College of Natural and Applied Sciences

Permanent URI for this community

http://192.168.13.253:4000/handle/123456789/1249

Back to the main page

Browse

Now showing 1 - 20 of 1510

Preliminary plant design and economics for the extraction and purification of mafura nut oil from mafura nuts
(University of Dar es Salaam, 1881) Mwaipopo, L. J. N
A preliminary plant design and economics of a plant for the extraction and purification of Mafura nut oil for edible purposes has been carried out. A plant capacity of 4000 MT/year of edible oil is proposed, with 1000 MT/year of low grade oil and 700 MT/year of Free Fatty Acids (FFA} as by-products to be sold to soap manufacturers. The main raw material is the Mafura nuts from the mafura tree (Trichiliaemetica), a tropical tree found in most parts of the country. Mbeya region, the proposed plant location is currently estimated to be able to supply approximately 20 % of the 10,800MT/year of nuts required to feed the plant. It is assumed that the rest will be obtained from individual farmers and from government mafuru plantations to be set up in advance of the establishment of the plant. The design of the process has been based on mechanical and solvent extraction principles, Fupi's work on the removal of the bitter and emetic principle(s) from the oil, and on the practical experiences gained by the Morogoro based Multipurpose Oilseeds Processing Company. Mechanical expression followed by solvent extraction with n-Hexane has been chosen in favour of both mechanical expression alone and solvent extraction alone because the former method gives a rather low extraction efficiency while the latter is expensive. Degumming of the oil is achieved by mixing with acetic anhydride (0.1% v/v) followed by water (3.0 % v/v) and centrifugation. Neutralization of the Free Fatty Acids in the oil is achieved by use of 1 .OM NaOH followed by centrifugation. The oil is then washed twice with 15 w% portions of 0.25M NaOH and once with 15w % water and centrifuged each time. During the refining process, low grade oil and crude Free Fatty Acids are recovered as by-products. The oil is vacuum dried and vacuum bleached and deodorized and finally filtered thorough polishing filter to packaging or to storage at 550c. The economic viability of the project has been established. With an estimated total capital investment of 47:4 million Tshs s after tax Rate of Return on Investments was found to be 32% with a Discounted Cash Flaw Rate of Return {DCFRR) of 40%. The break-even point was found to be at 50% of plant capacity with a pay-back period of 2½ years and the shut-down point at 28% plant capacity. This economic analysis was arrived at by using the following estimated prices for raw material and products;- Delivered Raw mafura nuts -1.85 Tshs/kg, Edible Mafura oil - 20 Tsh/kg, Low grade oil -10 Tshs/kg FFA-5 Tshs/kg.
Degeneration and regeneration in the insect central nervous system
(University of Dar es Salaam, 1968) Boulton, Patricia Suzanne
Reactive Axons show non-degenerative morphological changes in the portion of connective between the injury and ganglion (the reactive segment of the connective). Degenerating Axons lose axoplasmic integrity, show autolytic changes, and are gradually phagocytosed during the first twelve days after injury. Regenerating Axons form new tissue distal to the reactive region; this is the regenerating portion of the connective. A Neuroma forms when growth from out axon tip is directed back into the reactive portion of the connective.
Comparative morphometry and breeding in the family istiophoridae in the equatorial western Indian ocean
(university of Dar es Salaam, 1968) Merrett, Nigel Robert
A tuna longline survey of billfish (family Istiophoridae) has been carried out from latitude 00° to 13°S, and from the coast of eastern Africa to longitude 45°E. during this survey, From September 1964 to October 1967, 265 specimens of istiophorids were caught, consisting of: 77 sailfish, Istiophorus gladius (Bloch) 1793; 156 striped marlin, Tetrapterus auday Philippi 1887; 7 shortbill spearfish, Tetrapterus angustirostris Tanaka 1914; 17 blue marlin, Makaira nigricans Lacepede 1803; and 8 black marlin, Makaira indica (Cuvier) 1831. On the basis of morphometric analyses involving the pelvic, dorsal and anal fins together with vertebral and fin ray counts, the co-specificity of the istiophorid fish in the equatorial western Indian Ocean with those from the Pacific Ocean evidence provides a useful picture in the consideration of co-specificity, it is conclusions on population structure. Distribution and seasonal abundance of the species under review are discussed in terms of catch per 100 hooks. Distribution is considered by depth range and degrees latitude, and seasonal abundance by monsoon periods. The evidence indicates that I.gladius, T.audax and M. indica are more abundant during the N.E. monsoon. The abundance of T. angustirostris and M. nigricans is shown to increase in the S.E. monsoon. It is shown that I. gladius and T. audax. For the remainder, however, too few data were available for similar meaningful computations. Size composition of the catches is shown by the analysis of length and weight frequencies, and preliminary estimayes of year classes present in the catches of T. audax are given. The sex ratio of the species is examined. The overall catches of I.gladius indicate a significant preponderance of males, although when considered by seasons this is not so. A significant preponderance of males, although when considered by seasons this is not so. A significant majority of female T. audax occurs both in the overall catches and those during the S.E. monsoon, but during the N.E. monsoon the ratio is 1:1. No reliable estimate is it present possible for the other species. The morphology of the urino-genital system is described for all species and it is shown to be uniform except for T. angustirostris. The gonads of this species are shown to be Y-shaped rather than bilaterally symmetrical as in the other istiophorids. The histology of the gonads is described and is related to the spermatogenic and cogenic cycles. Gonad maturation indices for males and females are established based on both macroscopic and histological evidence. The indices are used to study breeding in the species caught from the survey area. The relative gonad weight is also considered as a means of assessing the stage of godan development. This ratio is shown to have a significant correlation with maturity in females, but not in males. Evidence of godan examination indicates that no species spawns internsively in the area. From the same evidence it is concluded that the seasonal increase in istiophorid numbers in the survey area is primarily due to a feeding migration, rather than to breeding activity. The size at first maturity of the species investigated is considered and provisional observations made. It is emphasized that information is sparse and that further analysis must involve more detailed information. The fecundicy of females I. gladius, T. audax and T. angustirostris is examined by estimation from the ovaries of gravid specimens. It is suggested from the evidence that this increased with size in individuals of the same species.
