Performance of a Customized Cryo-Cooling System Designed for the Measurement of the Lifetime of Nuclear Excited States at Cryogenic Temperatures

Theoretical predictions that the lifetime of nuclear excited states can be varied if the nucleus is subjected to a condition that allows multiple coherent emission and re-absorption of gamma photons by the nucleus is of much interest to the nuclear physicists. Therefore, an experiment has been designed to study the possibility of lifetime variation. Based on the theory requirements, lifetime variations can be observed when the nucleus is cooled to cryogenic temperatures. Both the cryo-cooling system and the fast timing system have been developed. In the current work, the design, operation and performance of the developed cryo-cooling system is discussed. Furthermore, the effect of operating the cryo-cooling system on the gamma detection system was also studied. The cooling system has been observed to be capable of cooling the radioactive source down to 38 K. Temperature fluctuations of only 0.128% of the selected temperature were observed. This indicates the desired stability of the cooling system. On the other hand, both energy and timing resolution of the detection system were found to be affected by the mechanical vibrations of the cooling system. The effect can be reduced by cushioning the detectors and the remaining minor differences in time resolution can be accounted in the experimental uncertainty budget.Keywords: Cryogenic temperature; Cryo-cooling System; Nuclear State; Lifetime Variation; Fast Timing System; Detector

JUMBA—Strategic R4D platform for research and development in Babati District, Tanzania

United States Agency for International Developmen

Rethinking the Policies for Nurturing Teacher Identity Development in Indonesia

This study explored supports given by in-service teachers to student-teachers for professional identity development in Indonesia. In this qualitative study, sixteen student teachers taking the course of Curriculum Development at an Islamic higher education institution in Aceh were grouped into six and assigned to six schools (primary to senior high) in two districts in Aceh, Indonesia, to communicate with classroom teachers regarding lesson plan and teaching materials. We also expected them to observe classroom practices if possible. In this way, student teachers gain real experiences on how the teachers develop their lesson plans and implement them in actual lessons, as part of their professional identity development. We then interviewed all of them to delve into their experiences and perceptions of lesson preparation and teaching. The results showed that even though most schoolteachers provide spaces for student-teachers to practice designing lesson plans, most in-service teachers did not allow student teachers to observe classroom practices. This leaves a gap in the trajectory of student teacher identity development as there are few opportunities for support from the in-service teachers in this regard. However, some participants admitted that their teacher identity had been shaped by the good images of the school they visited, the courses on pedagogy they learned at university, and the instructional approaches former teachers used at schools. This study is significant because its findings can fill in the gap in the trajectory of teacher identity development by alerting in-service teachers, teacher trainers, and the government about the importance of providing school support to student teachers for developing their identity

Effects of Temperature and Salinity on Incubation Time, Hatching Success, and Larvae Survival of the Giant Tiger Prawn Penaeus monodon under Experimental Conditions

Prawns are commercially one of the most important marine resources. However, in their early developmental stages, they face challenges related to physico-chemical and environmental changes. This study aimed at investigating the effects of temperature and salinity on egg incubation time, hatching success, larval and postlarval survival of the giant tiger prawn, Penaeus monodon (Fabricius 1798) obtained from the coastal waters of Tanzania. The adult females P. monodon collected off Rufiji delta were left to acclimatize and spawn at 28.5 ± 0.5 °C and 32 ppt in the hatchery. Spawned eggs were incubated at experimental temperatures of 27 °C, 31 °C and 35 °C with three subgroups of salinities of 30 ppt, 35 ppt and 40 ppt. The incubation time was longest (15.2 hours) at 27 °C and 30 ppt, and shortest (10.7 hours) at 35 °C and 40 ppt. Hatching success was highest (85.2%) at 31 °C temperature and 30 ppt salinity, and lowest (69.45%) at 35 °C and 40 ppt. Larval and postlarval survival was suitable at 27–31 °C and 30–35 ppt. These findings suggest that optimum rearing temperature and salinity for P. monodon range 27–31 °C and 30–35 ppt, respectively. Changes in temperature and salinity above the optimum range may jeopardize the hatching and subsequent survival of P. monodon especially at their early developmental stages which are more sensitive to environmental changes. Keywords:    Penaeus monodon, Temperature, Salinity, Incubation time, Hatching success, Survival rate

Characterization and genetic analysis of maize germplasm for resistance to northern corn leaf blight disease in Tanzania.

Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2012.The majority of farmers in Tanzania have not yet adopted modern maize varieties and still cultivate landraces and open pollinated varieties (OPVs) with low production potential and susceptible to diseases like maize streak virus (MSV), grey leaf spot (GLS) and northern corn leaf blight (NLB). The NLB disease is among the major causes of low yield and has been reported in all 21 maize growing regions in Tanzania. Breeding for host plant resistance with high yielding potential and involving the community in the breeding process is expected to address the problem of low yield, NLB disease susceptibility and low rate of F1 hybrid adoption. Therefore, the study was conducted to obtain additional sources of resistance to NLB disease, high yielding cultivars with community acceptable traits adapted to Tanzanian conditions. The main objective was to contribute to increased maize productivity in the western zone of Tanzania. The specific objectives of this study were therefore to : 1) investigate maize production limiting factors for smallholder farmers in western Tanzania, 2) identify farmers and stockist perceptions, opinions and maize variety selection criteria in western Tanzania, 3) establish NLB disease status in farmers’ fields of western Tanzania, 4) determine the genetic relationships among landraces and assess maize landraces as sources of breeding materials, 5) determine the combining ability and heterosis for NLB disease resistance of eleven maize inbred lines adapted to Tanzanian conditions, and 6) determine the gene action and inheritance of resistance to NLB disease in five maize inbred lines adapted to Tanzanian conditions. The study was conducted from 2008-2011 in three diverse environments which represent all the maize growing regions in the country The participatory rural appraisal (PRA) was conducted in three districts to investigate farmers’ and stockists preferred traits for maize selection in western Tanzania, determine maize production constraints facing farmers and assess NLB disease prevalence in the same area. A focus group of 30 farmers was selected in each of the three villages. Transect walks, wealth ranking and historical profiles were used in an informal survey. One hundred and fifty questionnaires were used in a formal survey. The recorded yield was only 1 t haˉ¹. Thirteen major maize production constraints, 13 insect pests and vermin and, 11 diseases were recorded. The NLB disease was reported to be increasing in severity in all farmers’ fields. Farmers’ preferred traits included resistance to abiotic and biotic stresses, early maturity, preferred milling qualities, high storage qualities and high yielding potential. Stockists mentioned 12 preferred maize variety traits which included high yielding, disease and insect pest resistance, heavy grain, large cob size and large grain sizes. Similarity between farmers and stockist variety preference ranking were found to exist. The occurrence and distribution of northern leaf blight (NLB) disease study was conducted to assess the incidence and severity of NLB disease in farmers’ fields in seven districts. The study was conducted for two seasons. In each season, 175 fields with 5600 plants were sampled. There were sixteen varieties grown with wide NLB disease reaction variation. Gembe, a landrace, was among the three observed resistant varieties. The NLB disease has changed its distribution pattern affecting all districts of the western zone. The disease incidence in season two (2009/2010) significantly increased from season one (2008/2009) t= -3.25 (348), P= 0.001. About 30% of both means of blight incidence and severity were recorded in the area. Characterization and screening of maize landraces for northern leaf blight disease resistance was conducted to determine the genetic relationships among landraces, assess maize landraces as sources of NLB disease resistance and assess important agronomic traits for future maize improvement. Ninety breeding materials consisting of 71 landraces and 19 commercial varieties were evaluated. The average yield of landraces under research management was 2.3 t haˉ¹. Landrace TZA 3075 was identified as NLB disease resistant. Yield potential, dent grain texture, white endosperm and husk cover were important agronomic traits observed among landraces. There were high variations in terms of morphology and NLB disease resistance among the landraces. Five principal components contributed to 71.98 % of total variation. Clusters analysis revealed five distinct groups of landraces. Leaves/plant, infested leaves/plant, lesion number, lesion length, lesion width and NLB disease incidence traits highly contributed to variation and grouping of landraces. Combining ability analysis for northern leaf blight disease resistance was conducted to estimate the combining ability for NLB disease resistance of 11 maize inbred lines adapted to Tanzanian conditions, determine maternal effects which are involved in NLB disease resistance in maize germplasm, and determine the heterosis in the F1 hybrids. A full 11 x 11 diallel cross was performed. All top ten experimental hybrids in each of the three sites had negative midparent heterosis for NLB disease severity. The overall mid-parent heterosis means for yield across sites was 152%. The mean sum of squares for GCA was highly significant (P< 0.001) on disease severity indicating additive gene action effects. Mean sum of squares for SCA were highly significant for disease severity and yield implying non-additive gene action effects. The mean squares for reciprocal effects were highly significant on yield and non-maternal sum of squares had significant effect (P<0.05) on yield. The GCA contribution was high for disease severity (91%) and lesion number (85%). Almost, all GCA effects for NLB disease resistance were negative implying contribution to disease resistance. Due to preponderance of the additive gene action, recurrent selection could be used to improve the resistance of inbred lines while the non-additive gene action could be exploited in breeding for disease resistant hybrids. Generation mean analysis of northern leaf blight disease resistance was conducted to determine the mode of gene action involved in the inheritance of resistance to NLB disease in five inbred lines adapted to Tanzania at contrasting environments, estimate heterosis and heritability in five tropical inbred lines. Generation mean analysis was conducted using a six parameter model comprising P1, P2, F1, F2, BCP1 and BCP2 generation progenies. The mean sum of squares for environment, replication with the nested environment, generations, generations x environment interactions were highly significant (P<0.001). The full model of additive, dominance, additive x additive and additive x dominance epistatic effects was highly significant (P<0.001). Nonetheless, the additive gene effects were predominant ranging between 57% and 89% which was matched by large heritability (54%-85%). The average degree of dominance ranged between -0.52 and 0.88 supporting observations of partial dominance. The NLB disease severity showed a continuous distribution in all three sets for F2, BCP1 and BCP2 populations which is an indication of quantitative nature of inheritance and additive gene effects. The mid parent heterosis ranged from -19 to 1%. Therefore, resistance to NLB disease could be improved through selection by exploiting the additive gene effects. The epistatic gene effects would cause less complications because they were negligible (<25%). The client oriented breeding for maize northern leaf blight disease resistance was carried out to perform farmers and stockists assessment on the 110 F1 experimental maize hybrids and compare them with breeders selection criteria. Breeders selection criteria ranked 10 top high yielding experimental hybrids. Farmers developed 14 while stockists developed 13 selection criteria. The most preferred hybrids by farmers were VL 05616 x CML 159, CML 159 x KS03- 0B15-47 and EB04-0A01-304 x CML 442 while stockists preferred VL 05616 x CML 395, EB04-0A01-304 x CML 442 and VL 05616 x CML 159. Two F1 experimental hybrids EB04- 0A01-304 x CML 442 and CML 159 x CML 442 appeared in all top five ranked hybrids by breeders, farmers and stockists. Generally, findings showed that, farmers, stockists and breeders coincide in some selection criteria but also differ in other cases

