Demonstration of an optical-coherence converter

Studying the coherence of an optical field is typically compartmentalized with respect to its different optical degrees of freedom (DoFs) -- spatial, temporal, and polarization. Although this traditional approach succeeds when the DoFs are uncoupled, it fails at capturing key features of the field's coherence if the DOFs are indeed correlated -- a situation that arises often. By viewing coherence as a `resource' that can be shared among the DoFs, it becomes possible to convert the entropy associated with the fluctuations in one DoF to another DoF that is initially fluctuation-free. Here, we verify experimentally that coherence can indeed be reversibly exchanged -- without loss of energy -- between polarization and the spatial DoF of a partially coherent field. Starting from a linearly polarized spatially incoherent field -- one that produces no spatial interference fringes -- we obtain a spatially coherent field that is unpolarized. By reallocating the entropy to polarization, the field becomes invariant with regards to the action of a polarization scrambler, thus suggesting a strategy for avoiding the deleterious effects of a randomizing system on a DoF of the optical field.Comment: 7 pages; 6 figure

The role of growth centres in rural development: I. theory, methodology, data

This paper summarizes the basic theory, methodology and data Of an extensive research project carried on in Muranga District from June 1972 to August 1973. This project was a joint venture between the Department of Geography, University of Nairobi and the Department of Geography, Carleton University, Ottawa. The project was funded by the International Development Research Centre, Ottawa, Canada. The concept of growth centres plays an important part in the 1970-74 Development Plan and the basic hypothesis of this project is that the growth centre strategy, if refined and further developed could play a vital role in rural development in Kenya. In essence, it could form the keystone of a spatial strategy of rural development. It is argued that rural problems and urban problems should not be viewed in isolation but as an inter-related spatial system. The small place in the rural areas becomes vital in such a strategy as it is the interface between urban and rural systems, and an effective rural development strategy should concentrate on this interface. The research project set out to answer two basic questions; 1) What is the role of the growth centre in rural development? 2) How can this role be made more effective? To answer these questions it was necessary to build up a comprehensive data bank on the existing small centres and the people in their hinterlands. There were a number of elements involved. These included an understanding of the history of the centres; discernment and measurement of growth indicators especially the performance of the informal sector; the participation and involvement of the people; the linkages and interactions among centres and their hinterlands; the identification of the most likely centres for potential growth and diffusion of innovations and the spatial patterns of the centres together with the distribution of population. This paper will deal primarily with the methodology used and the data collected; a second paper will further develop the basic theory and give the major conclusions

Hypertension and obesity among HIV patients in a care programme in Nairobi

Objective: To determine the prevalence of hypertension and obesity among HIV patients enrolled in the Sex Worker Outreach Programme (SWOP), Nairobi, Kenya.Design: A retrospective astudy.Setting: SWOP managed by the University of Manitoba, Nairobi team.Subjects: We selected clinic visit records from HIV patients seen between 2011 and 2014, which had valid blood pressure and age entries.Interventions: We analysed data to determine prevalence and correlates of hypertension and obesity in the study population. Associations were tested using chi-square for categorical variables and t-test for continuous variables.Main outcome measures: Hypertension and obesity.Results: Three thousand one hundred ninty seven subjects were included in the study. All were HIV-positive and most (97.8%) were on ART. The mean age was 39.7 years (standard deviation = 8.8) and 72.4% of the subjects were female. The prevalence of hypertension was 7.7% (246/3197) and 31% of the study cases (798/2590) were either overweight or obese. Males were more likely to have hypertension (p < 0.001) while females were more predisposed to obesity (p < 0.001).Conclusion: Hypertension and obesity are important co-morbidities among HIV patients. Preventive and management strategies should be adopted as part of the comprehensive packages on offer at all existing HIV care and ART centres targeting those enrolled for services as well as their relatives and the community at large

Census and ear-notching of black rhinos (Diceros bicornis michaeli) in Tsavo East National Park, Kenya