Survey of culicoides (diptera: ceratopogonidae) of East Africa: their taxonomy and distribution.
(University of East Africa, 1968) Khamala, Canute P. M.
Synonymy affecting the family name, Ceratopogonidae, is discussed: A historical review of the discovery of Culicoides in East Africa between 1900 and 1966 and the medical and veterinary importance of Culicoides as vectors of disease, particularly those caused by viruses and filariae, is given. A brief account of the morphological characters used in identification is given together with information on materials and methods used for collecting and studying the adult Culicoides captured. Sixty one species of Culicoides were found, 25 of which are new to science and 48 (including the new species) are recorded for the first time in East Africa. Among established species, the female of kibatiensis and the males of trifasciellus, expectator, brucei, guinquelineatus, albopunctatus and adersi are described for the first time. Reasons for grouping the 61 species into 15 "species groups" of closely related members and definitions of quantitative characters used in classification and identification are given. Separate keys for identifying slide-mounted female and male Culicoides that were collected from East Africa during this study, together with a detailed description of each taxonomic entity (established species being compared with published descriptions) are given. Confusing synonyms are fully discussed. A distribution list of East African Culicoides according to ecological zones is attempted. The generic identity of Ceratopogon imperfectus (= Culicoides imperfectus Goetghebuer) is fully discussed and a detailed description of Ceratopogon imperfectus is given.
Aspects of green manuring with special reference to soil carbon dioxide evolution
(university of Dar es Salaam, 1969) Henson, Henry Michael George
Early investigations into the effects of the incorporation of a green crop into the soil in tropical areas produced conflicting results. There was evidence in Nigeria particularly to show that green manures benefited the succeeding crops. In Uganda, however, no lasting effects were found and the practice was abandoned as a means of maintaining soil fertility. The objective of the experiments to be described was to re-examine the practice of incorporating green manure in terms of yield from a succeeding crop and effects on the soil. The work was carried out at Makerere University College Farm, ten miles from Kampala, Uganda. In part I the green manuring experiment, chemical analysis of the soil and test cropping results are described. The crops grown as green manures were sunn hemp (Crotalaria juncea) and maize and they were compared to weed fallow. The crops were incorporated by rotary cultivation and four crops were grown in one year. Supplementary water was applied to two of the treatments to determine whether water was a factor limiting growth, and nitrogen fertilizer was applied to two of the maize green manure treatments. The total dry matter incorporated in the year from the weed fallow was 3,400 1bs/acre (3,800 kg/ha) and from the sunn hemp 11,000 ibs/acre (12, 400 kg/ha). The maize green manure without nitrogen produced 20,800 1bs/acre (23, 300 kg/ha) and with nitrogen 29,000 1bs/acre (32, 550 kg/ha). A test crop of maize was then planted to determine if in fact there was any effect on soil fertility as measured by yield. The original green manure plots were split for fertilizer in the ratio of 3:2:1 of Nitrogen, Phosphate and Potash respectively, the other none. The growth of the test crop was followed by height measurements. The analysis of the data obtained showed that there was a significant inter-action between the fertilizer applied and the green manure treatments. When the test crop was harvested, the only significant response was to the application of the fertilizers, for the test crop did not respond to the intensive green manuring. Soil chemical analysis showed that the incorporation of green manures significantly increased soil carbon, potassium and calcium plus magnesium. Foliar analysis of the test crop showed that nitrogen, phosphorus and potassium levels were all above the accepted critical levels. Also the analysis showed that greatest response of the leaves was to nitrogen in the fertilizers applied to the test crop. In Part II some aspects of soil carbon dioxide evolution are discussed. The objectives of this series of experiments were to measure the soil carbon dioxide flux, to relate the loss of carbon dioxide to the breakdown of organic matter, to examine the effects of temperature and moisture and to compare an accepted laboratory method with results obtained in the field. In Chapter 3 the field experiments are described where a method using soda lime as a carbon dioxide absorbent was employed. Measurements of carbon dioxide flux were made on the green manuring experiment, where it was found that the soil in the maize green manure treatments produced significantly larger quantities of carbon dioxide than either the sunn hemp or weed fallow treatments. An equation of the type dx/dt = A –yx, where A = kg carbon returned per year, x = total carbon in the active soil layer and y = fraction of total carbon lost annually by decomposition, was used to relate the carbon loss with time. On the weed fallow treatment the half-life of organic matter was found to be 6.4 years. The moisture content of the soil was found to be the most important factor governing the production of soil carbon dioxide. When the soil was dry and saturated with water the carbon dioxide. When the soil was dry and saturated with water the carbon dioxide flux was severely reduced. Soil temperatures at 5cm depth did not have any effect on carbon dioxide flux. An experiment was carried out to determine the effect of cultivation on carbon dioxide flux and also whether