Percy A
- Date: 1972
- Subjects: Jupiter (Planet) , Radio astronomy , Radio noise
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5516 , http://hdl.handle.net/10962/d1011051 , Jupiter (Planet) , Radio astronomy , Radio noise
- Description: Decameter radiation was first observed from Jupiter by Burke and Franklin (JGR 60, 213, 1955). In 1964 Bigg (Nature, 203, 1008, (1964)) found that 1o exerted a profound effect on the radiation. The majority of the early theories to explain the origin of the decameter emissions, attributed the radiation to an emission process occurring at or near the electron gyrofrequency or the plasma frequency. Intro., p. 1. The majority of the early theories to explain the origin of the decameter emissions, attributed the radiation to an emission process occurring at or near the electron gyrofrequency or the plasma frequency (for a review see eg. Warwick, Space Sci. Rev. &" 841 (1967)). More recent work centred around the question of how 10 modulates the emission (see the article of Carr and Gulkis (Annual Review of Astronomy and Astrophysics Vol 8 (1970)) for a detailed review).
- Full Text:
- Date Issued: 1972
- Authors: Deift, Percy A
- Date: 1972
- Subjects: Jupiter (Planet) , Radio astronomy , Radio noise
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5516 , http://hdl.handle.net/10962/d1011051 , Jupiter (Planet) , Radio astronomy , Radio noise
- Description: Decameter radiation was first observed from Jupiter by Burke and Franklin (JGR 60, 213, 1955). In 1964 Bigg (Nature, 203, 1008, (1964)) found that 1o exerted a profound effect on the radiation. The majority of the early theories to explain the origin of the decameter emissions, attributed the radiation to an emission process occurring at or near the electron gyrofrequency or the plasma frequency. Intro., p. 1. The majority of the early theories to explain the origin of the decameter emissions, attributed the radiation to an emission process occurring at or near the electron gyrofrequency or the plasma frequency (for a review see eg. Warwick, Space Sci. Rev. &" 841 (1967)). More recent work centred around the question of how 10 modulates the emission (see the article of Carr and Gulkis (Annual Review of Astronomy and Astrophysics Vol 8 (1970)) for a detailed review).
- Full Text:
- Date Issued: 1972
The performance of a 22 GHz radio telescope
- Authors: Gaylard, Michael John
- Date: 1977
- Subjects: Radio telescopes , Paraboloid
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5520 , http://hdl.handle.net/10962/d1011946 , Radio telescopes , Paraboloid
- Description: The performance of the Rhodes 22 GHz radio telescope and its improvement are discussed in this thesis. The reflector surfaces of the Cassegrain antenna were surveyed and the surface errors minimised, while the magnitude of thermal and gravitational defomations was calculated. The design and operation of the microwave front end has been improved, and the mixer performance characterised. The continuum and spectral line receivers and their sensitivity are described. The aperture efficiency, which has been raised from 0,47 to 0,57, was deduced from solar and lunar observations and atmospheric attenuation measurements. The antenna beam pattern was also obtained from the observations, with the aid of a computer program, and is compared to that predicted for the telescope.
- Full Text:
- Date Issued: 1977
- Authors: Gaylard, Michael John
- Date: 1977
- Subjects: Radio telescopes , Paraboloid
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5520 , http://hdl.handle.net/10962/d1011946 , Radio telescopes , Paraboloid
- Description: The performance of the Rhodes 22 GHz radio telescope and its improvement are discussed in this thesis. The reflector surfaces of the Cassegrain antenna were surveyed and the surface errors minimised, while the magnitude of thermal and gravitational defomations was calculated. The design and operation of the microwave front end has been improved, and the mixer performance characterised. The continuum and spectral line receivers and their sensitivity are described. The aperture efficiency, which has been raised from 0,47 to 0,57, was deduced from solar and lunar observations and atmospheric attenuation measurements. The antenna beam pattern was also obtained from the observations, with the aid of a computer program, and is compared to that predicted for the telescope.