A GATE-based Monte Carlo simulation of a dual-layer pixelized gadolinium oxyorthosilicate (GSO) detector performance and response for micro PET scanner

The purpose of this study was to simulate the GSO detector of a micro PET using GATE simulation platform. The performance and responses of the simulated GSO detector assembly were evaluated by comparing the simulated data to the experimental and XCOM data to validate the simulation platform and procedure. Based on NEMA NU-4 2008 protocols, the performance of GSO detector in terms of sensitivity was simulated and compared to the experimental data. Similarly, the GSO detector response to photons interaction was simulated and compared against the XCOM data for absorbed intensity ratio in the GSO detector and survived intensity ratio in Pb blocks. Results showed that simulated and experimental sensitivities agreed well with R2 of 0.995 and two overlapping bands at 95% confidence. An agreement with R2 of 0.972 and 0.973 as well as with overlapping bands at 95% confidence was obtained in simulated and XCOM data for absorbed and survived intensity ratio in the GSO detector and Pb blocks, respectively. The observed agreements demonstrate the accuracy of the simulation method to mimic the behaviour of the GSO detector. The validated GATE algorithm for micro PET scanner is therefore recommended for simulation and optimisation of collimator design in further studies. Keywords: GATE simulation, Experimental data, XCOM data, GSO detector, micro PET. &nbsp

Reproductive Potential of the Mackerel Scad, Decapterus macarellus (Cuvier, 1833) in the Coastal Waters of Tanzania

This study investigated the reproductive biology of Decapterus macarellus&nbsp;locally known as ''Msumari", one of the most economically important scad fish along the coastline of Tanzania. Fish samples were collected from ring net artisanal fishers operating in Tanga and Bagamoyo coastal waters, monthly between April 2019 and September 2020. Findings indicated that&nbsp;D. macarellus&nbsp;spawns throughout the year with peaks in August at Tanga and September at Bagamoyo. Overall sex ratios (M: F) were 1:1.03 (Tanga) and 1:1.2 (Bagamoyo) in favour of females. The males and females of&nbsp;D. macarellus&nbsp;at Tanga attained the first maturity at 145.5 mm and 153.2 mm, respectively, whereas at Bagamoyo males attained first maturity at 149.9 mm and females at 156.9 mm. Batch fecundity was not statistically significant (U&nbsp;= 500.5;&nbsp;p&nbsp;= 0.73), with Tanga having mean values (± SE) of 46,105.9 ± 4243.4 ova and Bagamoyo 43,082 ± 2272.9 ova. Although this species appears to spawn all year round, management interventions such as seasonal closure and reduced fishing effort should be used during their spawning peaks to protect the spawners, recruits and ensure the species' long-term survival in the Tanzanian coastal waters. Keywords: Scad; Decapterus macarellus; reproductive potential; ring net fishery; Tanzania

Scaffolded assistance in Kenyan secondary school classrooms :the case of Maseno University student teachers of English