maize decomposed more quickly than sunn hemp. After rotary cultivation of both maize and sunn hemp, carbon flux rose significantly but after two weeks fell back to its original level. There similar quantities of maize and sunn hemp were incorporated it was found that firstly there was a linear relationship between carbon dioxide flux and quantity of matrial incorporated and secondly sunn hemp decomposed more quickly than maize. Maize and sunn hemp were grown in hydroponic beds to determine the influence of root respiration on total carbon dioxide flux. The roots of the maize and sunn hemp were found to produce about 3.5 gm carbon dioxide/m^2/day; as the root weights were found to be higher than in the field the figure was probably rather lower under examined the use of the macro-respirometer was found to be unsatisfactory. A barium peroxide method was used, showed that sunn hemp decomposed more quickly than maize and that when the quantity of material was increased, so the carbon recovered rose. A comparison was made between the laboratory and field methods, and it was found that where similar quantities of dry matter were incorposition by about 400%. Measurements of the heats of combustion and carbon content of the green manures were made, so that an estimate of the accuracy of the field method of measuring carbon dioxide flux could be obtained. When equations relating energy content of the organic matter with energy liberated in the evolution of carbon dioxide were used, the calculated and measured carbon dioxide fluxes compared very favourably, indicating that the field method was reasonably accurate. Part III is a discussion of some aspects of the experiments. Soil moisture and temperature records from the green manuring experiment are described in the Appendix, together with methods of soil and foliar analysis, and rainfall confidence limits at the experimental area.
A study on the growth and development op grasses with emphasis on their root systems
(University of Dar es Salaam, 1969) Taerum, Ragnar
The growth, of six grasses, grown as spaced plants under two ecologically different habitats in Kenya, were studied with the object of obtaining basic information on their growth and development. This information is an essential part of general research aimed at the improvement of stability and value of rangelands in East Africa. An introduct¬ion to the grass species and the experimental sites are given and methods employed are described. Plots of Cenchrus ciliaris var. biloela, Chloris gayana var. mbarara and Panicum maximum var. makueni were established at Muguga in April 1968 and sampled nine times until March 1969. In addition, at Muguga (2,086 m, high rainfall) and Kedong (1,878 m, low rainfall) the above mentioned grasses and Cenchrus ciliaris var. mbalambala,; Sragrostis superba and Theme da triandra were sampled five times from April 1967 to February 1968 and sub¬sequently during May to July of the same year.
The macroscopic and Microscopi Functional Anatomy of the Female Reproductive Organs of the Impala (Aepyceros Welampus Lightein, 1812)
(University of Dar es Salaam, 1969) Kayanja, Bantubano
The impala is a medium- sized antelope found in eastern and central Africa. It is an intermediate feeding type of ” browsing” species with selective grazing habits but shows little tendency to migrate. A population in the rift valley near lake elmenteita was studied between January 1967 and September 1969, during which period 69 animals were collected. The prenatal and postanal female organs of reproduction were investigated by dissection, histological and histochemical techniques. The placentas was also examined with the electron microscope.Ovulation occurred at random from the left and right ovary although the embryo was always found in the right uterine horn. The development of the ova and follicles was investigated and a biphasic relationship was established. The process of follicular a tresia was studied and evidence put forward suggesting that two waves of follicular destruction occurred at around estrus time.The various stages leading to the establishment and growth of the corpus luteum were studied. The corpora lutea were tested for the presence of hydroxyteroid dehydrogenase. The mean volume of the corpora lutea as well as the mean luteal cell volume showed a rise during early pregnancy and a precipitous fall just prior to parturition. The mean luteal cell volume continued to rise even when there was evidence to show that the cell were no longe producing increasing amounts of progesteronc. Pigment was present in the luteal cells towards the end of pregnancy. The degeneration of the corpus luteum was studied. The investigation of the oviduct revealed that the epithelium undergoes remarkable charges during the sexual cycle and pregnancy. The uterotubal junction was examined.The position attachment and relations of the female reproductive organs were investigated by dissection. Observations were recorded on the extensive uterine enlargement during pregnancy. The prenatal growth of impalas was studied and cube-root weight relationship suggested for a substantial period of fetal development. The establishment and development of the placenta was examined. The relationship between the maternal and fetal tissues was studied with the electron microscope, and an epitheliochorial barrier was found. Observations were made on the vagina and vestibulum vaginae during the prenatal and postnatal stages. Sexual maturity was attained in females shortly after 12 months of age. Although the impalas bred throughout the year, two peaks of calving were detected during February to may and October to December. The observations were discussed and compared to the body of information already available on reproduction in the farm animals.
Plankton analysis relative to the feeding habits of Sardinella in Dar es Salaam waters.