- Full Text:
- Date Issued: 1977
A study of conditions in the upper atmosphere and their deduction from radio measurements
- Gledhill, J A, Szendrei, M E
- Authors: Gledhill, J A , Szendrei, M E
- Date: 1948
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:21181 , http://hdl.handle.net/10962/6795
- Description: Summary: In part 1 (a), after a brief historical outline of methods of ionospheric investigation and their development, the construction in this laboratory of manually operated equipment for sounding the ionosphere is described. Photographic records of good definition were taken at regular intervals over a period of four months during the summer of 1945-6. These were fully sealed for critical frequencies, true heights and thicknesses of all the layers present, and mean monthly values of these quantities for each hour are tabulated. An extensive correlation with magnetic data from Hermanus indicated good correlation between magnetic activity and disturbed ionospheric conditions. On these grounds some disturbed days were rejected, and others were eliminated on ionospheric grounds. Smoothed mean values are tabulated and graphs drawn. These are presented in concise form on "electron density maps", which are graphs showing lines of constant electron density plotted as functions of time and height. In part 1 (b), a new theory of layer-formation is developed, in which the temperature is assumed to vary linearly with height. The equations are compared at each step with those obtained by Chapman in his theory of layer-formation in an isothermal atmosphere. The equations for the maximum of electron density and its height are also given. The effect of the parameters on the shape of the layer is shown in graphical form. The equations are somewhat complex in form, but an ingenious graphical method has been devised suitable for the application of the theory to results given in the form of those in section 1 (a). From this application values are obtained for the temperature gradient, the temperature at 200 km. and its variation over the middle part of the day. The results obtained are in accordance with previous estimates, and offer numerical confirmation of the theory that the atmosphere expands bodily upwards during the middle part of a summer day.
- Full Text:
- Date Issued: 1948
- Authors: Gledhill, J A , Szendrei, M E
- Date: 1948
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:21181 , http://hdl.handle.net/10962/6795
- Description: Summary: In part 1 (a), after a brief historical outline of methods of ionospheric investigation and their development, the construction in this laboratory of manually operated equipment for sounding the ionosphere is described. Photographic records of good definition were taken at regular intervals over a period of four months during the summer of 1945-6. These were fully sealed for critical frequencies, true heights and thicknesses of all the layers present, and mean monthly values of these quantities for each hour are tabulated. An extensive correlation with magnetic data from Hermanus indicated good correlation between magnetic activity and disturbed ionospheric conditions. On these grounds some disturbed days were rejected, and others were eliminated on ionospheric grounds. Smoothed mean values are tabulated and graphs drawn. These are presented in concise form on "electron density maps", which are graphs showing lines of constant electron density plotted as functions of time and height. In part 1 (b), a new theory of layer-formation is developed, in which the temperature is assumed to vary linearly with height. The equations are compared at each step with those obtained by Chapman in his theory of layer-formation in an isothermal atmosphere. The equations for the maximum of electron density and its height are also given. The effect of the parameters on the shape of the layer is shown in graphical form. The equations are somewhat complex in form, but an ingenious graphical method has been devised suitable for the application of the theory to results given in the form of those in section 1 (a). From this application values are obtained for the temperature gradient, the temperature at 200 km. and its variation over the middle part of the day. The results obtained are in accordance with previous estimates, and offer numerical confirmation of the theory that the atmosphere expands bodily upwards during the middle part of a summer day.
- Full Text:
- Date Issued: 1948
A new model of the IO-Controlled Jovian decametric radiation
- Authors: Goertz, Christoph K
- Date: 1972
- Subjects: Jupiter (Planet) Radiation Magnetosphere Ionosphere
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5521 , http://hdl.handle.net/10962/d1012043
- Description: Jupiter, the largest planet in the solar system, is not only an emitter of thermal radiation like any other planet. Jupiter also emits relatively high-intensity non-thermal radiation in two bands, the decimetre wavelength range and the decametre wavelength range (5 MHz< f < 40 MHz). The decimetric radiation is believed to be due to synchrotron radiation of electrons trapped in a kind of Jovian "Van Allen belt". This thesis deals almost exclusively with the decametric radiation. Although the decametric radiation has been observed for 15 years since its discovery by Burke and Franklin in 1955, there is no generally accepted theoretical model of its generation to be found in the literature as yet. This is not surprising, as there are many complex and confusing aspects of the radiation. And since our knowledge of the Jovian ionosphere, magnetosphere and magnetic field is very limited indeed, every theoretical model must be based on some more or less well justified assumptions. It is, however, possible to draw some conclusions from the observed properties of the decimetric and decametric radiation. The radiation in both bands is polarized. It has been shown that at least part of the polarization is an intrinsic property of the radiation source at Jupiter, This indicates the existence of a Jovian magnetic field. The magnitude and shape of the magnetic field, however, is open to discussion, although a dipole field does seem to be a good approximation at least for large distances from Jupiter. Intro. p. 1-2.