This paper updates the status of the black rhino population in Tsavo East National Park (NP). Data were acquired through aerial counts of the black rhino between 3 and 9 October 2010 using three fixed-wing husky aircrafts and a Bell 206L helicopter in an area of about 3,300 km2. Based on previous sightings of rhinos, the area was divided into 14 blocks, with each block subdivided into 400 m transects. An aircraft flying at about 500 m above the ground was assigned to carry out the aerial survey following these transects within each block. Observers scanned for rhinos about 200 m on either sides of the flight paths. Intensive searches in areas with dense vegetation, especially along the Galana and Voi Rivers and other known rhino range areas was also carried out by both the huskies and the helicopter. The count resulted in sighting of 11 black rhinos. Seven of these individuals were ear notched and fitted with radio transmitters and the horns were tipped off to discourage poaching. Three of the seven captured rhinos were among the 49 animals translocated to Tsavo East between 1993 and 1999. The other four animals were born in Tsavo East. Two female rhinos and their calves were not ear-notched or fitted with transmitters. It is recommended that another count be carried out immediately after the wet season as the rhinos spend more time in the open areas while the vegetation is still green. The repeat aerail count is to include blocks north of River Galana

Hypertension and obesity among HIV patients in a care programme in Nairobi

Objective: To determine the prevalence of hypertension and obesity among HIV patients enrolled in the Sex Worker Outreach Programme (SWOP), Nairobi, Kenya.Design: A retrospective a study.Setting: SWOP managed by the University of Manitoba, Nairobi team.Subjects: We selected clinic visit records from HIV patients seen between 2011 and 2014, which had valid blood pressure and age entries.Interventions: We analysed data to determine prevalence and correlates of hypertension and obesity in the study population. Associations were tested using chi-square for categorical variables and t-test for continuous variables.Main outcome measures: Hypertension and obesity.Results: Three thousand one hundred ninety seven subjects were included in the study. All were HIV-positive and most (97.8%) were on ART. The mean age was 39.7 years (standard deviation = 8.8) and 72.4% of the subjects were female. The prevalence of hypertension was 7.7% (246/3197) and 31% of the study cases (798/2590) were either overweight or obese. Males were more likely to have hypertension (p < 0.001) while females were more predisposed to obesity (p < 0.001).Conclusion: Hypertension and obesity are important co-morbidities among HIV patients. Preventive and management strategies should be adopted as part of the comprehensive packages on offer at all existing HIV care and ART centres targeting those enrolled for services as well as their relatives and the community at large

Methodological Decisions in Context: The Dilemmas and Challenges of Novice African Scholars

This paper emerges out of a panel discussion during a PhD week and subsequent 8th International Environmental Education Invitation Seminar held at Rhodes University in 2004 and 2005 respectively. It illuminates some insights into our struggles (as novice African researchers) in trying to respond to contextual realities as we research education and social change in African contexts, seeking insight into what counts as legitimate research in this context. The paper considers our struggles at conceptual, methodological, analytical and data generation levels, and in a politics of research. This is done by means of examples drawn from five current doctoral research projects being undertaken in east and southern African regions, using a review framework that represents fairly common dimensions of PhD research. We conclude that research, when defined rigidly within research disciplines/paradigms (as have been defined in some – primarily Western – research trajectories) may fail to take into account African social and contextual realities when applied uncritically. We argue that there is need for researchers in Africa to consider a multiplicity of approaches if research is to be meaningful in, and responsive to, social and contextual realities. In particular, we argue for taking account of socio historical and socio-cultural contexts in creating African epistemology in and through research

Genetic diversity, inter-gene pool introgression and nutritional quality of common beans (Phaseolus vulgaris L.) from Central Africa