(University of Dar es Salaam, 1971) Okera, Wazir
This work has involved the study of the composition and temporal fluctuations of the in shore zooplankton and the role of the different zooplanktoners as food items of the two species of sardines. From December 1968 to January 1970, night zooplakton samples were collected in darkness and under artificial light from Msasani Bay and adjacent areas and once in the Sinda Kendwa waters using a planktonnet based on the designs of CF 70 and Indian Ocean Standard nets. Surface sea water temperature of the above areas was recorded on the sampling night and salinity determination of the water was carried out for the first seven months. Over approximately the same period of 14 months, the stomach content of the commercially important East Africa Sardinella gibbosa and Sardinella albella caught in the light fishery operating in Msasani Bay and Sida Kundwa waters was studied. Morphometrics, fat content and gonad condition of the two species of sardines were also recorded. The results show that the various species of calanoide are the most regularly abundant zooplanktoners, followed by larvaces, Cypridina simosa and Cory caeus spp;l Oithona spp; Sagita spp; Euterpina, Lucifer and Oncea spp, in that order. All these zooplanktoners had a mean percentage proportion in the plankton of more than 1%. Of the lawvac of benthic invertebrates, caridean lawvac were the most abundant (mean proportion of about 4%). The members of a great majority of zooplanktoners were generally higher during the North East Monsoon. Stomach contents of S albella and S. Gibbosa showed that these two species of sardines feed principlaly on about the same fifteen zooplanktoners which are also the more abundant. The sizes of the zooplanktoners consumed varied from about 0.5 mm to about 30mm and it is suggest that within the range or organisms consumed, either size nor shape seem to be of critical importance. Feeding was found to be continuous through out the sampling period. Fishes caught during the North East Monsoon months were found to have high fat content compared to those of South East Monsoon month whose gonads however were not mature than those of the N.E. M. months.
Pathogenesis and Pathology of East Coast fever in Cattle
(University of Dar es Salaam, 1971) Munyua, William Kimani
East Coast fever (theileria parva infection) is an important killing disease of entile in east and Certain parts of Africa. The research on this disease has been recognized to be of great importance in various institutions with possible and result of finding a vaccine or a currible remendy. Pathogenesis and Pathology. “Highy –grade” steers 6-9 months old of various exotic breeds and brought from farms operating vigorous tick control were used for the study of pathogenesis and pathology of E.C.F. The parasite used for experimental infection of cattle was Theileria parva (Muguga) and also a local strain of parasite isolated from a field case of E.C.F. the pathogenesis and Pathology of the disease in the steers was evaluated on symptomatology, appearance of different stages of the parasite, haematology, changes in serum proteins and enzymes, gross pathology and histopathology. There was slight decrease in haemoglobin and packed cell levels in protracted cases. Also changes were noted in the differential leukocyte counts and slight elevation of SGOT levels again in protected causes. No changes were noted in sorum proteins. Gross and microscopical lesions were observed in most of the organs. There was often enlargement of the lymph nodes more so in the early stages of the development of the disease. Other gross lesions which were almost constantly encountered were lung oedem and abomsal ulcers. Significant microscopioal changes were lymphcytic cell infiltration in the body organs. In the lymphoid tissues, there was often lymphocytic cell proliferation but in protracted cases there was depletion of the cells from the lymphoid tissues. Degenerative changes were also noted in some organs.
The biology and fishery potential of palinurid lobsters in Tanzania.
(University of Dar es Salaam, 1973) Bwathondi, Philip Odoyo Joseph
Representatives of the crustacean genus Panulirus are widely distributed throughout the Indo-West Pacific waters. This genus is represented by five species in Tanzanian coastal waters. The five species, in the order of their abundance, are P. ornatus, P. homarus, P. versicolor and P. penicilillatus. The habitat of the adults and the larvae of each species are investigated and discussed. Length/weight relationships of both male and female P.ornatus and P.longipes have been determined. Females have been found to be slightly longer and heavier than the males (having the same carvapace length) of the same species. The gross and histological anatomy of the reproductive systems of both males and females of this genus were investigated by vital staining techniques and by standard histological sectioning techniques. Function of each system was ascertained. Captive females were reared during and after breeding to determine the number of ovulations per breeding season, moulting cycle and growth per moult. Following gonad maturity states and the abundance of barried and spent forms for one complete year, breeding season has been established. The improvement of the common methods employed in fishing and some conservation measures have been suggested.