PhD ThesisThe thesis furthers understanding of sociocultural perspectives on teaching and learning by investigating the process of scaffolding in whole class interactions among pre-service teachers of English in the Kenyan secondary school context. While the linguistic features of scaffolding have been previously investigated, the research, most commonly undertaken in Western contexts such as Europe or North America, often assumes the availability of physical tools and artefacts, technological equipment and class sizes more commonly found in such contexts. This study provides insight into the linguistic features of scaffolding in a non-Western context where such resources are uncommonly available to teachers working with much larger classes. Further, this thesis provides insight into some of the factors limiting the practice of scaffolding as a social process of teaching English and proposes some ways of improving the use of scaffolding in terms of the pedagogy of teaching English in the Kenyan context. A qualitative embedded case study design was employed using the case of Maseno University student teachers of English, during their teaching practicum in schools. Research data comprised of: 17 video-recorded English lessons; a selection of Maseno University teacher education documents relevant to the student teachers’ education; and an interview with a Maseno University English teaching lecturer. A microanalysis of teacher discourse moves in 11 interactive episodes, labelled as learner-centred were compared with examples of the far more commonly found teacher-led episodes to reveal and understand the scaffolding strategies used by student teachers to assist learner’s learning of English. A sociocultural analysis of Kenyan secondary school classroom environments, together with a content analysis of the course documents and key themes identified in the interview provided information on the background factors affecting the manner in which scaffolding is practiced in Kenyan classrooms. The findings show that scaffolded assistance in the Kenyan context is characteristically achieved by teacher-learner interactions in whole-class activity. The learner-centred episodes revealed that in response to learner needs, student teachers guide interactions and create dialogic spaces for learner participation in joint and productive problem solving by contingently using discourse strategies. The discoursal strategies found fall under five key mechanisms of assistance namely: collaboration, modelling, questioning, feedback and instructing. Challenges such as: the culture of teaching and learning in Kenya; an incoherence iii between the teacher education syllabi and the prescribed syllabus for learning English in secondary schools; large class sizes and the scarcity of teaching resources were found to have a genuine impact on the use of pedagogical approaches encouraging learner-centred scaffolding. Moreover, student teachers’ understanding of the practice of scaffolding as a process of teaching was also hindered by the lack of theoretical or pedagogical foundation work in relation to a sociocultural approach to learning in the language teacher education curriculum. The findings imply a relationship between the education culture and language as mediational tools in different contexts and therefore the need for a context driven approach to the adoption and application of sociocultural theory in different teaching and learning contexts. Furthermore, it suggests that employing a sociocultural perspective to guide the policy and practice of teacher education could support improved quality in the teaching of English in Kenya. This thesis also presents ways forward for this complex task in educational contexts with large classes, limited physical resources, and a prescribed curriculum, such as Kenya.The Commonwealth Scholarship Commission, United Kingdom

Metaphorical expressions for successful doctoral study abroad

Timely positive feedback to students pursuing a Ph.D. program motivates completion.  Drawing upon Skinner's Reinforcement theory and Lakoff and Johnson's Conceptual Metaphor Theory (CMT), this study aimed at uncovering metaphors employed in feedback practices by exploring the linguistic expressions of supervisors and peers, which encouraged students to complete their Ph.D. studies in Australia. The methodology employed the use of a semi-structured interview to delve into the lived experiences of two Indonesian Ph.D. students (currently EFL lecturers) during their studies in Australia. The results that the use of positive expressions from supervisors and peers strongly motivated the students to complete their Ph.D. programs. The four types of expressions used served to praise, give hope, give direction as feedback to support completion, and reminders to keep the student on track. The following expressions were commonly used to motivate completion: "Do not worry, mate, you will get there," and "Wow, it's great work! I understand it is not easy to write academically in such good English, but you did." These expressions metaphorically imply that:  "PhD study is a journey," and "Work speaks louder than words." These findings suggest that positive verbal feedback from supervisors' and peers' can motivate PhD students' completion

Review of the Imaging Performance and the Current Status of the Cascade Gamma-Rays Coincidence Imagers

Various studies that have investigated the detection of gamma coincidence events have revealed that design factors and image reconstruction approaches dictate the spatial resolution, coincidence efficiency, and levels of statistical noise of the detection system. In the case of imaging, cascade gamma-ray coincidence (CGC) imagers coupled with collimated detectors offer promising values for both spatial resolution and coincidence efficiency. However, to date, no CGC imager with single or multiple collimated detectors has reported a performance level beyond 6.7 mm spatial resolution (FWHM) and 6.0 ×1ncidence efficiency. Given the recent developments and the current interests in high resolution and localization of an individual decaying nucleus, there is a need for CGC imagers with higher performance in terms of spatial resolution and efficiency. Therefore, deploying a CGC imager coupled with multiple collimated detectors may prove to be of value in nuclear imaging and probably in clinical application