- Full Text:
- Date Issued: 1972
- Authors: Goertz, Christoph K
- Date: 1972
- Subjects: Jupiter (Planet) Radiation Magnetosphere Ionosphere
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5521 , http://hdl.handle.net/10962/d1012043
- Description: Jupiter, the largest planet in the solar system, is not only an emitter of thermal radiation like any other planet. Jupiter also emits relatively high-intensity non-thermal radiation in two bands, the decimetre wavelength range and the decametre wavelength range (5 MHz< f < 40 MHz). The decimetric radiation is believed to be due to synchrotron radiation of electrons trapped in a kind of Jovian "Van Allen belt". This thesis deals almost exclusively with the decametric radiation. Although the decametric radiation has been observed for 15 years since its discovery by Burke and Franklin in 1955, there is no generally accepted theoretical model of its generation to be found in the literature as yet. This is not surprising, as there are many complex and confusing aspects of the radiation. And since our knowledge of the Jovian ionosphere, magnetosphere and magnetic field is very limited indeed, every theoretical model must be based on some more or less well justified assumptions. It is, however, possible to draw some conclusions from the observed properties of the decimetric and decametric radiation. The radiation in both bands is polarized. It has been shown that at least part of the polarization is an intrinsic property of the radiation source at Jupiter, This indicates the existence of a Jovian magnetic field. The magnitude and shape of the magnetic field, however, is open to discussion, although a dipole field does seem to be a good approximation at least for large distances from Jupiter. Intro. p. 1-2.
- Full Text:
- Date Issued: 1972
Construction of a wide-frequency range double heterodyne conductance bridge and its use in the investigation of polarisation errors in conductance measurements
- Authors: Govinden, Herby Silvester
- Date: 1961
- Subjects: Electrodynamics Electrolytes -- Conductivity
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5522 , http://hdl.handle.net/10962/d1012074
- Description: (1) Developments in a.c. conductance techniques during the past ninety years have been reviewed, and a brief outline is given of the older theories regarding electrolytic polarisation. (2) A conductance bridge - incorporating the double heterodyne principle - has been constructed, capable of giving resistance readings to an accuracy of 0.01% over a range of frequencies covering the best part of 100 kc/s. It has also been found possible to calibrate the oscillator so that frequency settings can be guaranteed to an accuracy of , at least, 0.1% in the range: 2 kc/S to 50 kc/S. (3) The Wheatstone Bridge Network has been slightly modified to enable measurements at the high frequencies. (4) Resistances in the measuring arm of the bridge have been calibrated 'in situ' by the method of intercomparison. (5) A brief description is given of the modern theories regarding electrode processes and modern methods of eliminating electrode effects. (6) Two types of conductance cells, with bright Pt electrodes, have been used to carry out measurements on potassium chloride solutions: (a) Thomas- Gledhill Cell (b) Nichol-Fuoss Cell. The latter incorporates concentric, cylindrical electrodes with the lead to the outer electrode acting as an electrical shield for the lead to the inner electrode. This cell was constructed and used for the first time in this laboratory. (7) From resistance-frequency graphs plotted, it is shown that the Jones and Christian extrapolation procedure cannot be applied (with any degree of confidence) to obtain the true resistance, when measurements are effected over an extended range of frequencies. (8) The method of resistance-reactance diagrams is discussed and applied to various networks of resistances and capacitances. (9) By drawing resistance-reactance diagrams for the experimental readings obtained, equivalent circuits have been derived - for all the solutions investigated in the N-F cell, and for the approx. O.OlD solution in the T-G cell - which approximate to cell behaviour in the range: 500 c/s to 75 kc/s. The less concentrated solutions in the T-G cell show peculiar behaviour at the high frequencies. (10) Probable reasons are advanced for deviations from linearity on resistance-frequency graphs. (11) A new method is proposed for determining the true resistance of solutions measured in cells of the N-F type. Summary, p. 166-167.