The indigenous elements of theatre in Bunyoro and Tooro (Uganda)
(University of Dar es Salaam, 1973) Balikuddembe, Joseph M
In the available literature about Banyoro and Batooro, the social, religious, political, economic and historical aspects have had the greatest emphasis; the cultural heritage of these people has hitherto remained in the background. Consequently, indigenous rituals, ceremonies and forms of entertainment have received little or no attention as developments towards theatre. This study sets out to examine some cultural aspects of present-day Bunyoro and Tooro in order to demonstrate the existence of those elements which are forms of theatre or which possess recognizable characteristics of theatre. The necessity for this demonstration rises from the rigorous measures taken by some colonial governments in Uganda and some missionary activities not only to discredit these elements as part of kinyoro-Kitooro culture but also to exterminate them as undesirably primitive and merely pagan practices. This attitude seems to have hinged on a failure to understand that these rituals, ceremonies and forms of entertainment expressed a distinctive way of life, exhibited basic interrelationships within a specific feudalistic system and represented an attitude towards art and an effort by the people to understand and influence their environment and transform nature ages before the advent of colonialists and missionaries. The Introduction conteins a discussion of some basic concepts of theatre following the theme that theatre is an act by a performer to entertain an audience while communicating some ideas or interpretations of reality to that audience. In Part I, Chapter One surveys the present-day scene and brings out existing indigenous elements of theatre in Bunyoro and Tooro; and Chapter Two discusses significant historical factors influencing these elements, and portrays the attitude of some early missionaries and colonial administrators who have regarded indigenous rituals, ceremonies and forms of entertainment as primitive and pagan practices indiscriminately worthy of suppression. In each of the subsequent parts, there is a description and assessment of the theatrical content of each of the relevant elements. Part II embodies elements using theatrical techniques; here Folk stories and Marriage Ceremonies contribute readily to the evolution of some type characters. Part III concerns elements which are incipient forms of theatre including improvised plays; here an evolution from ritual to theatre is discernible and the best example is the gradual separation of an actor's role from that of a spirit medium. Part IV is restricted to professional and non-professional performers. A development from song to drama is emerging; one sees, for instance, love-stories acted by Runyege Troupe Dancers accompanied by song and drum rhythms. The Conclusion provides some suggestions for the development of these elements towards contemporary popular theatre; a legitimate and theatrically convincing development of these elements would require plays based on them to have an early point of attack and a quick introduction of characters and situations. There is also room for further investigation in some rituals, such as those connected with the Spirit Medium Cult, which have been found partly secret and therefore less accessible. The Appendices provide some useful and self-explanatory information regarding theatre elements in this thesis. This study covers only Bunyoro and Tooro, and the evidence about some rituals or their components is partly from the writer's personal observation and partly from reports of persons who have directly participated. However, it is hoped that the overall contribution of this study will not only throw more light on the individual theatre elements examined but will also underline the need of a justifiable development of a post-colonial theatre which will be valid for Uganda, not in terms of tribal distribution but more in terms of synthetic progress towards a profound national culture.
Investigation of the ion exchange behaviour of chromium (III) in oxalic acid solutions.
(University of Dar es Salaam, 1974) Mosha, Donnati Morris Sirito
The distribution coefficients of aluminium (III) and ion (III) in oxalic acid hydrochloric acid media were determined for strongly basic and strongly acidic ion exchange resins. In hydrochloric acid media alone and in the concentration range of 0 to 0.4 M HCL the distribution coefficients of AL (III) and Fe (III) are of the same order of magnitude. Under those conditions therefore selective separation of those metal ions is not possible. In hydrochloric acid oxalic acid solutions the situations is different. By careful choice of hydrochloric acid oxialic acid proportion it is possible to obtain sufficiently large difference in the values of the distribution coefficients of the respective metals. Results have shows that good separations are obtained by eluting those metals from anion exchange resins with a 0.3M hydrochloric acid solution containing 0.019M oxalic acid. Elution characteristics at this optimal concentration of the eluting reagents are presented. Aluminium appears first in the eluate due to a lesser degree in the retention of its oxalate complexes on the rasin this is accounted for by the relatively lower stability of the Al-oxalate complexes. The Fe (III) oxalate complexes have a higher relative stability and hence due to stronger retention; Fe(III) is selectively desorbed after the AL fraction. As a consequence of the kinetic inertness that is characteristics of Cr (III), results obtained for the substitution reaction of hexaquochromium (III) indicate a poor rate in the formation of sorbable anionic chromium oxalate complexes. This difference in properties offers a unique possibility for selective anion exchange separation of chromium (III) from the multi-component system Cr (III) - Fe (III) AL (III). By use of low temperature, moderate concentrations of oxalic acid and minimal times of interactions between (Cr (III) and oxalic acid the unreacted hexaquochromium (III) posses uretained through the column and almost 100 percent recoveries are possible by washing with cold oxalic acid at high flow rate. The retained AL (III) and Fe (III) are selectively eluted with HCL oxalic acid solution. Selective cation exchange separation of two component mixture Cr (III) AL (III) or Cr(III) Fe (III) is also discussed. By a similar manipulation of conditions, the unreacted chromium (II) is retained on the cation exchange resin while AL (III) or Fe (III) is eluted by washing with oxalic acid. The disruption of Cr (IIII) from the resin in this case is best affected by peroxide oxidation to Cr (IV).
The NI (5200 A) emissions in the tropical atmosphere
(University of Dar es Salaam, 1974) Njau, Ernest C.
