African Journals Online
Tanzania Journal of Science

Volume 27 2001
Abstracts

PRODUCTION OF CELL WALL ENZYMES IN PEPPER SEEDLINGS, INOCULATED WITH ARBUSCULAR MYCORRHIZA GLOMUS ETUNICATUM


AC Odebode
Department of Botany, University of Dar es Salaam
P.O. Box 35060, Dar es Salaam, Tanzania

AO Salami and O Osunubi
Department of Botany and Microbiology
University of Ibadan, Nigeria

ABSTRACT
Pepper seedlings inoculated with arbuscular mycorrhizal AM fungus, Glomus etunicatum, produced cellulase, polygal-acturonase and pectin methylestrase enzymes. The activities of the enzymes increased as the pepper seedlings matured in age, showing that the activity of the enzymes in the seedlings was age mediated. The pectinases showed higher activity than the cellulase enzyme which may indicate establishment of the mycorrhizal in the host. The significance of this finding is that there is an initial infectivity factor in (AM) fungi interactions with plant just like in other host-parasite interaction. 


CASHEW NUT SHELL LIQUID AS AN ALTERNATIVE CORROSION INHIBITOR FOR CARBON STEELS


JYN Philip, J Buchweishaija and LL Mkayula
Department of Chemistry, University of Dar es Salaam,
P. O. Box 35061, Dar es Salaam, Tanzania


ABSTRACT
Cashew Nut Shell Liquid (CNSL) has been tested as a corrosion inhibitor for carbon steel in 3% aqueous NaCl solution (pH 6) saturated with carbon dioxide gas at 30°C under static conditions using ac-impedance and potentiodynamic polarisation techniques. It was found that CNSL reduces the extent of the electrochemical processes taking place on carbon steel undergoing corrosion. The corrosion rate of the carbon steel was reduced by over 92 % when only 300 ppm of CNSL was applied. This indicates that CNSL is a potential corrosion inhibitor for carbon steels in CO2 environment.


THE GEOCHEMISTRY OF BANDED IRON FORMATIONS IN THE SUKUMALAND GREENSTONE BELT OF GEITA, NORTHERN TANZANIA: EVIDENCE FOR MIXING OF HYDROTHERMAL AND CLASTIC SOURCES OF THE CHEMICAL ELEMENTS


MAH Maboko
Department of Geology, University of Dar es Salaam
P.O. Box 35052, Dar es Salaam, Tanzania


ABSTRACT
Major and trace element compositions of samples of Banded Iron Formations (BIF) from the Neoarchaean Sukumaland Greenstone Belt of Geita in northern Tanzania reveal that the BIF precipitated from hydrothermal solutions. Fe-Ti-Al-Mn systematics suggest that the hydrothermal deposits have been contaminated, by up to 20% by weight, with detrital material having a composition similar to modern deep-sea pelagic clays. SiO2 and Fe2O3 contents are 48.2 to 88.5% and 8.9 to 49.1% respectively. Al2O3 contents lie between 0.33 and 2.1% and show no correlation with either Fe2O3 or SiO2. Al2O3 is, however, positively correlated with Ti, Ga, Hf, Rb,Th, Zr and Sr but not with CaO, the alkalies and the total Rare Earth Elements (REE). The other major element oxides are generally present in negligible amounts. The samples are characterised by mean Zr/Hf and 144Sm/143Nd ratios of 48± 5 (2 SE) and 0.10±0.01 (2 SE) respectively, similar to mean upper continental crustal values. Shale-normalised REE patterns are nearly flat, except for small positive Eu and very slight negative Ce anomalies and reveal that, compared to average upper crust, the abundances of the REE in the BIF are up to an order of magnitude lower. Chondrite-normalised patterns are characterised by light (L) REE enrichment, flat to slightly depleted heavy (H) REE, slightly positive Eu anomalies and very small negative Ce anomalies. The HREE-depleted patterns are similar to patterns derived from granite-dominated upper continental crust and indicate that the bulk of the REE in the Geita BIF can not have been derived from a mixture of Neoarchaean sea water and bottom hydrothermal solutions. The trace element data, and the REE in particular, indicate that, despite their relatively low proportions, granitic detritus probably derived from contemporaneous felsic flows and pyroclastics are the cause of the dominant trace element geochemical signature of the BIF. 




