Digital Commons Network^™

Comparison Of Various Methods For Estimating Wave Incident Angles In The Nearshore Zone, As Ngusaru

Tanzania Journal of Science

Five different methods were examined for their suitability in estimating the inshore wave incident angles on a nearshore zone with a complex topography. Visual observation provided preliminary estimates. Two frequency independent methods and one frequency dependent method based on current meter measurements were examined. Another frequency dependent method based on collocated bottom pressure and current meter measurements was also examined. The results from all the methods provided a reasonably consistent estimate of the inshore wave incident angles. The frequency independent methods gave exactly the same results while the frequency dependent methods had a 5% relative error among themselves. Between frequency …

The Polarising Effects In Sintered Kaolin, Fm D'Ujanga, Y Kaahwa, L Atteraas

Tanzania Journal of Science

The polarizing effects in sintered kaolin samples were analysed in terms of the sample density (or porosity) using direct current (dc) techniques. More porous samples exhibited higher polarizing effects than the less porous ones. The conduction carriers in kaolin samples at room temperature were found to be mainly electrons, with ionic conduction being enhanced by the moisture content with the pores. The influence of the uniaxial pressure and particle-size on the compacted and sintered density of the ceramic have been studied, and a density-pressure relationship before- and after-sintering conditions obtained

Studies On Benthic Denitrification In The Chwaka Bay Mangrove Sediments, Zanzibar, Sm Mahommed, Rw Johnstone

Tanzania Journal of Science

Denitrification was measured at three sites in a narrow tidal creek in the Chwaka mangrove ecosystem. Denitrification arising from water column nitrate (Dw) was low (< 0.1μM Nm-2h-1) and there was little spatial and seasonal variation in Dw rates in the creek. Coupled nitrification-denitrification (Dn) was found to be low, but within the range measured in other mangrove sediments. Average values ranged from 0.01 to 0.45 μM Nm-2h-1 and showed strong spatial variations. The low denitrifcation rates observed in the creek were possibly as a result of the low availability of NO3 and high C:N values of the organic matter in the sediment. Spatial variations in denitrification rates were due to variations in concentration levels of organic matter and possibly to disproportionate competition for inorganic nitrogen between denitrifiers and benthic autotrophs among sites. There were no seasonal differences in denitrification rates. Results from the present study suggest that sediment denitrification does not play a major role as a sink for N in this ecosystem

Interpretation Of Refelction Seismic Data From The Usangu Basin, East African Rift System, Ei Mbede

Tanzania Journal of Science

Reflection seismic data collected by AMOCO Tanzania Oil Company in the 80s, are herin used to correlate the main Usangu Basin parameters to those estimated from outcrop, gravity and aeromagnetic data. The seismic data are further used to constrain the geometry of crustal extension in this south-western sector of the East African Rift System (EARS) in Tanzania. Three distinct sedimentary packages on top of the basement reflector are interpreted and correlated to the Permo-Carboniferous Karoo rocks, the Jurassic/Cretaceous and Miocene Red Sandstone Group and Miocene to recent Lake Beds in the adjacent Rukwa basin, where the ages of the sedimentary …

Tectonic Setting Of Gabbroic Rocks In The Western Part Of The Lupa Gold Field, South-West Tanzania, Sr Mnali

Tanzania Journal of Science

There is a pronounced occurrence of gabbroic rocks in the western part of the Lupa gold field, SW Tanzania. These rocks occur in the peripheral part around the Saza-Chuya granodiorite with which it makes a gradiational, unchilled contact. The rocks have been altered or metamorphosed to low-grade greenschist facies as indicated by the presence of secondary epidote, penninite, chlorite, sericite and calcite. The majority of major-element oxides show scattered variation trends against immobile elements such as Zr, indicating some degree of element mobility during post-crystallization processes of alteration or metamorphism. Major-trace-element data show that the gabbroic rocks in the study …

Mobility And Immobility Of Mid-Ocean Ridges And Their Implications To Mantle Dynamics, Me Kamwaya

Tanzania Journal of Science

In the past two decades, the mobility of mid-ocean ridges relative to the mantle (absolute migration) have been correlated with major observable features, such as, spreading asymmetry and asymmetry in the abundance of seamounts. The mobility of mid-ocean ridges is also thought to be an important factor that influences the diversity of ridge-crest basalts. However, the mobility of mid-ocean ridges have not yet been defined and mapped. The absolute migration of global mid-ocean ridges since 85 Ma has been computed and mapped. Global mid-ocean ridges have migrated extensively at varying velocities during that period. Presently, the fast-migrating ridges are the …

Comparative Development And Population Growth Of An Exotic Stemborer, Chilo Partellus (Swinhoe), And An Ecologically Similar Congener, C. Orichalcociliellus (Strand) (Lepidoptera: Crambidae), Jacob C. Mbapila, William A. Overholt, Hosea Y. Kayumbo

All Peer-Reviewed Publications

Studies were conducted to determine the effect of temperature and diet on the development of Chilo partellus (Swinhoe) and Chilo orichalcociliellus (Strand) (Lepidoptera: Crambidae). Developmental times of C. partellus and C. orichalcociliellus for the egg, larval and egg-adult life stages were inversely related to temperature. The larval developmental period of C. orichalcociliellus reared on artificial diet was longer than the developmental period on natural diet. Chilo partellus had a higher intrinsic rate of natural increase than C. orichalcociliellus at all diet/temperature combinations except natural diet at 31°C. © 2002 ICIPE.