The afterglow of nitrogen in a discharge tube was first observed in 1884 and up to 1946 attempts were made at intervals to explain it. It is generally agreed that the earliest photographic observations of the night sky spectrum were made by Slipher (1915-19197.5 these were followed by other spectrographic researches (e.g. Lord Rayleigh, 1920–1921(4) and 1922-1932; (5) Dufay, 1922–1923(6)7. An attempt to identify the atomic nitrogen spectral lines was made by McLennan, Ireton and Thompson (19267.' In this attempt, solid nitrogen was made luminescent by bombardment with energetic electrons. Among the lines recognized then were 5192.4 Å and 5204.4 Å. The chances of observing exactly the 5200 Å line were brightened after the observation of the atomic nitrogen? P’s line at 3466.4 Å by means of experiments incorporating high pressure. When the experiments were repeated, using panchromatic plates, the relatively weaker nebular line at approximately 5200 X was observed /J. Kaplan, 19397. The transition that leads to this line is forbidden. The excitation of such forbidden atomic lines which involves a change of electron spin cannot be accounted for by direct proton impact; it is necessary to consider secondary excitation mechanisms. In fact, as far back as 1954, there was little doubt /Seaton, 19537 that most of the forbidden atomic emissions arise from various secondary excitation processes and not from excitation of the main atmospheric constituents by direct proton impact. Although the existence of what is now termed "airglow" was established photometrical in 1909 /by Yntema7,9 the weak NI doublet: 5198 $ ( 453/2 - 2D5/2, 3/2 ) was first detected in the twilight several years later by Courtes (19507.(10) Subsequent observations of the same emission have been made (n. Dufay, 1951, 1952, 1953; Nicolet and Pastiels, (11) 19527. The NI 5200 Å line was later detected in the nightglow N. Dufay, 1959; Krassovskii, 1958; Blackwell et al., 19607.(12)(13) (14) Ttwa It was found to be an integral part of the Polar Auroral Spectrum (Evifte, 19597(15) although (surprisingly) no other NI lines between 5200 & and 6650 & were observed. Courtes T9507 (16) and Dufay /79507(17) reported that NI 2D - 4s 5198.5-5200.7 Å might be present in the nightglow spectrum, Besides, Courtes 7795071o detected some twilight line emissions "in the neighborhood" of 5199 Å which he attributed to? D - 4s 15198.5 - 5200.7 Å of NI. Gartlein and Spherman /19527 reported the appearance of 5199 | late in the display, and persisting when the rest of the spectrum dies away, thus hinting at a relatively longer lifetime of the N (CD). Seaton 7795371) estimated that I (5199) rarely exceed 14R. At about the same time, Hunten confirmed to Seaton (in a private communication) that while I (5199) is comparable to I (5228) (N, Negative Group; 0, 3) on photographic plates with exposures of an hour or two, it had not (by then) been detected using a high-speed photomultiplier. On further investigations, Dufay (1950, 1952, 1953718) discovered that this line emission forms an integral part of the early sunrise atmospheric airglow, though much feebler. Dufay observed that although it always appeared during twilight and early part of the night in summer, its appearance during winter was less frequent. Among its other properties as noted by Dufay are: - (i) Its average photon intensity along the zenith was about 2 x 107 cm-2 sec-1. (ii) Its height of emission was noted to be equal to or greater than 100 km. It exhibits no correlation with magnetic activity. Dufay (19507 proposed that the presence of 5199 line emissions results partly from the process N (As) + hy (5199 X) — 1(2) and especially the process N (4s) + hy (3466) -N (??) which is then followed by the process N (? P) > N (2D) + hr. (10,400 8). Owing to the fact that 1(2D) has a natural radiative life time of about 26 hours /Garstang, 19567(19) it was proposed that the 5199 Å emission proceeds after sunset, but this proposal received criticism from Bates /19527 because if allowance is made for collisional deactivation, the number of free nitrogen atoms required to account for the observed intensity is incredibly high (e.g. Seaton, 1955 (20) estimated such a number to be 2 x 10 cm). The role played by deactivation processes on N (D) is not to be under-estimated. Seaton (19537 obtained the value of the ratio I (5199)/1(3467) with and without consideration of deactivation processes. With the assumption that deactivation is absent, I (5199)/ (3467) is greater than 9.4 while the same ratio drops to within the range 0.0125 - 0.5 if deactivation processes are taken into account. These deactivation processes have been found to be responsible for the fact that the lifetime of N("D) in the upper atmosphere is less than the natural value of about 26 hours (e.g. it is about 15 min. at 175 km, 200 lm and 300 km). (21) Bates (79527(22) suggested that the source of the excited nitrogen atoms could be the dissociative recombination process 1+ (x) + 1 + n (?). Prior to this, Bates, Massey and Pearse /19487 had suggested as of importance the secondary excitation process N,* + e + N' whereby the energy available for excitation of the two atoms is the difference between the dissociation energy and the ionization potential of the neutral molecule. More than one value of the energy available for excitation has been obtained: 5.82 eV using the dissociation energy advocated by Gaydon (19527 (9.752 eV); 8.20 eV using the dissociation energy advocated by Herzberg (T9507 (7.373 eV). Other possible reactions which involve N (D) were suggested by Seaton (T9537, and they are 1 (?) + 0(3p) -> N (48) + O (')) + 0.41 eV and N (2p) + 1, 1(?) + ,'. In their conclusions, Bates (19527 and Seaton (T9537 seem to concur that the NI lines are excited by dissociative
Studies on the ecological genetics of the land snail sitala jenynsi (PFR)
(University of Dar es Salaam, 1975) Kasigwa, Peter R.F.
The shell-banding polymorphism of the arboreal snail S. jenynsi (Pfr.) was used for micro-evolutionary studies in Central Coastal Tanzania. This urocyclid pulmonate has a 12-month life-span), sperm transfer is reciprocated by the two partners and breeding soon follows before the parental die out. Growth rates and the shell’s ultimate metrics depend on the population in question. A knowledge of parameters like numbers, density, rates of survival, loss and dilution introduced the setting of the snail, population. In dimorphic populations (Main Campus, University of Dar es Salaam) morph-ratio distribution was spatially homogeneous, temporally stable and specific for a locally. The distribution was also locally-specific in trimorphic populations (Wazo) but was usually beterogeneous in space and the frequencies of non-predominant morphs fluctuated in time. Basing on clinal distribution of morph ratios, shell-size and weight, it is held that whole or sections of parapatrically differentiated subpopulations were reduced to founder stocks which are presently evolving under mainly unstable environments. Indications of the possible involvement of climatic selection and mating non-randommess in the maintenance of the polymorphism are presented: selective predation does not appear to operate.