HEAVY METALS IN GREEN VEGETABLES AND SOILS FROM VEGETABLE GARDENS IN DAR ES SALAAM, TANZANIA

OC Othman
Department of Chemistry, University of Dar es Salaam, 
P.O. Box 35061, Dar es Salaam, Tanzania


ABSTRACT
Edible portions of five varieties of green vegetables, namely amaranth, chinese cabbage, cowpea leaves, leafy cabbage and pumpkin leaves, collected from several areas in Dar es Salaam, were analyzed for lead, cadmium, chromium, zinc, nickel and copper. Except for zinc, the levels of heavy metals in the vegetables grown at Tabata area were much higher than in the vegetables from Ukonga and Kiwalani. Amaranth and pumpkin leaves had more than 60% higher content of heavy metals, especially copper, chromium and lead, than the other vegetables. All vegetables from Tabata, Buguruni and Sinza had lead-levels higher then the FAO/WHO recommended permissible levels in foods. Amaranth, leafy and chinese cabbages had high zinc content. Zinc levels in chinese cabbage and leafy cabbage from Kiwalani, Sinza and Ukonga areas were higher than the permissible FAO levels in foods. The soils from Tabata and Sinza areas had high levels of lead, chromium, zinc and copper while the soils from Kiwalani, Makongo and Ukonga areas had high levels of zinc and copper. There was a direct positive correlation between the zinc and lead levels in soils with the levels in vegetables. Such relation was absent for the other heavy metals. Considering an average daily intake of only 202g of fresh vegetables per person per day, all the vegetables grown at Tabata and Buguruni had lead concentration which would be a health hazard for human consumption.


PHYSICOCHEMICAL CHARACTERISTICS OF SOME LOCALLY MANUFACTURED EDIBLE VEGETABLE OILS MARKETED IN DAR ES SALAAM

FN Ngassapa and OC Othman 
Department of Chemistry, University of Dar es Salaam, 
P.O. Box 35061, Dar es Salaam, Tanzania


ABSTRACT 
The physicochemical properties (refractive index, saponification value, Free Fatty Acid (FFA) value, iodine value, acid value, peroxide value and tocopherol content) of seven edible vegetable oils manufactured in Tanzania, were assessed using standard procedures of the Association of Official Analytical Chemists (AOAC). Also determined were the levels of these properties with respect to shelf storage of the products. When compared with standard values recommended by the Codex Alimentarius Commission of FAO/WHO and with other published results, the locally produced vegetable oils were found to be of fair quality but of poor storage stability.


COMPARISON OF DIRECT RETURN AND BIRTH-DEATH RETURN RECEIVERS

HN Kundaeli
Department of Physics, University of Dar-es-Salaam, 
P.O. Box 35063, Dar-es-Salaam, Tanzania

ABSTRACT 
The performance of frame synchronized communication systems is governed largely by the design chosen for the receiver. Some systems employ a structure in which the receiver returns directly to the sync phase when a valid marker is encountered while in the loss verify state. These have been greatly studied. In some systems, the return path in the loss verify phase is implemented as a birth-death process. These systems have not received much attention. In this report, a receiver which employs a birth-death like structure in the loss path is investigated. Expressions for the performance parameters are derived and compared with those obtained for direct return systems. It is found that both types of receivers have the same performance at lower error rates and low loss verify number, M. At high error rates and high values of M, however, the birth-death receiver outperforms the direct-return receiver. To the knowledge of the author, this is the first time that performance expressions have been reported in this form.



THE ANALYSIS OF AN OPTICAL FIBRE COMMUNICATION SYSTEM USING LASER RATE EQUATIONS

HN Kundaeli
Department of Physics, University of Dar-es-Salaam, 
P. O. Box 35063, Dar es Salaam, Tanzania

ABSTRACT
Fibre dispersion has been the main limitation to high-speed data transmissions employing optical fibres. Various techniques and methods for combating this limitation have therefore been proposed. Such techniques include electrical and optical dispersion compensation, optical and electrical pulse shaping, and modifications of the fibre dispersion profiles. Some of these techniques and methods have resulted into very effective but expensive systems, and it has been difficult to adopt them. Others have resulted into inexpensive systems with moderate performance, and some of these have been adopted. In the present paper, the effect of electrical pulse shaping on dispersion-induced pulse distortion is investigated by computer simulation techniques. The results show that the detrimental effects of the dispersion can be greatly reduced without incurring very high costs. Moreover, this method is applicable to systems employing standard optical fibres, the major component in the already installed systems.