Assessment Of Heavy Metal Pollution In The Lupa Gold Field, Sw Tanzania, S. R. Mnali

Tanzania Journal of Science

The concentrations of AS, Cd, Cr, Cu, Hg and Pb were determined in water, stream sediments, soil, and mine tailings from Lupa Gold Field (LGF), SW Tanzania, in order to assess their pollution levels. As, Cd and Cr were determined by automated Graphite Furnace Absorption Spectrophotometry. Cu and Pb were analysed by Air-Acetylene Flame, while Hg was analysed by Cold Vapour Atomic Absorption Spectrophotometry. The mean concentrations obtained were: As: 0.44 ppb (water), 1.2 ppm (sediments), 0.44 ppm (soil) and 5.2 ppm (tailings); Cd: 0.03 ppb (water), 0.03 ppm (sediments), 0.03 ppm (soil) and 0.50 ppm (tailings); Cr: 1.4 ppb …

Tectonic Setting And Uplift Analysis Of The Pangani Rift Basin In Northern Tanzania Using Apatite Fission Track Thermochronology, E. I. Mbede

Tanzania Journal of Science

Thirty four new Apatite Fission Track (AFT) ages and 32 track length distributions from samples of basement rocks flanking the Pangani rift, East African Rift System (EARS) are presented, in an attempt to elucidate the uplift and erosion of the rift flanks. The ages fall in the range of 207±15 to 48±4 Ma, spanning from Early Jurassic to Early Tertiary. These ages are much younger than the last termal event in the Mozambique belt that form the basement complex and are interpreted to represent the most recent tectonic events. Track length (TL) distributions suggest that uplift and erosion of the …

Sources And Diagenetic Alteration Of Organic Matter In Coastal Waters At The Vicinity Of Dar Es Salaam, Tanzania, Ann Muzuka

Tanzania Journal of Science

The stable isotope compositions of organic carbon (OC) and nitrogen, contents of OC and nitrogen, and C/N ratios for four short cores, which were recovered from Msansani Bay (WO 57), off Msimbazi River (WO 76) and Dar es Salaam harbour (WO 62 and WO 74), are used to document temporal variation in the sources and diagenetic alteration of organic matter (OM). The δ15N and δ13C values at sites WO 57, WO 62 and WO 74 show a trend of down-core decrease to the base of the core, and such a down-core trend could be related to diagenetic loss of compounds …

The Emplacement Age Of Gabbroic Rocks And Associated Granitoids Of The Liganga-Msanyo Complex, South Eastern Tanzania, M. A. H. Maboko

Tanzania Journal of Science

The Msanyo Gabbro and the associated Mdando granitoids, which intrude Paleoproterozoic high-grade metamorphic rocks of the Ubendian Belt in southern Tanzania, yield imprecise Sm-Nd whole rock isochron ages of 1608±134 Ma (ε (Nd) = 2.1) and 1642±100 Ma (ε (Nd) = 1.6), respectively. These ages are indistinguishable at the 95% confidence level, indicating that the two rock suites were intruded at the same time. A more precise estimate of the time of emplacement is provided by a 5-point mineral isochron age of 1505±42 obtained from one of the gabbro samples. Calculated initial ε (Nd) values and mean crustal residence ages …

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, M A H Maboko

Tanzania Journal of Science

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 …

Physicochemical Characteristics Of Some Locally Manufactured Edible Vegetable Oils Marketed In Dar Es Salaam, F N Ngassapa, O C Othman

Tanzania Journal of Science

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, H N Kundaeli

Tanzania Journal of Science

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 …

Test Of The Additive-Dominance Model Of Grain Weight And Grain Uniformity Of Oat, Avena Sativa L, Genotypes, Sowm Reuben

Tanzania Journal of Science

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 …

Production Of Biogas From Water Hyacinth: Effect Of Subtrate Concentration, Particle Size And Incubation Period, J H Y Katima

Tanzania Journal of Science

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.