Study of selectively absorbing surfaces
(University of Dar es Salaam, 1975) Lushiku, Elias Musa
The present work was directed towards the production of low cost selective radiation absorbing surfaces. The optical constant n and k of electrode posited thick layers of black nickel (deposited on copper and zinc substrates at current densities ranging from 8A/m2 to 20A/m2) were measured using an ellipsometer of simple construction. Films of Black Nickel of thicknesses ranging from 10nm you 130nm were deposited on different copper and zinc substrates at constant current densities of 10A/m2 and 20A/m2 at 24oC by changing the times of electrode position. For each specimen the values of ellipsometer parameters Y and D were measured before and after electrode position. The curves of Y and D against time of electrode position (i.e. thickness) were compared with calculated variations Y and D versus film thickness using the theory of thin film optics. It was observed that the theoretical predictions were in good agreement with experimental results for black nickel on copper substrates. Hence the thickness of the films could be estimated. Results for zinc substrates were not in agreement with theory. The spectral reflectivity and hence the selectivity of single and double films of black nickel on copper substrates were computed as a function of thickness. Those predicted results were in good agreement with experimental observations of initial temperature rise and maximum temperature reached by specimen placed in simulated solar radiation.
Electrolytic production of HCI and KOH using ion exchange membranes
(University of Dar es Salaam, 1975) Makange, Abdallah A
The behaviour of a caution and an anion selective membrane in close contact was investigated. The double membranesyst4m were characterized under dynamic conditions. Concentration polarization on the double membrane system was found to be a function of current density though the system and depended on the amount of stirring of the solution bounding the membrane system. Current voltage characteristic of the double membrane separating HCL and KOH solutions showed a strong non-linear relationship. Similar relationship was obtained when membrane separations was increased to 0.1 cm. The possibility of producing a base and on acid from a salt and water in five compartments cell, separated by ion selective membranes was investigated. The following total reaction was found to occur. KCL +H20 = HCL + KOH. The acid and base produced were separated and analysed and the current efficiency of the membrane system established Efficiency as high as 97% was obtained. The efficiency was found to be dependent on membrane thickness and concentration of the bonding KCL solution. It was found however to be independent of current density as long as the system was under steady state conditions. Some analytical data on transport of anions OH and Cl across cation selective membrane and transport of cationsHr and Kr across anion selective membrane were obtained. The ion selectivity of the anion membrane was found to be slightly poor in comparison to that the caption membrane. The investigation though in laboratory scale indicate that the process may have advantages compared to other processes commonly used when the need is for an acid and base and where the usual by products of alkali electrolysis, H2 and C2 gases are not in demand. A theoretical treatment of the opposite reaction namely HCL + KOH = KCL + H20 is provided whereby it is pointed out that application of the above process would serve as a storage of electrical energy.
The determination of the film thickness of a stationary liquid film (Nernst film) on the surface of a cation exchange membrane
(University of Dar es Salaam, 1975) Migiro, Cleophas L. C
Ag(s) /AgC1(s)| NaC1 (aq. C)|Cation exchange membrane|NaC1 (aq. 0.1M)|AgC1(s) /Ag(s) The two cells together gave us a set up which enabled us to measure the limiting current values as a function of concentration in the anode chamber and the stirring rate in that compartment. The limiting current was the only unknown parameter in the equation which could be used to determine the thickness of a liquid film adhering on the surface of the cation exchange membrane. The equation was a mathematical derivation by theoretical consideration of what is happening in the liquid layer. Fick’s 1. Law and the depletion of the 〖Na〗^+ in the layer were considered. Two methods were tried out: first the measurement of the potential drop across the cation membrane with the variation of current in the system (42) and the secord one was based on the hypothesis that water molecules in the layer dissociate at a certain limiting current value into protons and hydroxyl ions. With an appropriate experimental set up the amount of produced protons could be determined as a function of current. The plot of the rate of change of the produced protons against current density could enable one determine the limiting current value by extrapolation. Permaplex C-20 and Permaplex A-20 from Permutit Co. Lts., were used as the cation and anion exchange membrane respectively. AG/aGc1 electrodes were used both for emf measurements and as current transporting electrodes. Sodium chloride was the electrolyte used.
A description of the coral Fauna of the cast African coast
(University of Dar es Salaam, 1975) Hamilton, Hamis George Hume
The first part of this report is a qualitative descriptive account of the distribution of corals on six selected reefs at Malindi, Kenya and Dar es Salaam, Tanzania. Some typical coral zonation patterns on various reef types are described, and notable features of the coral structure of East African reefs are defined. It is concluded that of other western Indian Ocean reefs for which data is available, particularly in the Seychelles and the Southern Maldive Islands; a notable feature of East African reefs is the importance of Galaxes clavus as a dominant species. The remainder of the paper is devoted to systematic description of a collection of reef-building corals made in Kenya and Tanzania. The collection is identified to a minimum of 88 species in 34 genera; the systematic descriptions are accompanied by photographic illustrations. The total number of hermatypic coral genera recorded from East Africa is increased to 50. The coral fauna of East Africa is discussed and compared with published data from reefs in the Western Indian Ocean, and faunal differences are shown to be mainly in the relative abundances of some genera and species comprising a basically common fauna.