- Full Text:
- Date Issued: 1961
- Authors: Govinden, Herby Silvester
- Date: 1961
- Subjects: Electrodynamics Electrolytes -- Conductivity
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5522 , http://hdl.handle.net/10962/d1012074
- Description: (1) Developments in a.c. conductance techniques during the past ninety years have been reviewed, and a brief outline is given of the older theories regarding electrolytic polarisation. (2) A conductance bridge - incorporating the double heterodyne principle - has been constructed, capable of giving resistance readings to an accuracy of 0.01% over a range of frequencies covering the best part of 100 kc/s. It has also been found possible to calibrate the oscillator so that frequency settings can be guaranteed to an accuracy of , at least, 0.1% in the range: 2 kc/S to 50 kc/S. (3) The Wheatstone Bridge Network has been slightly modified to enable measurements at the high frequencies. (4) Resistances in the measuring arm of the bridge have been calibrated 'in situ' by the method of intercomparison. (5) A brief description is given of the modern theories regarding electrode processes and modern methods of eliminating electrode effects. (6) Two types of conductance cells, with bright Pt electrodes, have been used to carry out measurements on potassium chloride solutions: (a) Thomas- Gledhill Cell (b) Nichol-Fuoss Cell. The latter incorporates concentric, cylindrical electrodes with the lead to the outer electrode acting as an electrical shield for the lead to the inner electrode. This cell was constructed and used for the first time in this laboratory. (7) From resistance-frequency graphs plotted, it is shown that the Jones and Christian extrapolation procedure cannot be applied (with any degree of confidence) to obtain the true resistance, when measurements are effected over an extended range of frequencies. (8) The method of resistance-reactance diagrams is discussed and applied to various networks of resistances and capacitances. (9) By drawing resistance-reactance diagrams for the experimental readings obtained, equivalent circuits have been derived - for all the solutions investigated in the N-F cell, and for the approx. O.OlD solution in the T-G cell - which approximate to cell behaviour in the range: 500 c/s to 75 kc/s. The less concentrated solutions in the T-G cell show peculiar behaviour at the high frequencies. (10) Probable reasons are advanced for deviations from linearity on resistance-frequency graphs. (11) A new method is proposed for determining the true resistance of solutions measured in cells of the N-F type. Summary, p. 166-167.
- Full Text:
- Date Issued: 1961
An investigation into the decametric radio emission by the planet Jupiter
- Authors: Gruber, Georg M
- Date: 1967
- Subjects: Jupiter (Planet) , Radio astronomy , Radio sources (Astronomy)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5545 , http://hdl.handle.net/10962/d1013410
- Description: From introduction: Jupiter is the largest planet in the solar system. Its distance from the Sun is five times that of the Earth and its mass is nearly two and a half times that of all the other planets added together. Jupiter turns about its own axis rather rapidly, once in just under ten hours, and it completes one revolution about the Sun in just under twelve years. Thus Earth has to pass almost directly between the Sun and Jupiter once every thirteen months. When this happens Jupiter is said to be in "opposition", as its position is then opposite to that of the Sun, when viewed from Earth. Around this time the planet will be most favourably placed for observations, as it is at its closest to Earth and up in the sky for a large part of the night. During the day observations on radio frequencies are more difficult, as the Sun is a source of great interference. Besides being an emitter of thermal electromagnetic radiation, as one would expect, Jupiter also emits two kinds of non-thermal radiation, one in the decimetre wavelength range and the other in the decametre wavelength range. A large number of scientists have worked on the problems of decimetre and decametre radiation. This thesis deals with some aspects of decametre radiation.
- Full Text:
- Date Issued: 1967
- Authors: Gruber, Georg M
- Date: 1967
- Subjects: Jupiter (Planet) , Radio astronomy , Radio sources (Astronomy)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5545 , http://hdl.handle.net/10962/d1013410
- Description: From introduction: Jupiter is the largest planet in the solar system. Its distance from the Sun is five times that of the Earth and its mass is nearly two and a half times that of all the other planets added together. Jupiter turns about its own axis rather rapidly, once in just under ten hours, and it completes one revolution about the Sun in just under twelve years. Thus Earth has to pass almost directly between the Sun and Jupiter once every thirteen months. When this happens Jupiter is said to be in "opposition", as its position is then opposite to that of the Sun, when viewed from Earth. Around this time the planet will be most favourably placed for observations, as it is at its closest to Earth and up in the sky for a large part of the night. During the day observations on radio frequencies are more difficult, as the Sun is a source of great interference. Besides being an emitter of thermal electromagnetic radiation, as one would expect, Jupiter also emits two kinds of non-thermal radiation, one in the decimetre wavelength range and the other in the decametre wavelength range. A large number of scientists have worked on the problems of decimetre and decametre radiation. This thesis deals with some aspects of decametre radiation.
- Full Text:
- Date Issued: 1967
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.
- Full Text:
- Date Issued: 1963
- 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.
- Full Text:
- Date Issued: 1963
Photofluorescence decay times of organic phosphors
- Authors: Hamilton, T D S
- Date: 1957
- Subjects: Fluorescence , Phosphorescence
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5525 , http://hdl.handle.net/10962/d1012136 , Fluorescence , Phosphorescence
- Description: The absorption and emission of energy is a fundamental property of any atomic system.When the emission occurs in the visible or near visible region the phenomenon is usually referred to as luminescence or fluorescence. This must be distinguished from thermal radiation as it does not follow Kirchoff's law.