Baseflow Separation Based On Storage-Outflow Modelling Of Streamflow Recessions, With Application To Semi- Arid Catchments In Tanzania, S Mwakalila

Tanzania Journal of Engineering and Technology (TJET)

Discharge in many rivers is Often fed by baseflow provided by drainage of the saturated zone in the shallow permeable soils. It is becoming clear that the outflow from this saturated zone is not linear proportional to storage as is commonly assumed in many algorithms. The objectives Of this study theretore, are first to explore the extent to which the assumption of linearity in storage-outflow relationships is valid and secondly to introduce an alternative approach to baseflow separation algorithms for estimating direct mnoff time series. Numerical analysis Of streamflow recessions from the semi-arid catchments of the Great Ruaha basin in …

Electrokinetic Cha Raci'erisation Of Colloidal A-Alumina, J Ntalikwa

Tanzania Journal of Engineering and Technology (TJET)

Electrophoretic mobility (uD is an important rneasurable parameter in studying the electrokinetic properties of a colloid dispersion. This parameter is Often convened into zeta potential (C) Which piays a great role in thc description Of the stability towards aggregation Of dispersed particles. In this paper, measurements of Of colloidal a-alumina dispersed in various concentrations of electrolyte arc reported. It was observed that, the isoelectric points (the pH at which us = O) occurred at 7.52 ± 0.32, 8.05 ± 0.11 and 7,95 ± 0.18 in Naci, KCI and NaNOs respectively. The isoelectric point was observed to be a function Of …

Comparative Analysis Of Rng K-E And 'Standard' K-C Models For Fluid Flow Around A Cylinder, A Temu

Tanzania Journal of Engineering and Technology (TJET)

A two-dimensional computational scheme for simulating fluid flow around a cylinder was investigated. RNG (Re-NOrmalisation Group) and 'standard' turbulent closure models were used. simulation was implemented with assistance OfFLOW-3D computational fluid dynamics (CFD) code. The governing equation Of fluid motion, in Eulerian form, included body forces as well as surface forces. The computational model predictions for fluid velocity showed good agreement between the two models. Comparison Of the viscosities showed a large deviation from the two models, with RNG k-E model giving a better approximation. Comparison Of the velocity around the cylinder, as obtained from RNG k-c model, with approximation …

Cerumen Composition By Flash Pyrolysis-Gas Chromatography/Mass Spectrometry, Craig N. Burkhart, Michael A. Kruge, Craig G. Burkhart, Curtis Black

Department of Earth and Environmental Studies Faculty Scholarship and Creative Works

Objective: To assess the chemical composition of cerumen by flash pyrolysis-gas chromatography/mass spectrometry.

Study Design: Collected earwax specimens were fractionated into residue and supernatant by means of deoxycholate. This natural bile acid produces significantly better disintegration of earwax in vitro than do presently available ceruminolytic preparations, and also has demonstrated excellent clinical results in vivo to date.

Patients: The sample for analysis was obtained from a patient with clinical earwax impaction.

Results: The supernatant is composed of simple aromatic hydrocarbons, C₅-C_{l 7} straight-chain hydrocarbons, a complex mixture of compounds tentatively identified as diterpenoids, …

Composition And Anaerobic Digestion Of Single And Combined Organic Fractions Of Municipal Solid Waste Of Dar Es Salaam, A K Kivaisi, J Mukisa

Tanzania Journal of Science

The composition of major categories of municipal solid waste (MSW) of Dar es salaam city was determined. Food remains and vegetable matter constituted 80-90% of the categories. Organic fractions of the individual categories contained 18-20 % total solid (TS), 30-50 % (dry weight) total fibre and 1-1.3 % nitrogen. The assorted organic fractions were tested for anaerobic conversion into biogas at 55°C in batch cultures for 14 days with a mixed population of microorganisms. At a substrate concentration of 6-8 g volatile solids per litre fermenter volume (g VS l-1 FV) individual fractions were degraded by 51-75% and gave methane …

Influence Of Endocrine Activity On Larval Development In Busseola Fusca (Fuller) (Lepidoptera:Noctudine), M Njau

Tanzania Journal of Science

The present study investigated the role of juvenile and moulting hormones in development of Busseola fusca. Morphometric measurements were used to distinguish differences in endocrine activity between non-diapause and diapause development with regard to the prothoracic glands and the corpora allata. The corpora allata of non-diapause larvae were similar in size to those of diapause larvae. The critical period for the prothoracic glands to produce the required titer of ecdysone for further development was by the third day after ecdysis to the last larval instar. Juvenile hormone extracts from haemolymph of Busseola fusca larvae in non-diapause and diapause development had …

Subsidence History Of The Rukwa Rift In South West Tanzania Analysed From Ivuna Well, E I Mbede