Studies on vesicular - arbuscular mycorrhiza in rice (Oryza - Sativa L.). Masters dissertation, University of Dar es Salaam. Available at(http://41.86.178.3/internetserver3.1.2/detail.aspx)
(University of Dar es Salaam, 1975) Mmbaga, Margaret Thomas
The morphology of V-A mycorrhiza was found to be similar in rice and species of Cerpus, Cyperus, Kyllinga, Digi taria, Eriochloa, Spilanthes and Commelina. Structures were similar to those described in the literature for Endone spp. on other plants. Extra-matrical vesicles on infected roots were ascribed to Gigaspora spp. Twelve different types of chlamydospore, azygospore and zygo spore extracted in soil sievings from nine collecting sites in Tanzania appeared to belong to the genera Gigaspora, Glomus and Acaulospora. Differences in intensity of infection and in spore numbers in the soil may be attributed to soil nutrients, soil moisture, pH or soil sand content. No correlation was established between spore numbers in the soil and infection intensity. Distribution of the different spore hypes did not appear to be associated with edaphic or host related factors. There was no evidence of host specificity; findings of a field survey and controlled experiments indicated that flooding reduced mycorrhizal infection but did not completely suppress it. Rate of mycorrhizal development was related to increase in root dry weight. Arbuscules were shown to be ephemeral structures whose disappearance coincided with maximum growth of the host. It is suggested that arbuscule degradation, however, may be a fungus rather than a host regulated phenomenon. The effect of mycorrhiza on rice plant growth was inconsistent increasing plant dry weight in some pot experiments but not in others. In two experiments it was shown that mycorrhiza increased phosphorus uptake by plants when soil phosphorus was low. The merits of different forms of inoculum and methods of application are discussed, spore-impregnated filter paper was satisfactory. Infected root pieces were more convenient but may have contained a mixture of fungi which could account some of the discrepancies in these results.
Students on the Ratio and Polymorphism in Hyperolius Puncticulatus (VFR) Rhacophorida eat Amani, Tanzania.
(University of Dar es Salaam, 1976) Muze, Siphiwe Elizabeth
Hyporoliuspuncticulatus (Rhacophoridae), were sampled from a man-made lake at Amani, in the Eastern Usambara Mountains, Tanzania. This sampling formed the basis of an ecological and genetical study, carried out between April and October, 1975.The primary sex ratio was found to fit with the normal 1:1 expectation, whereas the sex ratio in the adult population was found to be almost 9:1 in favors of males. The proportion of males to females did not remain constant from month to month as fluctuations were evident during the peak of the reproductive season and when young males returned to the lake from the forest peripheral to the lake. Several factors have been suggested as contributing, at least in part, to the sex ratio disparity. First, the females migrate from the lake to the peripheral forest more than the males. Second, there is evidence of selective predation accentuated by the dimorphic nature of the species. Third, there could be differential mortality between the sexes. The ecological and genetical significance of distorted sex ratios have also been discussed.The analysis of polymorphism in Hy-peroliuspuncticulatus has confirmed that, like most of the Hyperolius species, itis highly polymorphic with five distinct morphs identified and named substriatus, choloensis, maculztus, and reticular. The males are more polymorphic than female since the maculatus form consists of only males. The morph frequencies show that the most abundantand probably the most successful morph is substriatus, 60% of the total sampled population. The implications of polymorphism in this species are that it maximizes protection from a variety of predators under variable textural and seasonal conditions. Natural selection, therefore, is most influential in such polymorphisrns. Apostatic selection, Gene flow and possibly genetic constitution of the individual frogs have been suggested as major factors which may be maintaining polymorphism inH. puncticulatus at Amani. Apostatic selection has,however, been emphasized mainly because of the nature ofH. puncticulatus predators (snakes, birds, spiders) and their searchimage formation. The mimicry relationship of the spider and frog suggest a well-developed predation pressure situation. Some aspects of the genetics of these frogs have been elucidated, though inconclusively, due to the high mortality in the reared crosses. However, sex-linkage, sex-limited gene effects and differential selective advantage have been suggested as major factors which may be operating in maintaining some of the morphs. For example, the abundance of the all-male maculatus morph, especially in the light ofthe evident assortative matings in these frogs, implies that it has some selective advantages over the other morphs.Capture - recapture data analysis has revealed thatL. puncticulatus population at Amani is fairly large. The implication of a large population as an indication of stable gene frequencies has been stressed.The reproductive behaviour of these frogs was investigated and it has been shown. that the eggs are laid all at once in batches of c. 130 eggs, enclosed in a gelatinous mass and partially submerged in water. The ability of these eggs to develop in submerged and exposed conditions has been suggested to be evolutionarily significant for the survival of this species, especially in rapidly changing environmental conditions which H.puncticulatus may face. The growth rates of larvae using weights and lengths showed an initial rapid growth, which slowed down at metamorphosis. The post-metamorphosis juveniles show a uniform phenotype with characteristic cantho-dorsolateral and middorsal lines. The uniformity in phenotype and the migratory behaviour of these juveniles appear to play a major role in protecting the species against predators and against intraspecific competition, respectively.

Browse

Browsing College of Natural and Applied Sciences by Issue Date

Results Per Page

Sort Options