OCCURRENCE AND ACTIVITY BUDGET OF THE LEOPARD TORTOISE GEOCHELONE PARDALIS, IN NORTHERN TANZANIA 

J Kabigumila
Department of Zoology and Marine Biology, University of Dar es Salaam, 
P O Box 35064, Dar es Salaam, Tanzania


ABSTRACT
Occurrence and activity budget of the leopard tortoise, Geochelone pardalis were studied in northern Tanzania between October 1993 and June 1996. Tortoises occurred most frequently in short grass (51.5%) and along roads and track verges (33.9%), but only occasionally in the bush undergrowth (6.7%) and shambas (3.6%). Walking (46.3%) and feeding (37.2%) were the most frequent activities. Resting was observed only occasionally (13.6%) while courtship (1.9%) and drinking (0.9%) were rarely recorded. Activity budget differed significantly between the age classes and habitats, but not between the sexes. Juveniles walked more frequently (59.3%) than other age classes. Walking was most frequent along roads and tracks (68.8%). Adult tortoises rested more frequently (18.7%) than other age classes but the difference was not significant. The proportions of individuals resting in the various habitats differed significantly, with resting being most frequent in the shrub undergrowth (93.3%). Juveniles were observed feeding less frequently than other age classes but the difference was not significant. Feeding was recorded in all habitats, but it was least frequent in the shrub undergrowth. 




INCIDENCE OF INJURIES AND MORTALITY IN THE LEOPARD TORTOISE, GEOCHELONE PARDALIS, IN NORTHERN TANZANIA

J Kabigumila
Department of Zoology & Marine Biology, University of Dar es Salaam,
P O Box 35064, Dar es Salaam, Tanzania


ABSTRACT
Observations were made of injuries and mortality in the leopard tortoise (Geochelone pardalis) in northern Tanzania between October 1993 and June 1996. Tortoise injuries were more frequent at unprotected (15.3%) than at protected sites (4.7%). Fire was the most frequent cause, accounting for 44.0% of the injuries. Of the animals encountered, 12.9% were found dead. Dead animals were encountered more frequently at protected (25.4%) than at unprotected sites (8.3%). Carapace injuries (6.8%) and road kills (5.1%) were the only causes of mortality identified. Mortality was higher in adults (13.9%) than in immature animals (5.5%), and in females (13.9%) than in males (6.4%). Mortality was more frequent at the Arusha Region (46.8%) than at the Mara Region sites (7.6%). 




PRODUCTION OF BIOGAS FROM WATER HYACINTH: 
EFFECT OF SUBTRATE CONCENTRATION, PARTICLE SIZE AND INCUBATION PERIOD

JHY Katima
Department of Chemical and Process Engineering, 
University of Dar es Salaam, P.O. Box 35131 Dar es Salaam, Tanzania


ABSTRACT
A study was conducted, at constant temperature, to determine the effect of substrate concentration, particle size and incubation time on biogas production from water hyacinth. Substrate concentration was varied between 5-30 g/l of water, particle size between <1 mm - 3 mm and incubation period between 1-6 days. The maximum methane prodction of 72.53% v/v at substrate concentration of 25 g/1 and particle size less than 1 mm for water hyacinth shoots was achieved after five days of incubation. However, for the whole water hyacinth plant, methane content was 65.67% v/v at the same conditions.




TEST OF THE ADDITIVE-DOMINANCE MODEL OF GRAIN WEIGHT AND GRAIN UNIFORMITY OF OAT, AVENA SATIVA L, GENOTYPES


SOWM Reuben
Sokoine University of Agriculture, Department of Crop Science,
P. 0. Box 3005, Morogoro, Tanzania

ABSTRACT
An investigation of the genetic mechanisms controlling grain weights for the primary and secondary grains uniformity expressed in primary: secondary individual grain weight (P: S IGW) ratio and % tertiary grains produced was conducted using a backcross experiment'. Two oat, parental genotypes, I.L82-1657 (pistillate) and 10589 Cn (staminate) with different grain weight characteristics were hybridized to obtain 6 backcross generations viz. P1, P2, F1, B1, B2 and F2. The scaling test indicated that overall average, primary and secondary individual grain weights and % tertiary grain weight produced failed to satisfy the additive - dominance model and digenic interactions were detected except for the secondary individual grain weight. Grain weight uniformity expressed as P:S IGW ratio satisfied the additive - dominance model and was highly heritable (h2 narrow sense >98%). However, additive gene effect was important in the control of all the grain weight variables except the primary: secondary grain yield ratio. Dominance effect was important only for the overall average grain weight and the proportion of tertiary grains produced. Attainment of uniformity of oat grains looks promising through genetically improving the P:S IGW ratio but is challenged by the presence of non-allelic interactions in the control of % tertiary grain weight.