Tanzania Journal of Science

The variation in subsidence rate during rift basin development is a good indication for the Geodynamic history of a sedimentary basin. The sedimentary section of Ivuna Well is herein used to explain the structural evolution of Rukwa Basin within the Western Rift of the East African Rift System. The sedimentary record of Ivuna Well is extracted from published information. The effects of sedimentary load, corrected for compaction and variation in water depth, and lake-level have been removed to obtain the "tectonic subsidence." Curves show two phases of accelerated subsidence related to the fault controlled rifting phases: The Karoo rifting and …

Preliminary Evidence For A Second -525-545 Ma Old Event Of Granilate Facies Metamorphism In The Mozambique Belt Of Tanzania And Its Implication For A Two-Stage Model For Gondwana Assembly, M A H Maboko

Tanzania Journal of Science

Garnets from two samples of the Kitumbi granulites in the Mozambique Belt of north eastern Tanzania yield Sm-Nd ages of 525±15 Ma and 545±15 Ma. At the 95% confidence level, these ages are younger than the 576 ±15 to 634±16 Ma (Mean 606±12 Ma) ages previously reported from the more extensive Eastern Granulites. The Kitumbi garnets are therefore interpreted as dating cooling from a granulite facies event that is distinctly younger than the 630-700 Ma event that produced the Eastern Granulites. Unlike the Eastern Granulites, the Kitumbi rocks occur as small enclaves not separated from the surrounding amphibolite facies gneisses …

Heavy Metals And Organic Pollutants In Sediments Of Dar Es Salaam Harbour Prior To Dredging In 1999, J F Machiwa

Tanzania Journal of Science

Heavy metals and organic contaminants were analysed in the sediments of the inner area of the Dar es Salaam harbour. Complementary analytical parameters, such as, the organic carbon content and the silt/clay fraction of the sediments showed good positive correlation (r = 0.64). Stations that had high content of fine grain material in the sediment also indicated relatively high level of organic carbon and pollutants. The Florida criteria (MacDonald 1993) for assessment of pollution of tropical marine sediments was adopted in oredr to evaluate the extent of pollution in Dar es Salaam harbour sediments. The Florida criteria is one of …

Thermogravimetric Study Of Gadolinium Chlorotungstate In Air Between 25 And 1500°C., F N Ngassapa, N U Venskovskii

Tanzania Journal of Science

Using DTA, X-ray powder diffraction, chemical and optical methods, the thermostability of Gd3WO6Cl3 was investigated. The compound was relatively stable on heating in air up to 710oC. Above this temperature it exhibited two decomposition temperature ranges (710-900oC and 900-1130oC). The final product consisted of a mixture of gadolinium tungstate of different composition. This suggests the decomposition scheme of polyphase products

Application Of Vibrational Techniques In Determination Of Dynamic Properties Of Agricultural Products-State Of The Arton Of Vibrational Techniques In Determination Of Dynamic Properties Of Agricultural Products-State Of The Art, Silas Kajuna

Tanzania Journal of Engineering and Technology (TJET)

Vibration is one of the techniques employed in the determination of dynamic properties of fruits and vegetables. It entails generation of a mechanical or acoustic vibrational signal which is propagated through the flesh of the agricultural material. A transducer is either attached or held close to the specimen to monitor the propagation of the signal through the specimen. The manner in which the signal is transmitted through the material is analyzed, and the dynamic properties of the specimen which relate to its firmness or its internal being are derived. The technique has been around for the past 30 years or …

Mathematical Modelling Of Road Bumps, E. S. Massawe

Tanzania Journal of Engineering and Technology (TJET)

In this paper, a general mathematical model that may be used for construction of a road bump on an inclined road is developed. It is shown that if the parameters for the inclination are set to zero, the resulting model reflects the special case of a flat road. Existing experiences are briefly highlighted and a case study was done on different locations along the University Road to demonstrate the developed model.

Tidally Induced Flow In Chwaka Bay Zanzibar, O U. Mwaipopo

Tanzania Journal of Science

Time series data of currents and sea current levels recorded by current meter and tide gauges, respectively from Chwaka Bay, Zanzibar were obtained from the entrance near to Mapopwe Creek and at the middle of the bay. The analysis of the data reveals that the tidal currents had an asymmetry near the entrance to Mapopwe Creek where the ebb currents were stronger than flood currents although the ebb periods were considerably longer than flood periods.

Stable Isotope Compositions Of Sedimentary Organic Matter Off Zanzibar Town, Ann Muzuka

Tanzania Journal of Science

Stable isotope compositions of sedimentary organic carbon for sediments collected off the Zanzibar Town averaged -17.9%. Low isotope values of organic carbon, which were associated with high C/N ratios, were observed within Zanzibar harbour suggesting a significant contribution of terrestrial organic matter to the harbour. Sediments collected outside the Zanzibar harbour were richer in ¹³C than those collected within the harbour area. This 13 enrichment in ¹³C can be attributed to a decrease in the influence of terrestrial organic matter (0M) and high contribution of' sea grasses. A decrease in the influence of terrestrial OM is further supported …