- Full Text:
- Date Issued: 1957
- Authors: Hamilton, T D S
- Date: 1957
- Subjects: Fluorescence , Phosphorescence
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5525 , http://hdl.handle.net/10962/d1012136 , Fluorescence , Phosphorescence
- Description: The absorption and emission of energy is a fundamental property of any atomic system.When the emission occurs in the visible or near visible region the phenomenon is usually referred to as luminescence or fluorescence. This must be distinguished from thermal radiation as it does not follow Kirchoff's law.
- Full Text:
- Date Issued: 1957
Effects of precipitating electrons in the ionosphere
- Authors: Haschick, Aubrey D
- Date: 1974
- Subjects: Electrons , Electron precipitation , Ionosphere , Ionospheric electron density
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5526 , http://hdl.handle.net/10962/d1012220
- Description: As early as 1896, around the time of the discovery of the electron by J.J. Thompson, Birkeland was led to propose that aurorae were caused by fast moving electrons or similarly charged particles emitted by the sun and 'sucked in towards' the auroral zones by the geomagnetic field. He later supported this idea by firing electrons at a dipole field surrounding a sphere covered with a fluorescent coating. Extensive ground based observations of auroral features eventually led, in 1950, to the initial direct evidence of the fact that auroral emissions are due to energetic charged particles, consisting partly of protons, entering the earth's atmosphere (Meinel, 1951). However, it was only in 1952 and 1953 that the first measurements of what was later interpreted as bremsstrahlung X- rays from precipitating electrons were made at auroral latitudes. (Meredith et aI, 1955) During the IGY, 1957 - 1958, a number of rockets were fired through and near, visible aurorae and large fluxes of low energy electrons were detected ... Intro., p. 1.
- Full Text:
- Date Issued: 1974
- Authors: Haschick, Aubrey D
- Date: 1974
- Subjects: Electrons , Electron precipitation , Ionosphere , Ionospheric electron density
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5526 , http://hdl.handle.net/10962/d1012220
- Description: As early as 1896, around the time of the discovery of the electron by J.J. Thompson, Birkeland was led to propose that aurorae were caused by fast moving electrons or similarly charged particles emitted by the sun and 'sucked in towards' the auroral zones by the geomagnetic field. He later supported this idea by firing electrons at a dipole field surrounding a sphere covered with a fluorescent coating. Extensive ground based observations of auroral features eventually led, in 1950, to the initial direct evidence of the fact that auroral emissions are due to energetic charged particles, consisting partly of protons, entering the earth's atmosphere (Meinel, 1951). However, it was only in 1952 and 1953 that the first measurements of what was later interpreted as bremsstrahlung X- rays from precipitating electrons were made at auroral latitudes. (Meredith et aI, 1955) During the IGY, 1957 - 1958, a number of rockets were fired through and near, visible aurorae and large fluxes of low energy electrons were detected ... Intro., p. 1.
- Full Text:
- Date Issued: 1974
A critical analysis of the teaching of fundamental physical concepts and principles, with particular reference to South African schools
- Authors: Helm, Hugh
- Date: 1970
- Subjects: Physics -- Study and teaching -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5541 , http://hdl.handle.net/10962/d1013345
- Description: From introduction: The main purpose of the present study is to give a detailed critical survey of possible teaching approaches to fundamental physical ooncepts and principles which could reasonably be taught at sohool, and to consider the implications of this survey for the teaching of physical science in South Africa
- Full Text:
- Date Issued: 1970
- Authors: Helm, Hugh
- Date: 1970
- Subjects: Physics -- Study and teaching -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5541 , http://hdl.handle.net/10962/d1013345
- Description: From introduction: The main purpose of the present study is to give a detailed critical survey of possible teaching approaches to fundamental physical ooncepts and principles which could reasonably be taught at sohool, and to consider the implications of this survey for the teaching of physical science in South Africa
- Full Text:
- Date Issued: 1970
In-beam spectroscopy of ⁷²Ge
- Authors: Henninger, Katharine Rose
- Date: 2012
- Subjects: Nuclear shapes , Hyperfine structure
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5559 , http://hdl.handle.net/10962/d1018233
- Description: The high-spin states of the nucleus ⁷²Ge were populated via the ⁷°Zn(a,2n)⁷²Ge fusion-evaporation reaction at a beam-energy of 30 MeV. The ')'-decays were observed with the AFRODITE spectrometer array at iThemba LABS (Faure, South Africa). Twenty-seven new transitions, 18 new levels and 2 new bands were added to the ⁷²Ge level scheme, and several corrections were made to t he previously-known level scheme. Transitions were characterised using Directional Correlation from Oriented states (DCO) and polarisation measurements, and spin-parity assignments were made for 7 new levels. Spin and parity were also reassigned to a previously-known structure. One of the new bands was ident ified as part of an octupole-vibrational band. No tetrahedral states were observed in the scheme despite N = 40 and Z = 32 having been identified as tetrahedral magic numbers. The meaning of the new 14⁺ yrast level for the underlying structure of the ground state band is discussed