The Great Lakes region of Central Africa is a major producer of common beans in Africa. The region is known for high population density and small average farm size. The common bean represents the most important legume crop of the region, grown on over a third of the cultivated land area, and the per capita consumption is among the highest in the world for the food crop. The objective of this study was to evaluate the genetic diversity in a collection of 365 genotypes from the Great Lakes region of Central Africa, including a large group of landraces from Rwanda as well as varieties from primary centers of diversity and from neighboring countries of Central Africa, such as the Democratic Republic of Congo and Uganda, using 30 fluorescently labeled microsatellite markers and automated allele detection. In addition, the landraces were evaluated for their seed iron and zinc concentration to determine if genetic diversity influenced nutritional quality. Principal coordinate and neighbor-joining analyses allowed the separation of the landraces into 132 Andean and 195 Mesoamerican (or Middle American) genotypes with 32 landraces and 6 varieties intermediate between the gene pools and representing inter-gene pool introgression in terms of seed characteristics and alleles. Genetic diversity and the number of alleles were high for the collection, reflecting the preference for a wide range of seed types in the region and no strong commercial class preference, although red, red mottled and brown seeded beans were common. Observed heterozygosity was also high and may be explained by the common practice of maintaining seed and plant mixtures, a coping strategy practiced by Central African farmers to reduce the effects of abiotic and biotic stresses. Finally, nutritional quality differed between the gene pools with respect to seed iron and zinc concentration, while genotypes from the intermediate group were notably high in both minerals. In conclusion, this study has shown that Central African varieties of common bean are a source of wide genetic diversity with variable nutritional quality that can be used in crop improvement programs for the region

Locked entropy in partially coherent fields

We introduce a taxonomy for partially coherent optical fields spanning multiple degrees of freedom (DoFs) based on the rank of the associated coherence matrix (the number of non-zero eigenvalues). When DoFs comprise two spatial modes and polarization, a fourfold classification emerges, with rank-1 fields corresponding to fully coherent fields. We demonstrate theoretically and confirm experimentally that these classes have heretofore unrecognized different properties. Specifically, whereas rank-2 fields can always be rendered separable with respect to its DoFs via a unitary transformation, rank-3 fields are always non-separable. Consequently, the entropy for a rank-2 field can always be concentrated into a single DoF (thus ridding the other DoF of statistical fluctuations), whereas some entropy is always 'locked' in one DoF of a rank-3 field

Ellipsometric measurements by use of photon pairs generated by spontaneous parametric down-conversion

We present a novel interferometric technique for performing ellipsometric measurements. This technique relies on the use of a non-classical optical source, namely, polarization-entangled twin photons generated by spontaneous parametric down-conversion from a nonlinear crystal, in conjunction with a coincidence-detection scheme. Ellipsometric measurements acquired with this scheme are absolute; i.e., they do not require source and detector calibration.Comment: 10 pages, accepted for publication in Optics Letter

Anglo-American governance adoption in non-Anglo-American settings: Assessing practitioner perceptions of corporate governance across three emerging economies

© 2019, Emerald Publishing Limited. Purpose: Albeit the growing academic research on emerging economies corporate governance (CG) environments within accounting and finance literature, there exists a dearth of cross-country studies using a qualitative approach to understand practitioners’ behaviour vis-a-vis diffusion of international CG practices in emerging economies. This study aims to fill this oversight through a comparative analysis of the divergence and convergence of CG systems operational in three emerging economies (Cameroon, Kenya and Pakistan) while highlighting different institutional and contextual impacts on behaviour of governance actors. The paper uses an interface between critical realism and new institutional economics theory to explore the implementation and execution of CG in Cameroon, Kenya and Pakistan. Design/methodology/approach: The study analysed 24 in-depth semi-structured interviews and conducted with key governance practitioners across the three countries. Findings: The findings show that CG implementation processes in Cameroon, Kenya and Pakistan are nascent and driven by international forces rather than local initiatives. CG lacks institutional identity across the three countries as regulatory coercion acts as a key driver for CG adoption and practitioner accounts are mixed regarding the impact of CG on firm performance. Practical implications: The paper evidences that the lack of governance identify, compliance and slow implementation process of governance regulations and its impact on firm performance in emerging economies is caused by the fact that local institutional characteristics prevalent in these economies may not be suitable for a “copy and paste” of Western form of governance regulations. Furthermore, governance actors do not see the relevance of recommended CG practices except as a regulatory burden. Originality/value: The paper contributes to close the lacuna in the seemingly little qualitative comparative study that has examined practitioner’s perception vis-à-vis the diffusion of international governance practices in emerging economies. Specifically, it uncovers how different institutional and contextual factors impact on the behaviour of governance actors and how their behaviours may constrain adoption, implementation and compliance with recommended governance practices