- Full Text:
- Date Issued: 2012
- Authors: Henninger, Katharine Rose
- Date: 2012
- Subjects: Nuclear shapes , Hyperfine structure
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5559 , http://hdl.handle.net/10962/d1018233
- Description: The high-spin states of the nucleus ⁷²Ge were populated via the ⁷°Zn(a,2n)⁷²Ge fusion-evaporation reaction at a beam-energy of 30 MeV. The ')'-decays were observed with the AFRODITE spectrometer array at iThemba LABS (Faure, South Africa). Twenty-seven new transitions, 18 new levels and 2 new bands were added to the ⁷²Ge level scheme, and several corrections were made to t he previously-known level scheme. Transitions were characterised using Directional Correlation from Oriented states (DCO) and polarisation measurements, and spin-parity assignments were made for 7 new levels. Spin and parity were also reassigned to a previously-known structure. One of the new bands was ident ified as part of an octupole-vibrational band. No tetrahedral states were observed in the scheme despite N = 40 and Z = 32 having been identified as tetrahedral magic numbers. The meaning of the new 14⁺ yrast level for the underlying structure of the ground state band is discussed
- Full Text:
- Date Issued: 2012
An investigation into some aspects of Jovian decametric radiation
- Authors: Hill, I. E.
- Date: 1969
- Subjects: Jupiter (Planet) , Radiation , Magnetosphere
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5552 , http://hdl.handle.net/10962/d1015034
- Description: This thesis describes observations of the flne structure in Jovian decametric radiation made at Grahamstown during the 1967-68 apparition. It was found that pulses with duration less than 0.5 milliseconds were common during fine structure storms. The restrictions placed on the source for different theories of origin of the short pulses are discussed. The variation of the probability of occurrence from year to year is analysed on the assumption that the radiation is found in directions fixed with respect to the planet's magnetic field. It is concluded that there is a factor other than the declination of Earth and the Io effect which controls the probability of occurrence. A detailed analysis suggests a beam width of 3° in latitude at Jupiter but further work is necessary to check this.
- Full Text:
- Date Issued: 1969
- Authors: Hill, I. E.
- Date: 1969
- Subjects: Jupiter (Planet) , Radiation , Magnetosphere
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5552 , http://hdl.handle.net/10962/d1015034
- Description: This thesis describes observations of the flne structure in Jovian decametric radiation made at Grahamstown during the 1967-68 apparition. It was found that pulses with duration less than 0.5 milliseconds were common during fine structure storms. The restrictions placed on the source for different theories of origin of the short pulses are discussed. The variation of the probability of occurrence from year to year is analysed on the assumption that the radiation is found in directions fixed with respect to the planet's magnetic field. It is concluded that there is a factor other than the declination of Earth and the Io effect which controls the probability of occurrence. A detailed analysis suggests a beam width of 3° in latitude at Jupiter but further work is necessary to check this.
- Full Text:
- Date Issued: 1969
Precipitation effects on atmospheric electron densities
- Authors: Huang, Cheryl Yu-Yin
- Date: 1977
- Subjects: Precipitation (Chemistry)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5527 , http://hdl.handle.net/10962/d1012441 , Precipitation (Chemistry)
- Description: In this thesis the effects of precipitated electrons on electron densities in the upper atmosphere are investigated. A method for solving the continuity equation has been developed , and this has been used to calculate electron density profiles under various conditions: daytime equilibrium conditions, with and without additional ionization by precipitated electrons; and nighttime conditions, with and without precinitation . This preliminary study seems to show that certain effects may be attributable to precipitation, and that these effects may be significant at night.
- Full Text:
- Date Issued: 1977
- Authors: Huang, Cheryl Yu-Yin
- Date: 1977
- Subjects: Precipitation (Chemistry)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5527 , http://hdl.handle.net/10962/d1012441 , Precipitation (Chemistry)
- Description: In this thesis the effects of precipitated electrons on electron densities in the upper atmosphere are investigated. A method for solving the continuity equation has been developed , and this has been used to calculate electron density profiles under various conditions: daytime equilibrium conditions, with and without additional ionization by precipitated electrons; and nighttime conditions, with and without precinitation . This preliminary study seems to show that certain effects may be attributable to precipitation, and that these effects may be significant at night.
- Full Text:
- Date Issued: 1977
Students' conceptions of simple D.C. electricity circuits: a study of primary, inappropriate conceptions, learning difficulties of physics students, and implications for instruction
- Authors: Jiya, Zindlovu
- Date: 1990
- Subjects: Physical sciences -- Study and teaching (Secondary) -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5441 , http://hdl.handle.net/10962/d1001994
- Description: The work attempts to identify the general conceptual problems of the generations of Black students who pass through flrst year physics courses at the University of Fort Hare. In particular the alternative conceptions of students in the area of direct current electricity are investigated, using various techniques including written diagnostic tests. The main method used in the investigation of the student frameworks is the personal interview. A varied number of inappropriate conceptions are identifled in the students in significantly large proportions, and these are found to be dependent on many factors; for example the socio-cultural background like language and its metaphors, and media images. It is established that some of these are exacerbated by student perceptions about the nature of physics and of the scientific enterprise in general. Certain proposals are made about how to remedy the situation; relying mainly on the recently established innovative instructional strategies like conceptual change and cognitive conflict, and on making proposals about restructuring certain forms of presentation of the subject matter, paying attention to how language is used to address the speciflc problems of the students. The importance of providing practical experiences for the students is also emphasised
- Full Text:
- Date Issued: 1990
- Authors: Jiya, Zindlovu
- Date: 1990
- Subjects: Physical sciences -- Study and teaching (Secondary) -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5441 , http://hdl.handle.net/10962/d1001994
- Description: The work attempts to identify the general conceptual problems of the generations of Black students who pass through flrst year physics courses at the University of Fort Hare. In particular the alternative conceptions of students in the area of direct current electricity are investigated, using various techniques including written diagnostic tests. The main method used in the investigation of the student frameworks is the personal interview. A varied number of inappropriate conceptions are identifled in the students in significantly large proportions, and these are found to be dependent on many factors; for example the socio-cultural background like language and its metaphors, and media images. It is established that some of these are exacerbated by student perceptions about the nature of physics and of the scientific enterprise in general. Certain proposals are made about how to remedy the situation; relying mainly on the recently established innovative instructional strategies like conceptual change and cognitive conflict, and on making proposals about restructuring certain forms of presentation of the subject matter, paying attention to how language is used to address the speciflc problems of the students. The importance of providing practical experiences for the students is also emphasised
- Full Text:
- Date Issued: 1990
The response of pure organic crystals to ionising radiations
- Authors: King, J W
- Date: 1953
- Subjects: Inorganic scintillators , Crystals
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5529 , http://hdl.handle.net/10962/d1012641 , Inorganic scintillators , Crystals
- Description: The introduction contains introductory remarks on scintillation counters together with a brief description of the exciton theory believed to be the means of primary energy migration within organic crystals. Part I contains a review of the data published on the reletive responses of different organic crystals and the attempted correlations of these results with the molecular structures of the different phosphors. From data which may be accepted as being both reliable and suitable for comparison it is concluded that theories involving correlations between phosphor efficiencies and molecular structures may be tested only if the efficiency data has (i) been extrapolated to give results for crystals of very small thickness and {ii) been obtained at very low temperatures. Part II contains accurate calculations based on the exciton theory proposed by Birks (1951 ) to account for the response of crystals to different types of ionising radiations. Satisfactory agreement is obta1ned with all the avalable experimental data in the literature. In part III an account is given of the response of organic crystals observed by the author for low-energy ⋉particles, and of the similar behaviour found by Taylor et al, (1951 ) for low-energy electrons. A possible extension of the theory described in part II, allowing for the escape of excitons through the crystal surface is given accounting for this behaviour. An exciton mean free path in anthracene, terphenyl and stilbene of about 3 - 7/u is obtained. Results were obtained with strong ⋉-particle sources which could not be explained. in terms ot normal response of the phosphor used. This effect was inventigatea as described in part IV, and it is shown that photons are produced in air, glass and quartz when these materials are irradiated by ⋉particles. This luminescence was probably responsible for the "scintillations" which Richards and Cole (1951) have ascribed to thin films of various materials. Problems requiring further investigation are indicated.
- Full Text:
- Date Issued: 1953
- Authors: King, J W
- Date: 1953
- Subjects: Inorganic scintillators , Crystals
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5529 , http://hdl.handle.net/10962/d1012641 , Inorganic scintillators , Crystals
- Description: The introduction contains introductory remarks on scintillation counters together with a brief description of the exciton theory believed to be the means of primary energy migration within organic crystals. Part I contains a review of the data published on the reletive responses of different organic crystals and the attempted correlations of these results with the molecular structures of the different phosphors. From data which may be accepted as being both reliable and suitable for comparison it is concluded that theories involving correlations between phosphor efficiencies and molecular structures may be tested only if the efficiency data has (i) been extrapolated to give results for crystals of very small thickness and {ii) been obtained at very low temperatures. Part II contains accurate calculations based on the exciton theory proposed by Birks (1951 ) to account for the response of crystals to different types of ionising radiations. Satisfactory agreement is obta1ned with all the avalable experimental data in the literature. In part III an account is given of the response of organic crystals observed by the author for low-energy ⋉particles, and of the similar behaviour found by Taylor et al, (1951 ) for low-energy electrons. A possible extension of the theory described in part II, allowing for the escape of excitons through the crystal surface is given accounting for this behaviour. An exciton mean free path in anthracene, terphenyl and stilbene of about 3 - 7/u is obtained. Results were obtained with strong ⋉-particle sources which could not be explained. in terms ot normal response of the phosphor used. This effect was inventigatea as described in part IV, and it is shown that photons are produced in air, glass and quartz when these materials are irradiated by ⋉particles. This luminescence was probably responsible for the "scintillations" which Richards and Cole (1951) have ascribed to thin films of various materials. Problems requiring further investigation are indicated.
- Full Text:
- Date Issued: 1953
Static and ultrasonic elastic moduli of wool, mohair and kemp fibres
- Authors: King, Neville Edwin
- Date: 1969
- Subjects: Moduli theory , Mohair , Wool
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5528 , http://hdl.handle.net/10962/d1012640 , Moduli theory , Mohair , Wool
- Description: Fibres used in textiles can be classified broadly into natural fibres and synthetic fibres. Natural fibres can be either animal, such as wool, mohair and camel hair, or vegetable such as cotton, flax and hemp. In the development of synthetic fibres numerous polymers have emerged which have no real natural counterpart and are unique in their mechanical and chemical behaviour. Often the synthetic counterpart of a natural fibre has properties with certain advantages from the textile point of view, but, simultaneously, may exhibit other properties which have disadvantages. Nylon 6 and nylon 6-6, for exemple, are extremely strong and generally easier to dye than animal fibres. On the other hand, they absorb relatively little water vapour and therefore do not give the buffering action characteristic of hygroscopic fibres, once they are woven or knitted into cloth. All textile fibres belong to the chemical class of polymers, i.e. they are made up of repeating molecular units which are linked together to form long chains. In wool the chains are made up of amino-acids which cluster together to form protein chains. Three of these protein chains, coil around each other to form what is termed a proto-fibril. The proto-fibrils make up the micro-fibrils, each of these consisting of eleven of the three chain proto-fibrils. The micro-fibrils, in turn, pack together in bundles which run parallel to the length of the wool fibre and are termed macro-fibrils. Sulphur rich amino-acids fill up the spaces between the micro-fibrils forming a matrix which binds the system into a continuous material. Intro., p. 1.
- Full Text:
- Date Issued: 1969
- Authors: King, Neville Edwin
- Date: 1969
- Subjects: Moduli theory , Mohair , Wool
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5528 , http://hdl.handle.net/10962/d1012640 , Moduli theory , Mohair , Wool
- Description: Fibres used in textiles can be classified broadly into natural fibres and synthetic fibres. Natural fibres can be either animal, such as wool, mohair and camel hair, or vegetable such as cotton, flax and hemp. In the development of synthetic fibres numerous polymers have emerged which have no real natural counterpart and are unique in their mechanical and chemical behaviour. Often the synthetic counterpart of a natural fibre has properties with certain advantages from the textile point of view, but, simultaneously, may exhibit other properties which have disadvantages. Nylon 6 and nylon 6-6, for exemple, are extremely strong and generally easier to dye than animal fibres. On the other hand, they absorb relatively little water vapour and therefore do not give the buffering action characteristic of hygroscopic fibres, once they are woven or knitted into cloth. All textile fibres belong to the chemical class of polymers, i.e. they are made up of repeating molecular units which are linked together to form long chains. In wool the chains are made up of amino-acids which cluster together to form protein chains. Three of these protein chains, coil around each other to form what is termed a proto-fibril. The proto-fibrils make up the micro-fibrils, each of these consisting of eleven of the three chain proto-fibrils. The micro-fibrils, in turn, pack together in bundles which run parallel to the length of the wool fibre and are termed macro-fibrils. Sulphur rich amino-acids fill up the spaces between the micro-fibrils forming a matrix which binds the system into a continuous material. Intro., p. 1.
- Full Text:
- Date Issued: 1969